synapse

synapse

• each axon branches off and ends with a swelled tip of terminal knob which lies close to but not touching the dendrite or another neuron or organ

• the entire region is the synapse

neurotransmitters

• transmission of nerve impulses across a synaptic gap

• a type of chemical stored in vesicles at the end of the axon

two neurotransmitters

1. Noradrenalin- speeds up activity

2. acetylcholine - slows down activity

what happens when an impulse reaches the end of the axon

• sodium comes into the axon

• calcium moves out of the neuron and calcium ion binds with contractile protein that pull the neurotransmitter vesicles to the synaptic gap

what is a transmitters main job

• increase the permeability of the postsynaptic membrane to sodium ions

• the neurotransmitter then binds to a specific receptor site on the dendrite of the next neuron

• if the neurotransmitter stimulates the dendrite to reach threshold

• the neuron then will fire and the impulse will continue down the next neuron

about the period that neurotransmitter is released into the synaptic cleft

• it only takes a short amount of time

• enzymes break down the transmitter substance to clear the synapse

• the next impulse can then be transmitted

monoamine oxidase

breaks down adrenaline or nonadrenaline

acetylcholinesterase

breaks down acetylochline

painkillers

• act as a enzyme to break down the neurotransmitter to decrease the pain impulse