M5 C13 Neural Communication PMT QP1

Question 1

Outline the ways in which the structures of a sensory neurone and a motor neurone are similar. [4]

Answer 1

1 dendrite(s)
2 an axon
3 a cell body with a , nucleus / named organelle ;
4 myelin sheath / myelinated /
(covered with) Schwann cell / nodes of Ranvier ;
5 voltage-gated channels /
sodium-potassium (ion) pump

Question 2

Fever is accompanied by sweating.

Explain the effect that this sweating will have on the body.

Answer 2

cause body temperature to decrease as heat from the body will be used in order to evaporate the water, water has a high latent heat of evaporation

Question 3

Some people think that alcohol should be given to those who have hypothermia, as it makes them feel warmer. Alcohol causes vasodilation. Explain why it is not a good idea to give alcohol to someone with hypothermia.

Answer 3

• vasodilation causes blood to be closer to skins surface and so heat is lost more efficiently causing the core body T to decrease further and cause organs such as the liver not to function

Question 4

Why is the Pacinian corpuscle described as a transducer?

Answer 4

as it converts mechanical energy into another form ie. electrical energy

Question 5

Deformation of the plasma membrane of the tip of the neurone causes the membrane to
become more permeable to Na+. Suggest why.

Answer 5

as increased pressure causes sodium channels to open and holes to form between phospholipids

Question 6

The generation of an action potential follows the ‘All-or-Nothing’ law.
Explain what this means.

Answer 6

if the stimulus is not strong enough then the action potential will not reach the threshold value as the depolarisation of the membrane was not sufficient so an action potential is not generated

Question 7

Suggest an explanation for the fact that action potentials are not generated constantly whilst wearing clothes.

Answer 7

as there is constant pressure the sodium ion channels remain open and the membrane does not return to resting potential so an action potential cannot be generated as ion are on the wrong side

Question 8

Synapses are an integral part of the nervous system.

Outline the roles of synapses in the nervous system.

Answer 8

1. allows cells to communicate (cell signalling)
2. allows impulses to be transmitted in one direction only
3. allows convergence, many neurones to one neurone
4. allows divergence, one neurone to many
5. prevents over stimulation
6. inhibitory or stimulatory snaps can control the path of an impulse
7. filters out low level stimuli
8. can amplify many low level stimuli
9. permits learning and memory

Question 9

name one chemical that transfers chemicals from one neurone to another

Answer 9

acetylcholine

Question 10

draw a diagram of a liver section and name the parts

Answer 10

• sinusoid
• Kupffer cells
• bile duct
• hepatic artery
• hepatic portal vein
• hepatic vein