Intro to Nervous System 1

Question 1

What comprises the CNS?

Answer 1

Brain and spinal cord

Question 2

What comprises the PNS?

Answer 2

Nerves and ganglia

Question 3

What is a ganglion?

Answer 3

A group of neuron cell bodies outside of the PNS.

Question 4

What does the somatic nervous system do?

Answer 4

It supplies body parts that we are consciously aware of and have conscious control of – skin, fascia, skeletal muscles, and bones in the body wall and limbs = “the outer shell of the body”

Question 5

What does the autonomic nervous system do?

Answer 5

It has motor only; supplies viscera (internal organs), smooth and cardiac muscle, and glands – roughly speaking, those structures we have no conscious perception or control of - “the inner guts of the body”. Innervates smooth muscle in the wall of blood vessels - important role in controlling blood vessel diameter and peripheral resistance to blood flow.

Question 6

What are multipolar neurons?

Answer 6

Neurons with more than two processes (generally have many dendrites and one axon); most neurons within the CNS, including motor neurons that innervate (supply) skeletal muscles.

Question 7

What type of neurons are most of the neurons in the CNS?

Answer 7

multipolar neurons

Question 8

What are pseudo-polar neurons?

Answer 8

Neurons that carry sensory information (touch, pain, etc.) to the CNS; most are dorsal (posterior) root ganglion (DRG), or sensory, cells. They have a single short process arising from the cell body that branches into two longer processes – the peripheral process and the central process.

Question 9

Describe motor neurons

Answer 9

project FROM the CNSmultipolar cells in gray matter of spinal cord innervate (supply) an effector (e.g., a muscle or gland)

Question 10

Describe sensory neurons

Answer 10

project TO the CNSe.g., dorsal root ganglion (pseudounipolar) cellsbring information from the periphery (e.g. – skin) to the CNS

Question 11

Describe grey matter

Answer 11

• contains cell bodies of neurons;• organized into clusters of cells called nuclei;• resembles the letter “H” in the spinal cord;• organized into two dorsal (posterior) horns and two ventral (anterior) horns. In some regions, there are also two lateral horns

Question 12

What part of the grey matter deals with sensory processing?

Answer 12

The dorsal horn

Question 13

What part of the grey matter deals with visceral motor(autonomic) output?

Answer 13

The ventral horn

Question 14

Describe white matter

Answer 14

• axons wrapped by fatty myelin• surrounds the “H-shaped” gray matter• cell bodies of neurons absent.• white matter contains tracts (similar to nerves in the PNS)

Question 15

Describe the tracts of white matter

Answer 15

• containing many nerve fibers (axon processes of nerve cells)• interconnecting regions of the spinal cord with the periphery, with each other, and with the brain.• [These tracts are organized in dorsal (ascending, sensory), lateral (descending motor and ascending sensory), and ventral (mainly descending, motor) locations.

Question 16

Describe afferent nerve fibers

Answer 16

Afferents carry impulses to the CNS. Afferents that relay information from the body wall and limbs are called somatic afferents.

Question 17

Describe efferent nerve fibers

Answer 17

Efferents carry impulses from the CNS to “effectors” (muscles, glands, etc. - structures that perform an action). Those that relay information to the body wall and limbs are called somatic efferents. Somatic effferents innervate their targets. Efferents that relay information to smooth muscle, glands, and cardiac muscle are called visceral efferents.

Question 18

What do myotomes form?

Answer 18

Skeletal muscles of the trunk and limbs

Question 19

What do dermatomes form?

Answer 19

The dermis of the skin in posterior regions of the body.

Question 20

What do sclerotomes form?

Answer 20

The bones of the axial skeleton: ribs, vertebrae, and sternum.

Question 21

What are myotomes supplied by?

Answer 21

Somatic efferents AND somatic afferents (afferents inskeletal muscle monitor stretch)

Question 22

Where do somatic efferents terminate?

Answer 22

Only on skeletal muscles (NOT on smooth muscle,glands, or cardiac muscle;

Question 23

What are dermatomes and sclerotomes supplied by?

Answer 23

Somatic afferents (sensory nerve fibers).

Question 24

What does a spinal cord segment give rise to and receive?

Answer 24

Each segment gives rise to the ventral root and receives the dorsal root of a spinal nerve.

Question 25

What are the 5 regions of the spinal cord?

Answer 25

cervical, thoracic, lumbar, sacral and coccygeal

Question 26

What is the conus medularis?

Answer 26

The tapered end of the spinal cord, at about the L1/L2 level.

Question 27

Why is the spinal cord so much shorter than the vertebral column?

Answer 27

Because of differential growth.

Question 28

How many cervical segments are there?

Answer 28

8

Question 29

How many thoracic segments are there?

Answer 29

12

Question 30

How many lumbar segments are there?

Answer 30

5

Question 31

How many sacral segments are there?

Answer 31

5

Question 32

How many coccygeal segments are there?

Answer 32

Just one lonely segment. :(

Question 33

Where does each spinal nerve exit?

Answer 33

Through the intervertebral foramen below its corresponding vertebra. (exception - the C1 nerve exits ABOVE C1)

Question 34

What is the cauda equina?

Answer 34

The long dorsal and ventral roots at the end of the spinal cord, gathered together in a bushy structure within thevertebral canal that resembles a “horse’s tail.” There is no spinal cord below L1/L2, only the cauda equina.

Question 35

Clinically, what is a dermatome?

Answer 35

An area of skin supplied by a single spinal nerve. For example, the T-10 dermatome is a strip of skin at the level of the umbilicus (“belly button”) supplied by the T-10 spinal nerve.

Question 36

Tell me about myotomes

Answer 36

Myotomes consist of all of the muscles (or portions of muscles) innervated by single spinal nerve. Myotomes are complex because most limb muscles are innervatedby more than one spinal nerve. Myotomes are very important in neurological evaluation and can be successively tested in joints to help localize lesions. They are the key to strength testing and to interpreting tendon reflexes.

Question 37

CN I

Answer 37

Name: Olfactory NerveFx: Olfaction

Question 38

CN II

Answer 38

Name: Optic NerveFx: Vision

Question 39

CN III

Answer 39

Name: Oculomotor nerveFx: Eye movement, pupil constriction

Question 40

CN IV

Answer 40

Name: Trochlear nerveFx: Eye movement

Question 41

CN V

Answer 41

Name: Trigeminal nerveFx: Facial sensation, muscles of mastication

Question 42

CN VI

Answer 42

Name: Abducens NerveFx: Eye movement

Question 43

CN VII

Answer 43

Name: Facial nerveFx: Muscles of facial expression, taste, lacrimation, salivation

Question 44

CN VII

Answer 44

Name: Vestibulocochlear nerveFx: Hearing, equilibrium sense

Question 45

CN IX

Answer 45

Name: Glossopharyngeal nerveFx: Pharyngeal muscles, carotid body reflexes, salivation

Question 46

CN X

Answer 46

Name: Vagus nerveFx: Parasympathetics to most organs, laryngeal muscles (voice), pharyngeal muscles (swallowing), aortic arch reflexes

Question 47

CN XI

Answer 47

Name: Spinal accessory nerveFx: Head turning (trapezius and sternomastoid muscles)

Question 48

CN XII

Answer 48

Name: Hypoglossal nerveFx: Tongue movement