Postsynaptic effect of neurotransmission

Postsynaptic effect of neurotransmission

1. Action potential isn't produced by postsynaptic terminal right away

   • Result can be graded potentials that increase or decrease likelihood of an action potential being produced

2. NT receptors can open ion channels to produce an excitatory presynaptic potential (EPSP)

   • Via Na+ influx (depolarisation)

3. Integrating EPSP & IPSP

   • EPSP & IPSPs travel along dendrite to membrane
     • Action potentials aren't produced here
       • No voltage-gated Na+ & K+ channels
   • Graded potentials must reach axon hillock
     • So EPSP can produce action potential

4. NT receptors can open ion channels

   • Produce Excitatory Postsynaptic Potential (EPSP) via Na+ influx (depolarisation)
   • Inhibitory Postsynaptic Potential (IPSP) produced via Cl- influx or K+ efflux (hyperpolarisation)

5. Summation

   • Neuron can have >50,000 connections to others
     • Can receive enormous No. of EPSP & IPSP in space & time, which must be integrated
   • Temporal
     • Graded potentials that occur at approx same time on membrane
       • Summed & produce large EPSP or IPSP
   • Spatial
     • Graded potentials that occur at approx same place on membrane
       • Summed
     • Action potential produced when enough EPSPs sum to reach activation threshold

6. IPSP

   • Inhibits generation of action potentials
     • Because inhibition stabilises responses, control timing of signals, prevent too much electrical firing