Cholinergic Synapses and Neuromuscular Junctions

• where can Cholinergic Synapses be found>

  central nervous system and between neurones and muscle cells.
• why do biologists call these chemical synapses ‘cholinergic’?

  they use the neurotransmitter acetylcholine.
• what are 2 neurones separated by?

  a synaptic cleft.
• What would you expect the voltage-gated ion channels that only transport calcium ions to be called?

  voltage-gated calcium ion channels
• When an action potential arrives at a presynaptic neurone, it results in depolarisation of the membrane.

  This causes voltage-gated calcium channels to open.
• what do biologists call the sequence of event happening at a synapse?

  synaptic transmission
• What type of ions depolarise the post-synaptic neurone?

  sodium
• what are the binding sites for acetylcholine on sodium channels are called?

  receptor
• A constant action potential prevents the postsynaptic neurone from separating different action potentials into…

  discrete impulses.
• synaptic transmission

  1: An action potential arrives at the presynaptic neurone and causes the presynaptic membrane to become depolarised

  2: Voltage-gated calcium channels open. Calcium ions diffuse into the synaptic knob, which causes synaptic vesicles to move down the synaptic knob.

  3: Synaptic vesicles fuse with the presynaptic membrane, which leads to acetylcholine being released into the synaptic cleft.

  4: Acetylcholine diffuses across the synaptic cleft, where it binds to receptor sites on sodium channels, causing them to open.

  5: Sodium ions diffuse into the postsynaptic neurone, which leads to an action potential inside the postsynaptic neurone.

  6: Acetylcholinesterase breaks down acetylcholine into choline and ethanoic acid.

  7: Choline and ethanoic acid are taken back into the presynaptic neurone, where they're recombined to form acetylcholine.

  8: Acetylcholine is transported into synaptic vesicles using ATP.

  
• what is a neuromuscular junction?

  a synapse between a motor neurone and a muscle cell.
• what is a cholinergic synapse?

  synapse between 2 neurones
• List the similarities between cholinergic synapses and neuromuscular junctions.

  Both involve neurotransmitters packaged in vesicles that diffuse across a synaptic cleft when they are released.Ca2+ channels are involved in both.In both, there are sodium channels on the postsynaptic membranes with two receptor sites.In both, enzymes are involved in catalysing the reformation of the neurotransmitter, which is then packed back into vesicles in the presynaptic membrane using energy from ATP.In both, there is depolarisation of the postsynaptic membrane.
• List the differences between cholinergic synapses and neuromuscular junctions.

  The presynaptic neurone of cholinergic synapses can be a motor or relay neurone but in neuromuscular junctions, the presynaptic neurone is always a motor neurone.Cholinergic synapses link motor/relay neurones to other neurones or effector organs while neuromuscular junctions link neurones to muscles cells.Acetylcholine is the only neurotransmitter in cholinergic synapses. In neuromuscular junctions, many different neurotransmitters can be used.Nerve impulses end at a neuromuscular junction, as a muscle contraction occurs. In cholinergic synapses, the nerve impulse continues.
• what do Cholinergic synapses link?

  motor/relay neurones to other neurones, or motor neurones to effector organs
• neuromuscular junction diagram ->just flip over


  n

  
• cholinergic junction diagram ->just flip over


  c