Physioex 3
Neurophysiology of Nerve Impulses
ACTIVITY 1 The Resting Membrane Potential
1. Explain why increasing extracellular K+ reduces the net diffusion of K+ out of the neuron through the K+ leak channels.
If the extracellular K+ increases then the concentration of intracellular K+ will decrease causing a decrease in the steepness of the concentration gradient and fewer K+ ions would be drawn out.
2. 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?
If extracellular K+ is increased then the intracellular K+ will decrease. Fewer intracellular K+ ions would result in the membrane potential being less negative. The results of my prediction were the same.
3. Explain why a change in extracellular Na+ did not alter the membrane potential in the resting neuron.
There are less Na+ leak channels than K+ leak channels, and more of the K+ channels are open.
4. Discuss the relative permeability of the membrane to Na+ and K+ in a resting neuron.
Membrane permeability to Na+ is very low because there are only a few Na+ leak channels. The membrane is more permeable to K+ because of the higher number of K+ leak channels.
5. Discuss how a change in Na+ or K+ conductance would affect the resting membrane potential.
The resting membrane potential depends on the intracellular and extracellular concentrations of the Na+ and K+ ions. Conductance would change the concentration gradient causing either Na+ or K+ to flow into or out of the cell which would change the resting membrane potential.
ACTIVITY 2 Receptor Potential
1. Sensory neurons have a resting potential based on the efflux of potassium ions (as demonstrated in Activity 1). What passive channels are likely found in the membrane of the olfactory receptor, in the membrane of the Pacinian corpuscle, and in the membrane of the free nerve ending?
Chemical and pressure channels.
2. What
ACTIVITY 1 The Resting Membrane Potential
1. Explain why increasing extracellular K+ reduces the net diffusion of K+ out of the neuron through the K+ leak channels.
If the extracellular K+ increases then the concentration of intracellular K+ will decrease causing a decrease in the steepness of the concentration gradient and fewer K+ ions would be drawn out.
2. 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?
If extracellular K+ is increased then the intracellular K+ will decrease. Fewer intracellular K+ ions would result in the membrane potential being less negative. The results of my prediction were the same.
3. Explain why a change in extracellular Na+ did not alter the membrane potential in the resting neuron.
There are less Na+ leak channels than K+ leak channels, and more of the K+ channels are open.
4. Discuss the relative permeability of the membrane to Na+ and K+ in a resting neuron.
Membrane permeability to Na+ is very low because there are only a few Na+ leak channels. The membrane is more permeable to K+ because of the higher number of K+ leak channels.
5. Discuss how a change in Na+ or K+ conductance would affect the resting membrane potential.
The resting membrane potential depends on the intracellular and extracellular concentrations of the Na+ and K+ ions. Conductance would change the concentration gradient causing either Na+ or K+ to flow into or out of the cell which would change the resting membrane potential.
ACTIVITY 2 Receptor Potential
1. Sensory neurons have a resting potential based on the efflux of potassium ions (as demonstrated in Activity 1). What passive channels are likely found in the membrane of the olfactory receptor, in the membrane of the Pacinian corpuscle, and in the membrane of the free nerve ending?
Chemical and pressure channels.
2. What