Synaptic transmission

• what is a synapse?

  the junction at the axon terminal of one neuron and the dendrite of the next neuron.
• what happens when the action potential reaches the axon terminals?

  the message is converted into a chemical message at the synapse of the pre-synaptic neuron.
• what are the chemical messengers in synaptic transmission called?

  Neurotransmitters.
• which neuron is where the axon terminal is in synaptic transmission?

  the pre-synaptic neuron
• when the action potential reaches the axon terminal of the pre-synaptic neuron, what does it trigger?

  this triggers the action of the synaptic vesicles containing neurotransmitter molecules.
• where are the neurotransmitter molecules released into?

  the synaptic cleft where they diffuse across.
• what do the neurotransmitters bind with?

  receptors on the dendrite of the post-synaptic neuron.
• what are the two types of neurotransmitter?

  excitatory and inhibitory
• what are excitatory neurotransmitters?

  they increase the likelihood of the next neuron firing, by increasing the positive charge of the post-synaptic neuron.
• what are inhibitory neurotransmitters?

  they decrease the likelihood of the next neuron firing, by increasing the negative charge of the post synaptic neuron.
• what does normal brain functioning depend on?

  a regulated balance between excitatory (accelerator) and inhibitory (brake) influences.
• after the chemical messages have been delivered, what three processes can cause the amount of neurotransmitters at the synapse to drop?

  diffusion, breaking down by enzymes, reuptake by pre-synaptic neurons.
• What is an action potential?


  A short increase and decrease of electrical activity in the membrane of a neuron, transmitting a signal away from the cell body.
• What is a neurotransmitters?


  brain chemicals released from the synaptic vesicles that relay signals across the synapse from one neuron to another. Neurotransmitters can be broadly divided into those that perform an excitatory function and those that perform an inhibitory function.
• What is summation?


  The process that determines whether or not an action potential will be triggered, based on the combined effects of the excitatory and inhibitory signals of the neurotransmitters.
• When will an action potential in the postsynaptic neuron be triggered?


  If the net effect is excitatory, causing the inside of the postsynaptic neuron to become momentarily positively charged. Sum of excitatory and inhibitory signals at any one time reaches threshold.