Comprehensive Overview of the Peripheral and Autonomic Nervous System Components

Peripheral Nervous System components

made of nerves and ganglia

attached to the spinal cord, brain, and brainstem

runs to and from targets in soma and viscera

nerves

bundles of myelinated axons and dendrites

white matter in PNS

ganglia

small switching stations of neuron cell bodies/synapses

thicker than nerves

gray matter in PNS

tracts

white matter in CNS

nuclei

grey matter inside CNS

cortex

grey matter outside layer of brain in CNS

spinal nerves

segmentally arranged in pairs

exit through intervertebral foramina

named/numbered after vertebra

how many pairs of each spinal nerve

8 cervical pairs

12 thoracic pairs

5 lumbar pairs

5 sacral pairs

1 coccygeal pair

31 pairs total

Spinal Nerve Notations

C1-C8

T1-T12

L1-L5

S1-S5

Cx1

dermatomes

zones innervated by a specific spinal nerve

subdivisions of the NS carried by the spinal nerves

somatic motor

somatic sensory

visceral motor

visceral sensory

somatic plexi

spinal nerves join up to trade fibers

introduces redundancy into the innervation in event of trauma

plexus

network of crossing/trading fibers

somatic plexi categories

cervical plexus (C1-C4): to neck

brachial plexus (C5-T1): to UE

lumbar plexu (T12-L4): to thigh

sacral plexus (L4-Cx1): to rest of LE

intercostal nerves

nerves in T2-T11 that do not enter a plexus

lumbrosacral plexus

linked lumbar plexus and sacral plexus

reflexes

behaviors that are generated at the level of the spinal cord

types of reflexes

somatic reflexes

visceral reflexes

sides of the reflex arc

sensory stimulus (afferent signal)

motor response (efferent signal)

CNS lies between them

sensory signal

enters the back of the spinal cord

motor signal

exits the front of the spinal cord

Interneurons

make up 99% of the neurons in the nervous system

responsible for the majority of thinking and memory

Autonomic nervous system

controls visceral organs

sensory input from organs

motor output to smooth muscles and glands

ANS structures

hypothalamus

medulla oblongata

sympathetic trunk ganglia

splanchnic nerves

primary subdivisions of the ANS

visceral sensory input

Visceral motor

sympathetic nervous system

preps body for heightened physical activity (flight, fight, fornification)

increases heart and breathing rate

suppresses digestion / peristalsis

sweat production

vasoconstriction

dilate pupils

increases sexual arousal/orgasm

parasympatheric nervous system

brings body back to resting state

decreases heart and breathing rate

stimulates digestion/peristalsis

stimulates saliva production

constricts pupil

vasodilation

penil/clitoral erection

musculocutaneous nerve

most cranial branch nerve
fairly thin

sends motor branches into the biceps and brachialis

receives sensory branches from the skin

median nerve

superficial branch
thicker than musculocutaneous nerve
cross belly of teres major
motor branches to anterior muscle block of forearm

sensory branches from the skin of the radial half

ulnar nerve

most caudal of the superficial branch
crosses teres major

responsible for funny bone sensation

sends motor branches into a few of the anterior block muscles
receives small sensory branches from the ulnar half skin

radial nerve

deep branch
crosses ventral side of teres major

thickest branch

provides motor branches to the triceps head

splits elbow into superficial branch (Brachioradialis) and deep branch (posterior muscle block)

recieves sensory branches from skin over posterior surface of brachium, forearm, and forepaw

axillary nerve

second deep branch

crosses subscapularis

sends motor branches to all 3 heads of the deltoid

receives sensory branches from the skin over the shoulder

femoral nerve

runs between the sartorius and gracilis muscles

sends motor branches to the quads

small sensory branches enter from the skin over the thigh and medial side of the leg

obturator nerve

crosses proximal end of adductor magnus and longus

sends motor branch to the obturator foramen

supplies the medial muscle block of the thigh 

receieves sensory branch from the skin over medial thigh

sciatic nerve

largest nerve in body

passes deep to femoris muscle

2 main branches: common fibular nerve and tibial nerve

control the posterior thigh muscles, all leg muscles, all foot muscle, most of skin areas in LE

superficial branch

runs deep to the brachioradialis

deep branch

enters into the posterior muscle block of the forearm

thoracodorsal nerve

innervates the latissimus dorsi muscle

long thoracic nerve

runs distally along surface of the serratus anterior muscle