Nervous System Part 2

Question 1

Activation of Na+ channels occurs via a

Answer 1

positive

feedback loop

Question 2

Absolute Refractory Period

Answer 2

During this time it is impossible for the cell to fire another action potential

Question 3

why is it impossible to fire during an absolute refractory period?

Answer 3

Due to all-or-none activation & the voltage-gated Na+ channels’ closed inactivation gates

Question 4

Relative Refractory Period

Answer 4

During this time a larger-than-normal EPSP can elicit an action
potential.

Question 5

relative refractory period is due to

Answer 5

Some Na+ channels resetting to resting state After hyperpolarization

Question 6

Keeps the Action Potential flowing (propagating) in

Answer 6

one direction

Question 7

Δ[K+]ECF

Answer 7

Changes excitability of neurons and other excitable tissue

Question 8

Hyperkalemia

A. 3.5< [K+]ECF < 6 mM (2)

Answer 8

Increases membrane excitability

Depolarizes Vm moving closer to threshold

Question 9

Hyperkalemia

[K+] ECF > 6 mM (2)

Answer 9

Reduces membrane excitability
Depolarizes membrane and cause inactivation of voltage gated Na+
channels

Question 10

Hypokalemia (2)

Answer 10

Reduces membrane excitability

Hyperpolarizes membrane further from threshold

Question 11

Δ[Ca++]ECF

Answer 11

Ca++ binds to external surfaces of Na+ channel setting their excitable state

Question 12

Hypercalcemia

Answer 12

Reduces membrane excitability

Question 13

Hypocalcemia

Answer 13

Increases membrane excitability

Question 14

skipped

5 steps of depolarization

Answer 14

1. a graded potential above threshold reaches the trigger zone
2. voltage gated sodium channels open and sodium enters the axon
3. positive charge flows into adjacent sections of the axon by local current flow
4. local current flow from the active region causes new sections of the membrane to depolarize
5. the refractory period prevents backward conduction. loss of potassium from the cytoplasm depolarizes the membrane

Question 15

myelin functions as an

Answer 15

insulator

Question 16

Saltatory Conduction of AP

Answer 16

AP jumps from node to node

Question 17

what does the myelin sheath do?

Answer 17

speeds up conduction velocity ofAP

Question 18

myelin sheath conserves

Answer 18

axon energy

Question 19

conduction velocity of AP increases if (2)

Answer 19

axons have myelin

with increasing axonal diameter

Question 20

Guillain-Barre Syndrome

Answer 20

demyelination of the CNS

Question 21

Multiple Sclerosis

Answer 21

demyelination of the PNS