synaptic transmission

Question 1

what are synapses

Answer 1

junctions between neurons

info transmitted between neurones by chemicals called neurotransmitters

Question 2

structure of a synapse

Answer 2

presynaptic neurone:
- mit
- presynaptic bulb
- vesicles containing neurotransmitter(acetylcholine)
- ca2+ ion protein channels

post synaptic neurone:
- post synaptic memb
- receptors to neurotrans on na ion channels - 2 acteylcholinde mols bind to rceptor site

Question 3

features of synapses

Answer 3

• uidirectional - only past info from pre to post in one direction due to vesicles omly being pres in pre – grad
• spatial summation - no of diff pre neurones together release enough neurotrans to exceed thresh val of post – together trigger new action potent
• temporal summation - single pre neurone releases neuro trans many times over a short period – exceed thresh val – actio potent

Question 4

describe an inbititory synapse (less likely action potent will be created)

Answer 4

• pre rlease nuerotrans that binds to chloride ion protein channels on post
• causes chloride channels to open
• chloride ions move into post by fac diff
• binding of neuro trans also casuses opening of k channels casung k to move out of post
• neg charge in and pos out makes inside of post more neg and outside more pos
• memb potential inc to as much as -80mv
• called hypopolariatuon and makes less likely that action potent will be created as larger influx of na ions needed to produce one

Question 5

sequence of events at a synapse

Answer 5

• arrival of action potential at end of pre casues calcium ions channels to open and calc ions to enter the synaptic knob by fac diff
• influx of ca ions cause synaptic vesicles to fuse with pre memb releasing acetylcholine into synaptic cleft (exocytosis)
• acetly mols diff across synaptic cleft and binds to receptors on na protien channels on post memb causing them to open and na to diff in rapidly (depolarises post)
• generates action potential in post
• acetylcholinesterase hydrolyse acetlchline into choline and actetyl which diff back into pre and leads to discrete transfer of info across synapse
• ## atp used to recombine into acetlychilone and na channels shut in absecnce of it in receptor sites

Question 6

what is a neuromusular junction

Answer 6

point hwere motor neruone meets a skelatal muscle fibre same seq of events happen as at a synapse betwen 2 neurones

post memb called sarcolemma

Question 7

similarities between cholinergic synapse and nueromuscular junction

Answer 7

• both have neuro trans that are transported by diff
• both have recpetors that on binding with neurotrans casue an influx of na ions
• both have na/k pump to repolarize axon
• have enz to breakdown neurotrans

Question 8

differences between cholinergic synapse and nueromuscular junction

Answer 8

• could be exitatory or inhib, only exitatory
• links neurons to nureons or to effector orgs, only links neirpnes to muscles
• new action potent may be produced along anothe rneuron, action potent ends there
• m,s,r may be involved, only m
• actelycholine binds to receptors on post memb, bind to receptors on mucle fibre

Question 9

effects of drugs om synapses (stimulation)

Answer 9

• stimulation- create more action potentials in post synaptic neurones by mimicking neurotrans, stim relase of more neuro trans or inhibs enz that breaks down neurotrans

Question 10

effects of drugs om synapses (inhibition)

Answer 10

• create fewer action potents in post neirpns
• inhibs release of nuero trans
• blocks receptors on na or k ion channels on post

Question 11

what happens if a drug inhinit actionof excitatory neuro trans

Answer 11

will decrease an effect

Question 12

what happens if a drug inhibits action of inhibitaory nuerotrans

Answer 12

will enhance effect