Role of synapses, and summation and control

Question 1

How do synapses affect the direction of the impulse?

Answer 1

ensuire they are unidirectional

as the neurotransmitter receptors are only present on the postsynaptic membrane

impulses can only travel from the presynaptic neurone to the postsynaptic neurone

Question 2

What else is useful about synapses?

Answer 2

they can allow an impulse from one neurone to be transmitted to a number of neurons at multiple synapses, single stimulus creates a number of simultraneous responses

alternatively, a number of neurones may feed in to the same synapse with a single postsynaptic neurone

this results in stimuli from different receptors interacting to produce a single result

Question 3

What is spatial summation?

Answer 3

this occurs when a number of presynaptic neurones connect to one postsynaptic neurone

each releases neurotransmitter which builds up to a high enough level in the synapse to trigger an action potential in the postsynaptic neurone

Question 4

What is temporal summation?

Answer 4

this occurs when a single presynaptic neurone releases neurotransmitter as a result opf an action potential several times over a short period

this builds up in the synapse untill the quantity is sufficient enough to exceed the treshold level