Synaptic Transmission

• Information is passed down the axon of the neuron as an electrical impulse known as action potential.
• Once the action potential reaches the end of the axon it needs to be transferred to another neuron or tissue.
• The electrical impulse must cross over a gap between the pre-synaptic neuron and post-synaptic neuron, which is known as the synaptic gap.
• At the end of the neuron, in the axon terminal, are the synaptic vesicles which contains chemical messengers, known as neurotransmitters.
• When an electrical impulse (action potential) reaches the synaptic vesicles, it releases neurotransmitters.
• Neurotransmitters carry signals across the synaptic gap. They bind to receptor sites on the post-synaptic cell that then become activated.
• Neurotransmitters carry signals across the synaptic gap. They bind to receptor sites on the post-synaptic cell that then become activated.
• Some neurotransmitters are excitatory and some are inhibitory.
• Excitatory neurotransmitters (e.g. noradrenaline) make the post-synaptic cell more likely to fire. They create a positive charge
• Inhibitory neurotransmitters (e.g. GABA) make cells less likely to fire. They create a negative charge
• A synapse is a small gap between two neurons, where nerve impulses are relayed by a neurotransmitter from the axon of a presynaptic (sending) neuron to the dendrite of a postsynaptic (receiving) neuron.
• Dopamine and serotonin are common neurotransmitters found in the brain.
• When neurotransmitters get released into the synaptic cleft, not all of them are able to attach to the receptors of the next neuron.
• Imbalances in the way serotonin is transmitted between neurons through too much reuptake has implications for contributing to mood disorders like depression.
• SSRIs are antidepressants that prevent the reuptake of serotonin back into the pre-synaptic neuron.
• Action potential can only travel in one direction (from pre-synaptic to post-synaptic).
• Summation is the addition of positive and negative post-synaptic potentials. A neuron can receive both positive and negative potentials simultaneously. These are summed and if the net effect on the post-synaptic neuron is inhibitory, the neuron will be less likely to fire, and if the net effect is excitatory, the neuron will be more likely to fire.
• Signal termination allows the post-synaptic neuron to return to its resting potential state, ready for new signals.
• During synaptic transmission, the action potential triggers the synaptic vesicles of the pre-synaptic neuron to release neurotransmitters