Question

Q1. In order for a neuron to move from the absolute to the relative refractory period, a majority of that neuron's sodium channels must have their:

Select one:

a) inactivation gates open
b) activation gates closed
c) inactivation gates closed
d) activation gates open and inactivation gates closed

Q2. Which of the following is NOT true of graded potentials?

Select one:
a) They are produced after the binding of neurotransmitter to receptor
b) they will decrease in magnitude as the current flows away from the initial site
c) they are produced at chemically-gated ion channels
d) they are limited in duration by the refractory period of the membrane

Q3. Assume that a post-synaptic neuron has two pre-syanptic inputs: X and Y. When pre-synapitc neuron X is stimulated, the post-synaptic membrane becomes slightly

Select one:
a) excitatory
b) inhibitory
c) not enough info

Q4. assume that a post-synaptic neuron has two pre-syanptic inputs: X and Y. Given that pre-synaptic neuron X causes hyperpolarization of the post-synaptic membrane, what kind of permeability changes may have occurred in the post-synaptic neuron?

Select one:
a) increase permeability both Ca2+ and K+
b) increased permeability to K+ but not Na+
c) increased permeability to anionic proteins
d) increased permeability to Ca2+
e) increased permeability to both K+ and Na+

Answer 1

Ans 1: (a) inactivation gates open

Explanation: The period from the initiation of the action potential to immediately after the peak is referred as absolute refractory period (ARP). This is the time during which another stimulus given to the neuron will not lead to a second action potential because sodium channels are inactivated during this time. After the ARP, sodium channels begin to recover from inactivation by opening their gates and if a strong stimuli is given to neuron, it may respond again by generating new action potential. This situation will continue until all sodium channels have come out of inactivation. The period during which a stronger than normal stimulus is needed to elicit an action potential is referred to as the relative refractory period (RRP).