HTHSCI 1H06 Chapter Notes -Purine, Acetylcholine, Ligand-Gated Ion Channel
23 Sep 2013
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Document Summary
Depolariztion and repolarization of each adjacent segment of plasma membrane. Unmyelinated axons and muscle fibers exhibit continuous conduction. Action potentials travel faster along myelinated axons than unmyelinated axons. Uneven distribution of voltage-gated channels in membrane. Action potentail at first node generates ionic currents in cytosol and extracellular fluid that depolarize membrane to threshold, opening voltage- gated na+ channels at second node. Action potential leaps from node to node as each nodal area depolarizes to threshold. Factors that affect speed of propagation: amount of myelination, axon diameter, larger diameter axons propagate action potentials faster than smaller ones because of increased surface area, temperature, action potentials travel faster when heated. Presynaptic neuron nerve cell that carries nerve impulse towards synapse. Postsynaptic cell cell that receives nerve impulse signal. Postsynaptic neuron carries nerve impulse away from synapse or an effector cell that responds to impulse at synapse.
