Synaptic Transmission

• What is the process called through which neurons communicate with each other?

  Synaptic transmission
• What is the primary function of synaptic transmission?


  To send information from one neuron to the next
• What are the two main types of effects neurotransmitters can have on the postsynaptic neuron?


  Excitatory and inhibitory
• How do impulses travel along neurons?


  In the form of an action potential
• What is the junction between two neurons called?

  Synapse
• What are neurotransmitters?


  Chemicals that transmit messages across the synapse
• What happens when an action potential reaches the axon terminal?


  It causes synaptic vesicles to release neurotransmitters
• How do neurotransmitters move across the synaptic cleft?


  By diffusion from high to low concentration
• What is the role of receptor sites on the postsynaptic neuron?


  To bind neurotransmitters and activate the neuron
• What is the reuptake mechanism in synaptic transmission?


  It reabsorbs excess neurotransmitters for future use
• Why can information only travel in one direction at the synapse?

  Because synaptic vesicles are only present on the presynaptic neuron
• Which neurotransmitter is purely inhibitory?

  GABA
• What effect does an excitatory neurotransmitter have on the postsynaptic neuron?


  It makes the neuron more likely to fire
• What happens when an inhibitory neurotransmitter binds to its receptor?


  It makes the postsynaptic neuron less likely to fire
• What is an excitatory post-synaptic potential (EPSP)?


  An electrical charge that makes the postsynaptic cell more likely to fire
• What is an inhibitory post-synaptic potential (IPSP)?


  An electrical charge that makes the postsynaptic cell less likely to fire
• What determines whether a postsynaptic neuron fires an action potential?


  The summation of excitatory and inhibitory signals
• What are the key features of a synapse?

  • Synaptic cleft/gap: Separates the axon of one neuron from the next
  • Presynaptic neuron: The neuron that sends the impulse
  • Postsynaptic neuron: The neuron that receives the neurotransmitter
  • Synaptic vesicles: Contain neurotransmitters and release them into the synaptic cleft
  • Neurotransmitter receptors: Bind neurotransmitters on the postsynaptic neuron
• What is the process of synaptic transmission?

  1. Action potential travels down the axon
  2. Synaptic vesicles release neurotransmitters into the synaptic cleft
  3. Neurotransmitters diffuse across the cleft
  4. Bind to receptors on the postsynaptic neuron
  5. Produce excitatory or inhibitory effects
  6. Reuptake of excess neurotransmitters
• How do excitatory and inhibitory neurotransmitters affect the postsynaptic neuron differently?


  • Excitatory neurotransmitters:
  • Increase likelihood of firing
  • Example: Noradrenaline
  • Inhibitory neurotransmitters:
  • Decrease likelihood of firing
  • Example: Serotonin
• What is summation in the context of synaptic transmission?


  • The process by which multiple presynaptic neurons release neurotransmitters simultaneously
  • Determines if the postsynaptic neuron will fire based on net excitatory or inhibitory signals
• What is the threshold needed to fire an action potential?


  • The membrane potential that must be reached for an action potential to occur
  • Typically around -55 mV
• What happens to neurotransmitters after they have acted on the postsynaptic neuron?


  • They are either reabsorbed by the presynaptic neuron or destroyed by enzymes