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Neuron 4 regions: – Cell body – – Presynaptic terminals Dentrites – Contains nucleus Metabolic center Receive incoming signals from other nerve cells Axon Transports signals away to other neurons What is an Action Potential? Defn. Electrical signal conveyed down an axon What causes it? – An environmental stimulus (ex. Light, pressure, odor, mechanical contact, etc.) These stimuli cause the axon hillock (start of the axon) to create an action potential The action potential continues to the end of the axon Action Potential Properties Travel small or large distances (.1mm-3m) Rapid and transient (duration of about 1ms) Constant amplitude (100mV) All or none nerve impulse Travels in one direction (principle of dynamic polarization) (Dominos display) Action Potential Overview environmental stimulus Axon hillock (initial segment) resting membrane potential (-70mV) threshold (-55mV) Na+ influx thru open Na+ channel activation gates (+30mV) depolarization Repolarization K+ outflow thru open voltage-gated K+ channels Na+ channel inactivation gates close hyperpolarization membrane more permeable to K+ than normal K+ channel closes returns to resting potential adjacent membrane voltage gated Na+ channels open depolarization propagated (aka conduction) How does the action potential impact the neuromuscular junction? action potential axon terminals synaptic end bulbs synaptic vesicles binds to plasma membrane ACh binds to receptors at the muscle moter endplate located in mid-muscle cation (Na+) channel opens changing the resting membrane potential muscle action potential created muscle contraction