synapses questions

Question 1

What starts depolarisation

Answer 1

sodium chnallels opening

Question 2

what step requires the hyrdolysis of atp

Answer 2

active trasnport of sodium and potassium

Question 3

(b) Synaptophysin is a protein involved in the production of synaptic vesicles.
Scientists can use the presence or absence of synaptophysin to identify presynaptic and postsynaptic membranes in synapses.
Explain why they are able to use synaptophysin for this purpose.

Answer 3

Synaptic) vesicles (only) found in presynaptic (part of synapse)

Question 4

Dopamine is a neurotransmitter. Production of too much dopamine is associated with schizophrenia. A drug used to treat schizophrenia binds to dopamine receptors in synapses. This binding does not lead to the formation of an action potential.
(i) Suggest why the drug used to treat schizophrenia is able to bind to the same receptor as dopamine

Answer 4

Has similar shape/structure to dopamine

Question 5

(b) ATP is an energy source used in many cell processes. Give two ways in which ATP is a suitable energy source for cells to use.

Answer 5

3. Phosphorylates other compounds, making them more reactive;
4. Can be rapidly re-synthesised;
5. Is not lost from / does not leave cells.
6. Releases energy instantaneously;

Question 6

the membrane potential at Q was the same whether medium or heavy pressure was applied to the finger tip. Explain why.

Question 7

multiple sclerosis is a disease in which parts of the myelin sheaths surrounding neurones are destroyed. Explain how this results in slower responses to stimuli.

Question 8

The KDR plus allele codes for the sodium ion channels found in neurones.
When DDT binds to a sodium ion channel, the channel remains open all the Use this information to suggest how DDT kills insects

Answer 8

1)threshold reached
2. (Threshold or above) causes maximal response / all or nothing principle.

Question 9

Cannabinoid receptors are found in the pre-synaptic membrane of neuromuscular junctions. When a cannabinoid binds to its receptor, it closes calcium ion channels.
Suggest how cannabinoids could prevent muscle contraction.

Answer 9

1)less/no saltatory conduction
2)more depolarisation over length

Question 10

Cannabinoids include substances found in cannabis that can enter brain tissue. Scientists are developing artificial cannabinoids that can enter neuromuscular junctions but cannot enter brain tissue.
Suggest why these artificial cannabinoids would be better to use than cannabis when treating someone with MS

Answer 10

neurone remains depolarised
so no action potentials

Question 11

(b) The doctors used a statistical test to compare the results for AD and LD. They obtained a value for P of 0.047.
What does this result show about the difference between the means for AD and LD?
Use the words probability and chance in your answer.

Answer 11

Probability of obtaining this difference by chance;
Reject ‘results’ once only
This statement often split round 2.
3
2. Is less than 5% / less than 0.05 / less than one in twenty;
Accept is 4.7% / 0.047 but reject less than 4.7% / 0.047
Accept correct greater than 95% / greater than 0.95 arguments

Question 12

Serotonin is a neurotransmitter released in some synapses in the brain. It is transported back out of the synaptic gap by a transport protein in the pre-synaptic membrane.
(a) Serotonin diffuses across the synaptic gap and binds to a receptor on the post-synaptic membrane.

Describe how this causes depolarisation of the post-synaptic membrane.

Answer 12

causes sodium channels to open
sodium ions neter

Question 13

The black mamba’s toxin kills prey by preventing their breathing. It does this by inhibiting the enzyme acetylcholinesterase at neuromuscular junctions. Explain how this prevents breathing.

Answer 13

ach not broken down
na+ions enter
muscles stay contracted

Question 13

Different substances are involved in coordinating responses in animals.
(a) Synapses are unidirectional. Explain how acetylcholine contributes to a synapse being unidirectional.

Answer 13

(Acetylcholine) released from / in presynaptic side;
2. Receptors in postsynaptic (side) / binds on postsynaptic (side);

Question 14

Explain the effect of myelination on the rate of nerve impulse conduction.

Answer 14

myelin insulates / prevents ion movement; saltation / described re leaping node to node;

Question 15

describe how the resting potential is established in an axon by the movement of ions across the membrane.

Answer 15

active transport pf na+ out of axon
diffusion of k+out of axon

Question 16

sodium and potassium ions can only cross the axon membrane through proteins.
Explain why.

Answer 16

can not pass through phospholipid bilayer;
because water soluble / not lipid soluble / charged / hydrophilic / hydrated;

Question 17

When the postsynaptic membrane is stimulated by acetylcholine, an action potential is less likely if GABA is released at the same time. Explain why.

Answer 17

gaba opens k+ and cl- channels so k+ passes out and cl- passes in

requires increased stimulation

more na+ to enter to reach threshold

Question 18

Describe the sequence of events leading to the release of acetylcholine and its binding to the postsynaptic membrane.

Answer 18

16
(a) action potential arrives / depolarisation occurs; calcium ions enter synaptic knob;
vesicles fuse with membrane;
acetylcholine diffuses (across synaptic cleft); binds to receptors;

Question 19

the binding of GABA to receptors on postsynaptic membranes causes negatively charged chloride ions to enter postsynaptic neurones. Explain how this will inhibit transmission of nerve impulses by postsynaptic neurones.

Answer 19

inside becomes more negatively charged / hyperpolarised; stimulation does not reach threshold level / action potential not produced; depolarisation does not occur / reduces effect of sodium ions entering;

Question 20

Explain what causes the conduction of impulses along a non-myelinated axon to be slower than along a myelinated axon

Answer 20

non-myelinated – next section of membrane depolarised / whole membrane;
myelinated – depolarisation / ion movement only at nodes; impulse jumps from node to node / saltatory conduction;

Question 21

the change in membrane potential between points A and B,

Answer 21

sodium channels open / membrane more permeable to sodium (ions);

Sodium ions enter;
By diffusion

Question 22

the change in membrane potential between points B and C.

Answer 22

Sodium channels close;
Potassium channels open / membrane more permeable to potassium ions;
Potassium ions leave;
By diffusion / from high to low concentration (ONCE only);

Question 23

Describe how calcium ions are involved in synaptic transmission.

Answer 23

Ca to enter presynaptic neurone/membrane

causes fusion of vesicles with presynaptic membrane /
causes exocytosis / release of transmitter;

Question 24

taser is a device used by the police to arrest violent suspects. It fires electrical impulses very similar to action potentials into a suspect. The frequency of the impulses is between 15 and 20 per second.
(i) Suggest the effect a taser has on a suspect’s muscles.

Answer 24

Potassium channels open (and K ions diffuse out);

+ Sodium channels close