exam questions

• describe how dopamine acts as a neurotransmitter(4)

  • dopamine released from presynaptic membrane into synaptic cleft and diffuses across synaptic cleft
  • it binds to receptors on post-synaptic membrane
  • this opens sodium ion channels in post synaptic membrane
  • initiating depolarisation/action potential in post synaptic neurone
• describe how MDMA use could affect the transmission of impulses in the brain(2)

  • MDMA prevents the reuptake of serotonin thus increasing concentration in synaptic cleft
  • does this by blocking the pre-synaptic receptors
  • nerve pathways using serotonin are more likely to be stimulated/action potentials produced
• Describe how low serotonin levels in an individual can affect the transmission of impulses in their brain.(2)

  • there will be less neurotransmitter(serotonin)
  • less serotonin results in fewer depolarisations of post synaptic membranes
  • threshhold not achieved and less chance of action potential being produced in post-synaptic neurone
• The transmission of an impulse between a neurone in the optic nerve and a cell in the brain involves ions and neurotransmitter molecules.

  Describe how these ions and neurotransmitter molecules are involved in the transmission of an impulse(4)

  • calcium ions enter presynaptic neurone so vesicles with NT can move towards and fuse with presynaptic membrane
  • NT molecules diffuse across the synapse
  • NT binds with receptors on postsynaptic membrane
  • sodium ions diffuse into post-synaptic membrane leading to depolarisation
• describe the process that occurs at a synapse that leads to habituation(4)

  • repeated stimulus decreases permeability of pre-synaptic membrane, so calcium ion channels are not opening
  • fewer CA+ move into presynaptic membrane
  • so less NT released and diffuses across gap
  • depolarisation is less likely to occur in post-synaptic neurone
• explain how SSRIs help to maintain a feeling of wellbeing(3)

  • SSRIs bind to reuptake proteins
  • serotonin levels remain high in synapse
  • serotonin binds to receptors on post-synaptic membrane
  • depolarisation of post-synpatic membrane
  • action potentials/impulses continues