- Neurons are separated by a synaptic cleft (approx. 20-30nm wide)
- Presynaptic neurone refers to the neuron that released the neurotransmitter
- Postsynaptic neurone refers to the neuron that receives the neurotransmitter
- The enlarged section of an axon is synaptic knob
- Large amount of mitochondria
- Large amount of smooth endoplasmic reticulum
- Neurotransmitters Is stored in synaptic vesicles
- Once the neurotransmitter is released from the vesicle, it diffuses across the postsynaptic cleft
- Single impulse along one neurone to be transmitted to a number of different neurones at a synapse, therefore allowing a single stimulus to create a number of simultaneous responses
- A number of impulses to be combined at a synapse. This allows stimuli from different receptors to interact in order to produce a single response
- Action potential arrives at presynaptic neurone causing Ca2+ channels to open and therefore Ca2+ ions enter the synaptic knob
- Influx of Ca2+ into presynaptic neurone results in synaptic vesicles to fuse with the presynaptic membrane. This releases acetylcholine into the synaptic cleft
- Acetylcholine fuses with receptors on the sodium ion channel on the postsynaptic neurone resulting in sodium ion channels to open allowing Na+ to diffuse in rapidly along a concentration gradient
- Influx caused by the sodium ions generate a new action potential in the postsynaptic neurone
- Acetylcholinesterase hydrolyses acetylcholine into choline and acetyl (ethanoic acid) which diffuses back through the presynaptic neurone cleft. It also ensures that the acetylcholine does not continuously generate a new action potential in the new neurone.
- ATP released is used to recombine choline and acetyl to acetylcholine which is stored in the synaptic vesicles. Sodium ion channels close.