1. The Peripheral Nervous System
PART 3

2. Peripheral Nervous System

3. 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

4. Sensory Input and Motor Output
Sensory (afferent) signals picked up by sensor receptors, carried by nerve fibers of PNS to the CNS
Motor (efferent) signals are carried away from the CNS, innervate muscles and glands
Divided according to region they serve
Somatic body region
Visceral body region
Results in four main subdivisions
Somatic sensory
Visceral sensory
Somatic motor
Visceral motor

5. PNS Afferent Division
Afferent (sensory) division – transmits impulses from receptors to the CNS.
Somatic afferent fibers – carry impulses from skin, skeletal muscles, and joints
Visceral afferent fibers – transmit impulses from visceral organs

6. PNS Efferent Division
Motor (efferent) division – transmits impulses from the CNS to effector organs. Two subdivisions:
Somatic nervous system – provides conscious control of skeletal muscles
Autonomic nervous system – regulates smooth muscle, cardiac muscle, and glands

7. Types of Sensory and Motor Information
Figure 12.3

8. Sensory
General somatic senses – include touch, pain, vibration, pressure, temperature
Proprioceptive senses – detect stretch in tendons and muscle provide information on body position, orientation and movement of body in space
Special Senses - hearing, balance, vision, olfaction (smell), gustation (taste)

9. Motor General somatic motor Visceral motor
Signals contraction of skeletal muscles
Under our voluntary control
Visceral motor
Makes up autonomic nervous system (ANS)
Regulates the contraction of smooth and cardiac muscle, controls function of visceral organs
ANS has two divisions
Parasympathetic
Sympathetic

10. Divisions of the ANS Sympathetic - “fight or flight”
Catabolic (expend energy)
Mass activation prepares for intense activity.
Heart rate (HR) increases.
Bronchioles dilate.
Blood [glucose] increases.
Parasympathetic - “feed & breed”, “rest & digest”
Maintain homeostasis
Normally not activated as a whole, stimulation of separate parasympathetic nerves.
Relaxing effects:
Decreases HR.
Dilates visceral blood vessels.
Increases digestive activity.
Dual innervation of many organs — having a brake and an accelerator provides more control

11. Sympathetic Division Organization
Preganglionic neurons in segments T1 to L2
Ganglia near the vertebral column
Sympathetic ganglia
Paired sympathetic chain ganglia
Unpaired collateral ganglia
Preganglionic fibers to adrenal medullae
Epinephrine (adrenalin) into blood stream

12. The Autonomic Nervous System
Effects of Sympathetic Activation
Generalized response in crises
Increased alertness/energy
Increased cardiovascular activity
Increased respiratory activity
Increased muscle tone

13. Parasympathetic Division Organization
Preganglionic neurons in brain stem and sacral spinal segment
Ganglionic neurons (peripheral ganglia) in or near target organ
Sacral fibers form pelvic nerves

14. The Autonomic Nervous System
Effects of Parasympathetic Activation
Relaxation
Food processing
Energy absorption
Brief effects at specific sites

15. 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

16. Nerves Nerves – cablelike organs in the PNS
Consists of numerous axons wrapped in connective tissue
Endoneurium – layer of delicate connective tissue surrounding the axon
Perineurium – connective tissue wrapping surrounding a nerve fascicle
Nerve fascicles – groups of axons bound into bundles
Epineurium – whole nerve is surrounded by tough fibrous sheath
Axon is surrounded by Schwann cells

17. 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

18. The 12 Pairs of Cranial Nerves
Figure 14.5

19. Olfactory Nerves (I) Sensory nerves of smell 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
Table 14.3 (1 of 12)

20. Optic Nerve (II) Sensory nerve of vision Optic nerve (II)
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
Table 14.3 (2 of 12)

21. Oculomotor Nerve (III)
Innervates four of the extrinsic eye muscles
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
Table 14.3 (3 of 12)

22. Trochlear Nerve (IV)
Innervates the superior oblique muscle (an extrinsic eye muscle)
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
Table 14.3 (4 of 12)

23. Trigeminal Nerve (V) Provides sensory innervation to the face
Motor innervation to chewing muscles
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

24. Abducens Nerve (VI)
Abducts the eyeball – innervates lateral rectus muscle
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
Table 14.3 (6 of 12)

25. Facial Nerve (VII) Innervates muscles of facial expression
Vestibulocochlear
nerve (VIII)
Glossopharyngeal
nerve (IX)
Vagus nerve (X)
Accessory nerve (XI)
Hypoglossal nerve (XII)
Table 14.3 (7 of 12)

26. Vestibulocochlear Nerve (VIII)
Sensory nerve of hearing and balance
Facial nerve (VII)
Vestibulocochlear
nerve (VIII)
Glossopharyngeal
nerve (IX)
Vagus nerve (X)
Accessory nerve (XI)
Hypoglossal nerve (XII)
Table 14.3 (8 of 12)

27. Glossopharyngeal Nerve (IX)
Innervates structures of the tongue and pharynx
Facial nerve (VII)
Vestibulocochlear
nerve (VIII)
Glossopharyngeal
nerve (IX)
Vagus nerve (X)
Accessory nerve (XI)
Hypoglossal nerve (XII)
Table 14.3 (9 of 12)

28. Vagus Nerve (X)
A mixed sensory and motor nerve - “Wanders” into thorax and abdomen
Facial nerve (VII)
Vestibulocochlear
nerve (VIII)
Glossopharyngeal
nerve (IX)
Vagus nerve (X)
Accessory nerve (XI)
Hypoglossal nerve (XII)
Table 14.3 (10 of 12)

29. Accessory Nerve (XI)
An accessory part of the vagus nerve -innervates trapezius muscle
Facial nerve (VII)
Vestibulocochlear
nerve (VIII)
Glossopharyngeal
nerve (IX)
Vagus nerve (X)
Accessory nerve (XI)
Hypoglossal nerve (XII)
Table 14.3 (11 of 12)

30. Hypoglossal Nerve (XII)
Runs inferior to the tongue - innervates the tongue muscles
Facial nerve (VII)
Vestibulocochlear
nerve (VIII)
Glossopharyngeal
nerve (IX)
Vagus nerve (X)
Accessory nerve (XI)
Hypoglossal nerve (XII)
Table 14.3 (12 of 12)

31. 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)

32. Spinal Nerves
Connect to the spinal cord by the dorsal root and ventral root
Dorsal root – contains sensory fibers
Dorsal root ganglion – of afferent cell bodies
Ventral root – contains motor fibers arising from anterior gray column
Branch into dorsal ramus and ventral ramus both contain sensory and motor fibers
Rami communicantes connect to the base of the ventral ramus and lead to the sympathetic chain ganglia

33. Spinal Nerves White matter Ventral root Dorsal root Gray matter
ganglion
Dorsal and ventral
rootlets of spinal
nerve
Dorsal ramus
of spinal nerve
Ventral ramus
of spinal nerve
Spinal nerve
Rami communicantes
Sympathetic trunk
(chain) ganglion
(a)

34. 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

35. Innervation of the 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

36. Introduction to Nerve Plexuses
Nerve plexus – a network of nerves
Ventral rami (except T2 – T12)
Branch and join with one another
Form nerve plexuses
Cervical
Brachial
Lumbar
Sacral
Primarily serve the limbs
Fibers from ventral rami crisscross

37. The Cervical Plexus
Buried deep in the neck under the sternocleidomastoid muscle
Formed by ventral rami of first four cervical nerves (C 1 – 4)
Most are cutaneous nerves
Some innervate muscles of the anterior neck

38. Brachial Plexus Brachial plexus lies in the neck and axilla
Formed by ventral rami of C5 – C8 give rise to cords
Cords give rise to main nerves of the upper limb
Figure 14.9d

39. Lumbar Plexus
Arises from L1– L4
Smaller branches innervate the posterior abdominal wall and psoas muscle
Main branches innervate the anterior thigh

40. The Sacral Plexus Arises from spinal nerves L4–S4
Often considered with the lumbar plexus referred to as the lumbosacral plexus
Sciatic nerve – the largest nerve of the sacral plexus is 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