PhysioEx Exercise 3 > Activity 1: Overview and Pre-lab Quiz for The Resting Membrane Potential

Explain why increasing extracellular K+ reduces the net diffusion of K+ out of the neuron through the K+ leak channels.

Increasing the extracellular K+ reduces the steepness of the concentration gradient and so less K+ diffuses out of the neuron. There is usually more K⁺ inside the cell relative to the extracellular environment. Increasing extracellular K⁺ reduces the concentration gradient, thus reducing net diffusion of K⁺.

What effect did decreasing the extracellular sodium have on the resting membrane potential?

Only a small change occurred, because the resting neuron is not very permeable to sodium.

Discuss how a change in Na+ or K+ conductance would affect the resting membrane potential.

A change in K+ conductance would have a greater effect on the resting membrane potential than a change in Na+conductance would due to the greater number of K+ channels. A change in K+ conductance would have a greater effect on resting membrane potential than a change in Na+ conductance because the membrane is more permeable to K+.

Explain why increasing extracellular K+ causes the membrane potential to change to a less negative value. How well did the results compare with your prediction?

The membrane potential became less negative because less K+ diffused out. If more K+ stays in it is more positive or less negative. Resting membrane potential is negative because the negative charge inside the cell is greater than the positive charge outside the cell. Increasing extracellular K+ increases the positive charge outside the cell. This decreases the difference between the inside and outside of the cell.

What effect did increasing the extracellular potassium have on the resting membrane potential?

The resting membrane potential became less negative.

Which of the following describes a change from the resting membrane potential?

a receptor potential, a synaptic potential or an action potential

The conducting region of the neuron is the _______.

axon

Which of the following is NOT a functional region of a neuron? - receiving region - conducting region - secretory region - medullary region

last one

Which of the following statements about receptor potentials is FALSE? - They can trigger an action potential. - Odor molecules can act as stimuli - The receptor proteins respond to stimuli - The receptor potential is carried by neuroglia

last one

The channels that provide for the movement of potassium in the resting neuron are _______.

leakage

The typical concentration of sodium is _______.

lower than potassium intracellularly.

Establishing the resting membrane potential requires energy through the use of the _______.

sodium-potassium pump

Discuss the relative permeability of the membrane to Na+ and K+ in a resting neuron.

The resting neuron is approximately 4-5 times more permeable to K+ because of the increased number of K+ leakage channels Membrane permeability of a resting neuron to K+ is four to five times greater than for Na+.

Explain why a change in extracellular Na+ did not significantly alter the membrane potential in the resting neuron?

There are less Na+ leakage channels than K+ leakage channels, and more K+ leakage channels are open A change in extracellular Na+ results in little change to resting membrane potential because the plasma membrane of a neuron is only slightly permeable to Na+ because it contains relatively few Na+ leakage channels. This inhibits net diffusion of Na+ into or out of the cell.