LHD - Ionic Basis of the RMP and AP

Question 1

What is the resting potential, threshold potential and action potential of a neurone?

Answer 1

• Resting Potential: -65mV
• Threshold Potential: -55mV
• Action Potential: +40mV

Question 2

What are 4 properties of neurones?

Answer 2

1) Excitability
2) Integration/Filtering & propogation of signals
3) Transmission of signals
4) Plasticity

Question 3

What does plasticity involve?

Answer 3

The ability of the nervous system to adapt and change in response to experiences, learning, and injury

Question 4

What were the first detailed studies of neuron properties conducted on?

Answer 4

Giant squid axon

Question 5

What were the 3 main findings about membrane potentials?

Answer 5

1. Difference in ion concentration between inside and the outside of the axon
2. Selective permeability of the membrane to K+
3. Ion pumps maintain gradients

Question 6

How do you calculate the equilibrium potential for an ion?

Answer 6

Nernst Equation

Eion = (RT/zF) * ln([ion]outside/[ion]inside).

RT/Zf = 61.5 (mammalian)
RT/Zf = 58 (squid axon)

Question 7

Why is it important for the resting potential of a neuron to be sufficiently negative, such as -90mV?

Answer 7

Ensures that potassium ions do not move down their electrical gradient

Question 8

What would happen if the resting potential is at -120mV?

Answer 8

K+ ions would move into the cell and follow their electrical gradient over their concentration gradient

Question 9

What equation is used when dealing with more than one ion to calculate the membrane potential?

Answer 9

The Goldman Equation

Question 10

What occurs during the voltage-gated sodium channel mechanism?

Answer 10

(absence of Na+)

• Activation gate blocks the channel

(presence of Na+)

• Rapid opening of activation gate

(absence of Na+)

• Slow closing of inactivation gate