Synapses 2 Flashcards
Define summation.
It occurs when the effects of several excitatory post-synaptic potentials (ESPSs) are added together.
Is one ESPS enough to cause an action potential?
No. It takes several to reach the threshold and cause an action potential in the post-synaptic neurone.
What is temporal summation?
When summation results from several action potentials in the same pre-synaptic neurone.
What is spatial summation?
When action potentials arrive from different pre-synaptic neurones.
What are inhibitory post-synaptic potentials (IPSPs)?
They can reduce the effect of summation and prevent an action potential in the post-synaptic neurone.
What does spatial summation allow?
Action potentials from different parts of the nervous system to contribute to generating an action potential in one post-synaptic neurone - so creating the a particular response.
When is temporal summation useful?
When one action potential can be sent to several parts of the nervous system it is useful in a reflex arc. One post-synaptic neurone elicits the response, while another informs the brain.
What do synapses ensure?
That action potentials are transmitted in the correct direction. Only the pre-synaptic bulb contains acetylcholine.
How do synapses filter out unwanted low-level signals?
If a low-level signal creates an action potential in the pre-synaptic neurone it is unlikely to pass across the synapse to the next neurone, because several vesicles of acetylcholine must be released to create an action potential in the post-synaptic neurone.
When does a synapse become habituated?
When several impulses cause a synapse to run out of vesicles of neurotransmitter, this causes the synapse to become fatigued. This explains why we sometimes get used to background noises.
How are specific pathways created?
The creation and strengthening of specific pathways can be done. Synapses are adaptable in particular the post-synaptic membrane can become more sensitive to acetylcholine. This means that a particular post-synaptic neurone is more likely to fire an action potential , creating a specific pathway in response to a stimulus.
