the post synaptic membrane + transmission across the synapse

• the post synaptic membrane contains many specialised sodium ion channels that can respond to the neurotransmitter. These channels consist of five polypeptide molecules; two have a special receptor site that is specific to acetylcholine. when acetylcholine is present in the synaptic cleft, it will bind to the two receptor sites and cause sodium ion channels to open.
• what is the first step in transmitting an action potential across the synapse?

  An AP arrives at the synaptic bulb.
• what is the second step in transmitting an action potential across the synapse?

  The voltage gates calcium ion channels open
• what is the third step in transmitting an action potential across the synapse?

  Calcium ions diffuse into the synaptic bulb
• what is the fourth step in transmitting an action potential across the synapse?

  The calcium ions cause the synaptic vesicles to move to and fuse with the pre-synaptic membrane
• what is the fifth step in transmitting an action potential across the synapse??

  Acetylcholine is released through exocytosis
• what is the sixth step in transmitting an action potential across the synapse?

  Acetylcholine molecules diffuse across the cleft
• what is the seventh step in transmitting an action potential across the synapse?

  Acetylcholine molecules bind to the receptor sites on the sodium ion channels in the post synaptic membrane
• what is the eighth step in transmitting an action potential across the synapse?

  Sodium ion channels open
• what is the ninth step in transmitting an action potential across the synapse?

  Sodium ions diffuse across the post synaptic membrane into the post synaptic neuron.
• what is the tenth step in transmitting an action potential across the synapse?


  A generator potential or excitatory post synaptic potential is created
• what is the first step in transmitting an action potential across the synapse?

  If sufficient generator potentials combine ,the potential across the post synaptic membrane reaches the threshold value, and a new action potential is created in the post synaptic neuron.
• if acetylcholine is left in the synaptic cleft, it will continue to open the sodium ion channels in the post synaptic membrane which causes more action potentials to occur.
• Acetylcholinesterase is an enzyme found in the synaptic cleft, it hydrolyses the acetylcholine into ethanoic acid and choline; this stops the transmission of signals so that the synapse doesn't continue to create more action potentials in the post synaptic neuron.