Chapter 3

Question 1

Transmitting an impulse, down an axon

Answer 1

1. Resting membrane potential - Na outside, K inside - negative inside due to negatively large charged ions (-70mV)
2. Stimulus applied to nerve fibre
3. Slow depolarisation - threshold of -55mV reached
4. Depolarisation - sodium potassium pump, Na+ to diffuse inside cell and K+ out +30mV
5. Repolarisation - pump and ATP restore N+, K+ to its resting state

Question 2

Synapse?

Answer 2

Gap between successive neurons, the transmission is caused by the help of neurotransmitters

Question 3

Transmitting an impulse - across a synapse

Answer 3

1. Nerve impulse arrives at terminal, membrane becomes permeable to calcium ions
2. Calcium ions cause vesicles to burst, release of neurotransmitter (acetylcholine)
3. Protein receptors on dendrite of next neuron are stimulated…

Question 4

What can create more effective speed of transmission?

Answer 4

Myelinated fibres, large diameter and shorter in length

Question 5

Continuous conduction

Answer 5

Unmyelinated fibres have a slower transmission and don’t contain the myelin sheath.

Domino effect - sending electrochemical impulse along the nerve in an continuous wave…

The impulse is prevented from going backwards.

2 m/s = 7 km/h

Question 6

Saltatory conduction

Answer 6

Contains myelinated fibres therefore has a faster transmission.
It can jump from one node of ranvier to the next.

Myelinated fibres contain the myelin sheath.

18 m/s = 65 km/h.
140 m/s = 500 km/h.

Question 7

Neuromuscular junction?

Answer 7

Axon meeting a skeletal muscle.