The Structure and Roles of Synapses in Neurotransmitters

• what is a cholinergic synapse?

  • uses acetylcholine as its neurotransmitter
• what is summation?

  • occurs when the effects of several EPSPs are added together
• what are Excitatory post-synaptic potentials?

  • a small post-synaptic potential that makes the neurone more likely to fire an action potential
• what are Inhibitory post-synaptic potentials?

  • synaptic potential making a post-synaptic neurone less likely to generate an action potential and neurotransmitters may bind to the post-synaptic membrane and close ion channels
• what is temporal summation?

  • adding up several action potentials in the same pre-synaptic neurone
• what is spatial summation?

  • adding up due to action potentials arriving from several different pre-synaptic neurones
• what is habituation?

  • reduced neural signalling following repeated stimulation, due to the reduced release of neurotransmitter vesicles
• higher intensity of stimulus will produce more generator potentials in the sensory receptor, causing more frequent action potentials, more vesicles released, higher frequency of action potentials in post-synaptic neurone
• higher frequency of signals in neurones, more intense stimulus
• what is temporal summation mainly about?

  frequency
• what is spatial summation mainly about?

  collection of potentials
• how does temporal summation work?

  • small EPSPs in post-synaptic neurone don't create an action potential until they act together
• how does spatial summation work?

  • several pre-synaptic neurones may each contribute to producing an action potential
• how does the reflex arc work?

  • one pre-synaptic neurone diverges to several post-synaptic neurones
  • this can allow one action potentials to be transmitted to several parts of the nervous system
• EPSPs vs IPSPs

  • the combination of several EPSPs could be prevented from producing an action potential by one IPSP, which blocks Na+ channels or releases another ion to change the charge on the post-synaptic neurone
  • e.g. one IPSP would be GABA
• how does habituation work?

  • fatigued synapse may run out of vesicles containing a neurotransmitter
  • nervous system no longer responds to stimulus - we have become habituated to it
  • this helps avoid overstimulation of an effector, which could cause damage
• how does memory work in synapses?

  • creation and strengthening of specific pathways within the nervous system
  • synaptic membranes are adapted
  • post-synaptic neurone can be made more sensitive to acetlycholine by the addition of more receptors, so its more likely that the action potential will fire