Resting And Action Potentials

Question 1

What is the nearest equation and what does it show?

Answer 1

The equilibrium potential of an ion in certain temperature and charge

E= RT/zF ln(conc outside/conc inside)

Question 2

What are the equilibrium potentials of potassium and sodium?

Answer 2

-90mV = potassium

+72 mV = sodium

Question 3

What equation is used to give a more accurate equilibrium potential?

Answer 3

Goldman-Hodgkin-Katz equation

Takes into account permeability of membrane to other ions as well

Question 4

What are the differences between graded and action potentials?

Answer 4

Graded = proportional to strength of stimulus, decreases further from stimulus
Action potential = all or nothing, only when the graded potential is greater than threshold value, no change in magnitude

Question 5

What are the 5 stages of an action potential?

Answer 5

Resting potential 
Stimulus 
Depolarisation 
Repolarisation
Hyperpolarisation

Question 6

What are the 2 gates on a sodium channel

Answer 6

Activation gate
Inactivation gate = ball on a chain
Potassium does NOT have an inactivation gate

Question 7

Describe the stages of an action potential

Answer 7

• potassium channel closed, sodium activation gate closed, inactivation gate open
• activation gate of sodium opens = influx of Na+
• potassium channel opens
• reach peak
• activation and inactivation gate closes
• potassium channel remain open to allow resting potential to be achieved
• inactivation gate open

Question 8

Factor affecting velocity of conduction

Answer 8

Myelinated
Diameter - wider = faster
MS and diphtheria = reduce myelination
Cold, drugs, anorexia = decrease in speed

Question 9

What is elecrochemical equilibrium?

Answer 9

When the chemical gradient is equal to the electrostatic gradient

Question 10

What are the absolute refractory periods and relative refractory period?

Answer 10

Absolute = no action potential 
Relative = stronger than normal stimulus can generate action potential