Please answer all the questions, thank you. 1. A second action potential cannot
ID: 277195 • Letter: P
Question
Please answer all the questions, thank you.
1. A second action potential cannot be generated during the absolute refractory period because.....
Select one:
a. The voltage-gated Na+ is already open.
b. The voltage-gated Na+ channel has not been reset.
c. Voltage gated K+ channels are open.
d. Voltage-gated K+ channels have not been reset.
e. Both A and B are correct.
f. Both C and D are correct.
2. An EPSP is the result of activation of what kind of membrane protein?
Leak channel or Chemically-gated channel
3. Multiple sclerosis is a devastating disease because it...
produces degeneration of nerve terminals in unmyelinated axons.
stops the action of the Na+/K+ pump.
prevents neurotransmitter release in motor neurons.
produces a conduction block at the point of demyelination. (This is my guess)
blocks action potentials by blocking voltage-gated K+ channels.
Explanation / Answer
Q.1
Answer: The voltage-gated Na+ channel has not been reset.
Explanation: Absolute refractory period is a period which is immediately followed by the repetitive firing of nerve fiber,during which a new action potential cannot be generated even though you apply strong stimulus. At the peak of action potetial, all Na+ channels are inactivated and they can not open immediately. Re-activation of Na+ channels is a time dependent process which takes upto minimum of 4-5 minutes to open again. During this period, even though you apply strong stimulus these channels can not be opened. After a refractory period if you apply strong stimulus these channels open again and respond to the stimulus and generates the action potential.