Question

18. Assume the resting membrane potential of nerve cell to be -70 mV. If five EPSP’s (each with a voltage of 2 mV) and three IPSP’s (each with a voltage of 1 mV) arise in a nerve cell at the same time, what would the resulting graded potential be?

a. In the above question, if the resulting graded potential reaches threshold, what channels would open?

b. When an action potential reaches an axon terminal, what channels would open?

Answer 1

Answer 18:

Resting membrane potential is -70mV

Graded potential by five EPSPs of 2mV each = 5x2 = 10mV

Graded potential by three IPSPs of 1mV each = 3x1 = 3mV

Resulting graded potential = 10mV - 3mV = 7 mV

Final membrane potential = -70mV + 7mV = -63mV.

a): If resulting graded potential reaches the threshold potential, then voltage gated sodium channels open up due to which sodium ions diffuse inside and depolarization occurs.

b): When action potential reaches axon terminal the calcium channels open up due to which calcium enters inside the synaptic cleft which causes neurotransmitters to get released from the vesicles into the synapse at neuromuscular junctions.