Nerve impulses

Question 1

what is a nerve impulse

Answer 1

A nerve impulse is an electrochemical change that travels along a nerve fibre.

Question 2

what is an electrical potential

Answer 2

Is a difference in the concentration of charged particles between one point and another.

Question 3

what is the membrane potential

Answer 3

Is the movement of positive/negative ions across a membrane

Question 4

what is the resting membrane potential

Answer 4

Is the change in difference across a plasma membrane.

Question 5

what value of mili volts is measured at the resting membrane potential

Answer 5

70 mili volts

Question 6

what is found outside the plasma memebrane

Answer 6

sodium ions

Question 7

what is found inside the plasma membrane

Answer 7

potassium ions

Question 8

what charge is the outside of the plasma membrane

Answer 8

positively charged

Question 9

what charge is the inside of the plasma membrane

Answer 9

negatively charged

Question 10

what proteins can be found on the plasma membrane

Answer 10

1. potassium leakage channel proteins
2. sodium leakage channel proteins
3. closed voltage potassium channel
4. closed voltage sodium channel
5. sodium-potassium pump

Question 11

why is there a greater concentration of potassium inside the cell

Answer 11

As there is a greater number of potassium-associated proteins. Potassium has the largest effect on the resting membrane potential because the plasma membrane is more permeable to them.

Question 12

why is there a higher concentration of sodium ions outside the cell, but a low concentration inside the cell?

Answer 12

Because there are fewer sodium-associated proteins. The membrane isn’t permeable to sodium but this leak through.

Question 13

what is the sodium-potassium pump

Answer 13

controls the movement of potassium and sodium into and out of the cell

Question 14

what does the sodium-potassium pump require

Answer 14

ATP

Question 15

how does the sodium-potassium pump function

Answer 15

1. The protein binds three sodium ions and a molecule of ATP
2. The splitting of ATP provides energy to change the shape of the channel which releases the sodium ions.
3. Once released the new shape of the pump allows two potassium ions to bind
4. Potassium is released into the cell allowing the pump to revert back to its original shape

Question 16

what is an action potential

Answer 16

The rapid depolarisation and repolarisation of the cell membrane. A neurotransmitter will cause ligand-gated channels to open when they have a stimulus causing sodium to enter the cell.

Question 17

what causes the opening of the voltage-gated sodium channels

Answer 17

if the potential difference increases to negative 55mV.

Question 18

what does the opening of the voltage-gated sodium channels cause

Answer 18

an all or nothing response

Question 19

what happens if the potential difference increases to negative 55mV (depolarisation)

Answer 19

This causes the membrane to become more permeable to sodium and they are released into the cell. The rapid influx of sodium ions causes the depolarization of the membrane.

Question 20

what happens when the membrane potential reaches 30mV (repolarisation)

Answer 20

The sodium gates will close and the potassium voltage gates open causing potassium ions to rush out of the cell. This causes the repolarisation of the membrane as the movement of potassium ions causes to cell to become negatively charged.

Question 21

What is the refectory period

Answer 21

A short period following a stimulus during which a nerve cell or muscle fibre cannot be stimulated again.

Question 22

Define depolarised/depolarization

Answer 22

The membrane of a nerve cell when there is no difference in electrical charge between the inside and outside of the membrane.

Question 23

Define repolarised/repolarization

Answer 23

A membrane that has been returned to a polarised state.

Question 24

Define polarised

Answer 24

The inside of a nerve cell has a negative electrical charge compared with to the outside

Question 25

What is hyperpolarisation?

Answer 25

This occurs when too many potassium ions go out of the cell causing the membrane potential to drop lower than the resting membrane potential.

Question 26

What happens if the cell becomes hyperpolarised?

Answer 26

For the cell to reach a steady state period the sodium-potassium pump will function leading to the refractory period.