Physioex 9.0 Exercise 3 Essay

1260 Words Feb 24th, 2013 6 Pages
Activity 1
1. Increasing extracellular K+ reduces the net diffusion of K+ out of the neuron through the K+ leak channels because the membrane is permeable to K+ ions. Therefore, the K+ ions will diffuse down its concentration gradient from a region of higher concentration to a region of lower concentration.
2. Increasing extracellular K+ causes the membrane potential to change to a less negative value because the K+ ions diffuse out across the membrane. My results went well compared to my prediction because I predicted that the resting membrane potential would become less negative.
3. The extracellular Na+ did not alter the membrane potential in the resting neuron because the Na+ channels were mostly closed.
4. Na+ and K+ both have a
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3. The response at R2 after lidocaine application will necessarily be zero because lidocaine blocks the propagation of the action potential from R1 to R2.
4. Fewer action potentials are recorded at R2 when TTX is applied because TTX blocks the voltage-gated Na+ channels between R1 and R2, which blocks the propagation of the action potential from R1 to R2. Lidocaine is not always sensitive to the receptors and TTX causes irreversible damage. Lidocaine is slow at reacting and eventually wears off.
5. Fewer action potentials are recorded at R2 when lidocaine is applied because lidocaine blocks the voltage-gated Na+ channels between R1 and R2, which blocks the propagation of the action potential from R1 to R2.
6. The dentist should inject the lidocaine in the nerve in the gums where the stimulus occurs to block pain perception.
Activity 5
1. Inactivation as it applies to a voltage-gated sodium channel means some voltage-gated sodium channels inactivate after the peak of the action potential. Therefore, the Na+ channel no longer allows Na+ ions to pass through it.
2. Absolute refractory period is the interval at which the second action potential fails. It is also the time after an action potential when the neuron cannot fire a second action potential, no matter how intense the stimulus.
3. As the interval between the stimuli decreases, the threshold for the second action potential increased. My results went well will my prediction because I predicted that the

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