CH 3: PNS: fibers of the spinal nerves

Question 1

somatic nerves in the periphery=

Answer 1

the fibers that innervate the muscles, joints and skin of the body wall

Question 2

visceral nerves in the periphery=

Answer 2

innervate the internal organs of the body cavities and blood vessels throughout the body

Question 3

sensory fibers=

Answer 3

afferent

Question 4

motor fibers=

Answer 4

efferent

Question 5

general nerve fibers=

Answer 5

innervate skin, muscles, bones and viscera throughout the body

all nerve fibers in the spinal nerves are general

Question 6

special nerve fibers=

Answer 6

reserved for sensory organs and muscles found only in unique regions in the head (retina, inner ear)

cranial nerves as a group contain both general and special fibers

Question 7

general afferent fibers of the spinal nerves are ____ fibers with cells of origin in the _____

Answer 7

sensory fibers

dorsal root ganglia

Question 8

dorsal root ganglia cells are

Answer 8

round and have only 1 process leaving the cell body.

Question 9

the process from the dorsal root ganglia cells splits into..

Answer 9

1: peripheral branch: which enters the nerve
2: central branch: which passes through the dorsal root to the SC

Question 10

general somatic afferent (GSA) fibers carry:

Answer 10

1: exteroceptive information:
2: proprioceptive information:

Question 11

exteroceptive information from:

Answer 11

from receptors in the skin that mediate pain, temperature and touch

Question 12

proprioceptive information from:

Answer 12

from sensory endings in muscles, tendons, and joints that mediate position sense, muscle length, rate of change of muscle length and muscle contraction

Question 13

general visceral afferent (GVA) fibers carry:

Answer 13

interoceptive information

Question 14

interoceptive information from:

Answer 14

from receptors in visceral structures that mediate data concerning distension and contraction of these structures

Question 15

general efferent fibers are _____ fibers with cells of origin in the ______

Answer 15

motor fibers

spinal cord

Question 16

general somatic efferent (GSE) fibers consist of:

Answer 16

motor fibers
originating from the cell bodies of alpha, beta and gamma motoneurons in lamina IX. These fibers innervate striated skeletal muscles

Question 17

general visceral effect (GVE) fibers consist of:

Answer 17

pre-ganglionic and post-ganglionic autonomic fibers that innervate smooth muscle and cardiac muscle and regulate glandular secretion.

pre-ganglionic fibers from the SC synapse on the cell bodies of post-ganglioic autonomic neurons

Question 18

nerve fibers can be categorized according to:

Answer 18

fiber diameter

conduction velocity of the nerve impulse

sensory vs. motor

Question 19

the larger the diameter of the fiber..

Answer 19

the thicker the myelin sheath and the greater the AP conduction velocity

Question 20

compound nerve=

Answer 20

nerve containing many motor and sensory fibers

Question 21

electrophysiological classification is based on:

Answer 21

the conduction velocities of different types of motor and sensory nerve fibers

Question 22

conduction velocities separate fibers into 3 groups:

Answer 22

A: myelinated
further subdivided

B: myelinated

C: unmyelinated

Question 23

A fiber groups are further divided on the basis of mean conduction velocity and hence fiber size:

Answer 23

A alpha fibers: large diameter; innervate EXTRAFUSAL muscle fibers (striated skeletal muscle outside the muscle spindles)

A gamma fibers: small diameter; innervate INTRAFUSAL muscle fibers (located within muscle spindles)

A beta fibers: intermediate sized; includes fibers that innervate both types of muscle

Question 24

C fibers are subdivided into 2 classes:

Answer 24

sC fibers: postganglionic efferent sympathetic C fibers

drC fibers: afferent dorsal root C fibers

Question 25

sensory fibers are also divided into 4 groups:

Answer 25

I-IV
differentiated chiefly on the basis of diameter (and thus speed of conduction)

also divide fibers into groups according to the sensory receptors they innervate

Question 26

A alpha

Answer 26

motor: axons of alpha motoneurons of lamina IX, innervating extrafusal muscle fibers

Ia: primary afferents of muscle spindles

Ib:afferents of golgi tendon organs, touch and pressure receptors

Question 27

A beta

Answer 27

motor: motor axons innervating both extrafusal and intrafusal (muscle spindle muscle fibers)

II:secondary afferents of ms spindles, touch and pressure receptors and Pacinian corpuscles (vibratory sensors)

Question 28

A gamma

Answer 28

motor: axons of gamma motoneurons of lamina IX, innervating intrafusal fibers (muscle spindles)

Question 29

A delta

Answer 29

III: small, lightly myelinated fibers; touch, pressure, pain and temperature receptors

Question 30

B

Answer 30

motor: small, lightly myelinated preganglionic autonomic fibers

Question 31

C

Answer 31

motor: postganglionic autonomic fiber (all unmyelinated)

IV: unmyelinated pain & temperature fibers