synaptic transmission

• SYNAPTIC TRANSMISSION

  action potential arrives at the presynaptic membrane causing depolarisation. Vesicles containing neurotransmitters bind to presynaptic membrane and release neurotransmitters into synaptic cleft. they diffuse across, down a concentration gradient. Neurotransmitters then bind to postsynaptic receptors; their shapes are complementary to each other. Channels open in post synaptic membrane. If neutron is inhibitory it has less chance of firing (serotonin), whereas excitatory means it has an increased chance of firing (dopamine)
• Neurotransmitters can be excitatory or inhibitory (most can be both but GABA is purely inhibitory).

  • If the neurotransmitter is excitatory then the post synaptic neuron is more likely to fire an impulse.

  • If the neurotransmitter is inhibitory then the post synaptic neuron is less likely to fire

  an impulse.

  • The excitatory and inhibitory influences are summed, 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.