Powerphys Lab 3 - Action Potentials PDF

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Action Potentials...

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Lab 3 (= Lab 4 in PowerPhys): Action Potentials Total marks: /6 1.

Where was membrane potential measured? (1 mark)

The membrane potential was measured at the trigger zone. 1.

At which stimulation voltage(s) did you see decremental conduction of graded potential from axon hillock to axon? (1 mark)

Decremental conduction of graded potential from axon hillock to axon occurs at 2 V stimulation. 1.

What was the membrane potential at the axon hillock when the action potential was generated? (1 mark)

The membrane potential at the axon hillock was 31.3 mV (stimulus of 6V) and 30.2 mV (stimulus of 8V) when the action potentials were generated. 1.

In Experiment 1, discuss why the amplitude of the action potential did not increase as stimulation voltage increased above threshold. (1 mark)

The amplitude of the action potential did not increase as stimulation voltage increased above threshold because action potentials are said to be all-or-none signals, meaning they either occur fully or they do not occur at all. Increased stimulation voltage does not increase the amplitude of action potentials because a refractory period is needed between stimulation. 1.

In Experiment 2, explain why the number of action potentials generated varied with increased stimulation frequency. (1 mark)

The number of action potentials generated in experiment 2 varied with increased stimulation frequency because as stimulation frequency increased, the time period between stimulation decreased. When there is a high frequency of supra threshold stimulus, the number of action potentials produced decreases because the neuron needs time for the refractory period to conclude before firing another action potential. 1.

ECF potassium levels affect resting membrane potential. Hyperkalemia (excessive levels of potassium in the blood) and hypokalemia (abnormally low blood potassium levels) both affect the function of nerves and muscles. Explain how hyperkalemia will initially affect the resting membrane potential and the generation of an action potential. (1 mark)

Hyperkalemia will increase the concentration of potassium outside of the cell, making the concentration gradient lower, weakening the driving force of K+ out of the cell. This will make the resting membrane more positive, as there is a higher concentration of K+ ions inside the cell at rest. Action potentials will be generated more quickly because the cell will be dopolarized faster....