Neutrotransmitter

• 1.Neurones connect with other neurons or muscles fibres at a synaptic cleft.

  2. Neurotransmitters relay impulses across the synaptic cleft.

  3. Neurotransmitters are stored in vesicles in the axon endings of the presynaptic neuron

  4. When a nerve impulse passes through the pre-synaptic neuron and reaches the synaptic cleft it stimulates the vesicles.

  5. Vesicles with neurotransmitter move to and fuse with the pre-synaptic membrane

  6. They are released into the cleft on arrival of an impulse.

  7. They diffuse across the cleft and bind to receptors on the membrane of the post-synaptic neuron
• 8. Removal of neurotransmitters at the synapse by enzymes or reuptake prevent continuous stimulation of post synaptic neurons.

  9. Receptors determine whether the signal is excitatory or inhibitory.

  10. Synapses can filter out weak stimuli arising from insufficient secretion of neurotransmitter.

  11. A minimum number of neurotransmitter molecules must attach to receptors in order to reach a threshold on the post synaptic membrane to transmit the impulse.

  12. Summation of a series of weak stimuli can release enough neurotransmitter to trigger an impulse.