1t- Generation of a nerve impulse

Question 1

What is the resting membrane potential?

Answer 1

The state where 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 neurons initiate a response?

Answer 4

By binding to their receptors at a synapse

Question 5

How can neurotransmitters be described?

Answer 5

As ligand-gated ion channels

Question 6

What does depolaristation as the result of the entry of positive ions trigger?

Answer 6

The opening of voltage-gated sodium channels, and further depolarisation occurring

Question 7

What is depolarisation?

Answer 7

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

Question 8

What restores the resting membrane potential?

Answer 8

Inactivation of the sodium channels and the opening of potassium channels

Question 9

What does the binding of a neurotransmitter trigger?

Answer 9

The opening of ligand-gated ion channels at a synapse

Question 10

What occurs after the opening of ligand gated ion channels at a synapse?

Answer 10

Ion movement occurs and there is a depolarisation of the plasma membrane

Question 11

What happens if sufficient ion movement occurs, and the membrane is depolarised beyond a threshold value?

Answer 11

The opening of voltage-gated sodium channels is triggered and sodium ions enter the cell down their electrochemical gradient

Question 12

What does the entering of sodium ions through voltage-gated sodium channels into the cell lead to?

Answer 12

A rapid and large change in the membrane potential

Question 13

What happens a short time after the sodium channels open?

Answer 13

They become inactivated and then voltage-gated potassium channels open to allow potassium ions to move out of the cell to restore the resting membrane potential

Question 14

What does the depolarisation of a patch of membrane cause to happen?

Answer 14

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

Question 15

What happens when the action potential reaches the end of the neuron?

Answer 15

It cause vescicles containing neurotransmitter to fuse with the membrane- this releases neurotransmitter, which stimulates a response in a connecting cell

Question 16

What two things does the restoration of the resting membrane potential allow to happen?

Answer 16

• the inactive voltage-gated sodium channels return to a conformation that allows
  them to open again in response to further depolaristaion of the membrane
• ion concentration gradients are re-established by the sodium-potassium pump,
  which actively transports excess ions in and out of the cell