Lecture 6, Nerve/Muscle 2

Question 1

What is a gradient?

Answer 1

Gradients prepare neurons to generate action potentials for communication.

Question 2

What is an electrical gradient and why does it occur?

Answer 2

Ions will move down their electrical gradient as ions require a gradient to move. This will balance the electrical gradient until there is no net movement, when they are balanced, this are at equilibrium.

Question 3

What are the four stages of an action potential in order?

Answer 3

Resting membrane potential → Depolarisation → Repolarisation → Hyperpolarisation

Question 4

What is the resting membrane potential of an action potential?

Answer 4

-70mV

Question 5

What pumps ions against their electrochemical gradient and what does this action require?

Answer 5

Na+/K+-ATPase pump. Pushes ions up the hill and against their gradient, this requires ATP.

Question 6

At what voltage do voltage-gated ion channels open?

Answer 6

-60mV for Na+ voltage-gated channels, and +30mV for the K+ voltage-gated channel.

Question 7

What happens during depolarisation?

Answer 7

Input from the cells outside causes the cell to reach threshold (-60mV) which causes the voltage-gated Na+ channels to open, Na+ moves into the cell causing the cell to reach a positive charge of +30mV.

Question 8

Are the K+ channels open or closed at -60mV?

Answer 8

Closed.

Question 9

What happens during repolarisation (+30mV)?

Answer 9

Voltage-gated Na+ channels close, voltage-gated channels open, K+ leaves the cell and the cell becomes more negative.

Question 10

What happens during hyperpolarisation?

Answer 10

Voltage-gated K+ channels begin to close slowly at -40mV. RMP reestablished.

Question 11

At what voltage do voltage-gated K+ slowly start to close and when do they fully close?

Answer 11

-40mV and -80mV.

Question 12

True or false, all original values are reestablished when the cell reaches its resting membrane potential.

Answer 12

True