Synapses

• What are two types of neurones

  Excitatory and inhibitory
• What is a excitatory neurone


  Excitatory neurotransmitters result in the depolarisation of the post synaptic neurone, if threshold is met in the post synaptic neurone and action potential is triggered
• What is an example of a excitatory neurone

  Acetylcholine
• What does a inhibitory neurone do

  These neurotransmitters result in hyper polarisation of the post synaptic membrane, preventing an action potential being triggered
• What is an example of an inhibitory neurone

  GABA
• What is synaptic cleft

  The gap that separates the axon of one neurone from the dendrite of another neurone
• how big is synaptic cleft typically

  20-30nm
• What is the pre synaptic neurone

  The neurone where the impulse arrives
• What is the post synaptic neurone

  neurone that receives the neurotransmitters
• What is the synaptic knob


  The swollen end of the pre synaptic neurone
• What are synaptic vesicles

  Vesicles containing neurotransmitters and fuse with pre synaptic membrane
• What is a receptor

  Neurotransmitters bind to on the post synaptic neurone
• How does synaptic transmission occur

  1. action potential reachers the end of the pre synaptic neurone
  2. depolarising the pre synaptic membrane do calcium ion channels open
  3. calcium ions diffuse into pre synaptic knob
  4. vesicles then fuse with pre synaptic membrane so NTS released into synaptic cleft by excoytosis
  5. NTS diffuse across the cleft and bind with receptors on post synaptic membrane
  6. causing sodium ion channels to open diffusing inti post synaptic neurone
  7. This triggers and action potential along the post synaptic neurone
• What happens once an action potential has been triggered in the post synaptic neurone

  it is removed so that the stimulus is not maintained
• What is acetylcholine broken down by

  By enzymes and taken back into pre synaptic neurone
• Transmission across a Cholinergic synapse

  1. These synapses use the NT acetylcholine, commons where a motor neurone and a muscle cell meet
  2. when the NTS reach the receptors on the muscle cell it contracts
  3. acetylcholine released from vesicles into synaptic cleft and binds to specific receptors of post synaptic neurone
  4. triggering an action potential in post synaptic neurone or muscle
  5. once action potential is triggered acetylcholine is hydrolysed by acetylcholinesterase and breaks it down into choline and ethanols acid
• How many acetylcholine molecules can be broken down in one minute by acetylcholinesterase

  25,000 molecules
• What are three roles of a synapse

  1.ensure impulses are unidirectiona since the receptors are only present on post synaptic membrane

  2. Allow a impulse from one neurone to be transmitted to a number of neurones

  3. A number of neurones to feed an impulse to the same neurone
• What can a single Impulse in some neurones not produce

  An action potential
• What is the amount of neurotransmitters build up t reach the threshold called

  Summation
• what is spatial summation

  When a number of pre synaptic neurones connect to one post synaptic neurone to build up amount of neurotransmitters
• What is temporal summation

  when a pre synaptic neurone resales neurotransmitters serval times due to an action potential
• What do drugs that stimulate the nervous system do

  Create more action potentials in the post synaptic neurone resulting in enhanced responses
• How do drugs enhance the nervous system

  1.mimick the shapes of neurotransmitters

  2. Stimulate the release of more neurotransmitters

  3. Inhibit enzymes responsible for breaking them down

  4. Blocking receptors so neurotransmitters cannot bind