biopsych 8th Flashcards
the process of synaptic transmission
an action potential, once at the end of an axon, crosses the gap between the presynaptic neuron and the postsynaptic neuron (synaptic cleft).
synaptic vesicles at the end of an axon release chemical messengers (neurotransmitters), as the action potential reaches it, through exocytosis, which aids in the transfer of impulses.
once neurotransmitters cross, they bind to specialised receptors which recognise it and are activated by it.
this process takes a fraction of a second.
the effects are terminated by reuptake. the neurotransmitter is taken back by presynaptic neuron where it is stored for later use.
excitatory neurotransmitters (EN)
excitatory neurotransmitters such as noradrenaline are the nervous systems on switches. these increase the likelihood of excitatory signal being sent to postsynaptic cell, which is then more likely to fire.
EN binding with a postsynaptic receptor causes an electrical change in the membrane of that cell, resulting in EPSP. the postsynaptic cell then fires.
inhibitory neurotransmitters (IN)
such as serotonin are the nervous systems off switches.
decrease likelihood of neuron firing.
calm mind and body, induce sleep and filter out unnecessary excitatory signals.
IN binding with postsynaptic receptor results in IPSP making it less likely to fire.
what is EPSP/IPSP
excitatory/inhibitory postsynaptic potential
what is summation
nerve cells can receive EPSPs and IPSPs at the same time so the likelihood of the cell firing is determined by the summation.
the strength of EPSP is determined by spatial and temporal summation.
if excitatory synapses are more active, the cell fires at a high rate.
if inhibitory synapses are active, the cell fires at a low rate or not at all.
what is spatial summation
a large number of EPSPs generated at many different synapses on the same postsynaptic neuron at the same time.
what is temporal summation
a large number of EPSPs generated at the same synapse by a series of high-frequency action potentials on presynaptic neuron.
