1.4.4 nerve impules transmission

Question 1

what is meant by resting membrane potential

Answer 1

this is when there is no net flow of ions across the membrane

Question 2

what does the transmission of a nerve impulse require

Answer 2

changes in the membrane potential of the neurons plasma membrane

Question 3

what is an action potential

Answer 3

a wave of electrical excitation along a neurons plasma membrane

Question 4

how do neurotransmitters initiate a response

Answer 4

by binding to their receptors at a synapse

Question 5

what are neurotransmitter receptors

Answer 5

ligand gated ion channels

Question 6

what triggers the opening of voltage gated sodium channels

Answer 6

the depolarisation of the plasma membrane as a reuslt of the entry of positive ions

Question 7

what is depolarisation

Answer 7

a change in the membrane potential to a less negative value inside

Question 8

how can the resting membrane potential be restored

Answer 8

inactivating the sodium channels and the opening of potassium channels

Question 9

describe the process of restoring resting membrane potential

Answer 9

• binding of a neurotransmitter triggers the opening of a ligand gated ion channel at a synapse
• ion movement occurs and there is depolarisation of the plasma membrane
• if suffficient ion movement occurs, and the membrane is depolarised beyond a threshold value, the opening of voltage gated sodium channels is triggered and sodium ions enter the cell down their electrochemical gradient
• this leads to a rapid change and large change in the membrane potential
• a short time after opening, the sodium channels become inactivated.
• voltage gated potassium channels then open to allow potassium ions to move out of the cell to restore the resting membrane potential

Question 10

what does the depolarisation of a patch of membrane cause

Answer 10

neighbouring regions of membrane to depolarise and go through the same cycle as adjacent voltage gated sodium channels are opened

Question 11

what happens when the action potential reaches the end of the neuron

Answer 11

vesicles containing neurotransmitter fuse with the membrane, releasing neurotransmitter, stimulating a response in a connecting cell

Question 12

what does the restoration of the resting membrane potential allow

Answer 12

the inactive voltage gated sodium channels to return to a conformation that allows them to open again in response to depolarisation of the membrane

Question 13

what is responsible for reestablishing the ion concentration gradients

Answer 13

the sodium potassium pump

Question 14

what does the sodium potassium pump actively transport in and out of the cell

Answer 14

excess ions

Question 15

what happens following repolarisation

Answer 15

the sodium and potassium ion concentration gradients are reduced
voltage gated potassium channels open to allow potasssium ions to move out of the cell to restore the resting membrane potential

Question 16

what does the sodium potassium pump restore

Answer 16

the sodium and potassium ions back to resting potential levels

Question 17

what is the refractory period

Answer 17

a period in which neuron is unresponsive to stimulation because the ion distribution is being restored

Question 18

what is depolarization

Answer 18

an electrical change within a neuron from a relatively negative charge to a positive charge

Question 19

what is repolarization

Answer 19

an electrical change within a neuron from a relatively positive charge to a negative charge