NP1C

Question 1

The insulating material is lipid formed by glial cells and is known as:

Answer 1

myelin

Question 2

the exposed patches of axon membrane are known as nodes of :

Answer 2

Ranvier

Question 3

When a wave of depolarization reaches a lipid insulator, the ion flux is dampened and voltage gated __________________ in the insulated segment do not open

Answer 3

sodium channels

Question 4

describes the way an electrical impulse skips from node to node down the full length of an axon

Answer 4

saltatory conduction

Question 5

Why saltatory conduction?

Answer 5

it is fast, increasing velocity of impulse transmission by 5-50 fold
it conserves energy for the neuron

Question 6

(true/false) All Axons are myelinated

Answer 6

false

Question 7

Who makes myelin?

Answer 7

Oligodendrocytes = glial cells responsible for the synthesis of myelin in the central nervous system

Question 8

axons cannot be regenerated in the ________________

Answer 8

central nervous system

Question 9

One _____________ forms myelin segments for multiple different axons

Answer 9

oligodendrocytes

Question 10

___________ is a predominant membrane lipid constituting myelin. It serves as an excellent insulator that decreases ion flow through the axonal membrane approximately 500-fold. This insulation inhibits the continuous propagation of an action potential.

Answer 10

sphingomyelin

Question 11

supports induction of myelin formation:

Answer 11

Myelin-associated glycoprotein

Question 12

stabilizes the multilamellar structure:

Answer 12

Myelin basic protein

Question 13

_______________ are glial cells responsible for the synthesis of myelin in the peripheral nervous system (PNS)

Answer 13

Schwann cells

Question 14

What is one of the differences between oligodendrocytes and Schwann cells?

Answer 14

Unlike oligodendrocytes, Schwann cells myelinate a single segment of axon

Question 15

When is regeneration of the axon in the peripheral nervous system successful?

Answer 15

Regeneration of the axon may occur, but rein-nervation is only successful if there is a tract guiding the axon sprout to its destination

Question 16

What is very important in the process of rein-nervation ?

Answer 16

neurilemmal tract

Question 17

____________ provide supplemental metabolic support of the axon, highlighted by the fact that non-myelinated fibers are also closely associated with these cells

Answer 17

Schwann Cells

Question 18

Demyelination can be ____________, reflecting damage to the myelin-producing cell or the myelin sheath. The functional result is loss of saltatory conduction.

Answer 18

primary

Question 19

Demyelination can be __________.

Answer 19

secondary

Question 20

What factors from the axon are required for proper myelin maintenance so that if the axon dies (Wallerian degeneration), the myelin sheath will unwind.

Answer 20

Trophic factors

Question 21

if the axons are intact it is considered?

Answer 21

primary demyelination

Question 22

If the axons are degenerate it is?

Answer 22

secondary demyelination

Question 23

What are the causes of primary demyelination?

Answer 23

Viral infection (accompanied by inflammation)
Immune mediated (accompanied by inflammation)

Metabolic damage (no associated inflammation)
Toxins (no associated inflammation)

Question 24

canine distemper virus can infect oligodendrocytes, eliminating their ability to support myelin formation. This is an example of:

Answer 24

primary demyelination

Question 25

Some antigens in the CNS are shielded from the immune system during development so that T cells reacting to these antigens are not deleted. Damage or inflammation in the CNS can result in the inappropriate presentation of these antigens to autoreactive T cells, and the result is autoimmune ___________________. An example is multiple sclerosis

Answer 25

primary demyelination

Question 26

Loss of myelin can result in tissue discoloration and softening that is grossly apparent, the change is known as ______________ (primary demyelination)

Answer 26

malacia

Question 27

Leukoencephalomalacia denotes malacia that is restricted to :

Answer 27

White matter of the brain

Question 28

Developmental shunts between the hepatic portal vein and the caudal vena cava can occur, allowing blood from mesenteric veins to bypass processing by the liver. There are increases in blood ammonia and other small molecules that can be damaging to oligodendrocytes. This is an example:

Answer 28

primary demyelination

Question 29

Bromethalin-based rodenticides are in common use and are often ingested by dogs. Bromethalin causes the layers of myelin to separate and the cytoplasm in these layers to expand. This change is referred to as intramyelinic edema. this is example of:

Answer 29

primary demyelination

Question 30

Can myelin be replaced?

Answer 30

yes, but it is much more efficient in the PNS than the CNS since one Schwann cell is responsible for myelinating a single axon, whereas loss of a single oligodendrocyte can leave 20-50 axons with unmyelinated segments. Both Schwann cells and oligodendrocytes can proliferate (grow rapidly), although the capacity is much greater for Schwann cells.

Question 31

Defects in myelin formation:

Answer 31

hypomyelinogenesis

Question 32

What is the primary function of myelin?

Answer 32

Support saltatory conduction