Synaptic transmission

• Neurotransmitters are brain chemicals released from synaptic vesicles that relay signals across the synapse from one neuron to another. They either perform excitatory or inhibitory functions
• synaptic transmission is the process through which neighbouring neurons communicate with each other by sending chemical messages across the synaptic gap that separates them
• the process of synaptic transmission ;

  1. info is passed down the axon of the pre-synaptic neuron as an electrical impulse (action potential)
  2. action potential reaches the axon terminal, stimulating the release of neurotransmitters from the synaptic vesicles
  3. neurotransmitters carry the signal across the synaptic gap and bind to receptor cells on the post synaptic neuron which then become activated
• the process of synaptic transmission :

  4. neurotransmitters that have not bound to receptor cells will either be recycled or destroyed

  5. they will then either perform an excitatory force making the cell more likely to fire eg : noradrenaline or an inhibitory force making them less likely to fire eg : GABA

  6. summation is the net effect of the excitatory postsynaptic potentials (EPSPs) and the inhibitory postsynaptic potentials (IPSPs), adding up the positive and negative charge which decides what effect they will have on the post synaptic neuron
• only certain neurotransmitters can ‘unlock’ an impulse channel in certain receptors in the post synaptic neuron. when the right neurotransmitter binds with the right receptor, a specific ion channel in the membrane is opened. ions then flow through the membrane into the neuron along their specific pathways. this flooding of ions can cause a ‘potential‘ in the dendrites. these potentials can be excitatory or inhibitory
• excitatory neurotransmitters eg : dopamine, increase the positive charge of the post synaptic neuron, this increases the likelihood that the neuron will fire and pass on the electrical impulse
• inhibitory neurotransmitters eg : serotonin, increase the negative charge of the post synaptic neuron, this decreases the likelihood that the neuron will fire and pass on the electrical impulse