Question

Which of the following post-synaptic responses would NOT cause an EPSP:

	A.	ligand-gated Cl- channels close
	B.	ligand-gated Ca2+ channels open
	C.	ligand-gated Na+ channels open
	D.	ligand-gated K+ channels open

Answer 1

D. ligand-gated K+ channels open

• EPSP (Excitatory post synaptic potential) is positive change in membrane and makes generation action potential easier. It results due to influx of positive charge or efflux of negative charge.
• Opening of Na and Ca channel will lead to influx of Na and Ca respectively, therefore they will cause EPS.
• IPSP (Inhibitory post synaptic potential) is decrease in membrane potential and makes generation of action potential less likely. It results from influx of negative ion (like Cl) or efflux of positive Ion (like K)
• Opening of K channel will cause efflux of K (because concentration of K is higher in intracellular space), therefore it will cause IPSP.
• Closing of Cl channel will stop influx of Cl, and will result in EPSP