EX1; Excitable Cells; Electricity Flashcards Preview

AU14 Physiology > EX1; Excitable Cells; Electricity > Flashcards

Flashcards in EX1; Excitable Cells; Electricity Deck (34):
1

The electrical charge difference between the inside and outside of a cell is what

voltage

2

The voltage of a resting cell is steady, therefore the plasma membrane must have what

resistance

3

When a resistance changes, ions cross the membrane and this is what

current

4

This is the reciprocal of resistance

conductance

5

These two things are membrane properties

conductance and resistance

6

There is a higher concentration of solutes in 1 but why is there no voltage difference

Q image thumb

because the number of cations in 1 is the same as the number of anions in 1; and vice versa

7

Something causes permeability to increase, therefore X+ moves down the concentration gradient from 1 to 2, 1 aquires a negative charge and 2 aquires positive; but the movement of X+ stops before the concentration is equal, why?

Q image thumb

a charge difference develops (voltage); the system attains an equilibrium state

the concentration difference and voltage difference are directed oppositely

8

What does the Nernst equation describe

it relates the voltage difference between 1 and 2 and the concentration difference between 1 and 2

9

What is the Nernst equation

Ex= (58/z) log10 ([X1]/[X2])

z = valence

10

What does the Nernst equation yield

the equilibrium potential or a single ionic species

11

This is the voltage across a cell membrane that exactly balances the force in the concentration gradient of a permeable ion

equilibrium potential

12

What is a diffusion potential and what does it mean to be transient

they are due to asymmetic ion flow - an imbalance in the flow of an ion or several ions between two compartments

 they can disappear over time

13

What is an example of a transient diffusion potential

A membrane is equally permeable to Na and Cl, but Cl moves faster, therefore bringing the negative chage more into one compartment, one having an excess positive charge is a diffusion potential; eventually they will equal out

14

A diffusion potential can or cannot be maintained at a steady level over time

can be

15

What is an example of a steady diffusion potential

membrane becomes permeable to only K, the one compartment will have a high postive charge and the other a high negative chage; the change in voltage will slow the subsequent diffusion; when the concentration force is balanced by the electrical force diffusion potential stops changing

16

There is a high concentration of what inside the cell

K+

17

There is a higher concentration of what outside the cell

Na+

18

The membrane of a resting cell is most permeable to what ion

K+

19

What is the Pk/P(Na) ration

around 60; K+ ions diffuse across a typical membrane 60 times more readuly than Na+ when the cell is at rest

20

Equilibrium is reached with the force in the concentration gradient for K+ ions to move out of the cell is balanced by what

the opposing force in electrical gradient which favors keeping K+ ions inside the cell

21

This keeps the resting membrane potential slightly lower than Ek

Na+ diffuses into cell down both its concentration gradient and electrical gradient

22

What is the flow of ions when a cell is at rest

K+ ions diffuse out

Na+ ions diffuse in

23

The resting membrane potential is what; is not a transient diffusion potential

steady

24

The resting potential is not due to the instantaneous movement of ions, it is due to what

the fact the ions have moved across the membrane (specifically K+)

25

This protein moves K+ ions back into the cell and Na+ ions out of the cell when it is at rest; requires ATP

Na+/K+ ATPase pump

26

A change of the membrane potential toward 0mV is referred to as what

depolarization (or hypopolarization)

27

A change in the membrane potential away from 0mV, in the negative voltage direction is referred to as what

repolarization

28

An increase in membrane potential from the resting value (more negative toward resting potential; -70mV) is referred to as what

hyperpolarization

29

What is the resting potential

-70mV

30

True or False

The Na/K ATPase pump maintian concentration gradients for Na and K across membrane

True

31

What does the active transport via the Na/K ATPase pump counteract

the passive diffusion of ions; keeping the resting potential

32

The Na/K ATP-ase pump is an example of what

homeostasis

33

True or False

The number of ions that are required to cross the membrane, which results in large changes in the membrane potential is extremelly small compared to the total number of ions

True

34

True or False

The extracellular and intracellular concentrations of the ions that cross living cell plasma membranes, remain essentially unchanged, even during periods of intense excitation

True