1. The Peripheral Nervous System
Chapter 13

2. Functional Organization of the PNS
Central nervous system (CNS)
Peripheral nervous system (PNS)
Motor (efferent) division
Sensory (afferent) division
Sympathetic
division
Parasympathetic
Somatic sensory
General: Touch, pain,
pressure, vibration,
temperature, and
proprioception in
skin, body wall, and
limbs
Special: Hearing,
equilibrium, vision
Visceral sensory
General: Stretch,
pain, temperature,
chemical changes,
and irritation in
viscera; nausea and
hunger
Special: Taste, smell
Somatic nervous
system
Motor innervation of
all skeletal muscles
Autonomic
nervous system
(ANS)
Motor innervation
of smooth muscle,
cardiac muscle,
and glands
Figure 14.1

3. Figure 7.25
Slide 7.73
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4. 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) is the only cranial nerve that extends into the abdomen

5. Hypoglossal nerve (XII)
The 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)
Filaments of
olfactory nerve (I)
Olfactory bulb
Olfactory tract
Optic chiasma
Optic nerve (II)
Optic tract
Oculomotor
nerve (III)
Trochlear
nerve (IV)
Trigeminal
nerve (V)
Abducens
nerve (VI)
Cerebellum
Medulla oblongata
Figure 14.4a

6. Spinal Nerves Posterior View
Cervical
nerves
C1 – C8
Thoracic
T1 – T12
Lumbar
L1 – L5
Sacral
S1 – S5
Coccygeal
nerve
Co1
Cervical plexus
Intercostal
enlargement
Cauda equina
Brachial plexus
Lumbar plexus
Sacral plexus
Figure 14.5

7. 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)

8. Spinal Nerves Sensory axon and cell body Dorsal root ganglion Dorsal
Axon of
motor
neuron
Ventral
ramus
root
Neuromuscular
junction
Sensory receptors in
skin (e.g., free nerve
endings of sensory
neuron)
Dorsal root
ganglion
Dorsal
Sensory axon
and cell body
Nerves
Figure 14.6

9. Sensory Receptors: Classification by Stimulus Type
Mechanoreceptors—respond to touch, pressure, vibration, and stretch
Thermoreceptors—sensitive to changes in temperature
Photoreceptors—respond to light energy (e.g., retina)
Chemoreceptors—respond to chemicals (e.g., smell, taste, changes in blood chemistry)
Nociceptors—sensitive to pain-causing stimuli (e.g. extreme heat or cold, excessive pressure, inflammatory chemicals)

10. Spinal Nerves and Nerve Plexuses
Characteristics:
Somatic sensation (conscious) and somatic motor control (voluntary control) of skeletal muscles.
Mixed nerves
Sensory
Motor
Dorsal and ventral rami (nerve branches)  plexuses (network of nerves)

11. Comparison of Somatic and Autonomic Nervous Systems
Figure 7.24
Slide 7.69
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12. Spinal Cord Anatomy Exterior white mater – conduction tracts
Figure 7.19
Slide 7.53a
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13. Spinal Cord Anatomy Internal gray matter - mostly cell bodies
Dorsal (posterior) horns
Anterior (ventral) horns
Figure 7.19
Slide 7.53b
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14. Peripheral Nervous System
Nerves and ganglia outside the central nervous system
Nerve = bundle of neuron fibers
Neuron fibers are bundled by connective tissue
Slide 7.55
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

15. Structure of a Nerve Endoneurium surrounds each fiber
Groups of fibers are bound into fascicles by perineurium
Fascicles are bound together by epineurium
Figure 7.20
Slide 7.56
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16. Classification of Nerves
Mixed nerves – both sensory and motor fibers
Afferent (sensory) nerves – carry impulses toward the CNS
Efferent (motor) nerves – carry impulses away from the CNS
Slide 7.57
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17. Spinal Nerves
There is a pair of spinal nerves at the level of each vertebrae.
Slide 7.63
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18. Autonomic Nervous System
The involuntary branch of the nervous system
Consists of only motor nerves
Divided into two divisions
Sympathetic division
Parasympathetic division
Slide 7.67
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

19. Autonomic Functioning
Sympathetic – “fight-or-flight”
Response to unusual stimulus
Takes over to increase activities
Remember as the “E” division = exercise, excitement, emergency, and embarrassment
Slide 7.74a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

20. Autonomic Functioning
Parasympathetic – housekeeping activites
Conserves energy
Maintains daily necessary body functions
Remember as the “D” division - digestion, defecation, and diuresis
Slide 7.74b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

21. Development Aspects of the Nervous System
The nervous system is formed during the first month of embryonic development
Any maternal infection can have extremely harmful effects
The hypothalamus is one of the last areas of the brain to develop
Slide 7.75a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

22. Development Aspects of the Nervous System
No more neurons are formed after birth, but growth and maturation continues for several years (new evidence!)
The brain reaches maximum weight as a young adult
However, we can always grow dendrites!
Slide 7.75b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings