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PowerPoint® Lecture Slides
prepared by Leslie Hendon,
University of Alabama,
Birmingham
14
HUMAN
ANATOMY
fifth edition
MARIEB | MALLATT | WILHELM
PART 1
The
Peripheral
Nervous
System
Copyright © 2008 Pearson Education, Inc.,
publishing as Benjamin Cummings
The Peripheral Nervous System



Nervous structures outside the brain and spinal
cord
Nerves allow the CNS to receive information and
take action
Functional components of the PNS
 Sensory inputs and motor outputs
 Categorized as somatic or visceral
 Sensory inputs also classified as general or special
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
The Peripheral Nervous System

Autonomic nervous system (ANS)
 General visceral motor part of the PNS
 ANS has two divisions
 Parasympathetic
 Sympathetic
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Functional Organization of the PNS
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 14.1
Basic Structural Components of the PNS


Sensory receptors – pick up stimuli from inside
or outside the body
Motor endings – axon terminals of motor neurons
 Innervate effectors (muscle fibers and glands)

Nerves and ganglia
 Nerves – bundles of peripheral axons
 Ganglia – clusters of peripheral neuronal cell
bodies
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Basic Anatomical Scheme of the PNS
in the Region of a Spinal Nerve
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 14.2
Peripheral Sensory Receptors

Structures that pick up sensory stimuli
 Initiate signals in sensory axons
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Peripheral Sensory Receptors

Two main categories of sensory receptors
 Free nerve endings of sensory neurons
 Monitor general sensory information
 Complete receptor cells – specialized epithelial
cells or small neurons
 Monitor most types of special sensory information
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Peripheral Sensory Receptors


Wednesday
Sensory receptors also classified according to
 Location
 Type of stimulus detected
 Structure
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Classification by Location

Exteroceptors – sensitive to stimuli arising from
outside the body
 Located at or near body surfaces
 Include receptors for touch, pressure, pain, and
temperature
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Classification by Location

Interoceptors – (visceroceptors) receive stimuli
from internal viscera
 Monitor a variety of stimuli

Proprioceptors – monitor degree of stretch
 Located in musculoskeletal organs
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Classification by Stimulus Detected


Mechanoreceptors – respond to mechanical
forces
Thermoreceptors – respond to temperature
changes
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Classification by Stimulus Detected

Chemoreceptors
 Respond to chemicals in solution

Photoreceptors – respond to light
 Located in the eye

Nociceptors
 Respond to harmful stimuli that result in pain
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Classification by Structure

General sensory receptors
 Widely distributed
 Nerve endings of sensory neurons monitor
 Touch
 Pressure
 Vibration
 Stretch
 Pain
 Temperature
 Proprioception
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Classification by Structure

General sensory receptors are
 Divided into two groups
 Free nerve endings
 Encapsulated nerve endings
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Free Nerve Endings



Abundant in epithelia and underlying connective
tissue
Respond to pain and temperature
Monitor affective senses
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Free Nerve Endings

Two specialized types of free nerve endings
 Merkel discs – lie in the epidermis
 Slowly adapting receptors for light touch
 Hair follicle receptors – wrap around hair follicles
 Rapidly adapting receptors
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Unencapsulated Nerve Endings
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Table 14.1 (1 of 4)
Encapsulated Nerve Endings



Consist of one or more end fibers of sensory
neurons
Enclosed in connective tissue
Mechanoreceptors
 Include four main types
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Encapsulated Nerve Endings

Meissner’s corpuscles
 Spiraling nerve ending surrounded by Schwann
cells
 Occur in the dermal papillae
 Rapidly adapting receptors for discriminative touch
 Occur in sensitive, hairless areas of the skin
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Meissner’s Corpuscles
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Table 14.1 (2 of 4)
Encapsulated Nerve Endings

Pacinian corpuscles
 Single nerve ending surrounded by layers of
flattened Schwann cells
 Occur in the hypodermis
 Sensitive to deep pressure – rapidly adapting
receptors
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Encapsulated Nerve Endings

Ruffini’s corpuscles
 Located in the dermis and respond to pressure
 Monitor continuous pressure on the skin – adapt
slowly
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Pacinian Corpuscles and Ruffini’s Corpuscles
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Table 14.1 (3 of 4)
Encapsulated Nerve Endings

Proprioceptors
 Monitor stretch in locomotory organs
 Three types of proprioceptors
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Three Types of Proprioceptors

Muscle spindles – measure the changing length of
a muscle
 Imbedded in the perimysium between muscle


fascicles
Golgi tendon organs – located near the muscletendon junction
 Monitor tension within tendons
Joint kinesthetic receptors
 Sensory nerve endings within the joint capsules
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Proprioceptors
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Table 14.1 (4 of 4)
Structure of Proprioceptors
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 14.4
PowerPoint® Lecture Slides
prepared by Leslie Hendon,
University of Alabama,
Birmingham
14
HUMAN
ANATOMY
fifth edition
MARIEB | MALLATT | WILHELM
PART 2
The
Peripheral
Nervous
System
Copyright © 2008 Pearson Education, Inc.,
publishing as Benjamin Cummings
Cranial Nerves



Attach to the brain and pass through foramina of
the skull
Numbered from I–XII
Cranial nerves I and II attach to the forebrain
 All others attach to the brain stem

Primarily serve head and neck structures
 The vagus nerve (X) extends into the abdomen
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
The 12 Pairs of Cranial Nerves
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 14.5
Olfactory Nerves

Sensory nerves of smell
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Table 14.3 (1 of 12)
Optic Nerve

Sensory nerve of vision
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Table 14.3 (2 of 12)
Oculomotor Nerve

Innervates four of the extrinsic eye muscles
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Table 14.3 (3 of 12)
Trochlear Nerve

Innervates the superior oblique muscle (an
extrinsic eye muscle)
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Table 14.3 (4 of 12)
Trigeminal Nerve


Provides sensory innervation to the face
Motor innervation to chewing muscles
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Trigeminal Nerve
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Table 14.3 (5 of 12)
PowerPoint® Lecture Slides
prepared by Leslie Hendon,
University of Alabama,
Birmingham
14
HUMAN
ANATOMY
fifth edition
MARIEB | MALLATT | WILHELM
PART 3
The
Peripheral
Nervous
System
Copyright © 2008 Pearson Education, Inc.,
publishing as Benjamin Cummings
Abducens Nerve

Abducts the eyeball – innervates lateral rectus
muscle
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Table 14.3 (6 of 12)
Facial Nerve

Innervates muscles of facial expression
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Table 14.3 (7 of 12)
Vestibulocochlear Nerve

Sensory nerve of hearing and balance
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Table 14.3 (8 of 12)
Glossopharyngeal Nerve

Innervates structures of the tongue and pharynx
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Table 14.3 (9 of 12)
Vagus Nerve

A mixed sensory and
motor nerve
 “Wanders” into
thorax and abdomen
 Parasympathetic
innervation of
organs
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Table 14.3 (10 of 12)
Accessory Nerve

An accessory part of the vagus nerve
 Innervates trapezius muscle
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Table 14.3 (11 of 12)
Hypoglossal Nerve

Runs inferior to the tongue
 Innervates the tongue muscles
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Table 14.3 (12 of 12)
PowerPoint® Lecture Slides
prepared by Leslie Hendon,
University of Alabama,
Birmingham
14
HUMAN
ANATOMY
fifth edition
MARIEB | MALLATT | WILHELM
PART 4
The
Peripheral
Nervous
System
Copyright © 2008 Pearson Education, Inc.,
publishing as Benjamin Cummings
Spinal Nerves
 31 pairs – contain thousands of nerve fibers
 Connect to the spinal cord
 Named for point of issue from the spinal cord
 8 pairs of cervical nerves (C1–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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Spinal Nerves Posterior View
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Figure 14.6
Spinal Nerves

Connect to the spinal cord by the dorsal root and
ventral root
 Dorsal root – contains sensory fibers
 Cell bodies – located in the dorsal root ganglion
 Ventral root – contains motor fibers arising from
anterior gray column
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Spinal Nerves

Branch into dorsal ramus and ventral ramus
 Dorsal and ventral rami contain sensory and
motor fibers

Rami communicantes connect to the base of the
ventral ramus
 Lead to the sympathetic chain ganglia
(Chapter 15)
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Spinal Nerves
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 14.7a
Innervation of the Back

Dorsal rami
 Innervate back muscles
 Follow a neat, segmented pattern
 Innervate a horizontal strip of muscle and skin
 In line with emergence point from the vertebral
column
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Innervation of the Back
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 14.7b
Innervation of the Anterior Thoracic and Abdominal Wall

Thoracic region
 Ventral rami arranged in simple, segmented
pattern
 Intercostal nerves – supply intercostal muscles,
skin, and abdominal wall
 Each gives off lateral and anterior cutaneous
branches
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Introduction to Nerve Plexuses


Nerve plexus – a network of nerves
Ventral rami (except T2 – T12)
 Branch and join with one another
 Form nerve plexuses
 In cervical, brachial, lumbar, and sacral regions
 Primarily serve the limbs
 Fibers from ventral rami crisscross
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The Cervical Plexus

Buried deep in the neck
 Under the sternocleidomastoid muscle




Formed by ventral rami of first four cervical
nerves (cn 1 – 4)
Most are cutaneous nerves
Some innervate muscles of the anterior neck
Phrenic nerve – the most important nerve of the
cervical plexus
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The Brachial Plexus and Innervation of the Upper Limb



Brachial plexus lies in the neck and axilla
Formed by ventral rami of C5 – C8
Cords give rise to main nerves of the upper limb
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Figure 14.9d
Nerves from the Lateral and Medial Cords

Musculocutaneous – main branch of the lateral
cord
 Innervates the biceps brachii and brachialis

Median – originates from both lateral and medial
cords
 Innervates anterior forearm muscles and lateral
palm
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Nerves from the Lateral and Medial Cords

Ulnar – branches from the medial cord
 Innervates intrinsic hand muscles and skin of the
medial hand
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Nerves from the Posterior Cord

Radial – continuation of the posterior cord
 Largest branch of the brachial plexus
 Innervates muscles of the posterior upper limb

Axillary
 Innervates the deltoid and teres minor
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The Brachial Plexus
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 14.9a
Axillary and Radial Nerves
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Figure 14.11
PowerPoint® Lecture Slides
prepared by Leslie Hendon,
University of Alabama,
Birmingham
14
HUMAN
ANATOMY
fifth edition
MARIEB | MALLATT | WILHELM
PART 5
The
Peripheral
Nervous
System
Copyright © 2008 Pearson Education, Inc.,
publishing as Benjamin Cummings
The Lumbar Plexus and Innervation of the Lower Limb

Lumbar plexus
 Arises from L1– L4
 Smaller branches innervate the posterior abdominal
wall and psoas muscle
 Main branches innervate the anterior thigh
 Femoral nerve – innervates anterior thigh muscles
 Obturator nerve – innervates adductor muscles
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
The Lumbar Plexus
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Figure 14.12a, b
The Sacral Plexus



Arises from spinal nerves L4–S4
Caudal to the lumbar plexus
Often considered with the lumbar plexus
 Lumbosacral plexus
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Innervation of the Lower Limb

Sciatic nerve – the largest nerve of the sacral
plexus
 Actually two nerves in one sheath
 Tibial nerve – innervates most of the posterior lower
limb
 Common fibular (peroneal) nerve – innervates
muscles of the anterolateral leg
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Innervation of the Lower Limb

Superior and inferior gluteal nerves
 Innervate the gluteal muscles

Pudendal nerve
 Innervates muscles of the perineum
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The Sacral Plexus
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Figure 14.13
Innervation of the Skin: Dermatomes

Dermatome – an area of skin
 Innervated by cutaneous branches of a single spinal
nerve

Upper limb
 Skin is supplied by nerves of the brachial plexus

Lower limb
 Lumbar nerves – anterior surface
 Sacral nerves – posterior surface
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Map of Dermatomes – Anterior View
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Figure 14.14a
Map of Dermatomes – Posterior View
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Figure 14.14b
Disorders of the PNS

Shingles (herpes zoster)
 Viral infection
 Stems from childhood chicken pox
 Often brought on by stress
 Mostly experienced by those over 50
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Disorders of the PNS

Migraine headache
 Relates to sensory innervation of cerebral arteries
 Arteries dilate and compresses and irritate sensory
nerve endings

Myasthenia gravis
 Progressive weakening of the skeletal muscles
 An autoimmune disorder
 Antibodies destroy acetylcholine receptors
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
The PNS Throughout Life


Spinal nerves form late in week 4
Each of the 31 pairs of spinal nerves
 Sends motor fibers to an individual myotome
 Sends sensory fibers to the overlying band of skin

During week 5 nerves reach the organs they
innervate
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The PNS Throughout Life

Embryonic muscles migrate to new locations
 Some skin dermatomes become displaced
 Muscles and skin always retain their original nerve
supply
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings