5.1 Synapses Flashcards
what is a synapse?
the junction between two neurones
how does information pass across the synaptic cleft?
chemicals called NEUROTRANSMITTERS
what is the presynaptic neurone?
the neurone along which the impulse arrives
what is the synaptic knob and what does it contain?
swollen end of the presynaptic neurone containing many mitochondria and large amounts of ER to make neurotransmitters
what are synaptic vesicles? what do they do?
vesicles containing neurotransmitters
fuse with the membrane to release neurotransmitters
what is the synaptic cleft?
the gap separating the axon of one neurone from the dendrite of the next
what are receptor sites?
receptor molecules which the neurotransmitter binds to on the postsynaptic neurones membrane
what do synapses ensure about impulses?
they are UNIDIRECTIONAL
which two ways can an impulse be transmitted?
- to a number of neurones at multiple synapses resulting in a number of simultaneous responses
- a number of neurones can feed into the same synapse with a single postsynaptic neurone
- neurones are not in direct contact, what separates them?
the synaptic cleft
- when an action potential arrives at the end of a presynaptic neurone what does it cause to open?
calcium channels resulting in calcium flooding in to the axon
- what does increased levels of calcium stimulate?
synaptic vesicles to move toward membrane of presynaptic neurone.
- what neurotransmitter do the vesicles contain?
acetylcholine
- vesicles fuse with the membrane and acetylcholine is released into the synaptic cleft by what process?
exocytosis
- how does acetylcholine move across the synaptic cleft?
diffusion
- what does acetylcholine do when it reaches the post synaptic neurone and what does this result in?
binds to receptors on sodium ion channels, results in the channels opening allowing sodium to flood in
- what does the flooding in of sodium do to the postsynaptic membrane?
depolarizes it and if the threshold value is reached an action potential is generated
- what is acetylcholine broken down into?
ethanoic acid and choline
- what enzyme breaks down acetylcholine?
acetylcholinesterase
- where is acetylcholinesterase found?
in the synaptic cleft
- what do choline and ethanoic acid do?
diffuse back into the presynaptic neurone
- when choline and ethanoic acid diffuse back into the presynaptic neurone what happens?
ATP from the mitochondria used to recombine them back to acetylcholine
which sort of synapses use the neurotransmitter acetylcholine?
cholinergic synapses
where are cholinergic synapses found?
in the CNS of invertebrates at neuromuscular junctions
