ch 12 (nervous tissue)

Question 1

what does the central nervous system (CNS) consist of?

Answer 1

the brain and spinal cord.
- the spinal cord is connected to the brain through the foramen magnum of the occipital bone

Question 2

what does the peripheral nervous system (PNS) consist of?

Answer 2

it consists of all nervous tissue outside the CNS: some components include
- nerves
- ganglia
- enteric plexuses
- sensory receptors

Question 3

nerve

Answer 3

is a bundle of axons located in the PNS.

Question 4

ganglia

Answer 4

(= swelling or knot; singular is ganglion)
they are small masses of nervous tissue, consisting primarily of neuron cell bodies.
- <a>
- located in the PNS.</a>

Question 5

how many cranial nerves emerge from the brain?

Answer 5

twelve pairs!

Question 6

how many pairs of spinal nerves emerge from the spinal cord?

Answer 6

thirty-one pairs!

Question 7

sensory receptor

Answer 7

refers to a structure of the nervous system that monitors changes in external and internal environments.
- examples: touch receptors; olfactory receptors; etc.

Question 8

what are the 3 subdivisions of the peripheral nervous system - PNS?

Answer 8

1.) somatic nervous system (SNS)
2.) autonomic nervous system (ANS)
3.) enteric nervous system (ENS)

Question 9

what does the somatic nervous system (SNS) consist of?

Answer 9

1.) sensory neurons that convey info to the CNS from somatic receptors in the head, body wall, limbs, and special senses.
2.) and motor neurons that conduct impulses from the CNS to skeletal muscles only.

Question 10

nodes of Ranvier

Answer 10

gaps in the myelin sheath

Question 11

neurolemma

Answer 11

outer nucleated cytoplasmic layer of a Schwann cell, which encloses the myelin sheath.
ONLY found around axons in the PNS.

Question 12

myelin sheath

Answer 12

consists of up to 100 layers of Schwann cell membrane.

Question 13

nucleus

Answer 13

is a cluster of neuronal cell bodies located in the CNS.

Question 14

tract

Answer 14

is a bundle of axons that is located in the CNS.
- they interconnect neurons in the spinal cord & brain.

Question 15

summation

Answer 15

the process by which graded potentials add together.

Question 16

graded potential

Answer 16

small deviation from the resting membrane potential that makes the membrane more or less polarized.

Question 17

when a membrane is hyperpolarized, it is…

Answer 17

…more negative inside.

Question 18

when a membrane is polarized, it is…

Answer 18

…less negative inside.

Question 19

action potential (AP) / impulse

Answer 19

sequence of quick events that decrease and reverse the membrane potential, and then restore it to its original resting state; it has two phases:
1.) depolarization
2.) repolaraization

Question 20

what does endoneurium consist of?

Answer 20

collagen fibers, fibroblasts and macrophages.

Question 21

what does the perineurium consist of?

Answer 21

thick CT, 15 layers of fibroblasts and collagen fibers.

Question 22

what does epineurium consist of?

Answer 22

fibroblasts and thick collagen fibers.

Question 23

rami = ?

Answer 23

= branches

Question 24

what are the 5 plexuses?

Answer 24

cervical, brachial, lumbar, sacral, and coccygeal.

Question 25

which are the thoracic nerves / intercostal nerves that do not belong to a plexus?

Answer 25

anterior rami of spinal nerves T2-T12.

Question 26

cervical plexus:

Answer 26

C1-C4
some C5
- supplies skin and muscles of the head, neck, and superior shoulders and chest.

Question 27

brachial plexus:

Answer 27

C5-C8
some of T1

Question 28

explanation of the complexity of the brachial plexus!!

Answer 28

• anterior rami form roots.
• roots unite to form trunks (superior, middle, inferior trunks)
• trunks diverge into divisions (anterior & posterior)
• in axillae, divisions unite to form cords (lateral, medial & posterior cords)
• the branches form the principle nerves of the brachial plexus.

Question 29

what are the 5 large terminal branches that arise from the brachial plexus?

Answer 29

1.) axillary nerve
2.) musculocutaneous nerve
3.) radial nerve
4.) median nerve
5.) ulnar nerve

Question 30

axillary nerve

Answer 30

deltoid & teres minor muscles

Question 31

musculocutaneous nerve

Answer 31

anterior arm muscles.

Question 32

radial nerve

Answer 32

posterior aspect of arm and forearm.

Question 33

median nerve

Answer 33

most muscles of anterior forearm and hand.

Question 34

ulnar nerve

Answer 34

anteromedial muscles of forearm and most of hand.