Author: Bethannie Freeman
Document comments: Created by the \'abHTML to RTF .Net\'bb 5.8.2.9

Q1.
(a)     When a nerve impulse arrives at a synapse, it causes the release of neurotransmitter from vesicles in the presynaptic knob.
Describe how.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(3)
(b)     The presynaptic knob contains actin filaments and myosin molecules.
The myosin molecules can attach to mitochondria and move them towards the presynaptic membrane, as shown in the diagram.
 
Use your knowledge of how myosin and actin interact to suggest how the myosin molecule moves the mitochondrion towards the presynaptic membrane.
Do not include the roles of calcium ions and tropomyosin in your answer.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(2)
(c)     This movement of mitochondria happens when nerve impulses arrive at the synapse.
Suggest and explain one advantage of the movement of mitochondria towards the presynaptic membrane when nerve impulses arrive at the synapse.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(2)
(Total 7 marks)
Q2.
The diagram below shows a nerve pathway in an animal.
 
(a)     The nerve pathway shown in the diagram may be regarded as a simple reflex arc.
Use the diagram to explain why.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(1)
(b)     Suggest two advantages of simple reflexes.
1. _________________________________________________________________
___________________________________________________________________
___________________________________________________________________
2. _________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(2)
(c)     In the nerve pathway in the diagram, synapses ensure that nerve impulses only travel towards the muscle fibre.
Explain how.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(2)
(d)     Axon P was found to conduct impulses much faster than other axons in the nerve pathway shown in the diagram.
Describe and explain one feature of axon P that might cause this difference.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(2)
(Total 7 marks)
Q3.
(a)     Dopamine is a neurotransmitter released in some synapses in the brain. The transmission of dopamine is similar to that of acetylcholine.
Dopamine stimulates the production of nerve impulses in postsynaptic neurones.
Describe how.
Do not include in your answer the events leading to the release of dopamine and the events following production of nerve impulses at postsynaptic neurones.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(3)
(b)     Dopamine has a role in numerous processes in the brain including pain relief. The release of dopamine can be stimulated by chemicals called endorphins produced in the brain. Endorphins attach to opioid receptors on presynaptic neurones that release dopamine.
Morphine is a drug that has a similar structure to endorphins and can provide pain relief.
Explain how.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(2)
(c)     GABA is a neurotransmitter released in some inhibitory synapses in the brain. GABA causes negatively charged chloride ions to enter postsynaptic neurones.
Explain how this inhibits postsynaptic neurones.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(3)
(Total 8 marks)

Mark schemes
Q1.
(a)     1.      (Nerve impulse / depolarisation of membrane) causes Ca ^2+ channel (proteins) to open;
2.      Ca ^2+ enter by (facilitated) diffusion;
3.      Causes (synaptic) vesicles to fuse with (presynaptic) membrane;
Accept single reference to ions to cover 1 and 2
Penalise once for no reference to ions
1.      Reject carrier proteins
3.      Reject ref to release of vesicles
3.      Ignore vesicles bind to membrane (but accept merge with)
3
(b)     1.      Myosin head attaches to actin and bends / performs powerstroke;
2.      (This) pulls mitochondria past / along the actin;
3.      Other / next myosin head attaches to actin (and bends / performs powerstroke);
1.      Accept change shape / change angle
2.      Ignore pulls actin along
2.      Ignore refs to cytoskeleon
Accept plural or singular statements
2 max
(c)     1.      (Mitochondria) supply (additional) ATP / energy;
2.      To move vesicles / for active transport of ions / for myosin to move past actin
OR
Re-synthesis / reabsorption of neurotransmitter / named neurotransmitter;
1.      Reject produces energy
2.      Ignore ref. to ATP for opening calcium ion channels/making vesicles fuse with membrane
2
[7]
Q2.
(a)     Only 3 neurones / nerve cells (in reflex arc)
1
(b)     1.      Rapid;
2.      Protect against damage to body tissues;
3.      Do not have to be learnt;
4.      Help escape from predators;
5.      Enable homeostatic control.
2 max
(c)     1.      Neurotransmitter only made in / stored in / released from pre-synaptic neurone;
2.      (Neuro)receptors only on the post-synaptic membrane;
2
(d)     1.      Axon P is myelinated;
2.      So shows saltatory conduction / impulses jump between nodes of Ranvier
OR
3.      Axon P has a larger diameter;
4.      So less resistance to flow of ions.
Mark as 1 & 2 OR 3 & 4
2
[7]
Q3.
(a)     1.      (Dopamine) diffuses across (synapse);
2.      Attaches to receptors on postsynaptic membrane;
Ignore name/nature of receptor e.g. cholinergic
3.      Stimulates entry of sodium ions and depolarisation/action potential;
Accept Na^+ for sodium ions
Accept generator potential for action potential
3
(b)     1.      Morphine attaches to opioid receptors;
Reject reference to active site
2.      (More) dopamine released (to provide pain relief);
Reject receptors release dopamine
2
(c)     1.      (Inside of postsynaptic) neurone becomes more negative/hyperpolarisation/inhibitory postsynaptic potential;
Ignore K^+
Accept -75mV or any value below this as equivalent to more negative
Accept ‘decrease in charge’
2.      More sodium ions required (to reach threshold)
OR
Not enough sodium ions enter (to reach threshold);
Accept Na^+ for sodium ions
3.      For depolarisation/action potential;
Context must covey idea that depolarisation / action potential is less likely
3
[8]