02. Ionotropic Receptors and Synapses

• excitatory synapses generate an EPSP
• inhibitory synapses generate an IPSP

  • NTs = glycine in the spinal cord and GABA in the brain
  • receptors lead to chlorine channels opening causing hyperpolarisation
• glutamate is the main excitatory NT in the brain
• glutamate has two receptor types: NMDA and AMPA

  • both permeable to Na+ and K+ (Na+ entry exceeds K+ exit leading to excitation)
  • NMDA permeable to Ca2+ too

  AMPA is rapid while NMDA is slow
• NMDA is blocked by extracellular Mg2+at -80mVs, and APV (drug)

  • NMDA is voltage sensitive as depolarisation removes this block
  • Ca2+ enters which is associated with plasticity
  • therefore strong depolarisation = Ca2+ entry
  • leads to often used connections becoming stronger