Synapse and receptors

• Where are action potentials initiated. 


  Axon hillock.
• What type of conduction does mylination cause.

  Saltatary.
• Describe propagation down an unmyelinated Axon.

  1. Initial segment action potential.
  2. Local current depolarizes the adjacent portion to the threshold.
  3. Initial segment refractory period
  4. Repeat
• Describe saltatory propagation.

  1. Action potential at initial segment
  2. Node 1 depolarised to threshold
  3. Repeat
• Name the two types of synapses.

  • Chemical
  • Electrical
• How do electrial synapses work.

  Information is transmitted directly between neurones via gap junction channels.
• How do chemical synapses work.

  1. Action potential opens Ca2+ channels
  2. Vesicles fuse with Pre-synaptic membrane
  3. Transmitter released into synaptic cleft
  4. Receptors on post-synaptic membrane
  5. Catoblism or Reuptake of transmitter.
• Which cells are involved in reuptake of neruotransmitters.

  • Pre-synaptic neurone
  • Glial cells
• What are EPSPs


  Exitatory Post synaptic potentials.
• What are IPSPs


  Inhibitory post synaptic potentials.
• Two types of transmitter receptors.

  • Ionotropic
  • Metabotropic
• What type of effects to ionotropic receptors have and how.

  • Stimulatory
  • Open ligand-gated ion channels
• What type of receptors are metabotropic.

  • GPCR
• How are ionotropic receptors strucutred.

  4 or 5 subunits around a central pore.
• Examples of ionotropic ligands.

  1. Nicotinic ACh
  2. GABAa
  3. Glycine
  4. 5-HT3
  5. Glutamate [NMDA and non-NMDA]
• Describe metabotropic receptor structure.

  • 7 membrane-spanning regions [7TM]
  • 3 Extracellular transmitter sites
  • 4 Intracellular G-protein sites
• Examples of metabotropic receptors.

  • 5-HT
  • GABAb
  • Adrenergic receptors
  • mGlut
  • Muscunaric ACh receptors
  • Dopamine
• Describe GPCR actions.

  1. Transmitter binds
  2. GDP is Phosphorylised [Alpha subunit]
  3. G-protein dissociates [A,B,Y]
  4. Alpha activates ion channel
  5. GTP is hydrolysed
• What are the 3 main enzymes that GPCRs target

  • Phospholipase C [IP3 + DAG]
  • Adenylate Cyclase [cAMP]
  • Guanylate cyclase [cGMP]
• What are agnoists. 


  mimic neurotransmitters and stimulate receptor.
• What are antagnosits. 


  Mimic neurotransmitter and inhibit receptor.