Synapses

• What are vesicles filled with at a synapse?

  Neurotransmitter
• What is the role of the presynaptic neurone in synaptic transmission?

  It releases neurotransmitters into the synaptic cleft
• What is the synaptic cleft?

  The gap between presynaptic and postsynaptic neurones
• Why can impulses only travel in one direction at a synapse?

  Neurotransmitter is only in presynaptic neurone
• What happens when an action potential arrives at the presynaptic axon terminal?

  Calcium ion channels open
• What occurs after calcium ions diffuse into the neurone?

  Calcium binds to vesicles
• What process releases neurotransmitters from vesicles?

  Exocytosis
• What happens to neurotransmitters after they bind to receptors?

  Sodium ion channels open, causing depolarization
• What is the result of depolarization in the postsynaptic neurone?

  A new action potential is generated
• Why is the neurotransmitter broken down after binding?

  To prevent continuous stimulation of the postsynaptic neurone
• What do agonist drugs do?

  Mimic neurotransmitters and increase action potentials
• Which drug is an example of an agonist?

  Nicotine
• What do antagonist drugs do?

  Block neurotransmitters and reduce action potentials
• What is the role of serotonin in the brain?

  Links to moods and feelings
• Which neurotransmitter is found at neuromuscular junctions?

  Acetylcholine
• What does dopamine influence in the brain?

  Speech, movement, and balance
• What are the steps of synaptic transmission?

  1. Action potential arrives at presynaptic terminal
  2. Calcium channels open
  3. Calcium diffuses into neurone
  4. Calcium binds to vesicles
  5. Vesicles fuse with presynaptic membrane
  6. Neurotransmitter released by exocytosis
  7. Neurotransmitter diffuses across synaptic cleft
  8. Neurotransmitter binds to receptors on postsynaptic membrane
  9. Sodium channels open, leading to depolarization
  10. Neurotransmitter is broken down and reabsorbed
• What are the effects of agonist and antagonist drugs on neurotransmission?

  • Agonist drugs:
  • Mimic neurotransmitters
  • Increase action potentials
  • Antagonist drugs:
  • Block neurotransmitters
  • Reduce action potentials
• What are the main neurotransmitters mentioned and their functions?

  • Acetylcholine: Stimulates muscle contraction
  • Serotonin: Links to moods and feelings
  • Dopamine: Links to speech, movement, and balance