Download chapter 13 peripheral nervous system

CHAPTER 13
PERIPHERAL NERVOUS SYSTEM
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PERIPHERAL NERVOUS SYSTEM
Organization
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Figure 13.1 Place of the PNS in the structural organization of the nervous system.
Central nervous system (CNS)
Peripheral nervous system (PNS)
Sensory (afferent)
division
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Motor (efferent) division
Somatic nervous
system
Autonomic nervous
system (ANS)
Sympathetic
division
Parasympathetic
division
PERIPHERAL NERVOUS SYSTEM
Sensory Receptors
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Table 13.1 General Sensory Receptors Classified by Structure and Function (1 of 3)
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Table 13.1 General Sensory Receptors Classified by Structure and Function (2 of 3)
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Table 13.1 General Sensory Receptors Classified by Structure and Function (3 of 3)
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A receptor which responds to changes in
temperature is a…
1)
2)
3)
4)
5)
mechanoreceptor
thermoreceptor
photoreceptor
chemoreceptor
nociceptor
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PERIPHERAL NERVOUS SYSTEM
Sensory Perception – CNS Integration
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Figure 13.2 Three basic levels of neural integration in sensory systems.
Perceptual level (processing in
cortical sensory centers)
3
Motor
cortex
Somatosensory
cortex
Thalamus
Reticular
formation
Pons
2 Circuit level
(processing in
Spinal
ascending pathways) cord
Free nerve
endings (pain,
cold, warmth)
Muscle
spindle
Receptor level
(sensory reception Joint
and transmission
kinesthetic
to CNS)
receptor
1
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Cerebellum
Medulla
Which level of sensory integration is the level
at which the reticular formation and thalamus
distribute signals to appropriate cortical
regions?
1) Circuit level
2) Receptor level
3) Perceptual level
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PERIPHERAL NERVOUS SYSTEM
NERVES: Structure
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Figure 13.3b Structure of a nerve.
Endoneurium
Axon
Myelin sheath
Perineurium
Epineurium
Fascicle
Blood
vessels
(b)
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Figure 13.3a Structure of a nerve.
Blood vessels
Perineurium
Fascicle
Endoneurium
(a)
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Nerve fibers
The membrane surrounding a nerve is the...
1) endoneurium
2) epineurium
3) perineurium
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PERIPHERAL NERVOUS SYSTEM
NERVES: Classification & Location
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PERIPHERAL NERVOUS SYSTEM
Nerves: Ganglia
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A nerve is…
1) A neuron
2) A group of neuron cell bodies
3) A group of neuron axons wrapped in
connective tissue in the peripheral nervous
system
4) A group of neuron axons wrapped in
connective tissue in the central nervous
system
5) All of the above
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PERIPHERAL NERVOUS SYSTEM
Nerves: Regeneration and Repair
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Figure 13.4 Regeneration of a nerve fiber in a peripheral nerve (1 of 4).
Endoneurium
Schwann cells
Droplets
of myelin
Fragmented
axon
Site of nerve damage
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1 The axon
becomes
fragmented at
the injury site.
Figure 13.4 Regeneration of a nerve fiber in a peripheral nerve (2 of 4).
Schwann cell
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Macrophage
2 Macrophages
clean out the
dead axon distal
to the injury.
Figure 13.4 Regeneration of a nerve fiber in a peripheral nerve (3 of 4).
Aligning Schwann cells
form regeneration tube
Fine axon sprouts
or filaments
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3 Axon sprouts,
or filaments,
grow through a
regeneration tube
formed by
Schwann cells.
Figure 13.4 Regeneration of a nerve fiber in a peripheral nerve (4 of 4).
Schwann cell
Single enlarging
axon filament
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Site of new
myelin sheath
formation
4 The axon
regenerates and
a new myelin
sheath forms.
PERIPHERAL NERVOUS SYSTEM
Cranial Nerves
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Figure 13.5a Location and function of cranial nerves.
Frontal lobe
Temporal lobe
Infundibulum
Facial
nerve (VII)
Vestibulocochlear
nerve (VIII)
Glossopharyngeal
nerve (IX)
Vagus nerve (X)
Accessory nerve (XI)
Hypoglossal nerve (XII)
(a)
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Filaments of
olfactory
nerve (I)
Olfactory bulb
Olfactory tract
Optic nerve
(II)
Optic chiasma
Optic tract
Oculomotor
nerve (III)
Trochlear
nerve (IV)
Trigeminal
nerve (V)
Abducens
nerve (VI)
Cerebellum
Medulla
oblongata
Figure 13.5b Location and function of cranial nerves.
Cranial nerves
I – VI
I
II
III
IV
V
Olfactory
Optic
Oculomotor
Trochlear
Trigeminal
VI Abducens
Cranial nerves
VII – XII
VII Facial
VIII Vestibulocochlear
IX
X
XI
XII
Glossopharyngeal
Vagus
Accessory
Hypoglossal
(b)
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Sensory
function
Motor
function
PS*
fibers
Yes (smell)
Yes (vision)
No
No
Yes (general
sensation)
No
No
Yes
Yes
Yes
No
No
Yes
No
No
No
Yes
No
Sensory
function
Motor
function
PS*
fibers
Yes (taste)
Yes (hearing
and balance)
Yes
Some
Yes
No
Yes (taste)
Yes (taste)
No
No
Yes
Yes
Yes
Yes
Yes
Yes
No
No
*PS = parasympathetic
Cranial nerve I is also known as the…
1)
2)
3)
4)
Hypoglossal nerve
Olfactory nerve
Optic nerve
Vagus nerve
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PERIPHERAL NERVOUS SYSTEM
Spinal Nerves
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Figure 13.6 Spinal nerves.
Cervical plexus
Brachial plexus
Cervical
nerves
C1 – C8
Cervical
enlargement
Intercostal
nerves
Thoracic
nerves
T1 – T12
Lumbar
enlargement
Lumbar plexus
Sacral plexus
Cauda equina
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Lumbar
nerves
L1 – L5
Sacral nerves
S1 – S5
Coccygeal nerve Co1
PERIPHERAL NERVOUS SYSTEM
Spinal Nerves: Branches
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Figure 13.7a Formation of spinal nerves and rami distribution.
Gray matter
White matter
Ventral root
Dorsal root
Dorsal root
ganglion
Dorsal ramus
of spinal nerve
Ventral ramus
of spinal nerve
Spinal nerve
Dorsal and
ventral rootlets
of spinal nerve
Rami communicantes
Sympathetic trunk
ganglion
(a) Anterior view showing spinal cord, associated nerves, and vertebrae.
The dorsal and ventral roots arise medially as rootlets and join
laterally to form the spinal nerve.
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Figure 13.7b Formation of spinal nerves and rami distribution.
Dorsal ramus
Ventral ramus
Spinal nerve
Rami communicantes
Sympathetic trunk
ganglion
Intercostal nerve
Dorsal root
ganglion
Dorsal root
Ventral root
Branches of intercostal
nerve
• Lateral cutaneous
• Anterior cutaneous
Sternum
(b) Cross section of thorax showing the main roots and
branches of a spinal nerve.
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True or false: information only flows toward
the spinal cord in a dorsal ramus.
1) True
2) False
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PERIPHERAL NERVOUS SYSTEM
Spinal Nerves: Plexuses (Plexi?)
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Figure 13.8 The cervical plexus.
Ventral rami
Segmental
branches
Hypoglossal
nerve (XII)
Lesser occipital
nerve
Greater auricular
nerve
Transverse
cervical nerve
Ansa cervicalis
Ventral
rami:
C1
C2
C3
C4
Accessory nerve (XI)
Phrenic nerve
Supraclavicular
nerves
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C5
Figure 13.9a The brachial plexus.
Roots (ventral rami):
C4
C5
Dorsal scapular
Nerve to
subclavius
Suprascapular
Cords
C6
Posterior
divisions
C7
Lateral
C8
Posterior
T1
Upper
Middle
Trunks
Lower
Long thoracic
Medial pectoral
Medial
Lateral pectoral
Axillary
Musculocutaneous
Radial
Upper subscapular
Lower subscapular
Median
Ulnar
Medial cutaneous
nerves of the arm
and forearm
Thoracodorsal
(a) Roots (rami C5 – T1), trunks, divisions, and cords
Anterior
divisions
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Posterior
divisions
Trunks
Roots
Figure 13.9b The brachial plexus.
Musculocutaneous
nerve
Axillary nerve
Biceps brachii
Coracobrachialis
Median nerve
Radial nerve
branches to triceps
Lateral
cord
Posterior
cord
Medial cord
Radial nerve
Ulnar nerve
(b) Cadaver photo
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Figure 13.9c The brachial plexus.
Axillary
nerve
Anterior
divisions
Posterior
divisions
Humerus
Radial nerve
Musculocutaneous nerve
Ulna
Radius
Ulnar nerve
Median nerve
Radial nerve (superficial branch)
Dorsal branch of ulnar nerve
Superficial branch of ulnar nerve
Digital branch of ulnar nerve
Muscular branch
Median nerve
Digital branch
(c) The major nerves of the upper limb
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Trunks
Roots
Figure 13.9d The brachial plexus.
Anterior
divisions
Posterior
divisions
Major terminal
branches
(peripheral nerves)
Musculocutaneous
Median
Ulnar
Radial
Axillary
Trunks
Cords
Roots
Divisions
Anterior
Lateral
Medial
Posterior
Anterior
Posterior
Posterior
Anterior
Posterior
Trunks
Upper
C5
C6
Middle
C7
C8
Lower
(d) Flowchart summarizing relationships within the
brachial plexus
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Roots
(ventral
rami)
T1
Figure 13.10 The lumbar plexus.
Ventral rami
Iliohypogastric
Ilioinguinal
Genitofemoral
Lateral femoral
cutaneous
Obturator
Femoral
Lumbosacral
trunk
Ventral
rami:
Iliohypogastric
L1
Ilioinguinal
Femoral
Lateral femoral
L2
cutaneous
Obturator
L3
Anterior femoral
cutaneous
Saphenous
L4
L5
(a) Ventral rami and major branches
of the lumbar plexus
(b) Distribution of the major nerves from
the lumbar plexus to the lower limb
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Figure 13.10a The lumbar plexus.
Ventral rami
Ventral
rami:
L1
Iliohypogastric
L2
Ilioinguinal
Genitofemoral
Lateral femoral
cutaneous
L3
L4
Obturator
Femoral
L5
Lumbosacral
trunk
(a) Ventral rami and major branches
of the lumbar plexus
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Figure 13.10b The lumbar plexus.
Iliohypogastric
Ilioinguinal
Femoral
Lateral femoral
cutaneous
Obturator
Anterior femoral
cutaneous
Saphenous
(b) Distribution of the major
nerves from the lumbar
plexus to the lower limb
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Figure 13.11a The sacral plexus.
Ventral rami
Ventral rami:
L4
Superior
gluteal
Lumbosacral
trunk
Inferior
gluteal
Common
fibular
Tibial
Posterior
femoral
cutaneous
Pudendal
Sciatic
L5
S1
S2
S3
S4
S5
Co1
(a) Ventral rami and major branches
of the sacral plexus
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Figure 13.11b The sacral plexus.
Superior gluteal
Inferior gluteal
Pudendal
Sciatic
Posterior femoral
cutaneous
Common fibular
Tibial
Sural (cut)
Deep fibular
Superficial fibular
Plantar branches
(b) Distribution of the major nerves from
the sacral plexus to the lower limb
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Figure 13.11c The sacral plexus.
Gluteus maximus
(medial portion
removed)
Piriformis
Inferior gluteal
nerve
Pudendal nerve
Greater trochanter
of femur
Common fibular
nerve
Tibial nerve
Posterior femoral
cutaneous nerve
Sciatic nerve
Ischial tuberosity
(c) Cadaver photo
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PERIPHERAL NERVOUS SYSTEM
Spinal Nerves: Dermatomes
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Figure 13.12 Map of dermatomes.
C2
C3
C4
C5
C6
C7
C8
T1
T2
T3
T4
T5
T6
T7
T8
T9
T10
C2
C3
C4
C5
T1
T2
T3
T4
T5
T6
T7
T8
T9
T10
T11
T2
C5
C6
C6
C7
L1
C8
L2
T12
S2
S3
T2
C5
C6
L1
C8
L2
S1
L4
S2
S3
S4
S5
C6
C7
C6
C7
C8
C8
L2
S2
S1
L1
L3
L5
L4
T11
T12
L1
L3
L5
C7
C6
S1 S2
L3
C5
L2
L5
L4
L3
L5
L5
L4
S1
(a) Anterior
view
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S1
(b) Posterior
view
L4
L5
L4
L5
S1
True or false: Pain felt on the surface of a body
region is always related to skin problems.
1) True
2) False
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PERIPHERAL NERVOUS SYSTEM
MOTOR ENDINGS
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PERIPHERAL NERVOUS SYSTEM
MOTOR INTEGRATION
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Figure 13.13 Hierarchy of motor control.
Precommand level
• Cerebellum
• Basal nuclei
Precommand Level
(highest)
• Cerebellum and basal
nuclei
• Programs and instructions
(modified by feedback)
Internal
feedback
Feedback
Projection Level (middle)
• Motor cortex (pyramidal
system) and brain stem
nuclei (vestibular, red,
reticular formation, etc.)
• Convey instructions to
spinal cord motor neurons
and send a copy of that
information to higher levels
Projection level
• Primary motor cortex
• Brain stem nuclei
Segmental level
• Spinal cord
(b) Structures involved
Segmental Level (lowest)
• Spinal cord
• Contains central pattern
generators (CPGs)
Sensory
input
Reflex activity
Motor
output
(a) Levels of motor control and their interactions
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PERIPHERAL NERVOUS SYSTEM
REFLEX ARC
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Figure 13.14 The five basic components of all reflex arcs.
Stimulus
Skin
1 Receptor
Interneuron
2 Sensory neuron
3 Integration center
4 Motor neuron
5 Effector
Spinal cord
(in cross section)
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Figure 13.15 Anatomy of the muscle spindle and Golgi tendon organ.
Secondary sensory
endings (type II fiber)
Primary sensory
endings (type Ia
fiber)
Muscle spindle
Connective
tissue capsule
Efferent (motor)
fiber to muscle spindle
 Efferent (motor)
fiber to extrafusal
muscle fibers
Extrafusal muscle
fiber
Intrafusal muscle
fibers
Sensory fiber
Golgi tendon
organ
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Tendon
Figure 13.16 Operation of the muscle spindle.
Muscle
spindle
Intrafusal
muscle fiber
Primary
sensory (la)
nerve fiber
Extrafusal
muscle fiber
Time
Time
Time
(a) Unstretched
muscle. Action
potentials (APs)
are generated at
a constant rate in
the associated
sensory (la) fiber.
(b) Stretched
muscle. Stretching
activates the muscle
spindle, increasing
the rate of APs.
(c) Only motor
(d) - Coactivation.
neurons activated.
Both extrafusal and
Only the extrafusal
intrafusal muscle
muscle fibers contract.
fibers contract.
The muscle spindle
Muscle spindle
becomes slack and no
tension is mainAPs are fired. It is
tained and it can
unable to signal further
still signal changes
length changes.
in length.
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Time
Figure 13.17 The Stretch Reflex (1 of 2)
The events by which muscle stretch is damped
1 When muscle spindles are activated
2 The sensory neurons synapse directly with alpha
motor neurons (red), which excite extrafusal fibers
of the stretched muscle. Afferent fibers also
by stretch, the associated sensory
neurons (blue) transmit afferent impulses synapse with interneurons (green) that inhibit motor
neurons (purple) controlling antagonistic muscles.
at higher frequency to the spinal cord.
Sensory
neuron
Cell body of
sensory neuron
Initial stimulus
(muscle stretch)
Muscle spindle
Antagonist muscle
Spinal cord
3a Efferent impulses of alpha motor neurons
3b Efferent impulses of alpha motor
cause the stretched muscle to contract,
which resists or reverses the stretch.
neurons to antagonist muscles are
reduced (reciprocal inhibition).
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Figure 13.17 The Stretch Reflex (2 of 2)
The patellar (knee-jerk) reflex – a specific example of a stretch reflex
2
Quadriceps
(extensors)
1
3a
3b
3b
Patella
Muscle
spindle
Spinal cord
(L2 – L4)
Hamstrings
(flexors)
Patellar
ligament
1 Tapping the patellar ligament excites
muscle spindles in the quadriceps muscle.
2 Afferent impulses (blue) travel to the
spinal cord, where synapses occur with
motor neurons and interneurons.
3a The motor neurons (red) send
+ Excitatory synapse
– Inhibitory synapse
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activating impulses to the quadriceps
causing it to contract, extending the
knee.
3b The interneurons (green) make
inhibitory synapses with ventral horn
neurons (purple) that prevent the
antagonist muscles (hamstrings) from
resisting the contraction of the
quadriceps.
Figure 13.19 The crossed-extensor reflex.
+ Excitatory synapse
– Inhibitory synapse
Interneurons
Efferent
fibers
Afferent
fiber
Efferent
fibers
Extensor
inhibited
Flexor
stimulated
Site of stimulus: a noxious
stimulus causes a flexor
reflex on the same side,
withdrawing that limb.
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Arm
movements
Flexor
inhibited
Extensor
stimulated
Site of reciprocal
activation: At the
same time, the
extensor muscles
on the opposite
side are activated.
True or false: The flexor-crossed extensor
reflex involves multiple integration neurons.
1) True
2) False
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