Download The Nervous System Introduction Organization of Neural Tissue

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Introduction
The Nervous System
The Brain
Organization of Neural Tissue
• White matter versus gray matter
Gray matter: short,
non-myelinated neurons
and neuron cell bodies
White matter: myelinated
and non-myelinated axons
Integration
Memory
Learning
Sensation and perception
Organization of Neural Tissue
• Fiber bundles
– Nerve fibers = axon + myelin
– Bundles of nerve fibers
CNS tracts
CNS = tracts
PNS = nerves
Gray
matter
White
matter
PNS nerves
Organization of Neural Tissue
Organization of Neural Tissue
• Nerve cell bodies
– Collections of nerve cell bodies
CNS = nucleus
Largely in gray matter
PNS = ganglion
Exception: basal ganglia in the brain
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Organization of Neural Tissue
– Generally
• Central cavity surrounded by a gray matter core
– External white matter
• Composed of myelinated fiber tracts
– Brain has additional areas of gray matter
• Not present in spinal cord
Cortex of
gray matter
Inner gray
matter
Central cavity
Migratory
pattern of
neurons
Cerebrum
Cerebellum
Outer white
matter
Gray matter
Region of cerebellum
Central cavity
Inner gray matter
Outer white matter
Brain stem
Gray matter
Central cavity
Outer white matter
Inner gray matter
Spinal cord
Figure 12.4
Organization of Neural Tissue
Similar pattern with additional areas of gray matter
The Brain
• Functions
– Conscious perception
– Internal regulation
• Average adult male 3.5 lbs
• Average adult female 3.2 lbs
The Brain
•
Same brain mass
to body mass ratio!
The Brain
4 Adult brain regions
1.
2.
3.
4.
Cerebral hemispheres (cerebrum)
Diencephalon
Cerebellum
Brain stem (midbrain, pons, and medulla)
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The Brain
• Four major regions are connected by ventricles and aqueducts
The Brain
• Ventricles
– Filled with cerebrospinal fluid
– Lined by ependymal cells
– Continuous with one another, the subarachnoid
space, and the central canal of the spinal cord
Anterior
The Cerebrum
• Cerebral hemispheres form superior part of
brain
• About 80% of brain mass
• 3 tissue layers
– Superficial cortex = gray matter
– Internal white matter
– Basal nuclei = islands of gray matter
Longitudinal
fissure
Frontal lobe
Cerebral veins
and arteries
covered by
arachnoid
mater
Parietal
lobe
Right cerebral
hemisphere
Occipital
lobe
Left cerebral
hemisphere
(c)
Posterior
Figure 12.6c
The Cerebrum
• Cerebral cortex
– Surface layer of cerebrum
– Gray matter
– “Executive Suite” – where the conscious mind is found
– Self-awareness, communication, memory,
understanding, voluntary movements
The Cerebrum
• Cerebral cortex
– Convolutions
• Gyri – elevated ridges
• Sulci – shallow grooves
• Fissures – deep grooves,
separate larger regions
of the brain
– May look random, but are
actually fairly consistent
between people
• Important landmarks
FISSURES
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The Cerebrum
• Fissures divide cerebral hemispheres into 4 lobes
The Cerebrum
• 3 types of functional areas in the cerebral cortex
1. Motor areas*
• Control voluntary movement
2. Sensory areas*
• Conscious awareness of sensation
3. Association areas
• Integrate diverse information
* Do not confuse these areas with motor and sensory neurons. All neurons in
the cerebral cortex are interneurons
The Cerebrum
• Functional areas of the cerebral cortex
– Contralateral orientation
• Each hemisphere is primarily concerned with functions on
the opposite side of the body
– Hemispheres are functionally specialized
• Language on left, attention on the right
Cerebral Motor Activity
Motor areas
Sensory areas and related
association areas
Primary somatosensory
cortex
Somatic
Somatosensory
sensation
association cortex
Central sulcus
Primary motor cortex
Premotor cortex
Frontal eye field
Broca’s area
(outlined by dashes)
Gustatory cortex
(in insula)
Prefrontal cortex
Working memory
for spatial tasks
Executive area for
task management
Working memory for
object-recall tasks
Solving complex,
multitask problems
Primary visual
cortex
Visual
association
area
Auditory
association area
Primary
auditory cortex
– Conscious behavior involves the entire cortex
• We are grossly oversimplifying
(a) Lateral view, left cerebral hemisphere
Primary motor cortex
Sensory association cortex
Taste
Wernicke’s area
(outlined by dashes)
Vision
Hearing
Motor association cortex
Primary sensory cortex
Multimodal association cortex
Figure 12.8a
Cerebral Motor Activity
• Primary motor cortex
Posterior
Motor Homunculus
Somatotopy of precentral
gyrus (primary motor cortex)
Motor
Anterior
Motor map in
precentral gyrus
– Large pyramidal cells of the precentral gyrus
– Long axons → pyramidal (corticospinal) tracts
• Project all the way to the spinal cord
• All other descending motor tracts are chains of neurons
Toes
– Allows conscious control
• Precise, skilled, voluntary movements
Motor homunculi:
upside-down caricatures
representing the motor
innervation of body regions
Jaw
Tongue
Swallowing
Primary motor
cortex
(precentral gyrus)
Figure 12.9
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Cerebral Motor Activity
• Primary motor cortex
– Most of the neurons here control muscles with the most
precise motor control – the face, tongue, and hands
– Individual neurons must work together to coordinate
movement
– Neurons that control related movements intermingle
Cerebral Motor Activity
• Premotor cortex
– Anterior to the precentral gyrus
– Controls learned, repetitious or patterned motor
skills
• “Muscle memory”
• Example: reaching the arm forward involves muscles in the
shoulder and elbow
– Neurons controlling unrelated movements do not
cooperate
• Example: hand and foot
Cerebral Motor Activity
• Premotor cortex
– Coordinates simultaneous or sequential actions
• Examples: playing an instrument, typing
– Involved in the planning of movements that depend
on sensory feedback
• Example: Feeling for a light switch in the dark
Cerebral Motor Activity
• Broca’s area
– Anterior to the inferior region of the premotor area
– Present in one hemisphere (usually the left)
– Motor speech area that directs muscles of the
tongue
• Active as one prepares to speak, and as one plans other
voluntary motor activities
Cerebral Motor Activity
Cerebral Motor Activity
• Frontal eye field
– Anterior to the premotor cortex and superior to
Broca’s area
– Controls voluntary eye movements
Motor areas
Central sulcus
Primary motor cortex
Premotor cortex
Frontal eye field
Broca’s area
(outlined by dashes)
Gustatory cortex
(in insula)
Prefrontal cortex
Working memory
for spatial tasks
Executive area for
task management
Working memory for
object-recall tasks
Solving complex,
multitask problems
Taste
Wernicke’s area
(outlined by dashes)
(a) Lateral view, left cerebral hemisphere
Primary motor cortex
Sensory association cortex
Sensory areas and related
association areas
Primary somatosensory
cortex
Somatic
Somatosensory
sensation
association cortex
Primary visual
cortex
Visual
association
area
Auditory
association area
Primary
auditory cortex
Vision
Hearing
Motor association cortex
Primary sensory cortex
Multimodal association cortex
Figure 12.8a
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Cerebral Vascular Accident (Stroke)
Stroke
• Types
– Ischemic stroke
– Hemorrhagic stroke
• Result
– Tissue death called an infarct
– Effects are determined by
• Where it occurs
• How large the area involved
Stroke
Cerebral Vascular Accident (Stroke)
• Damage to the primary motor cortex
– Paralyzes muscles controlled by those areas
– Only voluntary control is lost – muscles still
contract reflexively
• Damage to the premotor cortex
– Loss of motor skills, but not of muscle strength or
movement
– Reprogramming the skill to another set of
premotor neurons is possible
Cerebral Sensory Activity
Central sulcus
Motor areas
Primary motor cortex
Premotor cortex
Frontal eye field
Sensory areas & related
association areas
Primary somatosensory
cortex
Somatosensory
association cortex
Broca’s area
(outlined by dashes)
Gustatory cortex
(in insula)
Prefrontal cortex
Working memory
for spatial tasks
Executive area for
task management
Working memory for
object-recall tasks
Solving complex,
multitask problems
Taste
Primary visual
cortex
Visual
association
area
Auditory
association area
Primary
auditory cortex
• Widely dispersed
– Parietal, temporal & occipital lobes
• Concerned with conscious awareness of
sensation
Wernicke’s area
(outlined by dashes)
(a) Lateral view, left cerebral hemisphere
Primary motor cortex
Sensory association cortex
Somatic
sensation
Cerebral Sensory Activity
Vision
Hearing
Motor association cortex
Primary sensory cortex
Multimodal association cortex
Figure 12.8a
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Cerebral Sensory Activity
• Primary somatosensory cortex
Posterior
Sensory
Anterior
Sensory map in
postcentral gyrus
– In the postcentral gyri, parietal lobe
– Stimuli from skin, skeletal muscles, and joints
– Capable of spatial discrimination
• Identification of body region being stimulated
• Ability to perceive separate points of contact on the same
body part
Genitals
Primary somatosensory cortex
(postcentral gyrus)
Intraabdominal
Figure 12.9
Cerebral Sensory Activity
• Primary somatosensory cortex
– The amount of sensory cortex devoted to a body
region depends on that region’s sensitivity, not its
size
– Most sensitive regions in humans: face (especially
lips) and fingertips
Cerebral Sensory Activity
• Somatosensory association cortex
– Posterior to the primary somatosensory cortex
– Integrates sensory input from primary
somatosensory cortex
– Integrates and analyzes inputs
• Temperature, size, texture
• Recalls past sensory experiences with objects being felt
• Relationship of parts of objects being felt
– Example: reaching into pocket and discerning keys from coins
without looking
Cerebral Sensory Activity
• Visual areas
– Primary visual cortex
• Occipital lobe
• Receives visual information from the retinas
– Visual association area
• Surrounds the primary visual cortex
• Uses past visual experiences to interpret visual stimuli
– Example: color, form and movement
• Complex processing involves entire posterior half of the
hemispheres
• (Brain Games)
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Cerebral Sensory Activity
• Auditory areas
– Primary auditory cortex
• Temporal lobes
• Interprets information from inner ear
– Pitch, loudness and location
– Auditory association area
• Posterior to the primary auditory cortex
• Stores memories of sounds and permits perception of
sounds
– Allows us to differentiate between a scream, a song, thunder,
speech, etc.
Cerebral Sensory Activity
Central sulcus
Motor areas
Primary motor cortex
Premotor cortex
Frontal eye field
Primary somatosensory
cortex
Somatosensory
association cortex
Broca’s area
(outlined by dashes)
Gustatory cortex
(in insula)
Prefrontal cortex
Working memory
for spatial tasks
Executive area for
task management
Working memory for
object-recall tasks
Solving complex,
multitask problems
Somatic
sensation
Taste
Wernicke’s area
(outlined by dashes)
(a) Lateral view, left cerebral hemisphere
Primary motor cortex
Sensory association cortex
Association Areas
Sensory areas and related
association areas
Primary visual
cortex
Visual
association
area
Auditory
association area
Primary
auditory cortex
• Receive inputs from multiple sensory areas
• Send outputs to multiple areas
– Including the premotor cortex
Vision
Hearing
Motor association cortex
Primary sensory cortex
Multimodal association cortex
• Function
– Allows us to give meaning to information received,
store it as memory, compare it to previous
experience, and decide on action to take
– Damage to association areas leads to functional
deficits
Figure 12.8a
Association Areas
• Multimodal association areas (most of the
cortex)
– Seems to be where sensations, thoughts, and
emotions become conscious
– Where complex sensory input coordinates with
memory and the primary motor cortex to drive
action
Association Areas
• Example: You’re watching a volleyball match, and the ball is flying at
your face
Primary visual cortex:
Ball is getting bigger, shadow is moving
across the floor.
Primary auditory cortex:
Someone yells, “Look out!”
Visual association area:
That means the ball is moving closer to me.
Auditory association area:
That means danger.
Multimodal association area:
If I don’t move, I am going to get hit. I
should move!
Premotor cortex:
I should duck and put my hands in front of
my face.
Primary motor cortex:
Neck, shoulders, elbows, and arms, MOVE!!
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Cerebral Association Activity
Association Activity
Central sulcus
Motor areas
• Three areas
– Prefrontal cortex
– Posterior association area (not discussed here)
– Limbic association area
Primary motor cortex
Premotor cortex
Frontal eye field
Sensory areas and related
association areas
Primary somatosensory
cortex
Somatosensory
association cortex
Broca’s area
(outlined by dashes)
Gustatory cortex
(in insula)
Prefrontal cortex
Taste
Wernicke’s area
(outlined by dashes)
Working memory
for spatial tasks
Executive area for
task management
Working memory for
object-recall tasks
Solving complex,
multitask problems
(a) Lateral view, left cerebral hemisphere
Primary motor cortex
Sensory association cortex
Somatic
sensation
Primary visual
cortex
Visual
association
area
Auditory
association area
Primary
auditory cortex
Vision
Hearing
Motor association cortex
Primary sensory cortex
Multimodal association cortex
Figure 12.8a
Association Activity
• Prefrontal cortex
– Most complicated cortical region
– Involved with intellect, cognition, recall and personality
– Contains working memory (needed for abstract ideas),
judgment, reasoning and conscience
– Development depends on feedback from social
environment and develops slowly
Association Activity
• Prefrontal Labotomy
– Popular treatment for “delusions, obsessions, nervous
tensions, and the like” in the 1940s and 50s
– Involves cutting or scraping away most of the connections to
and from the prefrontal cortex
– Some patients died on the table or later committed suicide
– Some were severely brain damaged or developed seizures
– Some patients saw improvement of symptoms, but not
without impairments to personality, intellect, and empathy
– “Surgically induced childhood”
Association Activity
• Limbic association area
– Part of the limbic system
– Provides emotional impact that helps establish
memories
– Connections with prefrontal cortex regulate emotional
expression
Association Activity
• Walter Freeman and James Watt
– 1945 – developed the transorbital method of
lobotomy
– Required no surgery or anesthesia
– Initially pushed an ice pick (later a leukotome)
through the back of the eye socket
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Cerebral Association Activity
Central sulcus
Motor areas
Primary motor cortex
Premotor cortex
Frontal eye field
Cerebral Lateralization
Sensory areas and related
association areas
Primary somatosensory
cortex
Somatosensory
association cortex
Broca’s area
(outlined by dashes)
Gustatory cortex
(in insula)
Prefrontal cortex
Somatic
sensation
Taste
Wernicke’s area
(outlined by dashes)
Working memory
for spatial tasks
Executive area for
task management
Working memory for
object-recall tasks
Solving complex,
multitask problems
(a) Lateral view, left cerebral hemisphere
Primary motor cortex
Sensory association cortex
Primary visual
cortex
Visual
association
area
Auditory
association area
Primary
auditory cortex
Left hemisphere
Math
Logic
Language
Controls right side of body
Vision
• Right hemisphere
–
–
–
–
–
Visual-spatial skills
Intuition
Emotion
Art and music
Controls left side of body
Hearing
Motor association cortex
Primary sensory cortex
Multimodal association cortex
Figure 12.8a
Cerebral White Matter
• Responsible for communication between areas
of the brain and the spinal cord
• Consists largely of myelinated fibers bundled
into large tracts
• Tracts are classified by the direction in which
they run
White Matter Tracts
Cerebral White Matter
• Projection tracts
– Connect cerebrum w/other body locations
– Run vertically
• Association tracts
– Connect different parts of the same heisphere
– Adjacent gyri or different cortical lobes
• Commissural tracts
– Connect corresponding gray matter areas in the two
hemispheres
– Allows the brain to function as a whole
– Largest: corpus callosum (severed in some medical
experiments)
Cerebral Gray Matter
• Basal Nuclei
– Association of gray matter deep in cerebral
hemispheres
– Exact components controversial
– Contribute to muscle coordination and control by
excitatory innervation
• Examples: Determine intensity of movements, disorders
include Parkinson’s and Huntington’s
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Basal Nuclei
Cerebral Gray Matter
• Special notes…
• Your text refers to the putamen and the globus
pallidus – together, these structures make up
the lentiform nucleus
• Your study guide refers to the amygdaloid
nucleus, which requires a different plane of
section…
Review
•
•
•
•
•
White versus grey matter
Ventricles
4 brain regions
4 lobes of cerebral hemispheres
3 layers of cerebrum
– Cortex
• Motor
• Sensory
• Association
Copyright 2009 John Wiley & Sons, Inc.
Brain Regions
4 Adult brain regions
1. Cerebral hemispheres (cerebrum)
2. Diencephalon
3. Cerebellum
4. Brain stem (midbrain, pons, and medulla)
– White matter tracts
– Gray matter
Diencephalon
• Three paired structures
– Thalamus
– Hypothalamus
– Epithalamus
• Encloses the third ventricle
• Surrounded by cerebral
hemispheres
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Diencephalon
Cerebral hemisphere
Septum pellucidum
Corpus callosum
Fornix
Choroid plexus
Thalamus
(encloses third
ventricle)
Posterior commissure
Pineal gland
Interthalamic
adhesion
(intermediate
mass of
thalamus)
Interventricular
foramen
Anterior
commissure
Hypothalamus
Epithalamus
Corpora
quadrigemina
MidCerebral
brain
aqueduct
Arbor vitae (of
cerebellum)
Fourth ventricle
Choroid plexus
Cerebellum
Optic chiasma
Pituitary gland
Mammillary body
Pons
Medulla oblongata
Spinal cord
• Thalamus
– Several nuclei
– Gateway of the cerebral cortex
– Major relay station for most
sensory impulses
– Information is sorted, edited,
bundled, and sent to the
correct place
Figure 12.12
Diencephalon
• Thalamus
– Relay center for cerebral activation
– Associated with reticular formation
• Neural pathways in the brain stem mediating consciousness
– Relay center for somatosensory information
• Except olfaction
Diencephalon
• Hypothalamus
– Inferior to the thalamus
– Forms portions of walls of the third ventricle
– Caps the brain stem
– Consists of a number of nuclei
– Coma is associated with thalamic injury
• Vegetative state = damage to cortical pathways
Refer to diagram on CNS 8
Diencephalon
• Hypothalamus
– Infundibulum
• Connects pituitary to hypothalamus
– Mammillary bodies
• Relay stations for olfactory pathways
– Responsible for most neurogenic homeostasis of
the body
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Diencephalon
• Hypothalamic function
– Autonomic control center for many visceral functions
• Examples
– Blood pressure, rate and force of heartbeat
– Regulates body temperature
– Hunger and G.I tract regulation
Diencephalon
• Hypothalamic Function
– Water balance and thirst
– Controls release of hormones by the anterior
pituitary and produces posterior pituitary hormones
– Regulation of sleep-wake cycles
– Center for physical response to emotions
• Examples: Fear = pounding heart, dry mouth, high blood
pressure, sweating, paleness
– Tactile sexual response, not psychological/emotional
response
Diencephalon
Brain Regions
4 Adult brain regions
• Epithalamus
– Forms roof of third ventricle
– Pineal gland, choroid plexus
– Melatonin
– We’ll discuss it’s endocrine function later….
1. Cerebral hemispheres (cerebrum)
2. Diencephalon
3. Brain stem (midbrain, pons and medulla)
4. Cerebellum
The Brain Stem
• Functions
– Supports most of the automatic basic life functions
– Pathway for fiber tracts
– Origin for most cranial nerves
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The Brain Stem
Frontal lobe
Olfactory bulb
(synapse point of
cranial nerve I)
Optic chiasma
Optic nerve (II)
Optic tract
Mammillary body
Midbrain
Pons
• Midbrain
– Associated with visual and auditory reflexes
• Pupillary reflex, startle reflex
– Cranial nerves III and IV
– Red nucleus
Temporal lobe
Medulla
oblongata
Cerebellum
Spinal cord
• Descending motor pathways involved in voluntary
movement
Figure 12.14
View (a)
Optic chiasma
Optic nerve (II)
Crus cerebri of
cerebral peduncles
(midbrain)
Diencephalon
• Thalamus
• Hypothalamus
Mammillary body
Crus cerebri of
cerebral peduncles
(midbrain)
Hypothalamus
Diencephalon
Midbrain
Oculomotor nerve (III)
Trochlear nerve (IV)
Pons
Vestibulocochlear
nerve (VIII)
Pyramid
Superior colliculus
Inferior colliculus
Trochlear nerve (IV)
Superior cerebellar peduncle
Trigeminal nerve (V)
Pons
Middle cerebellar peduncle
Facial nerve (VII)
Abducens nerve (VI)
Glossopharyngeal nerve (IX)
Glossopharyngeal nerve (IX)
Hypoglossal nerve (XII)
Inferior cerebellar peduncle
Vestibulocochlear nerve (VIII)
Olive
Hypoglossal nerve (XII)
Thalamus
Vagus nerve (X)
Vagus nerve (X)
Ventral root of first
cervical nerve
Decussation of pyramids
Infundibulum
Pituitary gland
Brainstem
Medulla
oblongata
Trigeminal nerve (V)
Pons
Facial nerve (VII)
Middle cerebellar
peduncle
Abducens nerve (VI)
Thalamus
View (b)
Thalamus
Hypothalamus
Diencephalon
Midbrain
Accessory nerve (XI)
Accessory nerve (XI)
Pons
Brainstem
Medulla
oblongata
Spinal cord
(a) Ventral view
(b) Left lateral view
Figure 12.15a
The Brain Stem
• Pons
– Bridge between midbrain and medulla oblongata
– Consists chiefly of tracts connecting different parts
of the CNS
• Longitudinal tracts connect the cerebellum to the
cerebrum and spinal cord
• Transverse tracts connect the two sides of the cerebellum
– Cranial nerves V- VIII (vestibular branch)
Figure 12.15b
Frontal lobe
Olfactory bulb
(synapse point of
cranial nerve I)
Optic chiasma
Optic nerve (II)
Optic tract
Mammillary body
Midbrain
Pons
Temporal lobe
Medulla
oblongata
Cerebellum
Spinal cord
Figure 12.14
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The Brain Stem
Crus cerebri of
cerebral peduncles
(midbrain)
Thalamus
• Medulla oblongata
View (b)
Infundibulum
Pituitary gland
Superior colliculus
Inferior colliculus
Trochlear nerve (IV)
Trigeminal nerve (V)
Pons
Superior cerebellar peduncle
• Passage of motor & sensory impulses between brain &
spinal cord
Middle cerebellar peduncle
Facial nerve (VII)
Abducens nerve (VI)
Glossopharyngeal nerve (IX)
– Decussation of tracts in pyramids
Inferior cerebellar peduncle
Vestibulocochlear nerve (VIII)
Olive
Hypoglossal nerve (XII)
Thalamus
Vagus nerve (X)
Hypothalamus
Diencephalon
Midbrain
Accessory nerve (XI)
– Continuous with spinal cord
Pons
Brainstem
Medulla
oblongata
• Pyraminds: large corticospinal tracts descending from
motor cortex
• Reason that each cerebral hemisphere controls voluntary
movements of muscles on the opposite side of the body
(b) Left lateral view
Figure 12.15b
Longitudinal fissure
Superior
Commissural
fibers (corpus
callosum)
The Brain Center
Lateral
ventricle
Association
fibers
Basal nuclei
• Caudate
• Putamen
• Globus
pallidus
Corona radiata
Thalamus
Internal
capsule
Fornix
White matter
Pons
Projection
fibers
Cardiac – force and rate of heart contraction
Vasomotor – changes blood vessel diameter
Respiratory – rate and depth of breathing
Swallowing
Vomiting
– Cranial nerves VIII (cochlear branch) -XII
Decussation
of pyramids
Medulla oblongata
(a)
– Synapses with neurons in the hypothalamus give
rise to several vital centers
•
•
•
•
•
Gray matter
Third
ventricle
• Medulla
Figure 12.10a
Brain Regions
4 Adult brain regions
1. Cerebral hemispheres (cerebrum)
2. Diencephalon
3. Brain stem (midbrain, pons, and medulla)
4. Cerebellum
The Cerebellum
• Dorsal to the pons & medulla
• Subconsciously provides precise timing &
appropriate patterns of skeletal muscle
contraction
• Contains both white & gray matter
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The Cerebellum
• Functions
– Proprioception
Anterior lobe
Cerebellar cortex
Arbor vitae
(white matter)
• Sensing body position, motion, equilibrium
– Prime mover inhibition and antagonist activation
• Controls strength, direction, and extent of movements
– Progression
Cerebellar
peduncles
• Superior
• Middle
• Inferior
Medulla
oblongata
(b)
Flocculonodular
lobe
Posterior
lobe
Choroid
plexus of
fourth
ventricle
• Smooth transition from one body movement to another
• Dysfunction
– Dysmetria
– Dysarthria
Figure 12.17b
Functional Brain Systems
Functional Brain Systems
• Networks of neurons that work together & span
wide areas of the brain
– Limbic system
– Reticular formation
• Limbic system
– Structures on the medial aspects of cerebral
hemispheres and diencephalon
– Includes parts of the diencephalon and some
cerebral structures that encircle the brain stem
Functional Brain Systems
Septum pellucidum
Diencephalic structures
of the limbic system
•Anterior thalamic
nuclei (flanking
3rd ventricle)
•Hypothalamus
•Mammillary
body
Olfactory bulb
Corpus callosum
Fiber tracts
connecting limbic
system structures
•Fornix
•Anterior commissure
Cerebral structures of the
limbic system
•Cingulate gyrus
•Septal nuclei
•Amygdala
•Hippocampus
•Dentate gyrus
•Parahippocampal
gyrus
• Limbic system
– Emotional brain
• Recognizes angry or fearful facial expressions
• Assesses danger & elicits the fear response
• Plays a role in expressing emotions via gestures and resolves
mental conflict
• Connection to pre-frontal cortex allows us to “count to ten”
– Puts emotional responses to odors
• Example: skunks = smell bad
– Alcohol and other depressants affect limbic system
control
• Person is subject to exaggerated states of emotion
Figure 12.18
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1/1/2016
Radiations
to cerebral
cortex
Functional Brain Systems
• Reticular formation
– Broad columns of nuclei along the length of the
brain stem
– Far-flung axonal connections with hypothalamus,
thalamus, cerebral cortex, cerebellum & spinal cord
– Governs stimulation of the brain as a whole
Visual
impulses
Auditory
impulses
Reticular formation
Ascending general
sensory tracts
(touch, pain, temperature)
Descending
motor projections
to spinal cord
Figure 12.19
Functional Brain Systems
• Functions of the reticular formation
1. Somatic motor control
Reticulospinal tract = improves smoothness of movement
•
2. Autonomic control
Respiratory and cardiovascular centers
•
3. Arousal
Reticular Activating System
•
–
–
Keeps cortex alert and conscious
Filters incoming sensory information and discards 99% of it
4. Pain modulation
•
Can block pain transmission
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