05 - Action Potentials

Question 1

What is a cell membrane made of?

Answer 1

Phospholipid molecules

Question 2

What are the two important kinds of protein for electrical changes?

Answer 2

Ion channels and pumps

Question 3

What is an ion channel?

Answer 3

A transmembrane protein channel that allows a specific ion to diffuse across the membrane

Question 4

What do ions flow passively through?

Answer 4

Channels

Question 5

What may this movement of ions be driven by?

Answer 5

Electrical (voltage) or chemical (concentration)

Question 6

For the following types of ion channels answer what they are and if and when they are open/closed:
Ligand 
Voltage
Mechanical
Leakage

Answer 6

Ligand - open on ligand binding
Voltage - always open
Mechanical - open when receptor changes shape
Leakage - always open

Question 7

When does an action potential occur?

Answer 7

When the sodium channels open allowing a massive influx of sodium ions - this is called depolarisation

Question 8

What is the refactory period?

Answer 8

When the sodium channels close and cannot be reopened until the voltage returns to resting levels of -70mV

Question 9

What is depolarisation?

Answer 9

A change in a cell’s membrane potential such that the inside of the membrane is made less negative relative to the outside

Question 10

When does repolarisation occur?

Answer 10

When K+ channels open and the K+- escapes

Question 11

Where can action potential conduction take place?

Answer 11

Along the length of the axon

Between the neurons - at a synapse

Question 12

What structures contribute to action potential conduction?

Answer 12

Ion channels
Myelin sheaths
Nodes of Ranvier
Saltory conduction

Question 13

What is a myelin sheath?

Answer 13

An insulating coat of the cell membranes produced by Schwann cells (CNS) or oligodendrites (CNS)

Question 14

What is myelination essential for?

Answer 14

Rapid and accurate impulse connection

Question 15

What are nodes of ranvier

Answer 15

These are gaps in a myelin sheath between shwann cells of certain acorns where an action potential may be generated

Question 16

Is there any insulation at nodes of ranvier?

Answer 16

No, the axon membrane contacts with the extracellular fluid so the depolarisation and repolarisation can occur whereas it cannot in Schwann cells

Question 17

What are synapses the point of?

Answer 17

The signal is transferred by chemical exchange instead of electrical signal

Question 18

What is signal integration?

Answer 18

Where the target cell is another nerve, several impulses may be needed before the post synaptic is excited enough to fire an action potential

Question 19

What happens in the neuromuscular junction?

Answer 19

The transmitter released (acetylcholine) excites the muscle to give rise to an action potential in the muscle