Download The Peripheral Nervous System

14
The Peripheral
Nervous System
PowerPoint® Lecture Presentations prepared by
Leslie Hendon
University of Alabama, Birmingham
© 2014 Pearson Education, Inc.
I. The Peripheral Nervous System (PNS)
A. Nerves allow the CNS to receive information and initiate action
B. The PNS is functionally divided into sensory and motor divisions
C. Sensory (afferent) division
1. somatic sensory
2. visceral sensory
3. special sensory (e.g. eye, ear)
D. Motor (efferent) division
1. somatic motor
2. visceral motor (Autonomic Nervous System)
a. sympathetic division
b. parasympathetic division
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Central nervous system (CNS)
Peripheral nervous system (PNS)
Sensory (afferent) division
Somatic sensory
General: Touch, pain,
pressure, vibration,
temperature, and
proprioception in skin,
body wall, and limbs
Visceral sensory
General: Stretch, pain,
temperature, chemical
changes, and irritation
in viscera; nausea and
hunger
Special: Hearing,
equilibrium, vision
Special: Taste, smell
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Motor (efferent) division
Somatic nervous
system
Motor innervation of all
skeletal muscles
Autonomic nervous
system (ANS)
Motor innervation of
smooth muscle, cardiac
muscle, and glands
Sympathetic
division
Parasympathetic
division
II. General Terms
A. sensation - awareness of external/internal conditions
B. perception - conscious registration of conditions
C. stimulus - change that can initiate nerve impulse
E. transduction - changing stimulus signal into nerve signal
F. adaptation - decreased sensitivity with repeat stimuli
a. rapidly adapting - pressure, touch, smell
b. slowly adapting - pain, position, blood chemicals
G. afterimage - sensation even after stimulus is gone
H. modality - distinct property of each sensation
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I. receptor (sense organ) - converts stimulus to impulse
J. nerve – bundle of axons carrying sensory or motor information
a. can be motor only
b. can be sensory only
c. can be both sensory and motor (most)
K. ganglion – collection of nerve cell bodies located outside the CNS
a. mostly the autonomic nervous system
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III. General Classification of Receptors
A. Two main categories of sensory receptors
1. Free nerve endings of sensory neurons
a. monitor general sensory information
2. Complete receptor cells
a. specialized epithelial cells or small neurons
b. monitor most types of special sensory information
c. special senses = vision, hearing, smell, taste, balance
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B. Receptors Named by Location
1. exteroreceptors – (“outside”) respond to external environment
a. located at or near body surfaces
b. include receptors for touch, pressure, pain, and temperature
2. enteroreceptors – (“inside”) respond to internal environment
a. located in digestive tube, bladder, and lungs
b. monitor a variety of stimuli
i. chemical concentration, taste, tissue stretching, temperature
3. proprioreceptors - respond to body position/motion
a. located in skeletal muscles, tendons, joints, and ligaments
b. monitor degree of stretch
c. send inputs on body movement to the CNS
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C. Receptors Named by Type of Stimulus Detected
1. mechanoreceptors - any mechanical deviation
a. touch, pressure, vibration, proprioception etc.
b. baroreceptors – monitor blood pressure
2. thermoreceptors - changes in temperature
3. nocireceptors - pain; physical or chemical damage
4. photoreceptors - light; rods & cones of the eye
5. chemoreceptors - shapes of different molecules
a. taste, smell, chemicals of blood
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IV. General Sensory Receptors
A. General sensory receptors (not special – vision, hearing, etc.)
1. widely distributed
2. nerve endings of sensory neurons monitor:
a. touch, pressure, stretch, pain, temperature, proprioception
B. Divided into two different groups
1. free nerve endings
2. encapsulated nerve endings
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C. Free nerve endings
1. abundant in epithelia and underlying connective tissue
2. respond to pain and temperature
3. monitor affective senses (emotional response – e.g. pain!)
4. epithelial tactile complexes (Merkel discs)
a. tactile epithelial cell innervated by sensory nerve ending
b. slowly adapting receptors for light touch
5. hair follicle receptors—wrap around hair follicles
a. rapidly adapting receptors
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D. Encapsulated nerve endings
1. consist of one or more end fibers of sensory neurons
2. enclosed in connective tissue
3. mechanoreceptors
a. tactile (Meissner’s) corpuscles
b. lamellar (Pacinian) corpuscles
c. bulbous corpuscles (Ruffini endings)
d. proprioceptors
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4. Tactile (Meissner’s) corpuscles
a. spiraling nerve ending surrounded by Schwann cells
b. occur in the dermal papillae
c. rapidly adapting receptors for discriminative touch
d. occur in sensitive, hairless areas of the skin
5. Lamellar corpuscles
a. nerve ending surrounded by layers of flat Schwann cells
b. occur in the hypodermis
c. sensitive to deep pressure—rapidly adapting receptors
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6. Bulbous corpuscles
a. located in the dermis and respond to pressure
b. monitor continuous pressure on the skin - adapt slowly
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7. Proprioceptors
a. monitor stretch in locomotory organs
Three different types:
i. muscle spindles
► measure the changing length of a muscle
► embedded in the perimysium between muscle fascicles
ii. intrafusal muscle fibers
► modified skeletal muscle fibers located within muscle spindles
iii. anulospiral endings
► located around middle of intrafusal fibers
► stimulated by rate and degree of stretch
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c. tendon organs
► are located near the muscle-tendon junction
► monitor tension within tendons
d. joint kinesthetic receptors
► sensory nerve endings within the joint capsules
i. lamellar corpuscles
ii. bulbous corpuscles
iii. free nerve endings
iv. receptors resembling tendon organs
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Anulo-spiral
endings (primary
sensory endings)
Extrafusal
muscle fibers
(contact)
Muscle
spindle
Intrafusal
muscle fibers
Capsule
Sensory
fiber
Tendon organ
(tension)
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Tendon
V. Cranial Nerves – An Overview
A. Attach to the brain and pass through specific foramina of the skull
B. Numbered from I to XII (roman numerals)
1. Cranial nerves I and II attach to the forebrain
2. All others attach to the brain stem
C. Primarily serve head and neck structures
D. vagus nerve (X) is the only cranial nerve that extends into the abdomen
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Filaments of
olfactory nerve (I)
Optic nerve (II)
Oculomotor
nerve (III)
Trochlear
nerve (IV)
Facial nerve (VII)
Trigeminal
nerve (V)
Vestibulocochlear
nerve (VIII)
Abducens
nerve (VI)
Glossopharyngeal
nerve (IX)
Vagus nerve (X)
Accessory nerve (XI)
Hypoglossal nerve (XII)
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Olfactory nerve (I)
Optic nerve (II)
Oculomotor
nerve (III)
Trochlear
nerve (IV)
Trigeminal
nerve (V)
Abducens
nerve (VI)
Facial nerve (VII)
Vestibulocochlear
nerve (VIII)
Glossopharyngeal
nerve (IX)
Vagus nerve (X)
Accessory nerve (XI)
Hypoglossal nerve (XII)
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The Cranial Nerves
Cranial nerves
Sensory function
Motor function
Cranial nerves
Somatic Visceral Somatic Visceral motor:
sensory sensory motor parasympathetic
(SS)
(VS)
(SM)
(VM)
Smell
I Olfactory
II Optic
VII Facial
Vision
VIII Vestibulocochlear
III Oculomotor
SM
IV Trochlear
SM
V Trigeminal
General
VI Abducens
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VM
Sensory function
Motor function
Somatic
sensory
(SS)
Visceral Somatic Visceral motor:
sensory motor parasympathetic
(VS)
(SM)
(VM)
General
General;
taste
Hearing;
equilibrium
IX Glossopharyngeal General General;
taste
X Vagus
General General;
taste
SM
VM
Some
SM
VM
SM
VM
SM
XI Accessory
SM
SM
XII Hypoglossal
SM
Create your own memory device:
O__________________
F_________________
O__________________
V_________________
O__________________
G_________________
T___________________
V_________________
T___________________
A_________________
A___________________
H_________________
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Mike’s memory device (not for a mixed audience)
Oh!
Feel
Oh!
Very
Oh!
Good
To
V_________________
Touch
A_________________
And
H_________________
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The Cranial Nerves
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Olfactory Nerves (I)
A. Special visceral sensory - sense of smell
B. Olfactory receptor cells located in olfactory epithelium of
nasal cavity
C. Olfactory bulbs project fibers into the nasal cavity
C. Pass through the cribriform foramina of the ethmoid bone
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Olfactory Nerves (I)
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The Optic Nerves (II)
A. Special somatic sensory - vision
B. Originate on the retina of the eye
C. Pass through the optic canals of the sphenoid bone
D. Criss-cross at the optic chiasma
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Optic Nerves (II)
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The Oculomotor Nerves (III)
A. Somatic motor - innervate four extrinsic eye muscles
1. Superior rectus
2. medial rectus
3. inferior rectus
4. inferior oblique
B. Visceral motor
► Constricts pupil
► Controls shape of lens
C. Pass through the superior orbital fissure
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Oculomotor Nerves (III)
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The Trochlear Nerves (IV)
A. Somatic motor - the superior oblique muscle
B. Pass ventrally and laterally around midbrain
C. Pass through superior orbital fissure
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Trochlear Nerves (IV)
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The Trigeminal Nerves (V)
A. Largest of the cranial nerves
1. Ophthalmic division (V1)
superior oribital fissure
2. Maxillary division (V2)
foramen rotundum
3. Mandibular division (V3)
foramen ovale
B. Cell bodies of sensory neurons located in the trigeminal ganglion
C. Mandibular division = motor fibers that innervate chewing muscles
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Trigeminal Nerves (V)
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The Abducens Nerves (VI)
A. Somatic motor - innervates lateral rectus muscle
B. Pass through the superior orbital fissure
NOTE: III (oculomotor); IV (trochlear) and VI (abducens) =
innervation of the muscles of the eye
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Abducens Nerves (VI)
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The Facial Nerves (VII)
A. Special visceral sensory - taste buds on anterior two-thirds of tongue
B. Somatic motor - innervate facial muscles
C. Visceral motor - innervation of lacrimal glands, submandibular and
sublingual salivary glands
D. Enter temporal bone through the internal acoustic meatus
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Facial Nerves (VII)
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The Vestibulocochlear Nerves (VIII)
A. Sensory nerve of hearing and equilibrium
B. From inner ear - pass through the internal acoustic meatus
C. Carries information from vestibular apparatus and cochlea
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Vestibulocochlear Nerves (VIII)
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The Glossopharyngeal Nerves (IX)
A. General visceral sensory
1. posterior one-third of tongue
2. pharyngeal mucosa
3. chemoreceptors in carotid body
4. baroreceptors of carotid sinus
B. Somatic motor - elevate pharynx during swallowing
C. Visceral motor - innervate the parotid salivary gland
D. Fibers pass through the jugular foramen
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Glossopharyngeal Nerves (IX)
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The Vagus Nerves (X)
A. General visceral sensory - from thoracic and abdominal viscera
B. Special visceral sensory - taste buds on epiglottis
C. Somatic motor - skeletal muscles of the pharynx and larynx
D. Visceral motor - parasympathetic innervation to
1. Heart, lungs, abdominal organs
E. Fibers exit through the jugular foramen
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Vagus Nerves (X)
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The Accessory Nerves (XI)
A. Somatic motor - innervates trapezius and sternocleidomastoid
B. Pass into skull through foramen magnum
C. Exit skull through the jugular foramen
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Accessory Nerves (XI)
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The Hypoglossal Nerves (XII)
A. Somatic motor - innervate the tongue muscles
B. Exit the skull through hypoglossal canal
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Hypoglossal Nerves (XII)
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The Spinal Nerves
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VI. Spinal Nerves
A. 31 pairs - contain thousands of nerve fibers
B. Connect to the spinal cord
C. Named for point of issue from the spinal cord
8 pairs of cervical nerves (C1–C8)
(note: C8)
12 pairs of thoracic nerves (T1–T12)
5 pairs of lumbar nerves (L1–L5)
5 pairs of sacral nerves (S1–S5)
1 pair of coccygeal nerves (Co1)
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Ventral rami
Spinal nerves
Cervical plexus
Brachial plexus
Cervical
nerves
C1 – C8
Cervical
enlargement
Intercostal
nerves
Thoracic
nerves
T1 – T12
Lumbar
enlargement
Lumbar plexus
Lumbar
nerves
L1 – L5
Sacral plexus
Sacral
nerves
S1 – S5
Cauda equina
(spinal nerves)
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Coccygeal
nerve
Co1
D. Connect to the spinal cord by the dorsal root and ventral root
1. Dorsal root—contains sensory fibers
► cell bodies—located in the dorsal root ganglion
2. Ventral root—contains motor fibers
► arising from anterior gray horn of spinal cord
E. Each branch into dorsal ramus and ventral ramus
► Dorsal and ventral rami contain sensory and motor fibers
F. Sympathetic chain ganglia – from T1 – L2
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Sensory axon
and cell body
Dorsal root
ganglion
Dorsal root
Dorsal
ramus
Nerves
Spinal
nerve
Ventral
ramus
Axon of
motor
neuron
Ventral root
Sensory receptors in
skin (e.g., free nerve
endings of sensory
neuron)
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Gray matter
White matter
Ventral root
Dorsal root
Dorsal and ventral
rootlets of spinal
nerve
Dorsal root
ganglion
Dorsal ramus
of spinal nerve
Ventral ramus
of spinal nerve
Spinal nerve
Sympathetic chain
ganglion
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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VII. Innervation of the Back
A. Dorsal rami - innervate back muscles
1. follow a neat, segmented pattern
2. innervate a horizontal strip of muscle and skin
B. Ventral rami - arranged in simple, segmented pattern
1. intercostal nerves - supply intercostal muscles, skin, and
abdominal wall
2. each gives off lateral and anterior cutaneous branches
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Dorsal ramus
Ventral ramus
Spinal nerve
Intercostal nerve
Sympathetic chain
ganglion
Branches of intercostal nerve
Sternum
Cross section of thorax showing the main roots and branches of a spinal nerve
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VIII. Introduction to Nerve Plexuses
A. Nerve plexus - a network of spinal nerves that criss-cross with
each other – give rise to the nerves of the body
1. branch and join with one another
2. fibers from ventral rami crisscross (except T2–T12)
3. form the four nerve plexuses
a. cervical plexus
b. brachial plexus
c. lumbar plexus
d. sacral plexus
4. primarily serve the limbs
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B. Cervical plexus
1. formed by ventral rami of first four cervical nerves (C1–C4)
a. most are cutaneous nerves
b. some innervate muscles of the anterior neck
2. phrenic nerve C3–C5
a. the most important nerve of the cervical plexus
b. innervates the diaphragm
3. accessory nerve (XI) C5
Note: a nerve can have nerve fibers from different spinal nerves
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Ventral rami
Hypoglossal
nerve (XII)
Ventral
rami:
C1
C2
C3
Accessory nerve (XI) (C3,4,5)
Phrenic nerve (C3,4,5)
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C4
C5
C. Brachial plexus
1. lies in the neck and axilla
2. formed by ventral rami of C5–T1
3. cords give rise to 5 main nerves of the upper limb
a. musculotaneous nerve - biceps brachii and brachialis C5–C7
b. axillary nerve - deltoid and teres minor C5–C6
c. ulnar nerve - hand muscles and skin of the medial hand C8–T1
d. median nerve - anterior forearm muscles and lateral palm C5–T1
e. radial nerve - muscles of the posterior upper limb C5–T1
4. Roots >>> Trunks >>> Divisions >>> Cords >>> Nerves
Note: a nerve can be composed of fibers from different spinal nerves
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The Brachial Plexus
Major terminal
branches
(peripheral nerves)
Cords
Divisions
Trunks
Anterior
Musculocutaneous
Upper
Lateral
Posterior
Medial
Anterior
Median
Ulnar
Roots
(ventral
rami)
C5
C6
Middle
C7
Posterior
Radial
Posterior
C8
Anterior
Axillary
Lower
Posterior
T1
Flowchart summarizing relationships within the brachial plexus
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The Brachial Plexus
Roots (C5–T1)
C5
Divisions
C6
C8
Lateral
Cords
C7
T1
Posterior
Medial
Axillary
Musculocutaneous
Radial
Median
Ulnar
Anterior
divisions
Posterior
divisions
Trunks
Roots
Roots (rami C5–T1), trunks, divisions, and cords
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Upper
Middle
Lower
Trunks
Axillary nerve
The Brachial Plexus
Musculo-cutaneous nerve
Radial nerve
Median nerve
Ulnar nerve
Digital
branches
The major nerves of the upper limb
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The Brachial Plexus
Digital
branches
The major nerves of the upper limb
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D. Lumbar plexus
1. Arises from L1 to L4
2. innervate the posterior abdominal wall and psoas muscle
3. Main branches innervate the anterior thigh
a. femoral nerve - anterior thigh muscles L2–L4
b. obturator nerve - innervates adductor muscles L2–L4
Note: a nerve can be composed of fibers from different spinal nerves
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Ilioinguinal
nerve
Femoral nerve
Lateral
femoral
cutaneous
Nerves of the lumbar plexus,
anterior view
Ventral rami
Anterior division
Posterior
division
Obturator
Ventral
rami:
L1
Anterior
femoral
cutaneous
Saphenous
Iliohypogastric
L2
Ilioinguinal
Genitofemoral
L3
Lateral femoral
cutaneous
L4
Obturator
Femoral
Ventral rami and major branches of the
lumbar plexus
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L5
Distribution of the major nerves from the
lumbar plexus to the lower limb
Nerves of the lumbar plexus,
anterior view
Ventral rami
Anterior division
Posterior
division
Ventral
rami:
L1
L2
L3
L4
L5
Ventral rami and major branches of the
lumbar plexus
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Distribution of the major nerves from the
lumbar plexus to the lower limb
E. Sacral plexus
1. Arises from spinal nerves L4–S4
2. sciatic nerve - the largest nerve of the sacral plexus L4–S3
a. actually two nerves in one sheath
b. tibial nerve - most of the posterior lower limb L4–S3
c. common fibular nerve - muscles of anterolateral leg L4–S2
3. superior and inferior gluteal nerves - the gluteal muscles L4–S2
4. pudendal nerve - muscles of the perineum S2–S4
Note: a nerve can be composed of fibers from different spinal nerves
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Common fibular
nerve
Tibial nerve
Superior
gluteal
Inferior
gluteal
nerve
Sciatic nerve
Pudendal
nerve
Dissection of the gluteal region,
posterior view
Ventral rami
Anterior division
Posterior
division
Superior
gluteal
Sciatic
Ventral
rami:
L4
Common
fibular
L5
Tibial
Lumbosacral
trunk
Inferior gluteal
S1
Common
fibular
S2
Tibial
Posterior
femoral
cutaneous
Pudendal
Sciatic
Ventral rami and major branches of the
sacral plexus, anterior view
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Posterior
femoral
cutaneous
nerve
Deep
fibular
Superficial
fibular
S3
S4
S5
Co1
Distribution of the major nerves from
the sacral plexus to the lower limb, posterior view
Dissection of the gluteal region,
posterior view
Ventral rami
Anterior division
Posterior
division
L4
L5
S1
S2
S3
S4
S5
Co1
Ventral rami and major branches of the
sacral plexus, anterior view
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Distribution of the major nerves from
the sacral plexus to the lower limb, posterior view
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IV. Innervation of the Skin: Dermatomes
A. Dermatome - an area of skin innervated by cutaneous branches
of a single spinal nerve
B. Upper limb - supplied by nerves of the brachial plexus
C. Lower limb
1. lumbar nerves - anterior surface
2. sacral nerves - posterior surface
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C2
C3
Dermatomes of the
Anterior
C4
C5
T1
T2
T3
T4
T5
T6
T7
T8
T9
T10
T11
T2
C6
C5
C6
C7
L1
C8
L2
L3
L4
L5
S1
Anterior view
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T12
S2
S3
T2
C6
C5
L1
C8
L2
L3
L4
L5
S1
C6
C7
C2
C3
C4
C5
C6
C7
C8
T1
T2
T3
T4
T5
T6
T7
T8
T9
T10
Dermatomes of the
Posterior
C6
C7
C8
S1
L2
S2
S3
S4
S4
L4
S1 S2
T11
T12
C7
L1
L3 C8
L5
S2 S1
L1
L5
L2
L5
L3
L4
L4
L5
Posterior view
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L4
L5
S1
C6
IX. Disorders of the PNS
A. Shingles (herpes zoster)
1. viral infection - stems from childhood chicken pox
2. often brought on by stress
3. mostly experienced by people over 50
4. extremely painful
B. Migraine headache
1. relates to sensory innervation of cerebral arteries
2. arteries dilate and compress and irritate sensory nerve endings
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C. Peripheral neuropathy
1. pathological condition of peripheral nerves
2. symptoms of sensory nerve involvement:
a. paresthesia, pain, burning, loss of sensation
3. symptoms of motor nerve involvement:
a. muscle weakness and paralysis
4. causes:
a. trauma, repetitive use (e.g. carpal tunnel syndrome)
b. systemic disorders: HIV, diabetes, vitamin B deficiency
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