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Flashcards in Membrane potential Deck (16)
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1
Q

Define membrane potential?

A

Separation of opposite charges across the membrane

2
Q

What do excitable cells have?

A

(nerve and muscle) ability to produce rapid, transient changes in their membrane potential when excited (action potentials).

3
Q

Describe resting membrane potential in different cell types?

A

constant in non-excitable cells, and in excitable cells at rest

4
Q

What is the concentration gradient of K?

A

Outward

5
Q

What is the concentration gradient of Na?

A

Inward

6
Q

At resting membrane potential the membrane is …. more permeate to …than …?

A

100x
K+
Na+

7
Q

What are the opposing forces acting on K+?

A

1) Concentration gradient (tending to move K+ out of the cell)
2) The electrical gradient (tending to move K+ into the cell)

8
Q

What is the potential for K known as when forces are directly balanced?

A

Equilibrium potential for K+ (Ek)

9
Q

What is Ek?

A

-90mV

(the polarity of the excess charge on INSIDE of the membrane

10
Q

What is the nernst equation?

A

equilibrium potential for any given ion can be calculated using the Nernst equation.

Eion= 61log10(ion(O)/ion(i))

11
Q

What happens when the permeability for a given ion is high?

A

the greater the tendency for that ion to drive membrane potential towards the ion’s own equilibrium potential.

12
Q

What are all cells inside at resting membrane potential?

A

Negative

13
Q

What equation can be used to calculate Em?

A

goldman-hodgkin-katz equation

14
Q

What is the effect of the Na+/K+ mum on K+ and Na_ gradients?

A

Helps maintain them

Since its stoichiometry is 3Na+ exported for every 2K+ entering, the pump will generate a hyperpolarizing current.

15
Q

How much does the Na/K pump add to Em?

A

In skeletal muscle, it adds only 2-3mV to Em but in other cell types it can add +10mV, depending upon the resistance of the membrane and pump activity.

16
Q

Describe the specialised use of Em in nerve and muscle cells?

A

Rapidly and transiently alter their membrane permeabilities in response to appropriate stimulation, resulting in fluctuations in Em.

Nerve impulses in nerve cells and triggering contraction in muscle cells.
-Changes in Em linked to secretion of insulin from pancreatic B-cells.