synaptic transmission Flashcards
how many steps are there to synaptic transmission?
4
what is the 1st step in synaptic transmission?
the action potential arrives at the presynaptic membrane, causing depolarisation through the opening of calcium ion channels, and the consequent influx of calcium ions.
what is the second step in synaptic transmission?
the increased concentration of ca ions within the membrane causes the vesicles containing the NT to fuse with the presynaptic membrane and release their contents into the synaptic cleft through exocytosis.
what is the third step in synaptic transmission?
the NT diffuses across the synaptic cleft, down a conc gradient, and binds to complementary receptors on the post-synaptic membrane. This can result in an inhibitory or excitatory effect on the postynaptic membrane.
what is the fourth and final step of synaptic transmission?
the resultant action potential will then be transmitted along the axon of the following neuron, resulting in a cascade of neurotransmission.
why can neurotransmitters only transmit in 1 directions?
They can only transmit in 1 direction due to the specific function of the different parts of the neuron.
NT are released from presynaptic membrane and carry over the synaptic gap. NTs bind to specific receptor sites on the post synaptic mem.
Also, diffusion is from high conc of NT at the presynaptic mem, to low conc at the post-synaptic mem.
exhibition
when a NT increases the positive charge of the postsynaptic neuron. This increases the likelihood that the postsynaptic neuron will pass on the electrical impulse.
neuron more likely to fire.
inhibition
when a neurotransmitter, such as serotonin increases the negative charge of the postsynaptic neuron. This decreases the likelihood that the postsynaptic neuron will pass on the electrical impulse.
neuron less likely to fire.
whether a postsynaptic neuron fires is decided by …?
summation
what is summation?
Summation is the process that determines whether/how frequently the neuron will fire by the combined effects of excitatory and inhibitory signals.
The excitatory and inhibitory influences are summed.
so if the net effect is inhibitory, then the postsynaptic neuron is less likely to fire.
what is summation?
Summation is the process that determines whether/how frequently the neuron will fire by the combined effects of excitatory and inhibitory signals.
The excitatory and inhibitory influences are summed.
so if the net effect is inhibitory, then the postsynaptic neuron is less likely to fire.
the action potential of the postsynaptic neuron is only triggered if ….
…. if the sum of the excitatory and inhibitory signals at any one time reaches the threshold.
