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Flashcards in Cellular Physiology (Part 2) Deck (97)
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1

What is resting membrane potential?

The potential difference that exists across the membrane of excitable cells, such as nerve and muscle, in the period between action potentials

2

The resting membrane potential is established by what?

diffusion potentials, which result from the concentration differences for various ions across the cell membrane

3

Which ions will make the greatest contributions to the resting membrane potential?

Ions with the highest permeabilities at rest

4

Resting membrane potential of excitable cells falls in the range of −__ to −__mV

−70 to −80mV

5

What is the resting membrane potential close to?

The equilibrium potentials for K+ and Cl- because the permeability to these ions at rest is high

6

What is the resting membrane potential far from?

The equilibrium potentials for Na+ and Ca2+ because the permeability to these ions at rest is low

7

What role does the Na+ - K+ APTase play in creating the resting membrane potential?

It creates and maintains the K+ concentration gradient, which establishes the resting membrane potential

8

What is an action potential?

A phenomenon of excitable cells, such as nerve and muscle, and consists of a rapid depolarization (upstroke) followed by repolarization of the membrane potential

9

What is the basic mechanism for transmission of information in the nervous system and in all types of muscle?

an action potential

10

What is depolarization?

the process of making membrane potential less negative

11

What is repolarization?

The process by which the membrane potential returns the membrane potential to a negative value after the depolarization phase of an action potential

12

What is hyperpolarization?

the process of making the membrane potential more negative

13

What is inward current?

The flow of positive ions from the ECF into the ICF

14

What is an example of inward current?

The flow of sodium into the cell during the upstroke of the action potential

15

What is outward current?

The flow of positive ions from the ICF to the ECF

16

What is an example of outward current?

The flow of potassium out of the cell during the repolarization phase of the action potential

17

Inward currents _____ the membrane potential and outward currents ______ the membrane potential.

depolarize

hyperpolarize

18

What is threshold potential?

the membrane potential at which occurrence of the action potential s inevitable

19

An ____ current is required to depolarize the membrane potential to threshold

inward

20

The portion of the action potential where the membrane potential is positive is called what?

overshoot

21

The portion of the action potential, following repolarization, where the membrane potential is actually more negative than it is at rest is called what?

undershoot

22

What is the refractory period?

a period during which another normal action potential cannot be elicited in an excitable cell

23

Each normal action potential for a given cell type looks ____, depolarizes to the same potential, and repolarizes back to the ___ resting potential.

identical

same

24

Describe the propagation of an action potential

An action potential at one site causes depolarization at adjacent sites, bringing those adjacent sites to threshold.

* This propagation is nondecremental

25

What channel is responsible for the upstroke of the action potential in nerve and skeletal muscle?

the voltage-gated Na+ channel

26

What are the 2 types of gates on the Na+ channel?

activation and inactivation gates

27

In order for Na+ to move through the Na+ channel what gate must be open?

both

28

How do the gates on the Na+ channel respond throughout the course of an action potential?

1) during rest the activation gate is closed and the inactivation gate is open
2) during the upstroke of the action potential, the activation gate opens quickly (the inactivation gate is still open) allowing Na+ to flow through the channel
3) at the peak of the action potential the inactivation gate closes, stopping the passage on Na+ and repolarization begins

29

What are the 2 types of refractory periods?

Absolute or Relative

30

The absolute refractory period overlaps with how much of the action potential?

Almost the entire duration