Download Nervous System

Chapter 11
Nervous
System II
D- anatomy
and
physiology
1
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11.1: Introduction
• The central nervous system (CNS) consists of the brain and spinal
cord.
• The brainstem connects the brain to the spinal cord.
• Communication to the peripheral nervous system (PNS) is by way of
the spinal cord.
2
11.2: Meninges
• The meninges
• Membranes of CNS
• Protect the CNS
• Three (3) layers:
• Dura mater
• “Tough mother”
• Venous sinuses
• Falx
• Arachnoid mater
• “Spiderweb-like”
• Space contains
cerebrospinal fluid (CSF)
• Pia mater
• “Faithful mother”
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Skin
Scalp
Subcutaneous tissue
Cranium
Bone of skull
Cerebrum
Dural sinus (superior
sagittal sinus)
Tentorium
cerebelli
Arachnoid
granulation
Dura mater
Cerebellum
Arachnoid
mater
Pia mater
Vertebra
Subarachnoid space
Spinal cord
Falx cerebri
Meninges
(a)
Meninges
Gray matter
White matter
(b)
3
Cerebrum
Meninges of the Spinal Cord
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Spinal cord
Ventral root
Dorsal root
Spinal nerve
Dorsal root
ganglion
Subarachnoid
space
Pia mater
Arachnoid mater
Epidural space
Dura mater
Dorsal root
Dorsal branch
(dorsal ramus)
Spinal
nerve
Ventral branch
(ventral ramus)
Dorsal root
ganglion
Spinal cord
Ventral root
Epidural
space
Thoracic
vertebra
(a)
(b)
Body of
vertebra
4
11.3: Ventricles
and Cerebrospinal Fluid
• There are four (4) ventricles
• The ventricles are interconnected
cavities within cerebral hemispheres
and brain stem
• The ventricles are continuous with
the central canal of the spinal cord
• They are filled with cerebrospinal
fluid (CSF)
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Lateral ventricle
Interventricular
foramen
Third ventricle
Cerebral
aqueduct
Fourth ventricle
To central canal
of spinal cord
• The four (4) ventricles are:
• Lateral ventricles (2)
• Known as the first and
second ventricles
• Third ventricle
• Fourth ventricle
• Interventricular foramen
• Cerebral aqueduct
(a)
Interventricular
foramen
Lateral
ventricle
Third ventricle
Cerebral
aqueduct
Fourth
ventricle
5
(b)
To central canal
of spinal cord
Cerebrospinal Fluid
• Secreted by the choroid plexus
• Circulates in ventricles, central
canal of spinal cord, and the
subarachnoid space
• Completely surrounds the brain
and spinal cord
• Excess or wasted CSF is
absorbed by the arachnoid villi
• Clear fluid similar to blood
plasma
• Volume is only about 120 ml.
• Nutritive and protective
• Helps maintain stable ion
concentrations in the CNS
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Arachnoid
granulations
Blood-filled
dural sinus
Choroid plexuses
of third ventricle
Pia mater
Third ventricle
Cerebral aqueduct
Fourth ventricle
Subarachnoid space
Arachnoid mater
Dura mater
Choroid plexus of
fourth ventricle
Central canal of spinal cord
Pia mater
Subarachnoid space
Filum terminale
Arachnoid mater
Dura mater
6
11.4: Spinal Cord
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• Extends downward through vertebral
canal
• Begins at the foramen magnum and
terminates at the first and second
lumbar vertebrae (L1/L2) interspace
Brainstem
Foramen
magnum
Cervical
enlargement
Cervical
enlargement
Spinal cord
Vertebral
canal
Lumbar
enlargement
Lumbar
enlargement
Conus
medullaris
Cauda
equina
Conus
medullaris
Filum
terminale
8
(a)
(b)
Structure of the Spinal Cord
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Posterior horn
Posterior funiculus
Posterior median
sulcus
White matter
Gray matter
Gray commissure
Lateral funiculus
Dorsal root
of spinal nerve
Central canal
Anterior
funiculus
Dorsal root
ganglion
Ventral root
Anterior
of spinal nerve horn
(a)
Anterior
median
fissure
Portion of
spinal nerve
9
Functions of Spinal Cord
• Conduit for nerve impulses to and from the brain and brainstem
• Center for spinal reflexes
10
Reflex Arcs
• Reflexes are automatic, subconscious responses to stimuli within or
outside the body
• Simple reflex arc (sensory – motor)
• Most common reflex arc (sensory – association – motor)
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Sensory or
afferent neuron
Receptor
Central
Nervous
System
Motor or
efferent neuron
Effector
(muscle or gland)
11
12
(a)
Reflex Arcs
12
General Components of a
Spinal Reflex
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Spinal cord
Interneuron
Dorsal
1
Receptor
3
2
Sensory neuron
Cell body
of sensory
neuron
White matter
Gray matter
4
Ventral
Motor neuron
Central
canal
5
Effector
(muscle
or gland)
(b)
13
Patellar Reflex
• Example is the knee-jerk reflex
• Simple monosynaptic reflex
• Helps maintain an upright posture & prevents overstretching
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Axon of sensory
neuron
Cell body of
sensory neuron
Spinal cord
Cell body of
motor neuron
Axon of motor
neuron
Direction of impulse
Effector (quadriceps femoris
muscle group)
Receptor associated with
dendrites of sensory neuron
Patella
Patellar ligament
14
Withdrawal Reflex
• Prevents or limits tissue damage
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Cell body of sensory neuron
Axon of sensory neuron
Direction
of impulse
Effector (flexor
muscle contracts
and withdraws part
being stimulated)
Interneuron
Axon of
motor neuron
Spinal cord
Cell body of
motor neuron
Dendrite of
sensory
neuron
Pain
receptor
in skin
Tack
15
Crossed Extensor Reflex
•Contralateral reflex
•Maintain balance
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Interneuron
+
= Stimulation
–
= Inhibition
–
+
–
Sensory neuron
Extensor
relaxes
+
Extensor
contracts
Flexor
relaxes
Motor
neurons
Motor
neurons
Flexor contracts
17
16
Tracts of the Spinal Cord
• Ascending tracts conduct sensory impulses to the brain
• Descending tracts conduct motor impulses from the brain to motor neurons
reaching muscles and glands
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Dorsal column
Fasciculus gracilis
Fasciculus cuneatus
Posterior spinocerebellar tract
Lateral corticospinal tract
Lateral reticulospinal tract
Rubrospinal tract
Anterior spinocerebellar tract
Anterolateral
system
Lateral spinothalamic tract
Anterior spinothalamic tract
Anterior reticulospinal tract
Medial reticulospinal tract
Anterior
corticospinal
tract
17
Ascending Tracts
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• Major ascending (sensory) spinal cord
tracts:
• Fasciculus gracilis and fasciculus
cuneatus
• Spinothalamic tracts
• Lateral and anterior
• Spinocerebellar tracts
• Posterior and anterior
Sensory
cortex of
cerebrum
Cerebrum
(frontal
section)
Thalamus
Midbrain
Spinothalamic
tract
Brainstem
(transverse
sections)
Pons
Medulla
Spinal cord
(transverse section)
Sensory fibers
cross over
Fasciculus
cuneatus
tract
Sensory
impulse
from skin
temperature
or pain
receptors
18
Descending Tracts
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• Major descending (motor) spinal cord tracts:
• Corticospinal tracts
• Lateral and anterior
• Reticulospinal tracts
• Lateral, anterior and medial
• Rubrospinal tract
Motor cortex
of cerebrum
Cerebrum
(frontal
section)
Corticospinal
tract
Midbrain
Brainstem
(transverse
sections)
Pons
Motor fibers
cross over
Medulla
oblongata
Spinal cord
(transverse section)
Motor
impulse to
skeletal
muscle
19
Nerve Tracts of the Spinal Cord
20
Nervous System Subdivisions
21
11.6: Peripheral Nervous System
• Cranial nerves arising from the brain
• Somatic fibers connecting to the skin and skeletal muscles
• Autonomic fibers connecting to viscera
• Spinal nerves arising from the spinal cord
• Somatic fibers connecting to the skin and skeletal muscles
• Autonomic fibers connecting to viscera
22
Structure of a Peripheral Nerve
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Fascicle
Peripheral nerve
Epineurium
Motor neuron
ending
Axon
Perineurium
Endoneurium
Node of Ranvier
Schwann cell
Sensory receptor
Myelin sheath
Neurilemma
23
Nerve and Nerve Fiber
Classification
• Sensory nerves
• Conduct impulses into brain or spinal cord
• Motor nerves
• Conduct impulses to muscles or glands
• Mixed (both sensory and motor) nerves
• Contain both sensory nerve fibers and motor nerve fibers
• Most nerves are mixed nerves
• ALL spinal nerves are mixed nerves (except the first pair)
24
Nerve Fiber Classification
• General somatic efferent (GSE) fibers
• Carry motor impulses from CNS to
skeletal muscles
• General visceral efferent (GVE) fibers
• Carry motor impulses away from CNS
to smooth muscles and glands
• General somatic afferent (GSA) fibers
• Carry sensory impulses to CNS from skin
and skeletal muscles
• General visceral afferent (GVA) fibers
• Carry sensory impulses to CNS from
blood vessels and internal organs
25
Nerve Fiber Classification
• Special somatic efferent (SSE) fibers
• Carry motor impulses from brain to muscles used in chewing,
swallowing, speaking and forming facial expressions
• Special visceral afferent (SVA) fibers
• Carry sensory impulses to brain from olfactory and taste receptors
• Special somatic afferent (SSA) fibers
• Carry sensory impulses to brain from receptors of sight, hearing and
equilibrium
26
Spinal Nerves
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• ALL are mixed nerves (except the
first pair)
• 31 pairs of spinal nerves:
• 8 cervical nerves
• (C1 to C8)
• 12 thoracic nerves
• (T1 to T12)
• 5 lumbar nerves
• (L1 to L5)
• 5 sacral nerves
• (S1 to S5)
• 1 coccygeal nerve
• (Co or Cc)
C1
C2
C3
C4
C5
C6
C7
C8
T1
T2
Posterior
view
Cervical
nerves
T3
T4
T5
T6
T7
Thoracic
nerves
T8
T9
T10
T11
T12
L1
Cauda equina
L2
L3
L4
Lumbar
nerves
L5
S1
S2
S3
S4
S5
Co
Sacral
nerves
Coccygeal
nerve
27
Spinal Nerves
• Dorsal root (aka posterior
root)
• Sensory root
• Axons of sensory
neurons are in the dorsal
root ganglion
• Dorsal root ganglion
• Aka DRG
• Cell bodies of sensory
neurons whose axons
conduct impulses inward
from peripheral body parts
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Dorsal root
Dorsal root
ganglion
Dorsal branch
of spinal nerve
Ventral branch
of spinal nerve
Ventral root
Dorsal root
Paravertebral
ganglion
Posterior
median sulcus
Posterior
horn
Visceral branch
of spinal nerve
(b)
Lateral horn
Anterior
horn
Central
canal
(a)
Ventral branch
of spinal nerve (ventral ramus)
Dorsal branch
of spinal nerve (dorsal ramus)
Spinal nerve
Anterior
median
fissure
Paravertebral
ganglion
Ventral root
Visceral branch
of spinal nerve
28
Dermatome
• An area of skin that the sensory nerve fibers of a particular spinal nerve
innervate
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C2
C3
C4
C5
C6
C7
C2
C3
C4
C5
T1
T1
C8
C6
T1
T12
L1
L5
T12
S1
S2
S3
S4
S5
C0
L1
S2
L2
C6
C7
S3
L3
L1
L2
L4
C8
L3
L5
S1
L4
L5
29
(a)
(b)
Spinal Nerves
• Ventral root (aka anterior root)
• Motor root
• Axons of motor neurons
whose cell bodies are in the
spinal cord
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Dorsal root
Dorsal root
ganglion
Dorsal branch
of spinal nerve
Ventral branch
of spinal nerve
Ventral root
Dorsal root
Paravertebral
ganglion
Posterior
median sulcus
Posterior
horn
• Spinal nerve
• Union of ventral root
and dorsal roots
• Hence we now have a
“mixed” nerve
Visceral branch
of spinal nerve
(b)
Lateral horn
Anterior
horn
Central
canal
(a)
Ventral branch
of spinal nerve (ventral ramus)
Dorsal branch
of spinal nerve (dorsal ramus)
Spinal nerve
Anterior
median
fissure
Paravertebral
ganglion
Ventral root
Visceral branch
of spinal nerve
30
Nerve Plexuses
• Nerve plexus
• Complex networks formed by anterior branches (ventral rami) of spinal
nerves
• The fibers of various spinal nerves are sorted and recombined
• There are three (3) nerve plexuses:
• (1) Cervical plexus
• Formed by anterior branches of C1-C4 spinal nerves
• Lies deep in the neck
• Supply to muscles and skin of the neck
• C3-C4-C5 nerve roots contribute to phrenic nerves bilaterally
31
Plexuses
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Posterior view
C1
C2
C3
C4
C5
C6
C7
C8
T1
Musculocutaneous
nerve
Brachial plexus
(C5–T1)
T2
T3
Axillary nerve
Radial nerve
Median nerve
Ulnar nerve
Phrenic nerve
Cervical plexus
(C1–C4)
T4
T5
T6
T7
Intercostal
nerves
T8
T9
T10
T11
T12
L1
Cauda equina
L2
L3
L4
Femoral
nerve
L5
S1
S2
S3
S4
S5
Obturator nerve
Lumbosacral plexus
(T12–S5)
Co
Sciatic nerve
32
Brachial Plexus
• (2) Brachial plexus
• Formed by anterior branches C5-T1
• Lies deep within shoulders
• There are five (5) branches:
• 1. Musculocutaneous nerve
• Supply muscles of anterior arms
and skin of forearms
• 2. Ulnar and 3. Median nerves
• Supply muscles of forearms and
hands
• Supply skin of hands
• 4. Radial nerve
• Supply posterior muscles of arms
and skin of forearms and hands
• 5. Axillary nerve
• Supply muscles and skin of
anterior, lateral, and posterior arms
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C5
Ventral rami: C5, C6, C7, C8, T1
C6
Trunks: upper, middle, lower
C7
Anterior divisions
C8
C5
Posterior divisions
T1
Dorsal
scapular n.
C6
C7
Axillary n.
Suprascapular n.
Lateral pectoral n.
Humerus
C8
Medial pectoral n.
Lower subscapular n.
T1
Thoracodorsal n.
Musculocutaneous n.
Median n.
Median n.
Ulnar n.
Axillary n.
Radial n.
(a)
Musculocutaneous n.
Ulnar n.
Radial n.
Ulna
Radius
78
33
(b)
Lumbosacral Plexus
• (3) Lumbosacral plexus
• Formed by the anterior branches of
L1-S5 roots
• Can be a lumbar (L1-L5) plexus
and a sacral (S1-S5) plexus
• Extends from lumbar region into
pelvic cavity
• Obturator nerve
• Supply motor impulses to
adductors of thighs
• Femoral nerve
• Supply motor impulses to
muscles of anterior thigh and
sensory impulses from skin of
thighs and legs
• Sciatic nerve
• Supply muscles and skin of
thighs, legs and feet
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Ventral
rami
Anterior
divisions
Posterior
divisions
L1
Superior
gluteal n.
Inferior
gluteal n.
L2
Obturator n.
Pudendal n.
Sacral
plexus
Femoral n.
L3
Posterior
cutaneous n.
Sciatic n.
L4
Lateral
femoral
cutaneous n.
Saphenous n.
L5
Femoral n.
Obturator n.
Tibial n.
S1
Common
fibular
(peroneal) n.
S2
Superior
gluteal n.
S3
Inferior
gluteal n.
Sciatic n.
S4
Common
fibular
(peroneal) n.
Tibial n.
S5
Pudendal n.
(a)
(b)
(c)
34
11.5: Brain
• Functions of the brain:
• Interprets sensations
• Determines perception
• Stores memory
• Reasoning
• Makes decisions
• Coordinates muscular movements
• Regulates visceral activities
• Determines personality
• Major parts of the brain:
• Cerebrum
• Frontal lobes
• Parietal lobes
• Occipital lobes
• Temporal lobes
• Insula
• Diencephalon
• Cerebellum
• Brainstem
• Midbrain
• Pons
• Medulla oblongata
35
The Brain
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Gyrus
Skull
Sulcus
Meninges
Cerebrum
Corpus
callosum
Diencephalon
Fornix
Midbrain
Brainstem
Pons
Cerebellum
Medulla
oblongata
Spinal cord
(a)
Fornix
Cerebrum
Midbrain
Pons
Corpus
callosum
Transverse fissure
Diencephalon
Cerebellum
Medulla oblongata
Spinal cord
36
(b)
b: © Martin M. Rotker/Photo Researchers, Inc.
Brain Development
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• Neural tube
• Three primary vesicles:
• Forebrain
(Prosencephalon)
• Midbrain
(Mesencephalon)
• Hindbrain
(Rhombencephalon)
• Five secondary vesicles:
• Telencephalon
• Diencephalon
• Mesencephalon
• Metencephalon
• Myelencephalon
Prosencephalon (forebrain)
Mesencephalon (midbrain)
Rhombencephalon (hindbrain)
Neural tube
(a)
Telencephalon
Cerebral
hemispheres
Diencephalon
Diencephalon
Mesencephalon
Midbrain
Metencephalon
(b)
Pons and Cerebellum
Myelencephalon
Medulla
oblongata
Neural tube
Spinal cord
(c)
37
Brain Development
38
Structure of the Cerebrum
• Corpus callosum
• Connects cerebral
hemispheres (a commissure)
• Gyri
• Bumps or convolutions
• Sulci
• Grooves in gray matter
• Central sulcus of Rolando
• Fissures
• Longitudinal: separates the
cerebral hemispheres
• Transverse: separates
cerebrum from cerebellum
• Lateral fissure of Sylvius
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Central sulcus
Parietal lobe
Gyrus
Sulcus
Frontal lobe
Lateral sulcus
Occipital lobe
Transverse
fissure
Cerebellar
hemisphere
Temporal lobe
(a)
Central sulcus
Parietal lobe
Central sulcus
Longitudinal
fissure
Parietal lobe
Occipital lobe
Frontal lobe
Insula
Occipital lobe
Retracted
temporal lobe
(b)
(c)
39
Lobes of the Cerebrum
• Five (5) lobes bilaterally:
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• Frontal lobe
• Parietal lobe
• Temporal lobe
• Occipital lobe
• Insula aka ‘Island of Reil’
Central sulcus
Parietal lobe
Occipital lobe
Frontal lobe
Insula
Retracted
temporal lobe
(c)
40
Functions of the Cerebrum
• Interpreting impulses
• Initiating voluntary movements
• Storing information as memory
• Retrieving stored information
• Reasoning
• Seat of intelligence and personality
41
Functional Regions of the
Cerebral Cortex
• Cerebral cortex
• Thin layer of gray matter that constitutes the outermost portion of
cerebrum
• Contains 75% of all neurons in the nervous system
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Central sulcus
Motor areas involved with the control
of voluntary muscles
Sensory areas involved with
cutaneous and other senses
Concentration, planning,
problem solving
Frontal eye field
Parietal lobe
Auditory area
Sensory speech area
( Wernicke’s area)
Front lobe
Occipital lobe
Motor speech area
(Broca’s area)
Combining
visual images,
visual recognition
of objects
Lateral sulcus
Visual area
Interpretation of auditory patterns
Cerebellum
42
Temporal lobe
Brainstem
Functions of the Cerebral Lobes
43
Sensory Areas
(post-central sulcus)
• Cutaneous sensory area
• Sensory area for taste
• Parietal lobe
• Interprets sensations on
skin
• Near base of the central sulcus
• Sensory area for smell
• Arises from centers deep within
the cerebrum
• Visual area
• Occipital lobe
• Interprets vision
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Central sulcus
Motor areas involved with the control
of voluntary muscles
Sensory areas involved with
cutaneous and other senses
Concentration, planning,
problem solving
Frontal eye field
Parietal lobe
Auditory area
• Auditory area
• Temporal lobe
• Interprets hearing
Sensory speech area
( Wernicke’s area)
Front lobe
Occipital lobe
Motor speech area
(Broca’s area)
Combining
visual images,
visual recognition
of objects
Lateral sulcus
Visual area
Interpretation of auditory patterns
Cerebellum
Temporal lobe
Brainstem
44
Sensory Areas
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Arm
Trunk
Trunk
Pelvis
Thigh
Forearm
Forearm
Thumb,
fingers,
and hand
Leg
Foot and
toes
Facial
expression
Hand, fingers,
and thumb
Upper
face
Neck
Arm
Pelvis
Thigh
Leg
Foot and
toes
Genitals
Lips
Salivation
Vocalization
Mastication
Teeth and
gums
Tongue and
pharynx
Swallowing
Longitudinal
fissure
(a) Motor area
Longitudinal
fissure
(b) Sensory area
Frontal lobe
Motor area
Sensory area
Central sulcus
Parietal lobe
45
Association Areas
• Regions that are not primary motor or primary sensory areas
• Widespread throughout the cerebral cortex
• Analyze and interpret sensory experiences
• Provide memory, reasoning, verbalization, judgment, emotions
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Central sulcus
Motor areas involved with the control
of voluntary muscles
Sensory areas involved with
cutaneous and other senses
Concentration, planning,
problem solving
Frontal eye field
Parietal lobe
Auditory area
Sensory speech area
( Wernicke’s area)
Front lobe
Occipital lobe
Motor speech area
(Broca’s area)
Combining
visual images,
visual recognition
of objects
Lateral sulcus
Visual area
Interpretation of auditory patterns
Cerebellum
Temporal lobe
Brainstem
46
Association Areas
• Frontal lobe association areas • Temporal lobe association areas
• Concentrating
• Interpret complex sensory
• Planning
experiences
• Complex problem solving
• Store memories of visual scenes,
music, and complex patterns
• Parietal lobe association areas
• Understanding speech
• Choosing words to express
thought
• Occipital lobe association areas
• Analyze and combine visual
images with other sensory
experiences
47
Motor Areas
(pre-central sulcus)
• Primary motor areas
• Frontal lobes
• Control voluntary muscles
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Central sulcus
Motor areas involved with the control
of voluntary muscles
Sensory areas involved with
cutaneous and other senses
Concentration, planning,
problem solving
• Broca’s area
Frontal eye field
Parietal lobe
Auditory area
• Anterior to primary motor
cortex
• Usually in left hemisphere
• Controls muscles needed for
speech
Sensory speech area
( Wernicke’s area)
Front lobe
Occipital lobe
Motor speech area
(Broca’s area)
Combining
visual images,
visual recognition
of objects
Lateral sulcus
Visual area
Interpretation of auditory patterns
Cerebellum
Temporal lobe
Brainstem
• Frontal eye field
• Above Broca’s area
• Controls voluntary
movements of eyes and eyelids
48
Motor Areas
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Arm
Trunk
Trunk
Pelvis
Thigh
Forearm
Forearm
Thumb,
fingers,
and hand
Leg
Foot and
toes
Facial
expression
Hand, fingers,
and thumb
Upper
face
Neck
Arm
Pelvis
Thigh
Leg
Foot and
toes
Genitals
Lips
Salivation
Vocalization
Mastication
Teeth and
gums
Tongue and
pharynx
Swallowing
Longitudinal
fissure
(a) Motor area
Longitudinal
fissure
(b) Sensory area
Frontal lobe
Motor area
Sensory area
Central sulcus
Parietal lobe
49
Hemisphere Dominance
• The left hemisphere is dominant in most individuals
• Dominant hemisphere controls:
• Speech
• Writing
• Reading
• Verbal skills
• Analytical skills
• Computational skills
• Nondominant hemisphere controls:
• Nonverbal tasks
• Motor tasks
• Understanding and interpreting
musical and visual patterns
• Provides emotional and intuitive
thought processes
50
Memory
• Short term memory
• Working memory
• Closed neuronal circuit
• Circuit is stimulated over and over
• When impulse flow ceases, memory
does also unless it enters long-term
memory via memory consolidation
• Long term memory
• Changes structure or function
of neurons
• Enhances synaptic
transmission
51
Basal Nuclei
• Masses of gray matter
• Deep within cerebral
hemispheres
• Caudate nucleus, putamen,
and globus pallidus
Basal
nuclei
• Produce dopamine
• Control certain muscular
activities
• Primarily by inhibiting motor
functions
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Longitudinal
fissure
Right cerebral
hemisphere
Caudate
nucleus
Putamen
Globus
pallidus
Thalamus
Cerebellum
Hypothalamus
Brainstem
Spinal cord
52
Diencephalon
• Between cerebral hemispheres and above the brainstem
• Surrounds the third ventricle
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• Thalamus
• Epithalamus
• Hypothalamus
• Optic tracts
• Optic chiasm
• Infundibulum
• Posterior pituitary
• Mammillary bodies
• Pineal gland
Superior
colliculus
Corpora quadrigemina
Optic nerve
Inferior
colliculus
Optic chiasma
Pituitary gland
Thalamus
Mammillary body
Third
ventricle
Optic tract
Pons
Cerebral
peduncles
Pineal gland
Fourth
ventricle
Pyramidal tract
Olive
Cerebellar
peduncles
Medulla
oblongata
Spinal cord
(a)
(b)
53
Diencephalon
• Thalamus
• Gateway for sensory impulses heading to cerebral cortex
• Sensory relay station
• Receives all sensory impulses (except smell)
• Channels impulses to appropriate part of cerebral cortex for interpretation
• Hypothalamus
• Maintains homeostasis by regulating visceral activities (such as HR, BP,
temperature, H2O & electrolyte balance, hunger, thirst, sleep & wakefulness)
• Links nervous and endocrine systems (hence some say the neuroendocrine
system
54
Diencephalon
The Limbic System
• Consists of:
• Portions of frontal lobe
• Portions of temporal lobe
• Hypothalamus
• Thalamus
• Basal nuclei
• Other deep nuclei
• Functions:
• Controls emotional experiences &
produces feelings like rage, anger,
pleasure
• survival behavior
• Interprets sensory impulses
associated with smell
55
Brainstem
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Hypothalamus
Three parts:
1. Midbrain
2. Pons
3. Medulla Oblongata
Diencephalon
Thalamus
Corpus
callosum
Corpora
quadrigemina
Midbrain
Cerebral
aqueduct
Pons
Reticular
formation
Medulla
oblongata
Spinal cord
56
Midbrain
• Between diencephalon and
pons
• Contains bundles of fibers that
join lower parts of brainstem and
spinal cord with higher part of
brain
• Cerebral aqueduct
• Cerebral peduncles (bundles
of nerve fibers)
• Corpora quadrigemina (centers
for visual and auditory reflexes)
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Superior
colliculus
Corpora quadrigemina
Inferior
colliculus
Optic chiasma
Optic nerve
Pituitary gland
Thalamus
Mammillary body
Third
ventricle
Optic tract
Pons
Cerebral
peduncles
Pineal gland
Fourth
ventricle
Pyramidal tract
Olive
Cerebellar
peduncles
Medulla
oblongata
Spinal cord
(a)
(b)
57
Pons
• Rounded bulge on underside of
brainstem
• Between medulla oblongata and
midbrain
• Helps regulate rate and
depth of breathing
• Relays nerve impulses to and from
medulla oblongata and cerebellum
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Superior
colliculus
Corpora quadrigemina
Inferior
colliculus
Optic chiasma
Optic nerve
Pituitary gland
Thalamus
Mammillary body
Third
ventricle
Optic tract
Pons
Cerebral
peduncles
Pineal gland
Fourth
ventricle
Pyramidal tract
Olive
Cerebellar
peduncles
Medulla
oblongata
Spinal cord
(a)
(b)
58
Medulla Oblongata
• Enlarged continuation of
spinal cord
• Conducts ascending and
descending impulses
between brain and spinal
cord
• Contains cardiac,
vasomotor, and respiratory
control centers
• Contains various nonvital
reflex control centers
(coughing, sneezing,
swallowing, and vomiting)
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Superior
colliculus
Corpora quadrigemina
Inferior
colliculus
Optic chiasma
Optic nerve
Pituitary gland
Thalamus
Mammillary body
Third
ventricle
Optic tract
Pons
Cerebral
peduncles
Pineal gland
Fourth
ventricle
Pyramidal tract
Olive
Cerebellar
peduncles
Medulla
oblongata
Spinal cord
(a)
(b)
59
Reticular Formation
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• Complex network of nerve
fibers scattered throughout the
brain stem
• Extends into the
diencephalon
• Connects to centers of
hypothalamus, basal nuclei,
cerebellum, and cerebrum
• Filters incoming sensory
information
Midbrain
• Arouses cerebral cortex into
Pons
state of wakefulness
Hypothalamus
Diencephalon
Thalamus
Corpus
callosum
Corpora
quadrigemina
Cerebral
aqueduct
Reticular
formation
Medulla
oblongata
Spinal cord
60
Types of Sleep
• Slow wave
• Rapid Eye Movement (REM)
• Non-REM sleep
• Paradoxical sleep
• Person is tired
• Some areas of brain active
• Decreasing activity of reticular system • Heart and respiratory rates irregular
• Restful
• Dreaming occurs
• Dreamless
• Reduced blood pressure and
respiratory rate
• Ranges from light to heavy
• Alternates with REM sleep
61
Cerebellum
• Inferior to occipital lobes
• Posterior to pons and medulla
oblongata
• Two hemispheres
• Vermis connects hemispheres
• Cerebellar cortex (gray matter)
• Arbor vitae (white matter)
• Cerebellar peduncles (nerve fiber
tracts)
• Integrates sensory information
concerning position of body parts
• Coordinates skeletal muscle
activity
• Maintains posture
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Longitudinal
fissure
Corpus callosum
Thalamus
Superior peduncle
Pons
Middle peduncle
Inferior peduncle
Cerebellum
Medulla oblongata
62
Major Parts of the Brain
63
Cranial Nerves
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Olfactory bulb
Olfactory (I)
Olfactory tract
Optic (II)
Optic tract
Oculomotor (III)
Trochlear (IV)
Trigeminal (V)
Vestibulocochlear (VIII)
Abducens (VI)
Hypoglossal (XII)
Facial (VII)
Vagus (X)
Glossopharyngeal (IX)
Accessory (XI)
64
Cranial Nerves
• Remember:
• Cranial nerves are designated ‘C N’
• Cranial nerves are designated with Roman numerals (I – XII)
65
Functions of Cranial Nerves
67
11.7: Autonomic Nervous System
• Functions without conscious effort
• Controls visceral activities
• Regulates smooth muscle, cardiac muscle, and glands
• Efferent fibers typically lead to ganglia outside of the CNS
• Two autonomic divisions regulate:
• Sympathetic division (speeds up)
• Prepares body for ‘fight or flight’ situations
• Parasympathetic division (slows down)
• Prepares body for ‘resting and digesting’ activities
68
Autonomic Nerve Fibers
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Interneurons
• All of the neurons are motor
(efferent)
Dorsal root ganglion
Dorsal root
ganglion
• Preganglionic fibers
• Axons of preganglionic
neurons
• Neuron cell bodies in
CNS
Sensory
neuron
Sensory
neuron
Spinal cord
Autonomic
ganglion
Preganglionic
fiber
Somatic motor neuron
Postganglionic
fiber
Viscera
Skin
• Postganglionic fibers
• Axons of postganglionic
neurons
• Neuron cell bodies in
ganglia
Skeletal
muscle
(a) Autonomic pathway
(b) Somatic pathway
69
Sympathetic Division
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• Thoracolumbar division –
location of preganglionic
neurons
Spinal cord
Ventral root
Sympathetic
trunk
• Preganglionic fibers leave spinal
nerves through white rami and
enter paravertebral ganglia
Paravertebral
sympathetic
ganglion
Dorsal root
Dorsal root
ganglion
Pia mater
Arachnoid
mater
Spinal nerves
Dura
mater
• Paraverterbral ganglia and
fibers that connect them make
up the sympathetic trunk
Transverse
process
Vertebral notch
(forms part of
intervertebral
foramen)
Body of
vertebra
70
Sympathetic Division
• Postganglionic fibers extend
from sympathetic ganglia to
visceral organs
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Preganglionic
neuron
Postganglionic
neuron
Spinal cord
• Postganglionic fibers usually
pass through gray rami and
return to a spinal nerve before
proceeding to an effector
Gray
ramus
Dorsal root
ganglion
White
ramus
Dorsal root
Posterior horn
Sympathetic trunk
Lateral horn
Dorsal branch of
spinal nerve
Anterior horn
Ventral root
Ventral branch of
spinal nerve
Spinal
nerve
Paravertebral
sympathetic
ganglion
Visceral effector
(intestine)
• Exception: preganglionic fibers to
Collateral
ganglion
To visceral effectors
(smooth muscle
of blood vessels,
arrector pili
muscles, and
sweat glands)
adrenal medulla do not synapse with
postganglionic neurons
71
Sympathetic Division
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Lacrimal gland
Eye
Parotid gland,
submandibular and
sublingual glands
Blood vessels
Heart
Celiac and
pulmonary
plexuses
Trachea
Lungs
Skin
Celiac
ganglion
Fibers to
skin, blood vessels,
and adipose tissue
Liver
Gallbladder
Superior
mesenteric
ganglion
Stomach
Pancreas
Small intestine
Large intestine
Spinal
cord
Inferior
mesenteric
ganglion
Adrenal gland
Kidney
Sympathetic
chain ganglia
Urinary
bladder
Preganglionic Postganglionic
neuron
neuron
Ovary
Penis
Uterus
Scrotum
72
Parasympathetic Division
• Craniosacral division –
location of preganglionic
neurons
• Ganglia are near or
within various organs
• Terminal ganglia
• Preganglionic fibers of the
head are included in nerves III,
VII, and IX
• Preganglionic fibers of thorax
and abdomen are parts of
nerve X
• Short postganglionic fibers
• Continue to specific
muscles or glands
73
Parasympathetic Division
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Sphenopalatine
ganglion
Lacrimal
gland
Ciliary ganglion
Cranial
nerve III
Submandibular
and sublingual
glands
Submandibular
ganglion
Cranial
nerve
VII
Eye
Parotid
gland
Otic ganglion
Cranial
nerve IX
Heart
Cranial nerve X
(Vagus)
Trachea
Lung
Cardiac and
pulmonary
plexuses
Liver
Gallbladder
Stomach
Celiac
plexus
Spleen
Pancreas
Superior
hypogastric
plexus
Spinal
cord
Small intestine
Large intestine
Inferior
hypogastric
plexus
Kidney
Pelvic
nerves
Urinary
bladder
Preganglionic
neuron
Postganglionic
neuron
Scrotum
Uterus
Penis
Ovary
74
Autonomic Neurotransmitters
• Cholinergic fibers
• Release acetylcholine
• Preganglionic
sympathetic and
parasympathetic fibers
• Postganglionic
parasympathetic fibers
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ACh = acetylcholine (cholinergic)
Brain
NE = norepinephrine (adrenergic)
Visceral
effectors
Cranial
parasympathetic
neurons
Preganglionic fiber (axon)
ACh
Ganglion
ACh
• Adrenergic fibers
• Release
norepinephrine
• Most
postganglionic
sympathetic fibers
Sympathetic neurons
ACh
Postganglionic fiber (axon)
NE
Paravertebral
ganglion
ACh
NE
Collateral
ganglion
Sacral
parasympathetic
neurons
ACh
75
ACh
Actions of Autonomic
Neurotransmitters
• Result from binding to protein receptors in the membrane of effector cells:
• Cholinergic receptors
• Bind acetylcholine (Ach)
• Muscarinic
• Excitatory
• Slow
• Nicotinic
• Excitatory
• Rapid
• Adrenergic receptors
• Bind epinephrine and
norepinephrine
• Alpha and beta
• Both elicit different
responses on various
effectors
76
Terminating Autonomic
Neurotransmitter Actions
• The enzyme acetylcholinesterase rapidly decomposes the acetylcholine
that cholinergic fibers release.
• Norepinephrine from adrenergic fibers is removed by active transport.
77
Control of Autonomic
Activity
• Controlled largely by CNS
• Medulla oblongata regulates cardiac, vasomotor and respiratory activities
• Hypothalamus regulates visceral functions, such as body temperature,
hunger, thirst, and water and electrolyte balance
• Limbic system and cerebral cortex control emotional responses
78
11.8: Lifespan Changes
• Brain cells begin to die before birth
• Over average lifetime, brain shrinks 10%
• Most cell death occurs in temporal lobes
• By age 90, frontal cortex has lost half its neurons
• Number of dendritic branches decreases
• Decreased levels of neurotransmitters
• Fading memory
• Slowed responses and reflexes
• Increased risk of falling
• Changes in sleep patterns that result in fewer sleeping hours
79