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What is a synapse?

The point at which the axon of one neurone connects with the dendrite of another or with an effector


How do synapses transmit impulses from one neurone to another?

By the means of chemicals known as neurotransmitters


What is the name of the neurone that releases the neurotransmitter?

The presynaptic neurone


At the end of the axon of the presynaptic neurone, there is a swollen portion. What is this portion called?

The synaptic knob


What is contained within the synaptic knob?

Many mitochondria and large amounts of endoplasmic reticulum


Where is the neurotransmitter stored?

In the synaptic vesicles


Once the neurotransmitter is released from the vesicles, what does it diffuse across?

The postsynaptic neurone


What receives the neurotransmitter once it has diffused across the postsynaptic neurone?

Receptor molecules on its membrane


What allows stimuli from different receptors to interact and produce a single response?

A number of impulses can be combined at a synapse


At what point is the neurotransmitter released from the synaptic vesicle?

When the action potential reaches the synaptic knob


What does unidirectionality mean?

This means that synapses can only pass impulses in one direction - from the presynaptic neurone to the post synaptic neurone


Through what process can an insufficient amount of neurotransmitter be made to produce a new action potential?



What are the two methods of summation?

Spatial and temporal summation


What does spatial summation involve?

A number of different presynaptic neurones together release enough neurotransmitter to exceed the threshold value of the post synaptic neurone


What does temporal summation involve?

A single presynaptic neurone releases neurotransmitter many times over a short period to exceed the threshold value of the post synaptic neurone


What makes a new action potential less likely?

In inward diffusion of chloride ions into the post synaptic neurone causing hyperpolarisation