Notes: 9.14, 9.15

Peripheral Nervous System - consists of the nerves that branch out from the CNS and connect it to other body parts, also includes the cranial nerves

Somatic Nervous System (conscious activities)
Skin, skeletal system

Autonomic Nervous System (unconscious activities)
heart, viscera, glands

CRANIAL NERVES (12 pairs)

I
II
III
IV
V
VI
VII
VIII
IX
X
XI
XII

There is a mnemonic to help you remember the 12 cranial nerves:

On Old Olympus Towering Top, A Finn And German Viewed A Hop

Each letter corresponds with the first letter of the cranial nerves.

 

SPINAL NERVES (31 pairs)

These are not named individually, they are grouped according to the level from which they arise

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 (Co)

*Spinal cords ends at the level between the 1st and 2nd lumbar vertebrae
*The lumbar, sacral, coccygeal nerves descend from the end of the cord - CAUDA EQUINA (horse's tail)

Each nerve emerges from the spinal cord at points called ROOTS

Dorsal Root Ganglion - arises from the back side of the spinal cord
Ventral root ganglion - arises from the front side

Main portions of the spinal nerves combine to form complex networks called PLEXUSES

CERVICAL PLEXUSES

*phrenic nerves (diaphragm). neck

BRACHIAL PLEXUSES

*shoulders, arms, hands
* Ulnar, median, radial, axillary nerves

LUMBROSACRAL PLEXUSES

*pelvic area, genitalia, buttocks, thighs, legs, feet
*Obturator, femoral, sciatic nerves
*intercostals nerves (ribs)

9.15 AUTONOMIC NERVOUS SYSTEM

SYMPATHETIC - Energy, high stress, emergency; FIGHT or FLIGHT

PARASYMPTHETIC - restful, ordinary

*Divisions act antagonistically, one turns on (exhitatory), other turns off (inhibitory)

Cell body --> Preganglionic fiber (axon) leaves CNS and synapses with neurons in the autonomic ganglion --> Postganglionic fiber (axon)

See Figures 9.34 & 9.35

Autonomic Neurotransmitters

Cholinergic fibers (acetylcholine)
Adrenergic fibers (norepinephrine)