Peripheral Nerves

Nervous System: Peripheral Nerves

I). Cranial Nerves

A). 12 nerves Have both somatic and autonomic functions.

B). Summary Anterior of the Brain to Posterior

I. Olfactory
Sensory

nerves for smell

II. Optic
Sensory

nerve for vision.

III. Oculomotor
Somatic & Parasympathetic:

control of extrinsic eye muscles and pupil dilation.

IV. Trochlear
Somatic

control of muscles that surround the eye.

V. Trigeminal
Sensory & Somatic

control of facial nerves and muscles for chewing.

VI. Abducens
Somatic

muscle control of lateral movement of the eyeball.

VII. Facial
Sensory, Somatic & Parasympathetic

control over facial expression and taste.

VIII. Vestibulocochlear or Auditory Nerve
Sensory

nerve for hearing.

IX. Glossopharyngeal
Sensory, Somatic & Parasympathetic

control over taste, the tongue and the pharynx.

X. Vagus
Primary Parasympathetic

nerve with some Somatic and Sensory functions. Controls visceral organs.

XI. Accessory
Somatic

control over larynx, pharynx and sternocleidomastoid muscles

XII. Hypoglossal
Somatic

control over the tongue.

II). Spinal Nerves

A). 31 pairs of spinal nerves

Spinal roots

Rami

Nerve Plexus are interlaced nerve networks that form when the rami join together.

B). Somatic and Sensory nerves

1). C1 to C8 cervical nerves

a). Cervical plexus

Deep in neck under sternocleidomastoid muscle.

Works muscles in the neck, scapulae, trapezius, and diaphragm. (C3 to C4)

Sensory skin in neck, ear, and chest.

b). Brachial plexus

Found partly in the neck and axilla.

All of the nerves that innervate the upper limbs. (C5 to C8)

i). Axillary nerve: Deltoid & Teres minor

ii). Musculocutaneous nerve: Biceps brachii, brachialis and skin.

iii). Median nerve: Flexor muscles, wrist & fingers.

iv). Ulnar nerve: flexors not covered by median nerve. (Funny bone pain)

v). Radial nerve: Extensor muscle and skin.

2). T1 to T 12 thoracic nerves

a). Intercostal nerves

Supply intercostal muscles, abdominal wall and branch into the skin.

3). L1 to L 5 lumbar nerves

a). Lumbar plexus

L1 to L4 Innervates abdominal wall and interior and medial thigh.

i). Femoral nerve: Skin and quadriceps.

ii). Obturator nerve: Adductor muscles

iii). Saphenous nerve

4). S1 to S5 sacral nerves

a). Sacral plexus

L4 to S4 Buttock and lower limb

i). Sciatic nerve: Posterior thigh, hamstrings, flexors and extensors

ii). Tibial nerve: part of sciatic Posterior calf and foot.

iii). Common fibular nerve (peroneal): part of sciatic. Knee joint and anterolateral lower leg muscles.

5). C0 coccygeal nerve

III). Innervation of joints

Hilton’s Law:

Any nerve serving a muscle producing

movement at a joint also innervates the

joint itself and the skin over that joint.

IV). Innervation of skin

Dermatomes:

V). Reflex Arc

stimulus receptor

sensory neuron integration center

motor neuron effector

A). Definition

A reflex is involuntary rapid predictable motor response to a stimulus.

It is a spinal response that occurs without any input from the brain.

B). Necessary Components

1). Receptor

2). Sensory neuron

3). Integration Center:

4). Motor neuron:

5). Effector:

C). Classification

1). Autonomic:

2). Somatic:

D). Types

1). Spinal reflexes

a). Stretch & Deep Tendon

Control the rate and amount of stretch by contracting and relaxing muscle.

Muscle tone is adjusted reflexively in response to posture

i). Stretch Reflex:

Muscle contraction in response to muscle stretch or increased length.

ii). Deep Tendon Reflex:

Muscle lengthening in response to muscle contraction or shortening.

ie. Patellar (Knee jerk response)

process

Strike patellar tendon (stimulus)

Stretches the quadriceps muscle (receptor)

Stimulates muscle spindle (sensory neuron)

Afferent impulse to spinal column (integration center)

Impulses inhibit contraction of antagonist muscle (motor neuron)

Results in contraction of quadriceps and inhibition of hamstring. (effector)

b). Flexor Reflex

Withdrawal of body part in response to a painful stimulus. (either real of perceived)

c). Crossed Extensor Reflex

Withdrawal of body part while simultaneously extending the opposite of the body to maintain support.

d). Superficial Reflexes

Response to gentle cutaneous stimulation.

ie. Plantar Reflex:

VI. Autonomic Nervous System

(parasympathetic & sympathetic)

if you could control this system think in terms of:

Fight or flight: what do you do when there is a tiger in the room

Maintenance: what do you do when you are "vegging out" on the Lazy Boy.

A). Summary

Involuntary nervous system or visceral motor nervous system.

Functions in coordination with the somatic and sensory system and higher brain functions.

Both systems are fully integrated.

Dual system with the parasympathetic and sympathetic system innervating the same organs but causing opposite effects.

Sympathetic: Fight or Flight (tiger in the room)

Parasympathetic: Maintenance ("vegging out" on the Lazy Boy)

B). Comparison to Somatic Nervous System

1). Effectors

Somatic:

Skeletal muscle (only)

Autonomic:

Smooth muscle

Cardiac muscle

Glands

2). Efferent Pathways

Somatic: cell body in CNS axon attaches to skeletal muscle.

Conduction of impulses very fast

Autonomic: 2 neuron chain

Cell body of first neuron in the CNS

2^nd neuron outside CNS and attached to effector organ.

Conduction of impulses slower.

2). Neurotransmitter Effects

Somatic: Always excitatory

Autonomic: Excitation or Inhibition

C). Differences in Parasympathetic & Sympathetic Divisions

1). Functional Role

Parasympathetic: Maintenance functions

Conserves & stores energy

Sympathetic: Prepares the body for emergencies

Intense muscular activity

Fight or Flight

2). Origin sites

Parasympathetic: Brain & Sacral Spinal Cord

Sympathetic: Thoracic-Lumbar Spinal Cord

3). Length of ganglionic fibers

4). Neurotransmitters

Parasympathetic: Acetylcholine

Sympathetic: Some Acetylcholine in preganglia (first neuron that connects to the second neuron) but postganglia release Norepinephrine (common term Adrenaline) this goes to the effectors.

D). Parasympathetic Division (Maintenance division)

(When you are "vegging out" on the lazy boy you do not want your heart racing. This is a time to digest your hamburger and lounge around)

1). Parasympathetic fibers do not run in spinal nerves. (Vagus nerve is a cranial nerve, so are many of the parasympathetic nerves)

2). Nerves arise from the cranial, (brainstem) and the sacral region.

3). Nerves involved

i). Oculomotor nerves: constrict pupils focus on objects

ii). Facial nerves: activates glands

lacrimal glands & salivary glands

(Think of the oppisite when you are exicited your mouth dries up because the last thing you need is to process food)

iii). Glossopharyngeal nerves: salivary glands

iv). Vagus nerves:

Serves most of the visceral organs

Cardiac plexus: Slows the heart rate

Pulmonary plexus

Esophageal plexus: liver, gallbladder, stomach, small intestine, kidneys, pancreas, large intestine. (This is independent of the spinal cord)

5). Sacral nerves: pelvic organs, bladder, genitals & large intestine.

E). Sympathetic Division (fight or flight)

Innervates visceral organs, adrenal glands, sweat glands and hair raising glands and vascular smooth muscle.

When the tiger is in the room you do not want blood and energy going tot he visceral organs to digest your dinner you want blood going to the muscles (vascular dilation) and when you are running you are producing heat so you need to sweat)

Functions of Sympathetic and Parasympathetic Divisions

Look at this table and think of how to balance resources when there is a tiger in the room.

Organ/Gland

Parasympathetic

Sympathetic

Relaxing in the lazy boy

There is a tiger in the room

Cellular metabolism

-------------

Increases

Sweat gland,

Adrenal Glands,

Hair raising muscle

----------------

Stimulates

Digestion

Stimulates

Inhibits

Heart muscle

Heart rate

Decreases

Increases

Coronary

Blood vessels

Constricts

Dilates

Blood Vessels

-----------

Constricts visceral

Dilates skeletal muscle

Mental alertness

---------------

Increases

Bladder

Promotes voiding

Inhibits voiding

I. Olfactory Sensory nerves for smell
II. Optic Sensory nerve for vision.
III. Oculomotor Somatic & Parasympathetic: control of extrinsic eye muscles and pupil dilation.
IV. Trochlear Somatic control of muscles that surround the eye.
V. Trigeminal Sensory & Somatic control of facial nerves and muscles for chewing.
VI. Abducens Somatic muscle control of lateral movement of the eyeball.
VII. Facial Sensory, Somatic & Parasympathetic control over facial expression and taste.
VIII. Vestibulocochlear or Auditory Nerve Sensory nerve for hearing.
IX. Glossopharyngeal Sensory, Somatic & Parasympathetic control over taste, the tongue and the pharynx.
X. Vagus Primary Parasympathetic nerve with some Somatic and Sensory functions. Controls visceral organs.
XI. Accessory Somatic control over larynx, pharynx and sternocleidomastoid muscles
XII. Hypoglossal Somatic control over the tongue.

	Spinal roots
	Rami
	Nerve Plexus are interlaced nerve networks that form when the rami join together.

	Deep in neck under sternocleidomastoid muscle.
	Works muscles in the neck, scapulae, trapezius, and diaphragm. (C3 to C4)

	Found partly in the neck and axilla.
	All of the nerves that innervate the upper limbs. (C5 to C8)

stimulus		receptor
sensory neuron		integration center
motor neuron		effector

	Control the rate and amount of stretch by contracting and relaxing muscle.
	Muscle tone is adjusted reflexively in response to posture

	Afferent impulse to spinal column (integration center)
	Impulses inhibit contraction of antagonist muscle (motor neuron)

	Involuntary nervous system or visceral motor nervous system.
	Functions in coordination with the somatic and sensory system and higher brain functions.

	Sympathetic: Fight or Flight (tiger in the room)
	Parasympathetic: Maintenance ("vegging out" on the Lazy Boy)

	Cell body of first neuron in the CNS
	2^nd neuron outside CNS and attached to effector organ.
	Conduction of impulses slower.

	Cardiac plexus: Slows the heart rate
	Pulmonary plexus
	Esophageal plexus: liver, gallbladder, stomach, small intestine, kidneys, pancreas, large intestine. (This is independent of the spinal cord)

Organ/Gland	Parasympathetic	Sympathetic
	Relaxing in the lazy boy	There is a tiger in the room
Cellular metabolism	-------------	Increases
Sweat gland, Adrenal Glands, Hair raising muscle	----------------	Stimulates
Digestion	Stimulates	Inhibits
Heart muscle Heart rate	Decreases	Increases
Coronary Blood vessels	Constricts	Dilates
Blood Vessels	-----------	Constricts visceral Dilates skeletal muscle
Mental alertness	---------------	Increases
Bladder	Promotes voiding	Inhibits voiding