synaptic transmission Flashcards
How are signals transmitted between neurones
Chemically
What does a synapse allow
Messages to travel from one neuron to the next in the form of neurotransmitters
What letters can you use to remember the steps of synaptic transmission
V.R.R.E.R.R.S
What does each letter stand for in the synaptic transmission acronym
V: vesicles
R: release
R: receptors
E: enzymes
R: reuptake
R: replenished
S: summation
What happens at the vesicle stage of synaptic transmission
When electrical impulses reach the end of the axon at the pre synaptic terminal there are vesicles containing neurotransmitters at the axon terminal
What happens at the release stage of synaptic transmission
The electrical impulse that has travelled down the axon triggers the release of the neurotransmitter by exocytosis which diffuse across the synapse
What happens at the receptor stage of synaptic transmission
Neurotransmitters bind to receptors on dendrites of the next axon (post synaptic receptors) that chemical is converted back into an electrical impulse and carries on down the axon of the neuron
What happens at the enzyme stage of synaptic transmission
Enzymes are released to break down any neurotransmitters still in the synapse
What happens at the reuptake stage of synaptic transmission
Excess neurotransmitters that are still present are reabsorbed back to the pre synaptic terminal
What happens at the replenished stage of synaptic transmission
Vesicles are replenished with new reused neurotransmitters ready for the next impulse
What is excitation
When a neurotransmitter increases the positive charge of the post synaptic neuron which increase the likelihood that the neuron will fire and pass on the electrical impulse
What is inhibition
When a neurotransmitter increases the negative charge of the post synaptic neuron, this decreases the likelihood that the neuron will fire and pass on the electrical impulse
What is summation
The excitatory and inhibitory influences are summed and totalled up
If the total effect is inhibitory then the neuron is less likely to fire and vice versa
Why can neurons only transmit information in one direction at the synapse
Synaptic vesicles containing the neurotransmitter are only released from the pre synaptic membrane and the receptors for neurotransmitters are only present on the post synaptic membrane
Diffusion of the neurotransmitters means they can only travel from areas of high concentration to low concentration so therefore can only travel from the presynaptic membrane to the post synaptic membrane
