Synaptic tranmission

• How do neurons communicate with each other?

  In groups known as neural networks
• What is a neuron separated by?

  Synapses
• Synaptic transmission

  Diagram of synaptic transmission

  A) Axon

  B) Synapse

  C) Dendrite

  D) Neurotransmitter

  E) Synaptic vesicle

  F) Postsynaptic receptor

  G) Presynaptic terminal

  
• What happens when an electrical impulse reaches the presynaptic terminal?

  Triggers release of neurotransmitter
• Where are neurotransmitter released from?

  Synaptic vesicles
• What are synaptic vesicles?

  Tiny sacs
• What is the presynaptic terminal?

  End of the neuron
• How are signals transmitted between neurons?

  Chemically across the synapse
• What are neurotransmitters?

  Chemicals that diffuse across the synapse to the next neuron
• What happens once a neurotransmitter crosses the synapse?

  Taken up by postsynaptic receptor site
• Where are the postsynaptic receptor sites located?

  Dendrites of the next neuron
• What happens to the chemical message once it reaches the postsynaptic receptor site?

  Converted back into electrical impulse
• What can direction of travel only be?

  One-way
• Why can the direction of travel only be one-way?

  Neurotransmitters released from presynaptic terminal and received by postsynaptic neuron
• Several dozen types of neurotransmitter have been identified in the brain
• What does each type of neurotransmitter have?

  Its own specific molecular structure that fits perfectly into a postsynaptic receptor site
• What is an example of a neurotransmitter?

  ACh
• What does ACh stand for?

  Acetylcholine
• Where is ACh found?

  At each point where a motor neuron meets a muscle
• What will ACh do?

  Cause muscles to contract upon its release
• What is excitation?

  Where a neurotransmitter increases the positive charge of the postsynaptic neuron
• What is the effect of excitation?

  Increases the likelihood that the postsynaptic neuron will pass on the electrical impulse
• What is inhibition?

  When a neurotransmitter increases the negative charge of the postsynaptic neuron
• What is the effect of inhibition?

  Decreases the likelihood that the postsynaptic neuron will pass on the electrical impulse
• What is the process of synaptic transmission?

  1. Electrical impulse reaches presynaptic terminal
  2. Triggers release of neurotransmitters from synaptic vesicles
  3. Neurotransmitter diffuses across synapse
  4. Taken up by postsynaptic receptor site
  5. Chemical message converted back to electrical impulse and new action potential triggered
  6. Neurotransmitter broken down by enzymes/reuptaken
• What is the process of whether a neuron fires decided by?

  Summation
• What happens if the net effect on the postsynaptic neuron is inhibitory?

  Less likely to fire
• What happens if the net effect on the postsynaptic neuron is exhibitory?

  More likely to fire
• What is the action potential of the postsynaptic neuron only triggered if?

  The sum of inhibitory and exhibitory signals reaches the threshold