Introduction to Brain and Behavior

• Types of CNS Synapses: Axodendritic - axon to dendrite. Axospinous - axon to a dendritic spine. Axosomatic: axon to cell body. Axoaxonic: axon to axon.
• Autoreceptors: presynaptic receptors sensitive to NT released by presynaptic terminal. Cause inhibition of further NT release. Function as safety valve (negative feedback) because if enough NT to reach the receptor it notifies nerve terminal to slow release. Terminal or somatodendritic types. Almost all nervous systems have so drugs target.
• Types of CNS Synapses: Gray's type I: asymmetrical usually excitatory. Gray's type II: symmetrical usually inhibitory.
• Neuromuscular Junction: Archetypal synapse. Chemical synapses between motor neurons of spinal cord and skeletal muscle. Established principles of synaptic transmission (larger synapse, easier to study). Acetylcholine release cause muscle movement.
• Synaptic Transmission Steps: 1) NT/peptide synthesis 2) packaging into synaptic vesicles 3) vesicle fusion 4) NT release into synaptic cleft 5) Binding to postsynaptic receptors 6) Biochemical/electrical response elicited in postsynaptic cell 7) Removal of NT from synaptic cleft
• Criteria for NT: 1) Substance must be present in presynaptic terminal 2) Must be released in response to presynaptic depolarization and release must be calcium dependent 3) Specific receptors for the substance must be present on postsynaptic cell
• NT Synthesis and Storage: each neuron contains specialized enzymes required to synthesize NT in nerve terminal. Vesicular transporters in vesicle membrane concentrate NTs into synaptic vesicles. packing into synaptic vesicles protects NT from breakdown by enzyme in presynaptic terminal.
• Reserpine: meant to decrease blood pressure with vasal dilation. blocks vesicular storage of dopamine, serotonin, norepinephrine. led to first biological theory of depression
• Neuropeptides Synthesis and Storage: synthesized in ER, split in Golgi, and bud off into a secretory granule. Large dens-core vesicles. Precursor proteins borken down by enzymes during shipment to axon terminals. Not replenished quickly. Greater depolarization needed than NT