1. Cell to cell communication in the nervous system The synapse Electrical synapse Chemical synapse Role of calcium “neurocrines” Receptors Post-synaptic responses Terminating synaptic neurotransmission

2. The synapse Presynaptic cell Synaptic cleft Postsynaptic cell

3. Electrical synapse Rapid Few cns neurons, glia Cardiac muscle Smooth muscle

4. Chemical synapse Releases neurotransmitter Synaptic vesicles Docking

5. The effect of calcium on synaptic neurotransmission Action potential Voltage gated Ca++ channel Synaptic vesicle docking Neurotransmitter exocytosis Ligand/receptor binding on postsynaptic cell.

6. Substances released by neurons paracrines –Neurotransmitters (act at synapse) and neuromodulators (act away from synapse) –Neurohormones released into blood Autocrines, same signaling molecules act on the cell that releases them

7. Examples of neurotransmitters Acetylcholine- neuromuscular jn and CNS Amino acids – glycine, glutamate, GABA amino acid derived amines – epinephrine, norepinephrine, dopamine, serotonin Peptides – substance P, endorphins Purines - ATP Gases – nitric oxide

8. Multiple neurotransmitter receptors Ionotropic – ligand gated channels Metabotropic – ligands activate 2 nd messengers and/or G proteins that gate the channel

9. Metabotropic receptor Ionotropic receptor

10. Multiple neurotransmitter receptors: subtypes Cholinergic – nicotonic (neuromuscular jn), ligand gated –Muscarinic, 5 subtypes, G protein and 2 nd messenger linked

11. Adrenergic receptors Adrenergic – alpha and beta –Linked to G proteins and 2 nd messengers –Alpha and beta are linked to different G proteins and different 2 nd messengers

12. Glutaminergic receptors Important in the CNS Named for agonists AMPA receptors – ligand gated NMDA receptors – bind ligand (glutamate) but channel opens during depolarization

13. Glutamate Receptors AMPA receptor NMDA receptor

14. Duration of post-synaptic response Fast synaptic potential, usually from ionotropic receptors. –A channel is opened –Synaptic potential can be depolarizing or hyperpolarizing Slow synaptic potential –G proteins and 2 nd messengers –Slower and lasts longer

15. Neurotransmitter activity is quickly terminated Acetylcholine is broken down by acetylcholinesterase

16. Neurotransmitter activity is terminated Norepinephrine is actively transported back to the pre-synaptic axon CNS neurotransmitters (amines, peptides, amino acids) move into circulation or transported to pre-synaptic terminal.