Synaptic transmission

• Neurons communicate with each other within groups known as neural networks
• Each neuron is separated from the next by a synapse

  The synapse includes the space between them (called the synaptic cleft) as well as the pre synaptic terminal and postsynaptic recpetor site
• Signals within neurons are transmitted electrically, however signals between neurons are transmitted chemically (synaptic transmission)
• When the electrical impulse reaches the end of the neuron (the presynaptic terminal) it triggered the release of neurotransmitters from where?

  Synaptic vesicles (tiny sacs)
• What are neurotransmitters ?

  Chemicals that diffuse across the synapse to the next neuron in the chain
• Once the neurotransmitter crosses the gap, what is it taken up by?

  Postsynaptic receptors sites (the dendrites of the next neuron). Here the chemical message is converted back into an electrical impulse
• What can be used to describe the idea that each neurotransmitter has its own specific molecular structure that fits perfectly into a post-synaptic receptor site?

  Lock and key model
• What happens if the neurotransmitter doesn’t bind to receptors site?

  Reuptake
• Neurotransmitters have either an excitatory or inhibitory effect on the neighbouring neuron
• What does excitation mean?

  When a neurotransmitter increases the positive charge of the postsynaptic neuron. This increases the likelihood that the neuron will fire and pass on the electrical impulse
• What does inhibition mean?

  When a neurotransmitter makes the charge of the postsynaptic neuron more negative. This decreases the likelihood that the neuron will fire and pass on the electrical impulse
• Example of a neurotransmitter that causes inhibition?

  Serotonin
• Example of a neurotransmitter that causes excitation?

  Adrenaline
• Why can direction of travel only be one way?

  Neurotransmitters are released from the presynaptic neuron and received by receptors that only exist on postsynaptic neurons
• What is summation?

  When a postsynaptic neuron integrates multiple excitatory and inhibitory signals from presynaptic neurons to determine whether it will generate action potential, based on the net effect of these signals
• When is the only time the action potential of the postsynaptic neuron triggered?

  If the sum of the excitatory signal and inhibitory signals at any one time reaches the threshold