TISSUE EXITABILITY

Question 1

role of Na/K ATPase pump

Answer 1

1. in order for an action potential to occur the gradients of Na and K must be kept constant.
2. but if nothing replaced K in the cell and pumped Na out of the cell eventually the gradients would be destroyed
3. Na/K ATPase pump maintains these gradients

Question 2

tissue excitability

Answer 2

1. it is the change in membrane potential from resting potential to threshold potential.

A. tissue is more excitable if the distance between MP and TP is decreased.

B. if more + ions/Na moves into the cell, depolarization occurs which increases tissue excitability since MP is moving closer to TP and the chances of AP also increases

C. if MP move further from TP, HYPERpolarization occurs, there is more - inside the cell chances of AP decreases including tissue excitability

Question 3

hypokalemia

Answer 3

1. there is more K inside the cell compared to outside.
2. relative permeability of K is higher than of everything
3. hypokalemia is caused when K is lower than normal on the ECF
4. it can be caused by a loss in urine, vomiting, and diarrhea
5. concentration difference between ECF and ICF increases
6. potential gradient increases forcing K to go outside the cell.
7. inside the cell becomes more -, which causes hyperpolarization
8. MP moves away from TP decreasing tissue excitability and action potential
9. decrease RMP

Question 4

hyperkalemia

Answer 4

1. decreased K efflux since there is more K outside the cell.
2. concentration gradient decreases between the ECF and the ICF
3. inside the cell/RMP is less negative/more positive
4. nearly depolarised thus highly excitable.

Question 5

hyponatremia

Answer 5

1. Na is more in ECF than in ICF
2. low Na in the ECF
3. caused by overhydration
4. concentration gradient that will cause Na influx decreases
5. membrane hyperpolarize
6. slower Na influx- normal AP
7. no effect on RMP as it largely depends on K concentration
8. no effect on excitability

Question 6

hypernatremia

Answer 6

1. higher than normal Na in ECF
2. caused by severe dehydration and a lot of salt intake
3. concentration gradient increases
4. causing more Na influx
5. but Na has a relatively low permeability across the cell
6. normal AP
7. no effect on RMP
8. no effect on excitability

Question 7

hypocalcemia

Answer 7

1. Ca is high in ECF than in ICF
2. Ca determines where more Na voltage-gated channels are open or closed.
3. Ca not pass through voltage-gated channels instead they block them
4. less Ca in ECF due to vitamin D deficiency there are fewer Na voltage-gated channels blocked
5. more Na can move into the cell
6. depolarization occurs
7. increased chance of AP
8. increased excitability

Question 8

hypercalcemia

Answer 8

1. high Ca in ECF
2. caused by excess intake of vitamin D
3. more Ca blocks voltage-gated Na channels
4. less influx of Na
5. decreased chance of AP
6. decreased excitability.

Question 9

effect of ECF Mg ion concentration is similar to

Answer 9

that of Ca

Question 10

K, Na, Mg have an effect on

Answer 10

RMP, which is associated with the leak channels

Question 11

Ca have an effect on

Answer 11

AP, associated with voltage-gated channels

Question 12

A decrease in neuronal excitability is caused by increased extracellular K+ concentration.

Answer 12

false

Question 13

A decrease in neuronal excitability is caused by increased extracellular Ca2+ concentration

Answer 13

true

Question 14

A decrease in neuronal excitability is caused by increased extracellular Na+ concentration.

Answer 14

false

Question 15

A decrease in neuronal excitability is caused by increased extracellular Mg2+ concentration.

Answer 15

true