Nerves

Question 1

What is the main characteristic of a motor neurone? And why?

Answer 1

Long axons, transmit nerve impulses from the CNS to effectors all over the body.

Question 2

Describe the process of a nervous impulse (step one - stimulus)

Answer 2

Stimulus excites neurone cell membrane. na+ channels open. Membrane becomes more permeable to sodium. Na+ diffuse into neurone down electrochemical gradient. Makes inside less negatively charged.

Question 3

Describe the DEPOLARISATION step

Answer 3

If the potential difference reaches the threshold (around fifty five millivolts) more sodium ion channels opens more sodium ions diffuse into the neurone.

Question 4

REPOLARISATION

Answer 4

At a p.d. Of around 30mV the sodium ion channels close and potassium ion channels open so the membrane is more permeable to potassium so potassium ions diffuse out if the neurone down the potassium ion concentration gradient. This starts to return the membrane to resting potential.

Question 5

HYPERPOLARISATION

Answer 5

Potassium ion channels are slow to close so too many potassium ions diffuse out of the neurone, and the p.d. Goes lower than resting potential.

Question 6

RESTING POTENTIAL

Answer 6

The ion channels are reset and the sodium potassium pump returns the membrane to resting potential by pumping sodium ions out and potassium in by active transport.

Question 7

Draw a motor neurone, labelling the Schwann cell, nodes of Ranvier, dendrites and synaptic terminal.

Answer 7

Self mark.