chloringeric synapses

• Synapses are gaps between neurons. 
• Chemicals called neurotransmitters travel across the synaptic gap. 
• A new action potential is stimulated in the post synaptic neurone. 
• Step 1:

  Incoming action potential reaches the synaptic knob and depolarises the knob. This causes the voltage gated calcium ion channels to open, so calcium ions flood into the synaptic knob by facilitated diffusion. 

   
• Step 2:

  The calcium ions make the synaptic vesicles that contain neurotransmitter, move and fuse with the presynaptic membrane. This releases the neurotransmitter (acetylcholine) into the cleft which then diffuses across the gap to the post synaptic membrane.  

   
• Step 3:

  The neurotransmitter binds to the receptor site on the ligand gated sodium ion channels, when they bind they change the shape of the channel and make it open.

  The sodium ion channels are normally closed, when the neurotransmitter causes a shape change of the channel sodium ions flood in and cause depolarisation.
• Step 4:

  If enough sodium ions enter the threshold is exceeded and an action potential is triggered which travels along the neurone. 

   
• Step 5: acetylcholinesterase (enzyme)

  A hydrolytic enzyme which hydrolyses the neurotransmitter into acetate and chlorine which are the actively transported back into the synaptic knob and the sodium ion channels close again. Calcium ions are actively transported back out of the synaptic gap. 

   
• Step 6: remaking acetylcholine 

  ATP released by the mitochondria is used to combine acetate and choline to remake acetylcholine. The synaptic vessel are refilled with neurotransmitter. More acetylcholine can be made at the smooth endoplasmic reticulum.