topic 6 synaptic transmission Flashcards
how is an action potential transmitted across a synapse?
action potential reaches the presynaptic membrane
this stimulates the calcium channels to open and calcium ions enter the presynaptic membrane
this makes acetyl-choline containing vesicles move to the presynaptic membrane and fuse with it
acetylcholine is released into the synaptic cleft by exocytosis
acetylcholine diffuses to the post synaptic membrane and binds with a receptor protein
this causes gated sodium channels to open and the action potential to start again
the enzyme acetylcholineesterase converts acetyl choline into acetic acid and choline to stop nerve impulses from firing
what would the issue be if acetylcholine was not broken down?
may continuously generate new action potentials
how can acetyl choline be remade?
ATP recombines acetyl (ethanoic acid) and choline, which recycles the acetylcholine
where can acetyl choline be remade?
at the smooth endoplasmic reticulum
what are the parts of a synapse?
presynaptic neuron postsynaptic neuron synaptic cleft synaptic knob calcium ion channel sodium ion channel synaptic vesicles containing neurotransmitters smooth endoplasmic reticulum mitochondria
what is a synapse?
gap between neurons
what is the function of a synapse?
either
single impulse along one neuron- transmitted to many neurons to display simultaneous responses
different impulses combine at synpase, multiple stimuli interact to produce a single response
what is unidirectionality?
action potential is only sent from the presynaptic neuron to the postsynaptic neuron
due to the position of neurotransmitter vesicles and sodium channels
what is summation?
the rapid build up of neurotransmitters in the synapse to help generate an action potential
what is the issue with a low frequency action potential?
only release insufficent amounts of neurotransmitter to exceed the threshold
what is spatial summation?
presynaptic neurons share a presynaptic cleft
together release enough neurotransmitter for an action potential
what is temporal summation?
single synaptic neuron releases neurotransmitter many times over a short period
total exceeds threshold which generates an action potential
what is inhbition?
chloride channels on the postsynaptic membrane open, so chloride ions flood into the post synaptic membrane to hyperpolarise the neuron
so it is harder for an action potential to be generated
what is an excitatory neurotransmitter?
neurotransmitter that depolarises the membrane
makes it more likely to fire if the action potential is reached
what is an inhibitory neurotransmitter?
hyperpolarises the membrane
cell membrane is more negative which increases the stimulus required to reach the threshold
prevents an action potential firing
