L: Ionic basis of action potential

incomplete

What is extracellular sodium level?

140mM

What is extracellular potassium level?

5mM

What is intracellular sodium level?

10mM

What is intracellular potassium level?

140mM

What direction is the passive movement of potassium?

Potassium out of the cell

What ion is the cell membrane more permeable to out of sodium and potassium?

potassium

What membrane potential would result from potassium leaving the cell?

Potassium equilibrium potential would be negative

What intracellular potential would result from the membrane only being permeable to sodium?

The sodium equilibrium potential would be positive

Why does charge separation occur in the origin of the resting membrane potential?

K+ ions diffuse out of the cell due to the conc. gradient and because they are not accompanied by anions, the electrical potential of the cell interior becomes negative with respect to the extracellular solution

At rest is the membrane permeable to sodium?

Only slightly

How many times less is the membrane permeable to sodium at rest than potassium?

50 times less

Does the membrane potential become more positive or negative when it depolarises?

More positive

Does the membrane potential become more negative or positive when it hyper polarises?

More negative

What charge is the threshold potential?

-50mV

What must the initial depolarisation reach to create an action potential?

A critical threshold

Once the threshold is attained, the depolarising upstroke is …?

Regenerative

What charge does the potential peak around?

+30mV

What is the upstroke of depolarisation associated with?

A rapid increase in sodium permeability (x600)

What is repolarisation associated with?

A delayed 10 fold increase in PK

What type of feedback do Na+ channels use?

Postive feedback

What are the sodium channels and potassium channels dependent on?

Voltage - they are voltage gated channels