Synaptic transmission

Synaptic transmission

The process where neighbouring neurons communicate with each other by sending chemical messages across the synapse that separates them

Neurotransmitter

Brain chemicals released from synaptic vesicles that relay signals across the synapse from 1 neuron to another.

Perform excitatory or inhibitory functions depending on the type of receptor that they bind to.

Excitation

When a neurotransmitter (e.g. glutamate) increases the positive charge of the postsynaptic neuron.

Increases the likelihood that the postsynaptic neuron will generate an electrical impulse

Inhibition

When a neurotransmitter (e.g. GABA (Gamma-Aminobutyric acid) increases the negative charge of the postsynaptic neuron

Decreases the likelihood that the postsynaptic neuron generates an electrical impulse

Synaptic transmission description

V - Vesicles

R - Release

R - Receptors

E - Enzymes

R - Reuptake

R - Replenished

S - Summation

Vesicles

When the electrical impulse reaches the end of the axon it arrives at the pre-synaptic terminal.

Terminal boutons are made up of vesicles that contain neurotransmitters

Release

The electrical impulse that has travelled down the axon triggers the release of the neurotransmitter which diffuses across the synapse

Receptors

Neurotransmitters go to receptors on dendrites of the next neuron.

The chemical is converted back into an electrical impulse and carries on down the axon of the neuron

Enzymes

Enzymes are released to break down any neurotransmitters still in the synapse

Reuptake

Some excess neurotransmitters that are still in the synaptic cleft are reabsorbed back to the pre-synaptic terminal

Replenished

Vesicles are replenished with new and reused neurotransmitters ready for the next impulse

Summation

Whether the postsynaptic neuron generates an action potential.

Sum of excitatory and inhibitory responses

More excitatory than inhibitory

More positive charge overall. The neuron is more likely to fire

More inhibitory than excitatory

More negative charge overall. The neuron is less likely to fire