PNS fiber classification (Quiz 5)

Question 1

The formal boundary between the CNS and PNS is hard to see, but is a line where….

Answer 1

oligodendrocytes change to Schwann cells

Question 2

Nerves are large bundles of axons, subdivided into….

Answer 2

fascicles

Question 3

What is the epineurium mainly composed of?

Answer 3

collagen (strong, unbranched, fibers go in 1 direction) and fibroblasts (cells that form new CT)

Question 4

The epineurium is a loose sheath that surrounds peripheral nerves. It is thicker and more substantial around nerve trunks and closer to the spinal cord, and gets thinner at the ends of small branches and terminations. Peripheral nerves have a high tensile strength due to the collagen. What is continuous with the epineurium centrally?

Answer 4

dura mater

Question 5

The perineurium is a thin layer of concentrically arranged cells that has some collagen fibers interspersed. What is the perineurium continuous with centrally?

Answer 5

arachnoid mater

Question 6

The perineurium has perineural cells that have tight cell junction. What does this isolate?

Answer 6

epineural space and endoneural space

Question 7

The perineurium wraps fascicles. Each bundle is associated with a blood vessel. The endothelium of the capillaries are connected by tight junctions. This is a functional equivalent of the arachnoid BBB. This is called the ____________________. It shares many structural features with the BBB with the exception of astrocytes and the glial limiting membranes formed by astrocytes. In order to reach the endoneurial extracellular space, molecules need to cross the perineurium that surrounds the nerve fascicle.

Answer 7

blood nerve barrier (BNB)

Question 8

At the distal ends of a nerve, the perineurium continues, forming _________ of pacinian, meissners corpuscles, muscle spindles, and golgi tendon organs

Answer 8

capsules

Question 9

The _______________ is a loose connective tissue sheath within the perineurium. It surrounds individual fibers and provides isolation

Answer 9

endoneurium

Question 10

The endoneurial tube is a distensible _________ structure containing some matrix of the collagen tissue. It has a nutritive and protective function with properties analogous to the BBB.

Answer 10

elastic

Question 11

The endonerium plays an important role in fluid pressure. By maintaining a light positive pressure in the endoneurial space, it guarantees a constant environment for the nerve. Within the endoneurium, individual nerve fibers are surrounded by a liquid called the ___________________. It is similar to CSF in the CNS. During nerve irritation or injury, the amount of fluid may increase at the site of damage

Answer 11

endoneurial fluid

Question 12

The 3 distinct speeds recorded after peripheral stimulation have been named….

Answer 12

A, B, and C

Question 13

The fibers for the A tracing are A fibers and are myelinated sensory, motor, or both?

Answer 13

both

Question 14

B fibers are myelinated __________ fibers

Answer 14

visceral

Question 15

C fibers are myelinated or unmyelinated?

Answer 15

unmyelinated

Question 16

The other classification system is based on direct measurement of the axonal diameter. The axons are subdivided into….

Answer 16

I, II, III, and IV

Question 17

The other classification system is based on direct measurement of the axonal diameter. What are the myelinated fibers?

Answer 17

I, II, and III

note: I is larger than II, and III has the smallest diameter

Question 18

The other classification system is based on direct measurement of the axonal diameter. What are the unmyelinated fibers?

Answer 18

group IV

Question 19

Both PNS fiber classification systems are used by unmyelinated fibers are generally called….

Answer 19

C fibers not IV

Question 20

The A fibers can be further divided into….

Answer 20

alpha, beta, delta, gamma

A alpha fibers are the largest diameter and the fastest

A delta are the slowest

Question 21

The large axons innervating fibers of skeletal m. are….

Answer 21

A alpha (usually will just say alpha)

Question 22

The smaller axons innervating intrafusal muscle fibers are….

Answer 22

A gamma (usually will just say gamma)

Question 23

Preganglionic ANS fibers are in their own category and are called ______ fibers

test q

Answer 23

B

Question 24

The I fibers are all myelinated afferent. The largest group in I are found in muscle nerves and are split between 2 subdivisions. What are they?

Answer 24

1a= spindle primary fibers
1b= golgi tendon organ fibers

Question 25

Fibers in group II correspond with which group from the other classification system?

Answer 25

A beta

Question 26

Fibers in group III are small myelinated afferents, these are free nerve endings and transmit info on cold, sharp pain, hair movement, and visceral mechanoreception. These fibers correspond with which group from the other classification system?

Answer 26

A delta (usually just called delta fibers)

Question 27

Where are muscle spindles found?

Answer 27

within belly of muscles between extrafusal muscle fibers

Question 28

The specialized fibers that constitute the muscle spindle are known as ______________ and are stretch receptors that primarily detect changes in the length of the muscle. They contribute to fine motor control and providing axial and limb position info

Answer 28

intrafusal fibers

Question 29

What is the purpose of muscle spindles and the stretch reflex?

Answer 29

protect the body from injury caused by over-stretching and to maintain muscle tone

Question 30

Golgi tendon organs are proprioceptors that are specialized sensory receptors located within….

Answer 30

joints, muscles, and tendons

Question 31

Golgi tendon organs are sensitive to what?

Answer 31

tension and pressure

Question 32

As tension in the muscle increases, discharge of the golgi tendon organs ____________

Answer 32

increases