Chapter 7: Spinal CordAnatomy & Physiology

Kasprowicz

Quick Review• Gray matter vs. white matter

- location

- composition

Terminology:

CNS neurons - nuclei; tracts

PNS neurons - ganglia; nerves

Location & Appearance• cylindrical; ~ 17 inches (42 cm)

long• Glistening white appearance• Protected by the vertebrae & the

meninges• ~ size of thumb in diameter;

enlargements in the cervical and lumbar regions (near limbs)

Location & Appearance• Continuous with the medulla

oblongata; extends to the first or second lumbar vertebrae

(just below the ribs)• Ends in a collection of spinal

nerves called the cauda equina

General Functions• 2 way impulse conduction

pathway to and from the brain from the body

• Major reflex

center

Video Preview of Spinal Cord

Spinal Cord Anatomy· Internal gray matter (mostly cell

bodies); resembles a butterfly or the letter H

· Surrounds the central canal containing cerebrospinal fluid

Spinal Cord Anatomy·Dorsal (posterior) horns – contain interneurons and cell bodies of sensory neurons

· If damaged, sensation from the body will be lost

·Anterior (ventral) horns – contain cell bodies of motor neurons

Spinal Cord Anatomy· Exterior white matter

conduction tracts

·Sensory tracts – (afferent); tracts conducting sensory impulses to the brain

·Motor tracts – (efferent); carry impulses from the brain to skeletal muscles

· one side to the other

Chapter 7: Peripheral Nervous System

Anatomy & Physiology

Kasprowicz

Peripheral Nervous System

• Contains nerves (bundles of neuron axons) & ganglia (groups of neuron cell bodies) found outside the CNS

• Includes both sensory (afferent) and motor (efferent) nerves

Structure of a Nerve in the PNS

• Similar “packaging” to a muscle fiber

• Neuron fibers (axons) are bundled by connective tissue

Structure of a Nerve in the PNS

Structure of a Nerve in the PNS

• Individual nerve cell process is covered by the endoneurium.

• Groups of nerve cell processes are bundled together into a fascicle, surrounded by the perineurium.

• Fascicles are bound together by

the epineurium = NERVE

Cranial Nerves

• 12 pairs that innervate the head

and neck; the vagus nerves

travel to the thoracic and

abdominal cavities

Cranial Nerves: Function

I. Olfactory (bulb & tract)

sensory; sense of smell

II. Optic

sensory; sense of sight (vision)

Cranial Nerves: Function

III. Oculomotor

midbrain eye; motor control of the eyeball, eyelid, lens shape & pupil size

IV. Trochlear

midbrain eye; motor control of eye muscle

Cranial Nerves: Function

V. Trigeminal

pons face

- sensory impulses from skin on face; inside nose & mouth

- activate chewing (motor)

Cranial Nerves: Function

VI. Abducens

pons eye; motor control of eye muscle

Cranial Nerves: Function

VII. Facial

pons face;

- motor control of facial muscles, lacrimal & salivary glands

- sensory impulses from taste buds

Cranial Nerves: Function

VIII. Vestibulocochlear

inner ear brainstem;

sensory information

- vestibular (balance)

- cochlear (hearing)

Cranial Nerves: Function

IX. Glossopharyngeal

medulla throat;

- motor control of swallowing

- sensory input from taste buds & pressure receptors in carotid artery

Cranial Nerves: Function

X. Vagus

medulla thorax & abdomen

sensory/motor impulses from & to throat, voicebox, viscera of chest & abdominal cavities

(parasympathetic motor neurons)

Cranial Nerves: Function

XI. Accessory

medulla & superior spinal cord muscles of neck/back

motor control of

sternocleidomastoid &

trapezius muscles

Cranial Nerves: Function

XII. Hypoglossal

medulla tongue

sensory & motor impulses from/to the tongue

Mnemonic Device

•Oh, oh, oh, to touch and feel very good velvet, ahhh.

PNS: Spinal Nerves & Nerve Plexuses

Anatomy & Physiology

Kasprowicz

Spinal Nerves • 31 pairs consisting of the

ventral & dorsal roots of the spinal cord

• ½ long• Divide into the dorsal rami &

ventral rami

Spinal Nerves

Spinal Nerves • Dorsal rami skin/muscles of

posterior body trunk• Ventral rami

- T1-T12 (rib muscles,

skin/muscles of anterior &

lateral trunk)

- form plexuses

Plexuses• Complex networks of nerves

serving the sensory & motor needs of the limbs

1) cervical plexus

diaphragm, shoulder &

neck

Plexuses

2) brachial plexus shoulder, upper thorax,

arm & hand

3) lumbar plexus lower abdomen, hip & thigh

4) sacral plexus lower trunk, glutes, leg & foot

Lumbar

Plexus

Sacral Plexus

1

2

3

4

5

6

7

8

9

10

11

12

13

A

B

CD

E

F

A

B

C

D

E

F

G

H

I

J

front

back

L1

L2

L3

D3D2

D1

B3

B2

B1

C1

A

B C D

E

F