Nervous System

Question 1

Neuron function

Answer 1

Irritability - able to respond to stimuli

Conductivity - able to transmit an impulse

Question 2

Resting membrane potential

Answer 2

Inside is potassium,
Outside is sodium
Plasma membrane of neuron is at rest (polarised)
Slightly more negative inside than outside

Question 3

Importance of resting membrane

Answer 3

Allows generation and conduction of nerve impulses along an axon

Question 4

Starting a nerve impulse - 5 steps

Answer 4

1. Different stimuli excite neurons to become active and produce an impulse
2. Permeability of the membrane alters
3. Sodium rushes into cell
4. Inside cell becomes more positive than outside = depolarisation
5. Depolarisation generates action potential over the entire axon

Question 5

Action potential - 3 steps

Answer 5

1. Membrane becomes impermeable to sodium but permeable to potassium
2. Potassium rushes out, whilst sodium stays in = repolarisation
3. Sodium-Potassium pump restores original configuration

Question 6

Nerve Impulse propogation

Answer 6

Impulses travel faster with myelin sheath
Impulses jump from node to node
This is called saltatory conduction

Question 7

Synapse events - 3 steps

Answer 7

1. Neurotransmitter is released from axon’s terminal
2. Dendrites on other axon has receptors that are stimulated by neurotransmitter
3. Action potential is generated

Question 8

Sympathetic movement

Answer 8

Heart rate increases
Gut activity decreases
“Fight, fright, flight”

Question 9

Parasympathetic movement

Answer 9

Gut activity increases
Heart rate decreases
‘Rest and digest’

Question 10

Axons

Answer 10

Conduct impulses away from cell body

Question 11

Dendrites

Answer 11

Conduct impulses towards cell body