A&P Lab PhysioEx 3

25 July 2022
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14 test answers

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question
Explain why increasing extracellular K+ reduces the net diffusion of K+ out of the neuron through the K+ leak channels?
answer
Reduces the concentration gradient, so less K+ diffuses out of the neuron
question
Explain why increasing extracellular K+ causes the membrane potential to change to a less negative value?
answer
Increasing extracellular K+ increases the positive charge outside the cell, making the inside of the cell (membrane potential) more negative.
question
Explain why a change in extracellular Na+ did not alter the membrane potential in the resting neuron?
answer
Plasma membrane of a neuron contains relatively few Na+ leakage channels. This inhibits net diffusion of Na+ into or out of the cell.
question
Discuss the relative permeability of the membrane to Na+ and K+ in a resting neuron?
answer
The membrane is highly permeable to K because of the amount of K leak channels that are open. The membrane has a low permeability to Na ions because there are very few Na leak channels, and Na channels are closed.
question
Discuss how a change in Na+ or K+ conductance would affect the resting membrane potential?
answer
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+.
question
Define the term threshold as it applies to an action potential
answer
The level of stimulation required to trigger a neural impulse.
question
What change in the membrane potential (depolarization or hyperpolarization) triggers an action potential
answer
Depolarization causes change in the membrane potential by Na+ rushing in the interior of the cell.
question
How did the action potential at R1 (or at R2) change as you increased the stimulus voltage above the threshold voltage?
answer
The action potential didn't change as the stimulus voltage increased. This is because once the threshold is met, the event is all or none, not graded.
question
An action potential is an "all-or-nothing" event. Explain what is meant by this phrase.
answer
This means that once the threshold is met, an action potential occurs. If the stimulus is too small an action potential does not occur.
question
What part of a neuron was investigated in this activity?
answer
The trigger zone was investigated. This is where the axon hillock and the initial segment come together.
question
Define inactivation as it applies to a voltage gated sodium channel.
answer
Voltage gated Na+ channels are inactivated when they no longer allow Na+ to pass through them.
question
Define the absolute refractory period.
answer
The time when no action potential can be generated, no matter the strength of the stimulus.
question
How did the threshold for the second action potential change as you further decreased the interval between the stimuli?
answer
The threshold for the second action potential will be higher, which indeed requires increased strength in the stimulus.
question
Why is it harder to generate a second action potential during the relative refractory period?
answer
A stronger stimulus is required because voltage gated K+ channels that oppose depolarization are open during this time