Physioex 3

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ACTIVITY 1: THE RESTING MEMBRANE POTENTIAL
1. Explain why increasing extracellular K+ reduces the net diffusion of K+ out the neuron through the K+ leak channels? When the diffusion is greater on one side, the other side will slow down.

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 predictions? There are two potassium's for every sodium so the increase of potassium will make it more negative. Prediction was correct.

3. Explain why a change in extracellular Na+ did not alter the membrane potential in the resting neuron? The sodium channels are mostly closed during the resting state.

4. Discuss the relative permeability of the membrane to Na+ and K+ in a resting neuron. The sodium is outside, while the potassium is inside. If one diffuses at a higher rate, the permeability changes.

5. Discuss how a change in Na+ or K+ conductance would affect the resting membrane potential. A increase in potassium will cause a more negative resting 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 is meant by the term graded potential?
Graded potential are changes in the transmembrane potential that cannot spread far from the site of stimulus. 3. Identify which of the stimulus modalities induced the largest amplitude receptor potential in the Pacinian corpuscle. How well did the results compare with your prediction? High Pressure, my prediction was correct.

4. Identify which of the stimulus modalities induced the largest amplitude receptor potential in the olfactory receptors. How well did the results compare with your...
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