1.4 - nerve transmission

Question 1

All cells have…

Answer 1

an electrical potential difference (voltage) across plasma membrane.

Question 2

What is resting membrane potential?

Answer 2

A state where no net flow of ion across plasma membrane; typically between -60 and -80 mV

Question 3

What requires the membrane potential to change?

Answer 3

transmission of nerve impulses

Question 4

what is an action potential?

Answer 4

A wave of electrical excitation along a neuron’s plasma membrane.

Question 5

What generates and maintains resting membrane potential?

Answer 5

Na/K-ATPase

Question 6

What is nerve transmission?

Answer 6

A wave of depolarisation of the resting potential of a neuron.

Question 7

What is depolarisation?

Answer 7

an electrical state in an excitable cell; inside of the cell is less negative than outside.

Question 8

How do nerve transmissions begin?

Answer 8

they are stimulated by signal molecules (neurotransmitter) triggering the opening of ligand-gated ion channels at a synapse; may trigger depolarisation; means resting potential increases, which may trigger action potential if big enough change.

Question 9

Describe the spread of depolarisation…

Answer 9

depolarisation of a patch of membrane causes neighbouring regions of membrane to depolarise.

Question 10

How are neurotransmitters released from neurons?

Answer 10

Action potential reaches the end of neuron causing neurotransmitter containing vesicles to fuse with membrane, releasing neurotransmitters and stimulating response in connecting cell.

Question 11

Describe repolarisation…

Answer 11

resting potential restoration allows inactive Na+ channels to return to a conformation that allows them to open again in response; ion concentration gradients are re-established by Na/K-ATPase; K+ transported across plasma membrane.

Question 12

Describe nerve transmission… (step by step)

Answer 12

1. binding of a neurotransmitter triggers the opening of ligand-gated ion channels at a synapse.
2. ion movement occurs and there is depolarisation of the plasma membrane
3. if sufficient depolarisation beyond threshold value, voltage-gated ion channels are triggered to open and Na+ enter the cell down electrochemical gradient.
4. leads to rapid and large change in membrane potential
5. short time after opening, Na+ channels inactivate
6. voltage-gated K+ channels open to allow K+ to move out of cell to restore the resting membrane potential
7. ion concentration gradients are re-established by Na/K-ATPase which actively transports excess ions.