F214 1.2 - Nerves

Question 1

Action potential

Answer 1

A brief reversal of the resting potential across the cell surface membrane of a neurone. All action potentials have a value of +40 mV.

Question 2

All or nothing

Answer 2

Refers to the fact that a neurone either conducts an action potential or it does not.

Question 3

Central nervous system

Answer 3

The brain and spinal cord. It has overall control over the coordination of the nervous system.

Question 4

Depolarisation

Answer 4

The loss of polarisation across a membrane – when the membrane loses its resting potential.

Question 5

Generator potential

Answer 5

A small depolarisation of the membrane in a receptor cell.

Question 6

Hyperpolarised

Answer 6

The condition of a membrane that is more highly polarised than the usual resting state. The resting potential is lower than usual.

Question 7

Local currents

Answer 7

Movements of ions along a neurone close to the cell surface membrane, caused by influx or efflux of ions through the membrane.

Question 8

Neurotransmitter

Answer 8

A transmitter substance – a chemical that is released from the presynaptic membrane of one neurone to pass a signal to another neurone.

Question 9

Repolarisation

Answer 9

Return of the membrane potential to approximately -70mV in mammals

Question 10

Peripheral nervous system

Answer 10

The sensory and motor neurones connecting the central nervous system to the sensors and effectors around the body.

Question 11

Polarised

Answer 11

Membrane with a potential difference across it.

Question 12

Refractory period

Answer 12

The short period of time after firing during which it is more difficult to stimulate a neurone.

Question 13

Saltatory

Answer 13

Refers to way in which the action potential appears to jump from node to node.

Question 14

Sodium–potassium pumps

Answer 14

Protein carriers embedded in the membranes of some cells, which use energy from ATP to move sodium ions and potassium ions in opposite directions simultaneously, against their concentration gradients. They are chemically gated ion channels.

Question 15

Stimulus

Answer 15

Any change in the environment of an organism that causes a response.

Question 16

Summation

Answer 16

The way that several small potential changes can combine to produce one larger change in potential difference across a neurone membrane.

Question 17

Synaptic knob

Answer 17

The swelling at the end of a neurone where it forms a junction (synapse) with another neurone.

Question 18

Threshold potential

Answer 18

A potential difference (usually –50 mV)across the membrane. If the depolarisation of the membrane does not reach the threshold potential then no action potential is created. If the depolarisation reaches the threshold potential then more sodium ion channels open and an action potential is created.

Question 19

Voltage-gated channels

Answer 19

Channels in plasma membranes that allow the passage of ions. They respond to changes in potential difference (voltage) across a membrane and, as a result, open or close.