em to es hig rmal t wi lent e fol 17. Complete the following table (3 pts.) Na\'
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em to es hig rmal t wi lent e fol 17. Complete the following table (3 pts.) Na' Location of highest concentration intracellular or extracellular fluid) Intraaatlular de rn LI Direction of diffusion in or out) in a cell at rest Charge contributed to inside of membrane due to diffusion stiue NC Na concentration change following inhibition of Na -K pump in a normal nerve 1S. How does intracellular concentration sl cell (1 pt.)? 19. What will this do the flux of Na (1 pt.)? 20. How will this affect the membrane potential (1 pt.)? 21. Will inhibition of the Na'-K increase or decrease the likelihood of an action potential occurring (1 pt.)? 22. If you increase K* concentration in the extracellular fluid bathing a cell, what happens to the rate of its diffusion (1 pt.)? 23, What is the effect of this change on the membrane potential of a cell? Does it depolarize or hyperpolarize (l pt.)? 4Explanation / Answer
18. Normally, when there is no inhibition ,The Na-K pump pumps out 3 Na+ ions out of the cells in exchange of the 2 K+ ions which moves inside the cell .
Inhibition of this pump will cause the increase of the Na+ ions inside the cells and accumulation of the K+ outside the cells .
19. The Na+ movements towards the outside will decreases and finally cease if there is inhibition of the Na-K pump.
However , another type of channels , the sodium calcium antiport will try to decrease the extra sodium ions by exchanging with calcium. So there can be a mild outflux still going on in the cell.
20. Normally , the resting membrane potential is -70mV , which means the inside of the neuron is more negative than the outside . This is due to - Negatively charged proteins, chloride ions , less K+ ions as compared to outside .
When the Na-K pump is inhibited , the accumulation of Na+ inside the cell will the cell more positive on the inside , which means the resting membrane potential will tend towards more positive , i.e. towards zero.
21. The occurence of the action potential requires the neuron to reach the threshold of -55mV which is more positive than -70mV .
This is caused by the opening of sodium channels by the stimulus , which causes the inward movement of sodium .
But when the Na-K pump fails , the sodium will increase inside the cells. As this happens , the inside of the cells becomes more positive, means more nearer to the threshold potential.
So a little stimulus may cause the action potential. But the more positive ions inside the cell will make the attainment of the threshold really difficult . So the action potential generation will be very slow.
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