Membrane Potential

Question 1

How is resting membrane potential created

Answer 1

1. Selectively permeable membrane

2. Uneven distribution of individual ion species

Question 2

Vrest

Answer 2

-40 to -90 mV

Question 3

Depolarization

Answer 3

Reduction in charge separation

Membrane potential becomes more +

Question 4

Hyperpolarization

Answer 4

Increase in charge separation

Membrane potential becomes more -

Question 5

Capacitance

Answer 5

Ability to separate charge

Question 6

4 types of ion chnnals

Answer 6

1. Leak channels
2. Voltage gated channel
3. Ligand gated channels
4. Mechanosensory

Question 7

Nerst Equation

Answer 7

E (potassium) = 61log[ion in][ion out]

Normal range -85 to -95

Question 8

For neurons, what determines Vrest

Answer 8

E (potassium)

E (cl) negligable

Question 9

For muscles, what determines Vrest

Answer 9

Ecl

Question 10

Define steady state

Answer 10

Constant K out and K in = equal & opposite

Without ion exchange pumps

Question 11

What pumps do neurons rely heavily on for resting membrane potentential

Answer 11

Na\K ATPase

3Na out and 2 K in

Question 12

What does Oubain do?

Answer 12

Blocks Na\K ATPase so intracellular Na rises
Na\Ca runs in reverse
Na sent out and Ca sent in
Better cardiac contractions

Question 13

Rapid Onset Dystonia-Parkisonism

Answer 13

Loss of Na\K pump

Parkinson Like symptoms

Question 14

Myotonic Cognetia (Thomsen & Becker’s Disease)

Answer 14

Reduced Cl conductance
CLCN1 mutation
Rise in intracellular K not followed by Cl sent outside

Question 15

Myotonic Goats

Answer 15

K accumulates in T-tubles after repeated actition potentials

Cl channel are mutated and only open at very positive membrane potentials so get delayed repolarization

Question 16

Hyperkalemic Periodic Paralysis

Answer 16

Congenital defect of Na+ channel

Na channels open and stay open so get lots of depolarization so cannot respond to synaptic transmission