neuron & synaptic transmission

• What is synaptic transmission?

  It is a method of neurons communicating with each other.
• What role do sensory neurons play in synaptic transmission?

  They relay information to the central nervous system (CNS).
• How do motor neurons function in synaptic transmission?

  They send information to effectors to carry out responses dictated by the brain.
• What are the steps involved in the process of synaptic transmission?

  1. Action potential arrives at the presynaptic membrane.
  2. Depolarization occurs via opening of voltage-dependent calcium ion channels.
  3. Calcium ions influx leads to vesicle fusion and neurotransmitter release via exocytosis.
  4. Neurotransmitter diffuses across the synaptic cleft and binds to receptors on the postsynaptic membrane.
  5. This can result in either an inhibitory or excitatory effect.
  6. Action potential is transmitted along the axon of the following neuron.
• What triggers the opening of voltage-dependent calcium ion channels?

  An action potential arriving at the presynaptic membrane.
• What happens when calcium ions enter the presynaptic membrane?

  It causes vesicles containing neurotransmitter to fuse with the presynaptic membrane.
• What is the role of exocytosis in synaptic transmission?

  It allows the release of neurotransmitters into the synaptic cleft.
• How does the neurotransmitter affect the postsynaptic membrane?

  It can result in either an inhibitory or excitatory effect.
• What is the difference between inhibitory and excitatory neurotransmitters?

  Inhibitory neurotransmitters reduce the likelihood of an action potential, while excitatory neurotransmitters increase it.
• Give an example of an inhibitory neurotransmitter.

  Serotonin
• Give an example of an excitatory neurotransmitter.

  Dopamine
• How do inhibitory neurotransmitters affect the postsynaptic membrane's potential difference?

  They reduce the potential difference by closing voltage-dependent sodium ion channels.
• How do excitatory neurotransmitters affect the likelihood of generating an action potential?

  They increase the likelihood by opening more voltage-dependent sodium ion channels.
• What are the effects of neurotransmitters on the postsynaptic membrane?

  • Inhibitory neurotransmitters (e.g. serotonin):
  • Reduce potential difference
  • Close voltage-dependent sodium ion channels
  • Decrease likelihood of action potential generation
  • Excitatory neurotransmitters (e.g. dopamine):
  • Increase potential difference
  • Open more voltage-dependent sodium ion channels
  • Increase likelihood of action potential generation