Download Cerebral cortex

13
The Brain and
Cranial Nerves
PowerPoint® Lecture Presentations prepared by
Alexander G. Cheroske
Mesa Community College at Red Mountain
© 2011 Pearson Education, Inc.
Section 1: Functional Anatomy of Brain and
Cranial Nerves
• Learning Outcomes
• 13.1 Name the major regions of the brain, and
describe their functions.
• 13.2 Explain how the brain is protected and
supported, and how cerebrospinal fluid
forms and circulates.
• 13.3 List the components of the medulla
oblongata and pons, and specify the
functions of each.
• 13.4 List the main components of the
cerebellum, and specify the functions of each.
© 2011 Pearson Education, Inc.
Section 1: Functional Anatomy of Brain and
Cranial Nerves
• Learning Outcomes
• 13.5 List the main components of the midbrain, and specify
the functions of each.
• 13.6 List the main components of the diencephalon, and
specify the functions of each.
• 13.7 Identify the main components of the limbic system, and
specify the locations and functions of each.
• 13.8 Describe the structure and function of the basal nuclei of
the cerebrum.
• 13.9 Identify the major superficial landmarks of the cerebrum,
and cite the locations of each.
© 2011 Pearson Education, Inc.
Section 1: Functional Anatomy of Brain and
Cranial Nerves
• Learning Outcomes
• 13.10 Identify the locations of the motor, sensory,
and association areas of the cerebral cortex,
and discuss the functions of each.
• 13.11 Discuss the significance of the white matter of
the cerebral cortex.
• 13.12 CLINICAL MODULE Discuss the origin and
significance of the major categories of brain
waves seen in an electroencephalogram.
• 13.13 Identify the cranial nerves by name and
number, and cite the functions of each.
© 2011 Pearson Education, Inc.
Section 1: Functional Anatomy of Brain and
Cranial Nerves
• Brain characteristics
• Equals ~97% of body’s neural tissue in adults
• “Typical” brain
• Weighs 1.4 kg (3 lb)
• Has volume of 1200 mL (71 in.3)
• Size varies among individuals
• Male are ~10% larger than female
• Owing to differences in overall body size
• No correlation between size and intelligence
• Functional normal individuals with smallest (750 mL)
and largest (2100 mL) brains
© 2011 Pearson Education, Inc.
Section 1: Functional Anatomy of Brain and
Cranial Nerves
•
Brain development at 4 weeks
•
Neural tube is present
•
Hollow cylinder that is beginning of CNS
•
Has internal passageway (neurocoel)
•
Cephalic portion enlarges into three portions (primary
brain vesicles)
1.
Prosencephalon (proso, forward + encephalos, brain)
•
2.
Mesencephalon
•
3.
“Forebrain” is at tip of neural tube
“Midbrain” is an expansion caudal to prosencephalon
Rhombencephalon
•
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“Hindbrain” most caudal portion, continuous with spinal cord
A lateral view of the brain of an embryo after
4 weeks of development showing the neural tube
Rhombencephalon
Mesencephalon
Prosencephalon
Cerebrum
Diencephalon
(covered by
cerebrum)
Mesencephalon
(covered by
cerebrum)
Spinal
cord
Neurocoel
A lateral view of the brain of a 5-week-old embryo
Prosencephalon
Rhombencephalon
Pons
Metencephalon
Myelencephalon
Diencephalon
Medulla
oblongata
Cerebellum
Spinal cord
Telencephalon
Spinal
cord
Brain development in a child, showing
the cerebrum covering other portions
of the brain
Figure 13 Section 1
© 2011 Pearson Education, Inc.
Section 1: Functional Anatomy of Brain and
Cranial Nerves
• Brain development at 5 weeks
• Primary brain vesicles change position and
prosencephalon and rhombencencephalon
subdivide to form secondary brain vesicles
• Prosencephalon
• Diencephalon (dia, through + encephalos, brain)
• Becomes major relay and processing center for
information to/from cerebrum
• Telencephalon (telos, end)
• Becomes cerebrum in adult brain
© 2011 Pearson Education, Inc.
Section 1: Functional Anatomy of Brain and
Cranial Nerves
• Brain development at 5 weeks (continued)
• Secondary brain vesicles (continued)
• Rhombencephalon
• Metencephalon (meta, after)
• Adjacent to mesencephalon
• Forms cerebellum and pons in adult brain
• Myelencephalon (myelon, spinal cord)
• Becomes medulla oblongata in adult brain
© 2011 Pearson Education, Inc.
Module 13.1: Major brain regions
• Major brain regions
• Cerebrum
• Divided into pair of large cerebral hemispheres
• Surfaces covered by superficial layer of gray
matter
• = Cerebral cortex (cortex, rind or bark)
• Functions
• Conscious thought
• Memory storage and processing
• Regulation of skeletal muscle contractions
© 2011 Pearson Education, Inc.
Module 13.1: Major brain regions
• Superficial cerebral structures
• Fissures
• Deep grooves that subdivide hemispheres
• Gyri (singular, gyrus)
• Folds in cerebral cortex that increase surface
area
• Sulci (singular, sulcus)
• Shallow depressions in cerebral cortex that
separate adjacent gyri
© 2011 Pearson Education, Inc.
Module 13.1: Major brain regions
• Cerebellum
• Partially hidden by cerebral hemispheres
• Second largest structure of brain
• Functions
• Coordination and modulation of motor
commands from cerebral cortex
© 2011 Pearson Education, Inc.
A diagrammatic view of the brain
showing its major regions and
their general functions
Cerebrum
Is divided into a pair of large cerebral hemispheres whose surfaces are covered by a
superficial layer of gray matter called the cerebral cortex
Fissures
Sulci
Gyri
Diencephalon
Is the structural and functional
link between the cerebral
hemispheres and the rest of
the CNS.
Thalamus
Spinal cord
Not visible in this view; the
hypothalamus, or floor of the
diencephalon
Cerebellum
Functions in coordination and
modulation of motor commands
from the cerebral cortex
Brain stem
Includes three
structures
Midbrain
Pons
Medulla oblongata
Figure 13.1
© 2011 Pearson Education, Inc.
1
Module 13.1: Major brain regions
• Diencephalon
• Structural and functional link between cerebral
hemispheres and rest of CNS
• Two parts
• Thalamus
• Relay and processing centers for sensory information
• Hypothalamus (hypo-, below)
• Floor of diencephalon
• Contains centers involved with
• Emotions
• Autonomic function
• Hormone production
© 2011 Pearson Education, Inc.
Module 13.1: Major brain regions
• Brain stem (3 parts)
1. Midbrain
• Contains nuclei that coordinate visual and
auditory reflexes
• Contains centers that help to maintain
consciousness
2. Pons (pons, bridge)
• Connects cerebellum to brain stem
• Has tracts and relay centers
• Contains nuclei that function in somatic and
visceral motor control
© 2011 Pearson Education, Inc.
Module 13.1: Major brain regions
• Brain stem (3 parts, continued)
3. Medulla oblongata
• Relays sensory information to other areas of
brain stem and thalamus
• Contains major centers that regulate autonomic
function
• Examples: heart rate, blood pressure
Animation: Brain
© 2011 Pearson Education, Inc.
Two views of the ventricles, which are filled with cerebrospinal fluid
Cerebral
hemispheres
Cerebral
hemispheres
Ventricles of the Brain
Lateral ventricle
Interventricular foramen
Third ventricle
Aqueduct of midbrain
Fourth ventricle
Pons
Medulla oblongata
Central canal
Central canal
Cerebellum
Spinal cord
Ventricular system, lateral view
Ventricular system, anterior view
Figure 13.1
© 2011 Pearson Education, Inc.
2
Module 13.1: Major brain regions
• Ventricles of the brain
• Fluid-filled cavities
• Filled with cerebrospinal fluid
• Lined with ependymal cells
• Formed during development as neurocoel
expands within cerebral hemispheres,
diencephalon, and metencephalon
• Connected by narrow canals
© 2011 Pearson Education, Inc.
Module 13.1: Major brain regions
• Four ventricles
1. & 2. Lateral ventricles
•
Contained within each cerebral hemisphere
•
Each connected to third ventricle by
interventricular foramen
•
Separated medially by septum pellucidum
•
“Roof” partially formed by thick white matter tract
connecting hemispheres (corpus callosum)
•
Then narrows to become central canal of spinal
cord
© 2011 Pearson Education, Inc.
Module 13.1: Major brain regions
• Four ventricles (continued)
3. Third ventricle
•
Contained within diencephalon
•
Connected to fourth ventricle by aqueduct of
the midbrain
4. Fourth ventricle
•
Begins in metencephalon and extends into
superior portion of medulla oblongata
•
Then narrows to become central canal of spinal
cord
© 2011 Pearson Education, Inc.
Cerebral
hemispheres
Ventricles of the Brain
Lateral ventricle
Interventricular foramen
Third ventricle
Aqueduct of midbrain
Fourth ventricle
Pons
Medulla oblongata
Central canal
Spinal cord
Ventricular system, lateral view
Figure 13.1
© 2011 Pearson Education, Inc.
2
Cerebral
hemispheres
Ventricles of the Brain
Lateral ventricle
Interventricular foramen
Third ventricle
Aqueduct of midbrain
Fourth ventricle
Central canal
Cerebellum
Ventricular system, anterior view
Figure 13.1
© 2011 Pearson Education, Inc.
2
Two views of the ventricles, which are filled with cerebrospinal fluid
Corpus callosum
Lateral ventricles
Interventricular
foramen
Septum pellucidum
Third ventricle
Inferior tip of
lateral ventricle
Aqueduct of
midbrain
Fourth ventricle
Cerebellum
Central canal
Figure 13.1
© 2011 Pearson Education, Inc.
3
Module 13.1 Review
a. Name the major regions of the brain and the distinct
structures of each.
b. Describe the role of the medulla oblongata.
c. Compare the corpus callosum to the septum
pellucidum.
© 2011 Pearson Education, Inc.
Module 13.2: Cranial meninges and
cerebrospinal fluid
•
Cranial meninges
1. Dura mater
•
Consists of two layers
•
Separated by slender fluid-filled gap containing fluids
and blood vessels
1.
Outer (endosteal) layer
•
2.
Fused to cranial bones (no epidural space)
Inner (meningeal) layer
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Module 13.2: Cranial meninges and
cerebrospinal fluid
•
Cranial meninges (continued)
2. Arachnoid mater
•
Consists of
•
•
Arachnoid membrane
•
Provides smooth covering that does not follow
brain’s underlying folds
•
Subarachnoid space lies below
Arachnoid trabeculae
•
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Connect to pia mater
Module 13.2: Cranial meninges and
cerebrospinal fluid
•
Cranial meninges (continued)
3. Pia mater
•
Bound to brain surface by astrocyte processes
•
Extends into every fold and accompanies
cerebral blood vessels extending into surface
brain structures
© 2011 Pearson Education, Inc.
The three layers of the cranial meninges:
the dura mater, arachnoid mater, and pia mater
Subdural space
Cranium
(skull)
Arachnoid mater
Dura mater
Arachnoid membrane
Dura mater (endosteal layer)
Subarachnoid space
Dural sinus
Arachnoid trabeculae
Dura mater (meningeal layer)
Pia mater
Cerebral cortex
Is bound to the surface of the brain by astrocytes
Figure 13.2
© 2011 Pearson Education, Inc.
1
Module 13.2: Cranial meninges and
cerebrospinal fluid
•
Dural folds and sinuses
•
Dural folds
•
Dip into cranial cavity and return
•
Provide additional stabilization and support to
brain
•
Falx cerebri (falx, sickle shaped)
•
Projects between cerebral hemispheres
•
Inferior attachment to crista galli (anteriorly) and
internal occipital crest (posteriorly)
•
Superior and inferior sagittal sinuses lie within
© 2011 Pearson Education, Inc.
Module 13.2: Cranial meninges and
cerebrospinal fluid
•
Dural folds and sinuses (continued)
•
Dural folds (continued)
•
Tentorium cerebelli (tentorium, a tent)
•
•
Separates cerebrum from cerebellum
Falx cerebelli
•
Separates cerebellar hemispheres along midsagittal
line
•
Inferior to tentorium cerebelli
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Inferior
sagittal sinus
Superior sagittal sinus
The dural sinuses and dural folds
Tentorium cerebelli
Falx cerebri
Falx cerebelli
Figure 13.2
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2
Module 13.2: Cranial meninges and
cerebrospinal fluid
•
Cerebrospinal fluid (CSF)
•
Completely surrounds and bathes CNS
exposed surfaces
•
Materials diffuse between CSF and interstitial
fluid of CNS across ependymal walls
•
Total volume = ~150 mL
•
Entire volume replaced in ~8 hours
© 2011 Pearson Education, Inc.
Module 13.2: Cranial meninges and
cerebrospinal fluid
•
Cerebrospinal fluid (continued)
•
Choroid plexus (choroid, vascular coat;
plexus, network)
•
Consists of ependymal cells and capillaries
•
Produces CSF
•
•
~500 mL/day
Found in all ventricles
© 2011 Pearson Education, Inc.
Module 13.2: Cranial meninges and
cerebrospinal fluid
•
Cerebrospinal fluid circulation
•
Created and circulates between ventricles
•
From fourth ventricle, CSF can circulate
•
•
Down central canal of spinal cord
•
Out single median aperture and lateral
apertures into subarachnoid space
•
Down around spinal cord and cauda equina
•
Up around brain
Absorbed back into venous circulation through
arachnoid granulations within superior
sagittal sinus
© 2011 Pearson Education, Inc.
The sites of cerebrospinal fluid production,
circulation, and absorption into the venous
system
Superior sagittal sinus
Third ventricle
Aqueduct of the midbrain
Central canal
of spinal cord
Dura mater
Arachnoid
Subarachnoid space
Figure 13.2
© 2011 Pearson Education, Inc.
3
The sites of cerebrospinal fluid production, circulation, and
absorption into the venous system
Interstitial fluid
in thalamus
Nutrients,
O2
Capillaries
Waste products,
CO2
Neuron
Astrocyte
Choroid plexus
cells
Removal
of waste
Production
of CSF
Choroid plexus
© 2011 Pearson Education, Inc.
Ependymal
cells
Cerebrospinal
fluid in
third ventricle
Figure 13.2
3
Dura mater Superior
Cranium
sagittal sinus
Arachnoid
granulation
CSF
movement
Subdural
space
Cerebral
cortex
Arachnoid
membrane
Pia mater
An arachnoid granulation, the site at which
cerebrospinal fluid is absorbed into the
venous circulation
Figure 13.2
© 2011 Pearson Education, Inc.
4
Module 13.2 Review
a. From superficial to deep, name the layers that
constitute the cranial meninges.
b. What would happen if the normal circulation
or reabsorption of CSF became blocked?
c. How would decreased diffusion across the
arachnoid granulations affect the volume of
cerebrospinal fluid in the ventricles?
© 2011 Pearson Education, Inc.
Module 13.3: Medulla oblongata and pons
•
Medulla oblongata
•
All communication (sensory and motor) between
brain and spinal cord passes through
•
Center for coordination of relatively complex
autonomic reflexes and control of visceral functions
•
Major anatomical features
•
Olive (prominent bulge and anterolateral surface)
•
Pyramids (contain descending/motor tracts from
cerebral cortex)
•
Some fibers cross over to other side of spinal cord
•
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= Decussation (decussation, crossing over)
Structure of the medulla oblongata
The anterior surface of
the medulla oblongata
Pons
Pyramids
Site of decussation
Figure 13.3
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1
Module 13.3: Medulla oblongata and pons
•
Medulla oblongata components
•
Autonomic centers (controlling vital functions)
•
Reticular formation
•
Cardiovascular centers
•
Respiratory rhythmicity center
•
Solitary nucleus
•
Relay stations
•
Olivary nucleus
•
Nucleus cuneatus
•
Nucleus gracilis
© 2011 Pearson Education, Inc.
Structure of the medulla oblongata
Olive
Autonomic centers
Reticular formation
Attachment to
membranous
roof of fourth
ventricle
Cardiovascular centers
Respiratory rhythmicity
center
Two views of the structure
of the medulla oblongata
showing its landmarks
and structures
Solitary nucleus
Relay stations
Posterior
median sulcus
Olivary nucleus
Nucleus cuneatus
Spinal cord
Nucleus gracilis
Anterior view
Posterolateral view
Figure 13.3
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2
Figure 13.3
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2
Figure 13.3
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2
Module 13.3: Medulla oblongata and pons
•
Pons
•
Links cerebellum with midbrain, diencephalon,
cerebrum, medulla oblongata, and spinal cord
•
Contains:
•
Tracts (ascending and descending)
•
Respiratory centers (pneumotaxic and
apneustic)
•
Reticular formation
•
Loosely organized mass of gray matter containing
centers that regulate vital autonomic functions
•
Extends from medulla oblongata to mesencephalon
© 2011 Pearson Education, Inc.
The pons, which links the cerebellum
with the midbrain, diencephalon,
cerebrum, medulla oblongata, and
spinal cord
Tracts
Ascending tracts Descending tracts
Respiratory Centers
Pneumotaxic center
Apneustic center
Transverse fibers
Cerebellum
Midbrain
Fourth
ventricle
Pons
Medulla
oblongata
Olivary nucleus
Reticular formation
Spinal cord
Figure 13.3
© 2011 Pearson Education, Inc.
3
Module 13.3 Review
a. What is the function of the ascending and
descending tracts in the medulla oblongata?
b. Name the medulla oblongata parts that relay
somatic sensory information to the thalamus.
c. Describe the pyramids of the medulla
oblongata and the result of decussation.
© 2011 Pearson Education, Inc.
Module 13.4: Cerebellum
• Cerebellum
•
Is an automatic processing center that
monitors proprioceptive, visual, tactile,
balance, and auditory sensations
•
Has two primary functions
1. Adjusting postural muscles
2. Programming and fine-tuning movements
controlled at conscious and subconscious
levels
•
Ataxia (ataxia, lack of order)
• Disturbance of muscular coordination from
trauma, stroke, or drugs such as alcohol
© 2011 Pearson Education, Inc.
Module 13.4: Cerebellum
• Components (posterior view)
• Anterior and posterior lobes
• Separated by primary fissure
• Two hemispheres
• Separated by vermis (worm)
• Surface of gray matter (cerebellar cortex)
• Contains huge, highly branched Purkinje cells
that form many sensory and motor synapses
• Has folds (folia)
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Cerebellum
Structural features of the cerebellum
The posterior, superior surface of the cerebellum
Anterior lobe
Posterior view
Vermis
Primary fissure
Posterior lobe
Folia
Left Hemisphere
of Cerebellum
Right Hemisphere
of Cerebellum
Figure 13.4
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1
Dendrites
Cell body of Purkinje cell
Purkinje cell axons project
into the white matter of
the cerebellum.
Purkinje cells
LM x 400
Purkinje cells of the cerebellar cortex
Figure 13.4
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2
Module 13.4: Cerebellum
• Components (sagittal section)
• Cerebellar cortex
• Arbor vitae “tree of life”
• Branching pattern of inner cerebellar white matter
• Cerebellar peduncles
• Link cerebellum to brain stem
• Three on each side
1. Superior
2. Middle
3. Inferior
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A sagittal section through the vermis showing the internal organization of
the cerebellum and the locations of the three cerebellar peduncles
Midbrain
Anterior lobe
Arbor vitae
Cerebellar Peduncles
Pons
Superior cerebellar peduncle
Middle cerebellar peduncle
Inferior cerebellar peduncle
Cerebellar nucleus
Cerebellar cortex
Posterior lobe
Choroid plexus of
the fourth ventricle
Medulla oblongata
Spinal cord
Lateral view
Figure 13.4
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3
Figure 13.4
© 2011 Pearson Education, Inc.
3
Module 13.4 Review
a. Identify the components of the cerebellar gray
matter.
b. Describe the arbor vitae, including its
makeup, location, and function.
c. Describe ataxia.
© 2011 Pearson Education, Inc.
Module 13.5: Midbrain
•
Midbrain
• Most complex and integrative portion of brain
stem
• Can direct complex motor patterns at
subconscious level
• Influences activity level of entire nervous
system
© 2011 Pearson Education, Inc.
Module 13.5: Midbrain
•
Midbrain components
•
Corpora quadrigemina
•
•
Superior colliculus (colliculus, hill)
•
Receives visual inputs from thalamus
•
Controls reflex movements of eyes, head, and neck
in response to visual inputs
Inferior colliculus
•
Receives auditory data from nuclei in medulla
oblongata and pons
•
Controls reflex movements of head, neck, and trunk
in response to auditory inputs
© 2011 Pearson Education, Inc.
Module 13.5: Midbrain
•
Midbrain components (continued)
•
Reticular activating system (RAS)
•
Specialized part of reticular formation
•
Stimulation to RAS makes you more alert/attentive
•
•
Damage to RAS causes unconsciousness
Red nucleus
•
Receives information from cerebrum and cerebellum
•
Issues commands that affect upper limb position and
background muscle tone
•
Substantia nigra (nigra, black)
•
Dark cells that adjust basal nuclei activity in cerebrum
© 2011 Pearson Education, Inc.
A posterior view of the midbrain showing the major
superficial landmarks and the underlying nuclei
Posterior view of
brain stem and
diencephalon
Pineal gland
Thalamus
Red nucleus
Corpora Quadrigemina
Superior colliculus
Substantia nigra
Inferior colliculus
Cerebral peduncles
Reticular activating system (RAS)
Figure 13.5
© 2011 Pearson Education, Inc.
1
Two views of the brain stem showing the anatomy of the midbrain in relation to the brain stem as a whole
Midbrain
Cerebral peduncle
Cranial Nerves
of Brain Stem
Superior colliculus
Inferior colliculus
IV
III
IV
Cerebellar Peduncles
V
Superior cerebellar peduncle
Middle cerebellar peduncle
Pons
Inferior cerebellar peduncle
VI
VII
VIII
IX
X
XI
XII
Medulla oblongata
Medulla oblongata
Choroid plexus
in roof of fourth
ventricle
Spinal cord
Dorsal roots
of spinal nerves
C1 and C2
Spinal
nerve C1
Spinal
nerve C2
Ventral root
Spinal cord
Lateral view
Dorsal root
Posterior view
Figure 13.5
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3
Module 13.5: Midbrain
•
Midbrain components (continued)
•
Tectum
•
Roof of midbrain
•
Region posterior to aqueduct of midbrain
•
Tegmentum
•
Area anterior to aqueduct of midbrain
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A superior view of a horizontal section through the midbrain
Posterior
Superior colliculus
Tectum
Red nucleus
Aqueduct of
the midbrain
Substantia nigra
Tegmentum
Cerebral peduncle
Anterior
Figure 13.5
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2
Figure 13.5
© 2011 Pearson Education, Inc.
3
Module 13.5 Review
a. Cranial nerves III to XII arise from which
structure?
b. Identify the sensory nuclei contained within
the corpora quadrigemina.
c. Which area(s) of the midbrain control reflexive
movements of the eyes, head, and neck?
© 2011 Pearson Education, Inc.
Module 13.6: Diencephalon
•
Diencephalon components
•
Epithalamus
•
Thalamus
•
Hypothalamus
© 2011 Pearson Education, Inc.
Module 13.6: Diencephalon
•
Epithalamus
•
Roof of diencephalon, superior to third
ventricle
•
Anterior portion
•
•
Marked by:
•
Anterior commissure (tract interconnecting cerebral
hemispheres)
•
Optic chiasm (where optic nerves connect to brain)
Contains extensive area of choroid plexus that
extends into interventricular foramina
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Module 13.6: Diencephalon
•
Epithalamus (continued)
•
Posterior portion
•
Pineal gland
•
Secretes melatonin (hormone regulating day-night
cycles and some reproductive functions)
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Module 13.6: Diencephalon
•
Thalamus
•
On each side of brain, superior to midbrain
•
Final point for ascending sensory information to
be relayed or projected to cerebral cortex
•
•
Acts as a filter, only passing on small portion of
sensory information
Has regions that contain nuclei or groups of
nuclei that connect to specific regions of
cerebral cortex
© 2011 Pearson Education, Inc.
The regions of the thalamus, each of which contains
nuclei or groups of nuclei that connect to specific
regions of the cerebral cortex
Anterior
group
Medial group
Lateral group
V e n t r a l
g r o u p
Left thalamus
Posterior
group
Pulvinar
Medial geniculate
nucleus
Note: colors indicate
the associated areas
of the cerebral cortex
Lateral geniculate
nucleus
Figure 13.6
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3
Module 13.6: Diencephalon
•
Thalamus (continued)
•
Components
•
Interthalamic adhesion
•
•
Lateral geniculate (genicula, little knee) nucleus
•
•
Connects thalamic hemispheres, but no neural
fibers cross
Receives visual information over optic tract
and relays signals to midbrain and occipital
lobe
Medial geniculate nucleus
•
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Relays auditory information from inner ear
receptors to appropriate cerebral cortex area
The thalamus and important landmarks
made visible by the removal of the
cerebral hemispheres and cerebral
peduncles
Lateral geniculate nucleus
Thalamus
Medial geniculate nucleus
Optic chiasm
Optic tract
Cerebral peduncle
(midbrain)
Lateral view of the
left thalamus and midbrain
Figure 13.6
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2
Figure 13.6
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4
Module 13.6: Diencephalon
•
Hypothalamus
•
Contains important control and integrative
centers
•
Centers may be stimulated by:
1.
Sensory information from cerebrum, brain stem, and
spinal cord
2.
Changes in CSF and interstitial fluid composition
3.
Chemical stimuli from blood because this area lacks
blood–brain barrier
© 2011 Pearson Education, Inc.
Module 13.6: Diencephalon
•
Hypothalamus (continued)
•
Components
•
Infundibulum
•
•
Mamillary bodies
•
•
Connects to pituitary gland
Control feeding reflexes like licking and swallowing
Hormonal centers
•
Secrete chemical messengers that control endocrine
cells in anterior pituitary
•
Secrete two hormones released by posterior pituitary
© 2011 Pearson Education, Inc.
Module 13.6: Diencephalon
•
Hypothalamus (continued)
•
Components
•
Nuclei (autonomic centers that control
cardiovascular and vasomotor centers of medulla
oblongata)
•
Preoptic area
•
•
Regulates body temperature through adjustments in
blood flow and sweat gland activity
Suprachiasmatic nucleus
•
© 2011 Pearson Education, Inc.
Coordinates day-night cycles of activity/inactivity
A sagittal section of the brain showing the
structure of the hypothalamus
Hypothalamic Nuclei
Thalamus
Autonomic centers
Preoptic area
Suprachiasmatic nucleus
Hypothalamus
Hormonal centers
Pons
Infundibulum
Anterior Posterior
pituitary pituitary
gland
gland
© 2011 Pearson Education, Inc.
Mamillary body
Figure 13.6
4
Module 13.6 Review
a. Name the main components of the
diencephalon.
b. Damage to the lateral geniculate nuclei of the
thalami would interfere with what particular
function?
c. Which component of the diencephalon is
stimulated by changes in body temperature?
© 2011 Pearson Education, Inc.
Module 13.7: Limbic system
•
The limbic system
•
Includes nuclei and tracts along border of
cerebrum and diencephalon
•
Is a functional grouping rather than anatomical
•
Through experimental stimulation, many
functional areas/centers identified
• Emotional areas for rage, fear, pain, sexual arousal, and
pleasure
• Areas that produce heightened alertness/generalized
excitement, generalized lethargy, and sleep
© 2011 Pearson Education, Inc.
Module 13.7: Limbic system
•
Also known as motivational system
•
Functions
1. Establishing emotional states
2. Linking conscious, intellectual functions of
cerebral cortex with unconscious and autonomic
functions of brain stem
3. Facilitating memory storage and retrieval
© 2011 Pearson Education, Inc.
Module 13.7: Limbic system
•
•
Cerebral components (also called limbic lobe)
•
Cingulate gyrus (superior portion)
•
Parahippocampal gyrus (inferior portion)
•
Hippocampus
Diencephalon components
•
Anterior group of thalamic nuclei
•
Hypothalamus
•
Mamillary bodies
© 2011 Pearson Education, Inc.
A diagrammatic sagittal section showing the position and
orientation of the major components of the limbic system
Central
sulcus
Corpus
callosum Fornix
Pineal
gland
Components of the
Limbic System in the
Cerebrum
Limbic lobe
(shown in green)
Cingulate gyrus
(superior portion of
limbic lobe)
Parahippocampal gyrus
(inferior portion of limbic
lobe)
Components of the
Limbic System in the
Diencephalon
Anterior group of
thalamic nuclei
Hypothalamus
Mamillary body
Hippocampus
Temporal
lobe of
cerebrum
Figure 13.7
© 2011 Pearson Education, Inc.
1
Module 13.7: Limbic system
•
Specific functional areas
•
Anterior group of thalamic nuclei
•
•
Relay information from mamillary body to
cingulate gyrus on same side
Hippocampus
•
Shaped like a sea horse (hippocampus)
•
Important in learning, especially in storage and
retrieval of long-term memories
© 2011 Pearson Education, Inc.
Module 13.7: Limbic system
•
Specific functional areas (continued)
•
Fornix (arch)
•
•
White matter tract connecting hippocampus
with hypothalamus
Amygdaloid (amygdale, almond) body
•
Interface between limbic system and cerebrum
and various sensory systems
•
Plays a role in regulation of heart rate, control
of “fight or flight” response, and linking
emotions to specific memories
© 2011 Pearson Education, Inc.
A sectional view of important limbic system components and nuclei
Anterior group of thalamic nuclei
Cingulate
gyrus
Corpus
callosum
Fornix
Mamillary body
Hypothalamic nuclei
Olfactory tract
Parahippocampal
gyrus
Amygdaloid body
Hippocampus
Figure 13.7
© 2011 Pearson Education, Inc.
2
Module 13.7 Review
a. List the primary functions of the limbic
system.
b. Which region of the limbic system is
particularly important for the storage and
retrieval of long-term memories?
c. Damage to the amygdaloid body would
interfere with the regulation of which division
of the autonomic nervous system?
© 2011 Pearson Education, Inc.
Module 13.8: Basal nuclei of cerebrum
• Basal nuclei of cerebrum
• Also known as basal ganglia
• Are masses of gray matter within each hemisphere
deep to lateral ventricle floor
• Provide subconscious control of skeletal muscle
tone and help coordinate learned movement
patterns
• Normally do not initiate movement, but provide
general pattern and rhythm
© 2011 Pearson Education, Inc.
Module 13.8: Basal nuclei of cerebrum
• Basal nuclei of cerebrum components
• Caudate nucleus
• Lentiform (lens-shaped) nucleus
• Medial globus pallidus (pale globe)
• Lateral putamen
• Axon bundles connecting cerebral cortex to
diencephalon and brain stem pass around and
between basal nuclei
• = Internal capsule
© 2011 Pearson Education, Inc.
A lateral view of the brain showing the locations of the
caudate and lentiform nuclei, which constitute the
basal nuclei
Head of
caudate
nucleus
Lentiform
nucleus
Tail of caudate
nucleus
Amygdaloid
body
Thalamus
Lateral view
Figure 13.8
© 2011 Pearson Education, Inc.
1
A dissected horizontal section showing the
locations of the caudate nuclei
Caudate nucleus
Internal capsule
Putamen
Thalamus
Choroid plexus
Third ventricle
Lateral ventricle
Head of
caudate
nucleus
Lentiform
nucleus
Pineal gland
Fornix
Tail of caudate
nucleus
Amygdaloid
body
Horizontal section, dissected
Thalamus
Lateral view
Figure 13.8
© 2011 Pearson Education, Inc.
1
A frontal section of the brain showing the locations of the basal nuclei
Head of
caudate
nucleus
Lentiform
nucleus
Tail of caudate
nucleus
Amygdaloid
body
Thalamus
Lateral view
Lateral ventricle
Corpus callosum
Septum pellucidum
Internal capsule
Basal Nuclei
Claustrum
Caudate nucleus
Lateral sulcus
Putamen
Lentiform
nucleus
Anterior
commissure
Globus
pallidus
Tip of lateral
ventricle
Amygdaloid body
Frontal section
Figure 13.8
© 2011 Pearson Education, Inc.
1
Module 13.8 Review
a. Define the basal nuclei.
b. Describe the caudate nucleus.
c. What clinical signs would you expect to observe in
an individual who has damage to the basal
nuclei?
© 2011 Pearson Education, Inc.
Module 13.9: Cerebral superficial landmarks
• Cerebral superficial landmarks
• Help to divide each cerebral hemisphere into lobes
• Central sulcus
• Deep groove dividing anterior frontal lobe from more posterior
parietal lobe
• Precentral gyrus
• Anterior to central sulcus
• Contains primary motor cortex
• Postcentral gyrus
• Posterior to central sulcus
• Contains primary sensory cortex
• Receives sensory information from body
© 2011 Pearson Education, Inc.
Module 13.9: Cerebral superficial landmarks
• Parieto-occipital sulcus
• Separates parietal and occipital lobes
• Lateral sulcus
• Separates frontal and temporal lobes
• Insula (island)
• An “island” of cortex
• Medial to lateral sulcus
© 2011 Pearson Education, Inc.
A lateral view of the brain showing the lobes of the cerebral cortex in the left cerebral hemisphere
The lobes of the cerebral cortex in the left
cerebral hemisphere, shown
Precentral gyrus
in lateral view
Central sulcus
Postcentral gyrus
Parietal lobe
Frontal lobe
Lateral sulcus
Occipital lobe
Temporal lobe
Cerebellum
Pons
Medulla oblongata
Figure 13.9
© 2011 Pearson Education, Inc.
1
A lateral view of the brain showing the lobes of the
cerebral cortex in the left cerebral hemisphere
Retraction of the superficial cerebral cortex along
the lateral sulcus to expose the insula
Insula
Figure 13.9
© 2011 Pearson Education, Inc.
2
Figure 13.9
© 2011 Pearson Education, Inc.
2
A midsagittal view showing the inner boundaries of the lobes of the cerebral cortex
(Structures outside of the cerebrum are labeled in italics.)
Central sulcus
Precentral gyrus
Postcentral gyrus
Limbic lobe
Parietal lobe
Frontal lobe
Corpus callosum
Parieto-occipital sulcus
Occipital lobe
Thalamus
Pineal gland
Corpora quadrigemina
Hypothalamus
Aqueduct of the midbrain
Optic chiasm
Pons
Temporal lobe
Fourth ventricle
Cerebellum
Mamillary body
Medulla oblongata
Figure 13.9
© 2011 Pearson Education, Inc.
3
Figure 13.9
© 2011 Pearson Education, Inc.
3
Module 13.9: Cerebral superficial landmarks
• General facts about cerebral hemispheres to remember
• Each hemisphere receives sensory information from and
sends motor information to the opposite side of body
• Has no known functional significance
• Hemispheres may look identical but may have different
functions
• Mapping of specific functions to specific areas is imprecise
• Boundaries are indistinct and areas may overlap
• Some functions (like consciousness) may be found in multiple
regions
© 2011 Pearson Education, Inc.
Module 13.9 Review
a. Identify the lobes of the cerebrum and
indicate the basis for their names.
b. Describe the insula.
c. What effect would damage to the left
postcentral gyrus produce?
© 2011 Pearson Education, Inc.
Module 13.10: Specialized functional regions in
cerebral hemispheres
• Specialized functional regions in cerebral
hemispheres
• Motor cortex
• Neurons here are called pyramidal cells because of
their shape
• Somatic motor association area
• Responsible for coordination of learned movements
© 2011 Pearson Education, Inc.
Module 13.10: Specialized functional regions in
cerebral hemispheres
• Sensory areas
• Sensory cortex
• Receives somatic sensory information from receptors for
touch, pressure, pain, vibration, taste, or temperature
• Somatic sensory association area
• Monitors activity in primary sensory cortex
• Gustatory cortex
• Area within insula that receives taste receptor information
• Olfactory cortex
• Receives olfactory receptor information
© 2011 Pearson Education, Inc.
Module 13.10: Specialized functional regions in
cerebral hemispheres
• Sensory areas (continued)
• Auditory cortex
• Primary auditory cortex
• Monitors auditory (sound) information
• Auditory association area
• Monitors sensory activity in auditory cortex and
recognizes sounds, such as spoken words
© 2011 Pearson Education, Inc.
Module 13.10: Specialized functional regions in
cerebral hemispheres
• Sensory areas (continued)
• Visual cortex
• Primary visual cortex
• Receives information from lateral geniculate nuclei
• Visual association area
• Monitors activity in visual cortex and interprets results
• Example: recognizing “c” “a” “r” together is the
word “car”
© 2011 Pearson Education, Inc.
The motor and sensory cortexes and the association areas for each
Central sulcus
Motor Cortex
Sensory Cortex
Somatic motor
association area
Somatic sensory
association area
PARIETAL LOBE
Gustatory Cortex
OCCIPITAL
LOBE
Olfactory Cortex
FRONTAL
LOBE
Visual Cortex
Primary visual cortex
Lateral sulcus
Auditory Cortex
Visual association area
Primary auditory cortex
TEMPORAL LOBE
Auditory association area
Figure 13.10 1
© 2011 Pearson Education, Inc.
Module 13.10: Specialized functional regions in
cerebral hemispheres
• Integrative centers
• Concerned with performance of complex
processes such as speech, writing,
mathematics, and spatial relationships
• Restricted to either right or left hemisphere
© 2011 Pearson Education, Inc.
Module 13.10: Specialized functional regions in
cerebral hemispheres
• Integrative centers (continued)
• General interpretive area
• Also known as the Wernicke area
• Receives information from all sensory association areas
• Present only in one hemisphere (typically the left)
• Plays an essential role in personality by integrating sensory
information and accessing visual and auditory memories
• Speech center
• Also known as the Broca area or motor speech area
• Lies in same hemisphere as general interpretive area
• Regulates patterns of breathing and vocalization needed for
normal speech
© 2011 Pearson Education, Inc.
Module 13.10: Specialized functional regions in
cerebral hemispheres
• Integrative centers (continued)
• Frontal eye field
• Controls learned eye movements such as
scanning text
• Prefrontal cortex
• Coordinates information relayed from
association areas
• Performs abstract intellectual functions such as
predicting consequences of events or actions
© 2011 Pearson Education, Inc.
Locations of some integrative centers, which are concerned with the
performance of complex processes
Frontal eye field
Speech center (Broca area)
Prefrontal cortex
General interpretive area
(Wernicke area)
Figure 13.10 2
© 2011 Pearson Education, Inc.
Module 13.10: Specialized functional regions in
cerebral hemispheres
• Hemisphere lateralization (specialized
functions of each hemisphere)
• Left cerebral hemisphere
• Contains general interpretive and speech
centers
• Is responsible for language-based skills such as
reading, writing, speaking
• Premotor cortex controlling hand movements is
larger for right-handed individuals
• Important in performing analytical tasks such as
mathematics and logic
© 2011 Pearson Education, Inc.
Module 13.10: Specialized functional regions in
cerebral hemispheres
• Hemisphere lateralization (continued)
• Right cerebral hemisphere
• Analyzes sensory information and relates body
to sensory environment
• Examples: recognize faces, understanding 3-D
relationships
• Important in analyzing emotional context of
conversation
• Example: “Get lost!” or “Get lost?”
© 2011 Pearson Education, Inc.
Module 13.10: Specialized functional regions in
cerebral hemispheres
• Hemisphere lateralization (continued)
• Left-handedness
• Represents about 9% of population
• Controlled by primary motor cortex of right
hemisphere
• In an unusually high percentage of musicians and
artists
• Primary motor cortex and association areas on right
cerebral hemisphere are near spatial visualization and
emotion association areas
© 2011 Pearson Education, Inc.
A schematic representation of hemispheric lateralization
Right Cerebral Hemisphere
Left Cerebral Hemisphere
In most people, the left hemisphere contains the general
interpretive and speech centers and is responsible for
language-based skills. Reading, writing, and speaking, for
example, depend on processing done in the left cerebral
hemisphere, in addition, the premotor cortex that functions
in the control of hand movements is larger on the left side
for right-handed individuals than for left-handed
individuals. The left hemisphere is also important in
performing analytical tasks, such
as mathematics and logic.
The right cerebral hemisphere analyzes sensory
information and relates the body to the sensory
environment. Interpretive centers in this hemisphere enable
you to identify familiar objects by touch, smell, sight, taste,
or feel. For example, the right hemisphere plays a dominant
role in recognizing faces and in understanding
three-dimensional relationships. It is also important in
analyzing the emotional context of a conversation—for
instance, distinguishing
between the threat “Get
lost!” and the question
“Get lost?”
LEFT HAND
RIGHT HAND
Prefrontal
cortex
Prefrontal
cortex
Speech center
Writing
Auditory cortex
(right ear)
General interpretive center
(language and mathematical
calculation)
Visual cortex
(right visual field)
© 2011 Pearson Education, Inc.
Anterior commissure
C
O
R
P
U
S
C
A
L
L
O
S
U
M
Analysis by touch
Auditory cortex
(left ear)
Spatial visualization
and analysis
Visual cortex
(left visual field)
Figure 13.10 3
Module 13.10 Review
a. Where is the primary motor cortex located?
b. Which senses are affected by damage to the
temporal lobes?
c. Which brain part has been affected in a stroke
victim who is unable to speak?
© 2011 Pearson Education, Inc.
Module 13.11: White matter in the brain
• Functional groups of white matter in inner
cerebrum
• Association fibers
• Interconnect areas of neural cortex within a
hemisphere
• Shortest fibers connect one gyrus to another
(= arcuate fibers)
• Longest fibers are organized into bundles or fasciculi
and connect frontal lobe to other lobes of same
hemisphere (= longitudinal fasciculi)
© 2011 Pearson Education, Inc.
The locations of association fibers,
which interconnect areas of
neural cortex within a
single cerebral hemisphere
Arcuate fibers
Longitudinal fasciculi
Lateral view
Figure 13.11 1
© 2011 Pearson Education, Inc.
Module 13.11: White matter in the brain
• Functional groups of white matter in inner
cerebrum (continued)
• Commissural (commissura, crossing over) fibers
• Interconnect cerebral hemispheres
• Corpus callosum
• Most substantial and important of commissural fibers
• Contains more than 200 million axons carrying more than 4
billion impulses per second
• Anterior commissure
• Importance increases if corpus callosum is damaged
© 2011 Pearson Education, Inc.
Module 13.11: White matter in the brain
• Functional groups of white matter in inner
cerebrum (continued)
• Projection fibers
• Link cerebral cortex to other CNS areas
• Includes both sensory (ascending) and motor
(descending) fibers
• All must pass through diencephalon
• Entire mass known as the internal capsule
© 2011 Pearson Education, Inc.
The locations of important commissural fibers, which interconnect the cerebral
hemispheres, and projection fibers, which link the cerebral cortex to the rest
of the brain
Corpus callosum
Projection fibers of
internal capsule
Longitudinal
fissure
Anterior commissure
Anterior view
Figure 13.11 2
© 2011 Pearson Education, Inc.
Module 13.11 Review
a. What special names are given to axons in the
white matter of the cerebral hemispheres?
b. What is the function of the longitudinal
fasciculi?
c. What are fibers carrying information between
the brain and spinal cord called, and through
which brain regions do they pass?
© 2011 Pearson Education, Inc.
CLINICAL MODULE 13.12: Brain activity and
electroencephalograms
•
Neural function depends on electrical
impulses
•
Electrical activity changes as certain areas
are stimulated or quieted down
•
Electrical activity at any time generates an
electrical field that can be measured using
electrodes on the scalp
• A printout of that activity =
electroencephalogram (EEG)
• Electrical patterns observed = brain waves
© 2011 Pearson Education, Inc.
The four types of brain waves as they
appear on an electroencephalogram (EEG)
Figure 13.12 1
© 2011 Pearson Education, Inc.
CLINICAL MODULE 13.12: Brain activity and
electroencephalograms
•
Brain waves
•
Alpha waves
•
Occur in brains of healthy awake adults that are
resting with eyes closed
•
Vanish when sleeping or concentrating on a specific
task
•
Beta waves
•
Higher-frequency waves
•
Typical of people concentrating on a task or in a state
of psychological tension
© 2011 Pearson Education, Inc.
CLINICAL MODULE 13.12: Brain activity and
electroencephalograms
•
Brain waves (continued)
•
Theta waves
•
May appear transiently during sleep in normal adults
•
Most often observed in children and in intensely frustrated
adults
•
In certain circumstances, may indicate presence of brain
disorder such as a tumor
•
Delta waves
•
Very large amplitude, low frequency waves
•
Normally seen during sleep in all ages
•
Also seen in infants and awake adults with brain damage from
a tumor, vascular blockage, or inflammation
© 2011 Pearson Education, Inc.
The four types of brain waves as they appear on an electroencephalogram (EEG)
Alpha waves
Beta waves
Theta waves
Delta waves
Figure 13.12 1
© 2011 Pearson Education, Inc.
CLINICAL MODULE 13.12: Brain activity and
electroencephalograms
•
Abnormal brain activity
•
Electrical activity in each hemisphere is generally
synchronized by thalamus
•
Asynchrony may indicate localized damage or cerebral
abnormalities
•
Seizures
•
•
Temporary cerebral activity disorder accompanied by
•
Abnormal movements
•
Unusual sensations
•
Inappropriate behaviors
•
Some combination of above symptoms
Can start in one area and spread across cortical surface
© 2011 Pearson Education, Inc.
CLINICAL MODULE 13.12: Brain activity and
electroencephalograms
•
Abnormal brain activity (continued)
•
Epilepsies
•
Clinical conditions characterized by seizures
•
Also known as seizure disorders
© 2011 Pearson Education, Inc.
CLINICAL MODULE 13.12 Review
a. Define electroencephalogram (EEG).
b. Describe the four wave types associated with
an EEG.
c. Differentiate between a seizure and epilepsy.
© 2011 Pearson Education, Inc.
Module 13.13: Cranial nerves
•
Cranial nerves
•
Can be classified as:
• Sensory
• Special sensory
• Motor
• Mixed
•
Innervate head, neck, and some torso regions
© 2011 Pearson Education, Inc.
The branches of the 12 cranial nerves, their functions (motor, sensory, or mixed), and the structures they innervate
Optic nerve (II)
Abducens nerve (VI)
Oculomotor nerve (III)
Trochlear nerve (IV)
Olfactory nerve (I)
Motor nerve
to muscles of
mastication
Motor nerve
to facial muscles
Ophthalmic branch
Maxillary branch
Mandibular branch
Sensory nerve to
tongue and soft palate
Trigeminal
nerve (V)
Olfactory bulb
Facial nerve (VII)
Olfactory tract
Pituitary gland
Vestibulocochlear nerve (VIII)
Cochlear branch
Semilunar
ganglion (V)
Superior ganglion (IX)
Pons
Geniculate
ganglion (VII)
Inferior ganglion (IX)
Superior ganglion (X)
Medulla
oblongata
Vestibular branch
Glossopharyngeal
nerve (IX)
Inferior ganglion (X)
Vagus
nerve (X)
Hypoglossal
nerve (XII)
Accessory
nerve (XI)
Sensory nerve to
posterior tongue
Motor nerve to
pharyngeal muscles
KEY
To tongue
muscles
Sensory nerves
Motor nerves
To sternocleidomastoid
and trapezius muscles
© 2011 Pearson Education, Inc.
Figure 13.13
Figure 13.13
© 2011 Pearson Education, Inc.
Figure 13.13
© 2011 Pearson Education, Inc.
Module 13.13 Review
a. Identify the cranial nerves by name and
number.
b. Which cranial nerves have motor functions
only?
c. Which cranial nerves are mixed nerves?
© 2011 Pearson Education, Inc.
Section 2: Sensory and Motor Pathways
•
Learning Outcomes
• 13.14 Explain the ways in which receptors can
be classified.
• 13.15 List the types of tactile receptors, and
specify the functions of each.
• 13.16 Identify and describe the major sensory
pathways.
• 13.17 Describe the components, processes,
and functions of the somatic motor
pathways.
© 2011 Pearson Education, Inc.
Section 2: Sensory and Motor Pathways
•
Learning Outcomes
• 13.18 Describe the levels of information
processing involved in motor control.
• 13.19 CLINICAL MODULE Describe the roles
of the nervous system in referred pain,
Parkinson disease, rabies, cerebral
palsy, amyotrophic lateral sclerosis,
Alzheimer disease, and multiple
sclerosis.
© 2011 Pearson Education, Inc.
Section 2: Sensory and Motor Pathways
•
General senses
•
Our sensitivity to temperature, pain, touch,
pressure, vibration, and proprioception
•
Receptors that respond to these stimuli are found
throughout the body
•
Are relatively simple in structure
•
Size of the area each receptor monitors
(= receptive field) varies
•
Can be as large as 7 cm (2.5 in.) as on general body
surfaces or as small as 1 mm as on tongue or fingertips
•
Size of receptive field is inversely related to ability to
accurately describe location of stimulus
© 2011 Pearson Education, Inc.
Receptive fields, the areas monitored by a single
receptor cell
Receptive
field 1
Receptive
field 2
Figure 13 Section 2
© 2011 Pearson Education, Inc.
1
Section 2: Sensory and Motor Pathways
•
General senses (continued)
•
Sensory pathways begin at peripheral
receptors and often end at diencephalon
and/or cerebral hemispheres
•
Much sensory information does not reach
primary sensory cortex and our awareness
•
Sensation
•
•
Information carried by sensory pathway
Perception
•
Conscious awareness of sensation
© 2011 Pearson Education, Inc.
Section 2: Sensory and Motor Pathways
•
Basic events occurring along sensory and motor
pathways
•
Sensory pathway
•
Depolarization of receptor
•
•
Stimulus produces graded change in transmembrane
potential of receptor (= transduction)
Action potential generation
•
If depolarized to threshold, initial segment develops action
potentials
•
© 2011 Pearson Education, Inc.
Greater degree of sustained depolarization
higher frequency of action potentials
=
Section 2: Sensory and Motor Pathways
•
Basic events occurring along sensory and motor
pathways (continued)
•
Sensory pathway (continued)
•
•
Propagation over labeled line
•
= Information about one type of stimulus (touch, pressure,
temperature) carried on axons
•
Brain processes sensory information based on what type of
axons are transmitting information
CNS processing
•
Occurs at every synapse along labeled line
•
May occur at multiple nuclei and centers in CNS
© 2011 Pearson Education, Inc.
Section 2: Sensory and Motor Pathways
•
Basic events occurring along sensory and motor
pathways (continued)
•
Motor Pathways (one of two responses)
1. Immediate involuntary response
•
Processing centers in spinal cord or brain stem respond
before sensations reach cerebral cortex
2. Voluntary
•
Perception (only ~1% of sensations)
•
Voluntary response
•
© 2011 Pearson Education, Inc.
Can moderate, enhance, or supplement simple
reflexive response
Module 13.14: Receptor classification by
function and sensitivity
•
Free nerve endings
•
Can be stimulated by many different stimuli
•
Examples: chemical, pressure, temperature
changes, trauma
•
Sensitivity and specificity may be altered by
location and presences of accessory
structures
•
Are simplest receptors, being the dendrites of
sensory neurons
•
Have branching tips that are unprotected
© 2011 Pearson Education, Inc.
Free nerve endings, the branching tips
of the dendrites of sensory neurons
Free
nerve
endings
Figure 13.14 1
© 2011 Pearson Education, Inc.
Module 13.14: General sense receptor
classification by function and sensitivity
•
Functional classes
•
Nociceptors
•
Pain receptors
•
Free nerve endings with large receptive fields and
broad sensitivity
•
Two axon types carry pain information
1.
Type A fibers (fast pain)
•
Such as from injection or deep cut
•
Quickly reach CNS and trigger fast reflexive responses
•
Relayed to primary sensory cortex for conscious
attention
•
Stimulus can be located to an area within a few cm
© 2011 Pearson Education, Inc.
Module 13.14: General sense receptor
classification by function and sensitivity
•
Functional classes (continued)
•
Nociceptors (continued)
•
Two axon types carry pain information (continued)
2.
Type C fibers (slow pain)
•
Such as burning or aching
•
Cause generalized activation of thalamus and
reticular formation
•
Individual aware of pain but only general location
© 2011 Pearson Education, Inc.
Module 13.14: General sense receptor
classification by function and sensitivity
•
Functional classes (continued)
•
Thermoreceptors
•
Temperature receptors
•
Free nerve endings in dermis, skeletal muscles,
liver, and hypothalamus
•
3–4× more cold receptors than warm receptors
•
•
No structural differences
Chemoreceptors
•
Respond to water-soluble and lipid-soluble
substances dissolved in body fluids (interstitial
fluid, plasma, CSF)
© 2011 Pearson Education, Inc.
Module 13.14: General sense receptor
classification by function and sensitivity
•
Functional classes (continued)
•
Mechanoreceptors
•
Sensitive to stimuli that distort plasma
membrane
•
Contain mechanically gated ion channels that open
or close in response to:
•
Stretching
•
Compression
•
Twisting
•
Other distortions of membrane
© 2011 Pearson Education, Inc.
Module 13.14: General sense receptor
classification by function and sensitivity
•
Functional classes (continued)
•
Mechanoreceptors (continued)
•
Three main types
1.
2.
Proprioceptors
•
Monitor position of joints and muscles
•
Most complex of general sensory receptors
•
Example: muscle spindle
Baroreceptors (baro, pressure)
•
© 2011 Pearson Education, Inc.
Detect pressure changes in blood vessels and
portions of digestive, reproductive, and urinary
tracts
Module 13.14: General sense receptor
classification by function and sensitivity
•
Functional classes (continued)
•
Mechanoreceptors (continued)
•
Three main types (continued)
3.
Tactile receptors
•
Provide sensations of touch (shape or texture),
pressure (degree and frequency of distortion),
and vibration
•
Fine touch and vibration receptors give
detailed information
•
Crude touch and pressure receptors provide
poor localization and give little information
© 2011 Pearson Education, Inc.
A Functional Classification of General Sensory Receptors
Nociceptors
Thermoreceptors
Chemoreceptors
Mechanoreceptors
Pain
receptors
Temperature
receptors
Respond to
water-soluble
and lipidsoluble
substances
dissolved in body
fluids
Sensitive to
stimuli that
distort their
plasma
membranes
Myelinated Type A fibers
(carry sensations of
fast pain)
Unmyelinated
Type C fibers (carry
sensations of slow
pain)
Proprioceptors
(monitor the
positions of joints
and muscles)
Baroreceptors
(detect pressure
changes)
Tactile receptors (provide the
sensations of touch, pressure,
and vibration)
Figure 13.14 2
© 2011 Pearson Education, Inc.
Module 13.14: General sense receptor
classification by function and sensitivity
•
Receptor classes based on stimulation response
•
Tonic receptors
•
Always active
•
Frequency of action potentials generated reflects
background stimulation level
•
•
As stimulation changes, AP frequency changes
accordingly
Phasic receptors
•
Normally inactive
•
Become active transiently in response to changing
conditions
© 2011 Pearson Education, Inc.
Classification of receptors based on the nature of their response to stimulation
Stimulus
Increased
Normal
Normal
Stimulus
Normal
Increased
Normal
Frequency
of action
potentials
Frequency
of action
potentials
Time
Tonic receptors are always active and generate action
potentials at a frequency that reflects the background level
of stimulation. When the stimulus increases or decreases,
the rate of action potential generation changes accordingly.
Time
Phasic receptors are normally inactive, but
become active for a short time in response to a
change in the conditions they are monitoring.
Figure 13.14 3
© 2011 Pearson Education, Inc.
Module 13.14: General sense receptor
classification by function and sensitivity
•
Adaptation
•
Reduction in sensitivity in the presence of a
constant stimulus
•
Two types
1. Peripheral adaptation
•
Occurs at receptor
•
Receptor activity decreases with time
2. Central adaptation
•
Occurs along CNS sensory pathways
•
Generally involves inhibition nuclei along pathway
© 2011 Pearson Education, Inc.
Adaptation, a reduction in sensitivity in the presence of a constant stimulus
Receptor
Arriving
stimulus
Site of peripheral adaptation
Labeled line
CNS processing center
Site of central adaptation
Figure 13.14 4
© 2011 Pearson Education, Inc.
Module 13.14 Review
a. List the four types of general sensory
receptors based on function, and identify the
type of stimulus that excites each type.
b. Describe the three classes of
mechanoreceptors.
c. Explain adaptation, and differentiate between
peripheral adaptation and central adaptation.
© 2011 Pearson Education, Inc.
Module 13.15: Structural receptor classes in skin
•
Structural receptor classes in skin
•
Free nerve endings
• Most common receptors in skin
•
Root hair plexus
• Monitor distortions and movements of hair follicle
• Adapt rapidly
•
Tactile discs and Merkel cells
• Fine touch and pressure receptors
• Are extremely sensitive tonic receptors
• Have very small receptive fields
• Merkel discs are large epithelial cells in stratum germinativum
closely associated with tactile discs
© 2011 Pearson Education, Inc.
The types of receptors in the skin
Hair
Sensory nerves
Figure 13.15
© 2011 Pearson Education, Inc.
Free Nerve Endings
Are the branching tips of sensory
neurons; are unprotected and
nonspecific; can respond to tactile,
Free nerve
pain, and temperature stimuli
endings
Sensory
nerve
Figure 13.15 2
© 2011 Pearson Education, Inc.
Module 13.15: Structural receptor classes in skin
•
Tactile (Meissner’s) corpuscles
•
Are sensitive to fine touch, pressure, and low
frequency vibration
•
Adapt quickly
•
Fairly large (~100 µm in length and ~50 µm in width)
•
Most abundant in eyelids, lips, fingertips, nipples,
and external genitalia
•
Dendrites are highly coiled and interwoven
•
Surrounded by modified Schwann cells
•
Anchored in dermis by fibrous capsule
© 2011 Pearson Education, Inc.
Module 13.15: Structural receptor classes in skin
•
Lamellated (lamella, thin plate) corpuscles
•
Also known as pacinian corpuscles
•
Sensitive to deep pressure
•
Fast adapting
•
•
Very large receptors
•
•
May reach 4 mm in length and 1 mm in diameter
Surrounded by layers of collagen fibers separated by
interstitial fluid
•
•
Most sensitive to pulsing or high-frequency vibrating stimuli
Shield dendrite from other stimuli
Found in dermis of fingers, mammary glands, external
genitalia, in fasciae, joint capsules, and viscera
© 2011 Pearson Education, Inc.
Module 13.15: Structural receptor classes in skin
•
Ruffini corpuscles
•
Sensitive to pressure and distortion of reticular
dermis
•
Are tonic and show little (if any) adaptation
•
Surrounded by capsule that is continuous with
dermis
•
Within is a network of dendrites and collagen
fibers
© 2011 Pearson Education, Inc.
Module 13.15 Review
a. Identify the six types of tactile receptors
located in the skin, and describe their
sensitivities.
b. Which types of tactile receptors are located
only in the dermis?
c. Which is likely to be more sensitive to
continuous deep pressure: a lamellated
corpuscle or a Ruffini corpuscle?
© 2011 Pearson Education, Inc.
Module 13.16: Three major somatic sensory
pathways
1. Spinothalamic pathway
•
Neural path
•
First-order neuron
•
•
Second-order neuron
•
•
From receptor to synapse in spinal cord posterior gray horn
From posterior gray horn, crosses spinal cord and reaches
thalamus
Third-order neuron
•
From thalamus to primary sensory cortex
•
© 2011 Pearson Education, Inc.
Sensory homunculus (“little man”) maps somatic
sensations to discrete areas in cortex
Module 13.16: Three major somatic sensory
pathways
1. Spinothalamic pathway (continued)
•
Anterior spinothalamic tracts
•
•
Carry crude touch and pressure sensations
from body
Lateral spinothalamic tracts
•
Carry pain and temperature sensations from
body
© 2011 Pearson Education, Inc.
Module 13.16: Three major somatic sensory
pathways
2. Posterior column pathway
•
Carries sensations of highly localized “fine”
touch, pressure, vibration, and proprioception
•
Begins at peripheral receptor and ends in
primary sensory cortex
•
Sensory axons ascend in fasciculus gracilis
and cuneatus
•
Medial lemniscus (tract) leads to thalamus
© 2011 Pearson Education, Inc.
Module 13.16: Three major somatic sensory
pathways
3. Spinocerebellar pathway
•
Carries proprioceptive information about
position of skeletal muscles, joints, and
tendons to cerebellum
•
Posterior axons do not cross sides of spinal
cord
•
•
Pass through cerebellar peduncles of same
side
Anterior axons do cross over to opposite side
of spinal cord
© 2011 Pearson Education, Inc.
A cross section through the spinal cord showing the
locations of the somatic sensory pathways
Posterior column pathway
Spinocerebellar pathway
Spinothalamic pathway
Figure 13.16 4
© 2011 Pearson Education, Inc.
Module 13.16 Review
a. Define sensory homunculus.
b. Which spinal tracts carry action potentials
generated by nociceptors?
c. Which cerebral hemisphere receives impulses
conducted by the right fasciculus gracilis of
the spinal cord?
© 2011 Pearson Education, Inc.
Module 13.17: Somatic motor pathways
•
Somatic motor pathways
•
Always involve at least two motor neurons
1. Upper motor neuron
• Cell body in a CNS processing center
2. Lower motor neuron
• Cell body in a nucleus of brain stem or spinal cord
•
Upper motor neuron synapses on lower, which then
innervates a single motor unit of skeletal muscle
© 2011 Pearson Education, Inc.
Module 13.17: Somatic motor pathways
•
Corticospinal pathway
•
Provides voluntary control over skeletal muscles
•
Sometimes called the pyramidal system
•
Begins at pyramidal cells in primary motor cortex
•
Upper axons descend into brain stem and spinal
cord
•
Synapse with lower motor neurons that control muscles
© 2011 Pearson Education, Inc.
Module 13.17: Somatic motor pathways
•
Corticospinal pathway (continued)
•
Upper motor neurons begin along specific areas of the
primary motor cortex that map to muscles in specific
areas of the body (= motor homunculus)
•
•
Motor homunculus pattern varies with number of motor
units innervated and degree of motor control available
Synapses with lower motor neurons occur in two tracts
1.
Corticobulbar (bulbar, brain stem) tracts
•
Synapses occur in motor nuclei of cranial nerves
•
Provide conscious control over skeletal muscles that move
eye, jaw, face, and some muscles of neck and pharynx
© 2011 Pearson Education, Inc.
Module 13.17: Somatic motor pathways
•
Corticospinal pathway (continued)
•
Synapses with lower motor neurons occur in two
tracts (continued)
2. Corticospinal tracts
•
•
Visible along ventral surface of medulla oblongata as pair of
thick bands (pyramids)
•
~85% of corticospinal axons cross midline to enter
lateral corticospinal tracts
•
~15% descend uncrossed as anterior corticospinal
tracts (crossing over occurs through anterior white
commissure at specific spinal segment)
Provide conscious control over skeletal muscles that move
various body areas
© 2011 Pearson Education, Inc.
The corticospinal pathway, which provides
voluntary control over skeletal muscles
Motor
homunculus
To skeletal
muscles
Corticobulbar tract
Motor nuclei
of cranial
nerves
To skeletal
muscles
Cerebral
peduncle
Midbrain
Motor nuclei
of cranial
nerves
Pyramid
Lateral corticospinal tract
Medulla oblongata
Anterior corticospinal tract
KEY
Upper motor
neuron
Lower motor
neuron
© 2011 Pearson Education, Inc.
To skeletal
muscles
Spinal cord
Figure 13.17 1
Module 13.17: Somatic motor pathways
•
Two main pathways for subconscious motor
commands
1. Lateral pathway
•
Primarily concerned with muscle tone and precise
movements of distal limb parts
•
Red nucleus (primary nucleus of lateral pathway)
•
•
Receives information from cerebrum and cerebellum
•
Adjusts upper limb position and background muscle tone
Axons cross to opposite side of brain and descend
through rubrospinal (ruber, red) tracts
© 2011 Pearson Education, Inc.
Module 13.17: Somatic motor pathways
•
Two main pathways for subconscious motor commands
(continued)
2.
Medial pathway
•
Primarily concerned with muscle tone and gross motor control
of neck, trunk, and proximal limb muscles
•
Upper motor neurons located in three areas
1.
Superior and inferior colliculi
•
2.
Tectospinal tracts pass axons down to direct reflexive
movements of head, neck, and upper limbs to visual/auditory
stimuli
Reticular formation
•
© 2011 Pearson Education, Inc.
Reticulospinal tracts conduct impulses down spinal cord
Module 13.17: Somatic motor pathways
•
Two main pathways for subconscious motor
commands (continued)
2. Medial pathway (continued)
•
Upper motor neurons located in three areas
(continued)
3.
Vestibular nucleus (of CN VIII)
•
Receive information from inner ear about position
and movement of head
•
Issue motor commands through vestibulospinal
tracts to adjust muscle tone in neck, eyes, head,
and limbs
© 2011 Pearson Education, Inc.
The locations of centers in the cerebrum,
diencephalon, and brain stem that may issue
somatic motor commands as a result of processing
performed at a subconscious level
Motor
cortex
Thalamus
Basal
nuclei
Red nucleus
Cerebellar
nuclei
Nuclei of the Medial Pathway
Superior and inferior colliculi
Reticular formation
Vestibular nucleus
Medulla oblongata
Figure 13.17 2
© 2011 Pearson Education, Inc.
A cross section of the spinal cord showing the
locations of the medial and lateral pathways
Lateral
corticospinal
tract
Medial Pathway
Involved primarily with the control of
muscle tone and gross movements of
the neck, trunk, and proximal limb
muscles
Lateral Pathway
Involved primarily with the
control of muscle tone and
the more precise movements
of the distal parts of the
limbs
Rubrospinal tract
Reticulospinal tract
Vestibulospinal tract
Tectospinal tract
Anterior
corticospinal
tract
Figure 13.17 3
© 2011 Pearson Education, Inc.
Module 13.17 Review
a. Define corticospinal tracts.
b. Describe the role of the corticobulbar tracts.
c. What effect would increased stimulation of the
motor neurons of the red nucleus have on
muscle tone?
© 2011 Pearson Education, Inc.
Module 13.18: Levels of somatic motor control
•
Levels of somatic motor control
•
Many brain areas are involved in controlling body
movements
•
Generally, the closer the motor center to the
cerebral cortex, the more complex the motor
activity
• Cerebellum is the exception as it is involved at
multiple levels
© 2011 Pearson Education, Inc.
Module 13.18: Levels of somatic motor control
•
Brain areas involved in increasing levels of motor
complexity (as indicated by increasing numbers)
1.
Brain stem and spinal cord
•
2.
Simple cranial and spinal reflexes
Pons and medulla oblongata
•
3.
Balance reflexes and more complex respiratory reflexes
Hypothalamus
•
4.
Reflex motor patterns related to eating, drinking, and sexual
activity; also modifies respiratory reflexes
Thalamus and midbrain
•
Reflexes in response to visual and auditory stimuli
© 2011 Pearson Education, Inc.
Module 13.18: Levels of somatic motor control
•
Brain areas involved in increasing levels of motor
complexity (continued)
5. Basal nuclei
•
Modify voluntary and reflexive motor patterns at
subconscious level
6. Cerebral cortex
•
Plans and initiates voluntary motor activity
7. Cerebellum
•
Coordinates complex motor patterns through
feedback loops involving cerebral cortex, basal
nuclei, and nuclei of medial and lateral pathways
© 2011 Pearson Education, Inc.
The brain structures involved in increasing levels of motor complexity (as indicated by the numbers);
the cerebellum is involved in coordinating motor activities at multiple levels
Basal Nuclei
Thalamus and
Midbrain
Modify voluntary and
reflexive motor
patterns at the
subconscious level
Cerebral Cortex
Plans and
initiates voluntary
motor activity
Control reflexes in
response to visual
and auditory stimuli
Hypothalamus
Controls reflex motor
patterns related to
eating, drinking, and
sexual activity;
modifies respiratory
reflexes
Pons and Medulla
Oblongata
Cerebellum
Control balance
reflexes and more
complex respiratory
reflexes
Brain Stem and Spinal Cord
Control simple cranial and
spinal reflexes
Coordinates complex
motor patterns
through feedback
loops involving the
cerebral cortex and
basal nuclei as well as
nuclei of the medial
and lateral pathways
Figure 13.18 1
© 2011 Pearson Education, Inc.
Module 13.18: Levels of somatic motor control
•
Preparing for movement
•
Once a decision to move has been made,
information is relayed
•
Frontal lobes  motor association areas 
basal nuclei & cerebellum
© 2011 Pearson Education, Inc.
The path of information flow when
an individual makes a conscious decision
to perform a specific movement
Decision in
frontal lobes
Motor
association
areas
Cerebral
cortex
Basal
nuclei
Cerebellum
Figure 13.18 2
© 2011 Pearson Education, Inc.
Module 13.18: Levels of somatic motor control
•
Performing a movement
•
As movement begins, responses are relayed from motor
association areas
Motor association areas  primary motor cortex  medial
and lateral pathways
•
•
•
Basal nuclei adjust movement patterns in two ways
1.
Alter pyramidal cell sensitivity, adjusting corticospinal output
2.
Change excitatory or inhibitory output of medial and lateral
pathways
Cerebellum monitors somatic sensory input and adjusts
motor output as necessary
© 2011 Pearson Education, Inc.
The flow of information as an individual
begins a movement
Motor
association
areas
Primary
motor
cortex
Cerebral
cortex
Basal
nuclei
The basal nuclei adjust patterns
of movement in two ways:
1. They alter the sensitivity of the
pyramidal cells to adjust the
output along the corticospinal
tract.
2. They change the excitatory or
inhibitory output of the medial
and lateral pathways.
Other nuclei of
the medial and
lateral pathways
Cerebellum
Corticospinal
pathway
As the movement proceeds,
the cerebellum monitors
proprioceptive and vestibular
information and compares
the arriving sensations with
those experienced during
previous movements. It then
adjusts the activities of the
upper motor neurons
involved.
Lower
motor
neurons
Motor activity
Figure 13.18 3
© 2011 Pearson Education, Inc.
Module 13.18: Levels of somatic motor control
•
Effects of primary motor cortex damage
•
Individual loses ability to exert fine control of
skeletal muscles
•
Some voluntary movements can still be controlled
by basal nuclei
•
Cerebellum cannot fine-tune movements because
corticospinal pathway is inoperative
•
An individual can stand, balance, and walk
•
All movements are hesitant, awkward, and poorly
controlled
© 2011 Pearson Education, Inc.
Module 13.18 Review
a. The basic motor patterns related to eating and
drinking are controlled by what region of the brain?
b. Which brain regions control reflexes in response to
visual and auditory stimuli that are experienced while
viewing a movie?
c. During a tennis match, you decide how and where to
hit the ball. Explain how the motor association areas
are involved.
© 2011 Pearson Education, Inc.
CLINICAL MODULE 13.19: Nervous system
disorders
•
Nervous system disorders
•
Referred pain
•
Sensation of pain in part of body other than actual
source
•
Examples:
• Heart attack pain felt in left arm
• Strong visceral pain causing stimulation of interneurons
in specific spinal cord segment of spinothalamic
pathway causing pain at body surface
© 2011 Pearson Education, Inc.
Figure 13.19 1
© 2011 Pearson Education, Inc.
CLINICAL MODULE 13.19: Nervous system
disorders
•
Parkinson disease
•
When substantia nigra neurons are damaged or
secrete less dopamine
•
Basal nuclei become more active, increasing
muscle tone and producing stiffness and rigidity
•
Starting movements is difficult because
antagonistic muscle groups do not relax (must
be overpowered)
•
Movements controlled through intense effort and
concentration
© 2011 Pearson Education, Inc.
The substantia nigra from individuals with and
without Parkinson disease
Normal substantia nigra
Diminished substantia
nigra in Parkinson patient
Figure 13.19 2
© 2011 Pearson Education, Inc.
CLINICAL MODULE 13.19: Nervous system
disorders
•
Rabies
•
Bite from rabid animal injects rabies virus into
peripheral tissues
•
Virus spreads to synaptic knobs and is relayed
up axons into CNS through retrograde flow
•
Many toxins, pathogenic bacteria, and other
viruses also bypass CNS defenses through
retrograde flow
© 2011 Pearson Education, Inc.
A member of the dog family, common vectors
of the rabies virus
Figure 13.19 3
© 2011 Pearson Education, Inc.
The movement of rabies viruses in a peripheral axon
Rabies viruses
Retrograde flow
Synaptic knob
Figure 13.19 3
© 2011 Pearson Education, Inc.
CLINICAL MODULE 13.19: Nervous system
disorders
•
Cerebral palsy (CP)
•
Refers to a number of disorders that affect
voluntary motor performance
•
Appears during infancy or childhood and persists
throughout life
•
Cause may be:
•
Trauma associated with premature or stressful
childbirth
•
Maternal exposure to drugs (including alcohol)
•
Genetic defect that causes improper motor pathway
development
© 2011 Pearson Education, Inc.
An individual with cerebral palsy, a number of disorders that
affect voluntary motor
performance
Figure 13.19 4
© 2011 Pearson Education, Inc.
CLINICAL MODULE 13.19: Nervous system
disorders
•
ALS (amyotrophic lateral sclerosis)
•
Commonly known as Lou Gehrig disease (famous
Yankees player who died from disorder)
•
Noted physicist Stephen Hawking also is afflicted
•
Progressive, degenerative disorder that affects
motor neurons in spinal cord, brain stem, and
cerebrum
•
Affects both upper and lower neurons
•
•
Causes atrophy of associated skeletal muscles
Thought to be related to a defect in axonal
transport
© 2011 Pearson Education, Inc.
Lou Gehrig, the most famous person afflicted with
amyotrophic lateral
sclerosis (ALS), a
progressive,
degenerative disorder
that affects motor
neurons
Figure 13.19 5
© 2011 Pearson Education, Inc.
CLINICAL MODULE 13.19: Nervous system
disorders
•
Alzheimer disease (AD)
•
Progressive disorder characterized by loss of higher-order
cerebral functions
•
Most common cause of senile dementia
•
Symptoms may appear at ages 50–60 years but can affect
younger individuals
•
Estimated 2 million affected in United States
•
•
~15% of those over 65
•
~50% of those over 85
•
Causes ~100,000 deaths per year
AD patients have intracellular and extracellular
abnormalities in hippocampus
© 2011 Pearson Education, Inc.
The appearance of a neuron from an individual with Alzheimer
disease (AD), a progressive disorder characterized by the loss
of higher-order cerebral functions
Abnormal
dendrites,
axons, and
extracellular
proteins form
complexes
known as
Alzheimer
plaques.
Figure 13.19 6
© 2011 Pearson Education, Inc.
CLINICAL MODULE 13.19: Nervous system
disorders
•
Multiple sclerosis (MS; sklerosis, hardness)
•
Disease characterized by recurrent incidents of
demyelination in axons within optic nerve, brain, and spinal
cord
•
Common signs and symptoms include:
•
Partial vision loss
•
Problems with speech, balance, general motor coordination
(including urinary and bowel control)
•
In ~1/3 of cases, disease is progressive with more
functional impairment with each incident
•
First attack often in individuals 30–40 years old
•
1.5× more common in women
© 2011 Pearson Education, Inc.
Damage to a neuron from an individual with multiple
sclerosis (MS), a disease characterized by recurrent
incidents of demyelination that affects axons
Demyelinating neuron
Figure 13.19 7
© 2011 Pearson Education, Inc.
CLINICAL MODULE 13.19 Review
a. Define referred pain.
b. Describe how rabies is contracted.
c. Describe amyotrophic lateral sclerosis (ALS).
© 2011 Pearson Education, Inc.