1. Comparative Vertebrate Physiology
Communication between neurons The synapse

2. Synapses Types Electrical & chemical Membranes
presynaptic & postsynaptic
Synaptic cleft

3. Electrical synapse
Gap junctions
An all electrical event

4. Chemical synapse
An all chemical event

5. Chemical synapse ion influx presynaptic binding exocytosis diffusion
neurotransmitter breakdown and recycling
postsynaptic binding
extracellular ion influx

6. Postsynaptic membrane
Events
Ion influx (Na+, Cl-)
Ion efflux (K+)
Ach degradation (acetylcholinesterase)
Protein channel closes

7. Synaptic delay 0.3 - 5.0 msec Delay caused by fusion and diffusion
Reducing delay
reduce pathway length
reduce number of synapses
Start
Finish

8. Neurotransmitters Major categories Acetylcholine
Amino acids (glutamate, aspartate, glycine)
Biogenic amines (dopamine, norepinephrine, epinephrine)

9. Postsynaptic transmission
EPSP: a single depolarization
Na+ influx

10. Postsynaptic transmission
IPSP: a single hyperpolarization
K+ efflux or Cl- influx

11. Summation Temporal: PSP’s occur at different times
Spatial: PSP’s occur at the same time

12. Neural integration
Facilitation: neurons facilitate communication at the synapse using Ca++
Synaptic inhibition (pre- and post-)

13. Synaptic sensitivity pH Hypoxia Drugs
Alkalosis leads to hyperexcitability
Acidosis leads to coma
Hypoxia
Leads to unconsciousness
Drugs
Caffeine increases excitability
Strychnine increases excitability
Anesthetics decrease excitation