Lecture 17

Question 1

What is the membrane potentials for the ECF

Answer 1

High Na+ and Low K+

Question 2

What is the membrane potentials for the ICF

Answer 2

High K+ and low Na+

Question 3

What is the voltage at a close channel?

Answer 3

-70mV

Question 4

What is the voltage at an open channel?

Answer 4

-60mV

Question 5

What is the voltage at an inactivated channel?

Answer 5

+30mV

Question 6

What is the resting membrane potential?

Answer 6

-70mV

Question 7

What does it mean if there is a depolarisation of the membrane?

Answer 7

The membrane is becoming more positive

Question 8

When does the gate close?

Answer 8

When the membrane becomes very positive.

Question 9

What does the inactivation gate do?

Answer 9

It allows the inactivation gate to close very rapidly and eventually the activation gate will close too.

Question 10

What is the first step in the action potential of a myelinated axon?

Answer 10

A local or graded change in membrane potential occurs sufficient to depolarise the cell and open voltage gated Na+ channels.

Question 11

What is the second step in the action potential of a myelinated axon?

Answer 11

Voltage gated Na+ channels open and Na+ ions flow through.

Question 12

What is the third step in the action potential of a myelinated axon?

Answer 12

The membrane rapidly depolarises and then they close and at the same time voltage gated K+ channels open.

Question 13

What is the fourth step in the action potential of a myelinated axon?

Answer 13

Voltage gated K+ channels close and membrane repolarises to RMP

Question 14

What are the statuses of the gates at resting membrane potentials?

Answer 14

They are both shut and a few membrane channels open

Question 15

What does it mean when the membrane is at absolute refraction period?

Answer 15

Absolutely nothing else can occur at that membrane, no other action potentials can occur.

Question 16

What happens at the initiation point?

Answer 16

Membrane starts to depolarise

Question 17

What happens when the cell depolarises above the threshold value?

Answer 17

Voltage gated sodium channels open, making it positive inside and goes to +30mV.

Question 18

What occurs at +30mV?

Answer 18

Sodium gate inactivate/ close and at the same time voltage gated potassium ions channels open.

Question 19

What does the axon hillock control?

Answer 19

It controls whether or not to pass on action potentials. By the action potential being large enough to over come the axon hillock.

Question 20

What is the first step in action potential for an unmyelinated axon?

Answer 20

As an action potential develops at the initial segment, the membrane potential at this site depolarises to +30mV

Question 21

What is the second step in action potential for an unmyelinated axon?

Answer 21

As the sodium ions entering at spread away from the open voltage-gated channels, a graded depolarisation quickly brings the membrane in segment 2 to threshold

Question 22

What is the third step in action potential for an unmyelinated axon?

Answer 22

An action potential develops in segment 2.

The initial segment begins repolarisation (and is now refractory)

Question 23

What is the fourth step in action potential for an unmyelinated axon?

Answer 23

As the sodium ions entering at segment 2 spread laterally a graded depolarisation quickly brings the membrane segment 3 to threshold

Question 24

How do we increase our conduction speed?

Answer 24

Myelinating- Schwann cells, meaning it gets regenerated at each node.