NSCI426 Lecture Notes - Lecture 4: Nicotinic Acetylcholine Receptor, Neuromuscular Junction, Sympathetic Nervous System
19 Mar 2019
School
Department
Course
Professor
MPN
Thursday 2/21/19
Lecture 4: Action Potentials & Synaptic Transmission
• Cranial nerves
o 12 and used for all 5 senses
• Parasympathetic Nervous System
o Sympathetic: ACh then norepinephrine
o Parasympathetic: both ACh
• Action Potentials
o Voltage-gated sodium channels open and sodium enters the cell
o Then potassium channels open, and potassium leaves the cell
o Transmission of an action potential-along an axon the wave propagates
o Saltatory conduction-fast, depolarization gets regenerated at nodes of Ranvier (in between
myelin)
• Neurotransmitter Release
o Depolarization: Ca+2 channels open and allow vesicles to doc
o Vesicles fuse to synapse and release contents of neurotransmitters
o Neurotransmitters bind to receptor on receiving cell
o Life Cycle:
▪ Synthesis: L-dopa is precursor to dopamine & treatment for Parkinson’s
• Give cells dopamine, but can’t pass blood-brain barrier
• Can give patients L-dopa that will synthesize dopamine once entered in the brain
▪ Packaging-Ca+2 is released and encourages vesicles to doc with membrane
▪ Release-vesicles fuse with membrane and undergo exocytosis
▪ Post-synaptic binding
▪ Termination: neurotransmitter is terminated (deactivated) by enzymatic degradation
and reuptake into cells; broken down into other compounds that are not the NT
• Dopamine active transporter (DAT) for reuptake of dopamine
• Synapses
o 1) Chemical-slower than electrical, amount of raw material gets depleted
▪ Large life cycle process; multistep process
▪ Gives flexibility, ways to change, areas to target
▪ Tolerance, may lead to addiction
o 2) Electrical-automatic depolarization that spreads immediately to next neuron
▪ Sleek, simple, immediate
▪ Don’t really have two distinct cells that have their own characteristics
• Post-synaptic membrane: 2 receptor classes that bind to NT
o Ionotropic: ligand-gated ion channels
▪ Nicotinic receptor
o Metabotropic: G-protein coupled receptors
▪ Muscarinic receptor
▪ Indirect process with many steps
▪ NT binds→ G protein is activated → G protein changes conformation
▪ Amplification-of signal with G protein couples receptors
o Neurotransmitters-have different receptor subtypes
▪ Nicotinic-skeletal muscle; activated by nicotine
• Neuromuscular junction
