Physiology Chapter 2-Membrane potential

Question 1

What is membrane potential?

Answer 1

Difference in electrical potential between the ECF and ICF.

Question 2

What is membrane potential measured in?

Answer 2

Millivolts

Question 3

What is resting potential?

Answer 3

Constant membrane potential in the cells of non-excitable cells.

Question 4

What are the main ions responsible for the membrane potential?

Answer 4

Sodium, potassium and anions.

Question 5

What is the equilibrium potential of potassium?

Answer 5

-90mV

Question 6

What two forces contribute to potassium’s equilibrium potential?

Answer 6

The concentration gradient pushing it out of the cell and the electrical potential pulling it in.

Question 7

What is the sodium equilibrium potential?

Answer 7

+60mV

Question 8

How do sodium and potassium affect the membrane potential?

Answer 8

The greater permeability exists for potassium and therfore drives the membrane potential towards its eqb potential. It is however maintained at -70mV due to the input of sodium.

Question 9

How do excitable tissues use membrane potential?

Answer 9

They can rapidly and efficiently alter their membrane permeabilities to specific ions in response to appropriate stimulation bringing about fluctuations in membrane potentials.

Question 10

What is polarization?

Answer 10

Charges are separated across the membrane, so the membrane has potential. Any time the value of the membrane potential is not 0mV, the membrane is in a state of polarization.

Question 11

What is depolarization?

Answer 11

A reduction in the magnitude of the negative membrane potential.

Question 12

What is repolarization?

Answer 12

The membrane returns to resting potential after having been depolarized.

Question 13

What is hyperpolarization?

Answer 13

An increase in the magnitude of the negative membrane potential.

Question 14

Changes in ion movement brought about by changes in membrane permeability are done in response to what?

Answer 14

Triggering events

Question 15

What are different triggering events?

Answer 15

A change in the electrical filed in the vicinity of an excitable membrane.
An interaction of a chemical messenger with a surface receptor.
A stimulus.
A spontaneous change in potential caused by inherent imbalances in the leak-pump cycle.

Question 16

What are leak channels?

Answer 16

Membrane channels that are open all the time. Permit unregulated leakage of their chose ion across the membrane through the channels.

Question 17

What are gated channels?

Answer 17

Have gates that can alternatively open, permitting ion passage through the channels or;
closed, preventing ion passage through the channels.

Question 18

What are the four different types of gated channels?

Answer 18

Voltage gated, chemically gated, mechanically gated and thermally gated.

Question 19

What are the two different types of electrical signals?

Answer 19

Graded potentials and action potentials.