Question

12. Which of the following will occur after stimulating a chemically-gated potassium channel located on the cell body of a neuron?

	a.	potassium will enter into the cell body of the neuron and results in generation of depolarizing graded potential
	b.	potassium will exit out of the cell body of the neuron and this results in generation of depolarizing graded potential
	c.	potassium will exit out of the cell body of the neuron and this results in generation of hyperpolarizing graded potential
	d.	potassium will enter into the cell body of the neuron and this results in generation of hyperpolarizing graded potential

Answer 1

For this we first need to know what the normal concentration of potassium is in the extracellular space and inside the neuron.

K+ concentration is 140-150 mEq/L inside the cell and 3.5-5 mEq/L in the extracellular space.

If you open the K+ channel in this situation,K+ will move from its higher concentration (that is in the cell) to lower concentration (outside the cell), resulting in movement of K+ from the cell to extracellular fluid.This will reduce the positive charge inside the neuron and will further bring down the Resting membrane potential(RMP).In normal resting state the neuron is said to be in polarised state in which the inside of the cell is negative relative to the extracellular space,K+ movement out of the neuron will enhance this potential difference and will futher polarise the neuron,this is called hyperpolarization ( bringing RMP below its normal value).

So the correct answer is c.