An EPP: a. occurs because of Na+ movement inward at the motor end plate region a

Question

An EPP:

a. occurs because of Na+ movement inward at the motor end plate region as a result of permeability changes induced by binding of acetylcholine with end-plate receptor sites.

b. is usually smaller in magnitude than an EPSP.

c. is terminated when Ca^2+ inactivates acetylcholine.

d. both a and b above are correct.

e. all of the above are correct.

Debating on D or E, not sure if C is true.

Which of the following statements concerning receptor potentials is correct

A. Are usually depolarizing of receptors in response to adequate stimuli

B. Are graded potentials

C. Occur in neural cell bodies upon summation of pre synaptic input

D. Both a and b are correct

E. All of the above are correct

Debating between D or E, not sure if C is true. Need explained please.

Which of the following statements concerning action potentials in the heart is correct?

a. the rising phase of the action potential in cardiac autorhythmic cells is due to a rapid Ca2+ influx

b. the rising phase of the action potentil in cardiac contractile cells is due to a rapid Na+ influx

c. the plateau phase of the action potential in cardiac contractile cells is due to a slow Ca2+influx

d. both b and c are correct

e. all of the above are correc

D or E; explain

Explanation / Answer

1) D

Explaination : As action potential reaches towards the synaptic cleft , there is influx of calcium ions that binds to the vesicles containing acetylcholine . The binding of calcium ions to the vesicles causes them to bind to presynaptic membrane which finally ruptures and releases the neurotransmitter , acetylcholine . Hence , it activates acetylcholine .

2) E . The magnitude of receptor potential determines the frequency with which action potentials are generated and is controlled by a) adaptation b) stimulus strength c) temporal summation of successive receptor potentials .

3) E , The rising phase of action potential in cardiac autorhytmic cells i.e. " PACEMAKER TISSUE ( SA NODE & AV NODE ) is due to rapid Calcium influx whereas in cardiac contractile celss is due to rapic Na reflux

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