BIO 455) Uhons 1&2, Credits 4 5. (6 points) uppose a neuron is permeable to THRE

Question

BIO 455) Uhons 1&2, Credits 4 5. (6 points) uppose a neuron is permeable to THREE ions whose Nernst potentials are a Cl -80 mV K+ 74 mV Ca++ -70 mV suppose a brief depolarization occurs that drives the membrane potential from rest at -80 mV to -75 mV as shown in the figure. -75 mV -80 mV a) an increase in the permeability of which ion(s) might be SOLELY responsible (that is, without any permeability to other ions) b) a decrease in the permeability of which ion might be responsible c) how many possible ways could permeability changes create the depolarization; list (this is tricky)

Explanation / Answer

1. At resting membrane potential inside of cell is negative which means more potassium is inside and sodium is outside on stimulation permeability of sodium increases and cause depolarization.

2 permeability of potassium decreases during depolarization therefore polarity is reversed during depolarization

3 depolarization occurs due to Influx(moving inside the cell) of Cations (positively charged ions) or efflux(moving outside the cell) of anions(negatively charged ions)

Therefore it can occur by

1. Increase in permeability of sodium

2. Decrease in permeability of potassium

3. Increase in permeability of calcium

4. Decrease in permeability of chlorine.

Note: although both sodium and potassium are positively charged but here relative positive and negative is seen. Therefore sodium is considered positive and potassium is negative.

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