topic 8 - synapses

Question 1

describenhow a signal passes from one neurone to another (4)

Answer 1

• (action potential arrives depolarising pre-synsptic membrane)
• Ca2+ ions diffuse into pre-synaptic neurone
• vesicles of neurotransmitter fuse with pre-synaptic membrane
• neurotransmitter diffuses across synapse
• neurotransmitter binds to receptor
• voltage gated NA+ ion chanels open alowing Na+ to moven into post-synaptic membrane causing depolarisation
• neurotransmitter broken down to preent further stimulation

Question 2

give an additional role of the synapse

Answer 2

• ensures one way transmission of impulse
• amplifacation of impulse via summation
• divergance of an impulse

Question 3

describe how MDMA coud prevent the transmission of nervous impulses in the brain

Answer 3

• prevents reuptake of serotonin
• by binding to post-synpatic receptors
• nerve pathways using serotonin are more likely to be stimulated

Question 4

how do low serotinin levels effect the transmission of impulses to the brain?

Answer 4

• less neurotransmitter
• threshold potential not achieved

Question 5

how does the use of MDMA lead to symptoms of depression ?

Answer 5

• results in depletion of serotonin
• post-synaptic membrane becomes less responsive to serotonin
• lack of serotonin linjked to depression

Question 6

describe the process that occurs at the synapse that leads to habituation (4)

Answer 6

• repeated stimulation leads to decreased sensitivity of PSM
• fewer Ca2+ move into neurone
• fewer vesicles fuse with membrane
• less neurotransmitter released
• depolarisation less likely to occur

Question 7

why does habituation occur?

Answer 7

animals dont waste energy reponding to a non-thretening signal

Question 8

through what process does neurotransmitter leave the pre synaptic neurone

Answer 8

exocytosis

Question 9

what happens after action potential has been generated and why

Answer 9

neurotransmitter is broken down to prevent further stimulation of neurone

Question 10

what is summation

Answer 10

• a single impulse may be insufficient to generate an action potential
• small amount of neurotransmitter released, few channels opened, threshold not reached
• effect of multiple impulses can be added together to overcome this

Question 11

describe the differences in the visual region of a kitten that had one eye closed during the critical period compared to one who did not

Answer 11

• fewer synaptic connections
• by neurons to right occular dominace columns
• left occular dominace column contains more synapses to compensate