Question

QUESTION 59

1. Which, if any, of these is an example of an IPSP in a typical neuron?

   		a. a voltage change from 0 mV to +0.35 mV
   		b. a voltage change from -70 mV to -68 V
   		c. a voltage change from +35 mV to 0 mV
   		d. a voltage change from -70 mV to -72 mV
   		e. None of the above.

Answer 1

Question 59.

Which, if any of these, is an example of IPSP in a typical neuron?

Answer: d) a voltage change from -70 mV to -72 mV.

Explanation:

- Inhibitory post-synaptic potential (IPSP) is a local potential in which there is a slight hyperpolarization of post-synaptic membrane. A voltage change from -70 mV to -72 mV is an example of hyperpolarization and the resting membrane potential (RMP) of a neuron is -70 mV. Hence, the only possible example of IPSP is a voltage change from -70 mV to -72 mV.

- This IPSP occurs due to opening of ligand gated potassium channels (K+ efflux) and chloride (Cl-) influx. This IPSP causes release of inhibitory neurotransmitter from pre-synaptic membrane which binds to the post-synaptic membrane causing its hyperpolarization. This hyperpolarization of post-synaptic membrane inhibits the generation of action potential from the post-synaptic membrane.

Option a) a voltage change from 0 mV to +3.5 mV and option b) a voltage change from -70 mV to -68 mV are examples of depolarization hence neither can be an inhibitory post synpatic potential (IPSP) as IPSP is always caused by hyperpolarization. Depolarization of post-synaptic membrane produces excitatory post synaptic potential (EPSP).

Option c) a voltage change from +35 mV to 0 mV is caused by hyperpolarization but the resting membrane potential (RMP) of a neuron is -70 mV hence it can not be an IPSP.