Structure and Function of Synapses Flashcards
What is a synapse?
The point where one neurone communicates with another or with an effector
How do synapses transmit information between neurons?
Synapses transmit information between neurones by neurotransmitters, which diffuse across the synaptic cleft
What is the synaptic cleft?
A small gap that separates two neurones at a synapse
What is the neurone that releases the neurotransmitter called?
The presynaptic neurone
What is the swollen end of the presynaptic neurone’s axon called?
The synaptic knob
Why does the synaptic knob contain many mitochondria and large amount of endoplasmic reticulum?
To synthesise and package neurotransmitters into synaptic vesicles
Where is the neurotransmitter stored before release?
Its synaptic vesicles within the synaptic knob
What happens after the neurotransmitter is released into the synaptic cleft?
It diffuses across to the postsynaptic neurone and binds to specific§ receptor proteins on its membrane
What is meant by the term unidirectionality in synapses?
Synapses only transmit information from the presynaptic neurone to the postsynaptic neurone, ensuring one way communication
Why do synapses only pass impulses in one direction?
This is because neurotransmitter vesicles are only in the presynaptic neurone, and receptor proteins are only on the postsynaptic neurone
What is the function of unidirectional synapses?
They act like valved, ensuring nerve impulses trvael in the correct direction
What is summation in synapses?
The accumulation of neurotransmitter to reach the threshold value and trigger an action potential in the postsynaptic neurone
Why is summation necessary?
Low - frequency action potentials may release insufficient neurotransmitter to trigger an action potential, but summation allows neurotransmitter levels to build up
What is spatial summation?
When multiple presynaptic neurones release neurotransmitter simultaneously, increasing the total amount and triggering an action potential
What is temporal summation?
When a single presynaptic neurone releases neurotransmitter repeatedly in a short period, increasing its concentration enough to trigger an action potential
