A level Biology: Function of synapses

How do synapses provide integration and thus control and flexibility?
I dont really understand how synapses represent a point where transmission can be controlled.

thanks.

Reply 1

macpatgh-Sheldon

20

Hi,

Look at it this way:-

Synapses can be present where the neurotransmitter has an excitatory effect on the 2nd (called post-synaptic = after synapse) neurone e.g. with noradrenaline (producing an EPSP - excitatory post-synaptic potential) or it can have an inhibitory effect on the 2nd neurone e.g. with dopamine. (producing an IPSP - inhibitory post-synaptic potential).

e.g. in the basal ganglia in the brain, acetylcholine acts as a stimulatory neurotransmitter and dopamine as an inhibitory one - the balance of effects of the two, with in addition the fact that several pre-synaptic neurones can converge onto one post-synaptic one, with varying excitatory and inhibitory effects, means that the response of the final neurone will depend on various factors, so introducing an element of control and a summative effect (kind of integration) In the basal ganglia, if the effect of dopamine is reduced, the patient may suffer from Parkinson's disease.

If you are aiming for A*, also remember that IN GENERAL, excitatory neurotransmitters are stored in spherical vesicles in the pre-synaptic terminal, while inhibitory ones are stored in elongated vesicles (not in A level syllabus).

M (specialist biology tutor)

(edited 6 years ago)

Reply 2

AVP18

7

Original post by michaela0899

How do synapses provide integration and thus control and flexibility?
I dont really understand how synapses represent a point where transmission can be controlled.

thanks.

Are you referring to summation? A synapse may receive signals from multiple neurons, some will be excitatory and some will be inhibitory and together they may trigger an action potential in the recieving neuron, or a series of action potentials or not.

Reply 3

michaela0899

OP

13

Oh ok! so is that different from filtering out low-level stimuli then?

Reply 4

AVP18

7

Original post by michaela0899

Oh ok! so is that different from filtering out low-level stimuli then?

For an action potential to occur the stimulus has to be strong enough to breach the threshold for that particular neuron. So if the stimuli reaching the synapses is not strong enough no action potential fires and the signal stops. This is a way of filtering out low level stimuli.
However although a stimulus on its own may be too weak to breach the threshold, multiple stimuli at the synapses may sum to breach the threshold.
You may find this site helpful (ignore the 'for kids' - I know university students who've use the site for the basics.)
https://faculty.washington.edu/chudler/ap.html

Reply 5

michaela0899

OP

13

Original post by AVP18

For an action potential to occur the stimulus has to be strong enough to breach the threshold for that particular neuron. So if the stimuli reaching the synapses is not strong enough no action potential fires and the signal stops. This is a way of filtering out low level stimuli.
However although a stimulus on its own may be too weak to breach the threshold, multiple stimuli at the synapses may sum to breach the threshold.
You may find this site helpful (ignore the 'for kids' - I know university students who've use the site for the basics.)
https://faculty.washington.edu/chudler/ap.html

Thank you!

A level Biology: Function of synapses

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