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Action Potential - large fibers are myelinated smaller...

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nervous system Action Potential * A more dramatic change produced by voltage-gated ion channels in the plasma membrane * occurs where there is a high enough density of channels * soma 50-75 channels per square micrometer * trigger zone- 350-500 gates per square micrometer * if excitatory local potential spreads to the trigger zone and is strong enough when it arrives (reaching threshold), it can open Na + gates and generate an AP * Threshold- minimum level of depolarization to cause an AP PNS Unmyelinated Fibers Neural Conduction in Mylinated Fibers: Saltatory Conduction Speed of Nerve Impulses The speed of a nerve impulse is determined by * temperature- speed is faster at warmer temperatures * fiber diameter- speed is faster in larger diameter fibers due to larger surface area for conduction * presence or absence of myelin- speed is faster in myelinated fibers (saltatory conduction)
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Unformatted text preview: * large fibers are myelinated * smaller fibers are unmyelinated A regeneration tube or guidance channel is necessary for nerve regrowth and is formed by the neurilemma and endoneurium Neurotransmitter Criteria * The chemical must be produced within a neuron. * The chemical must be found within a neuron. * When a neuron is stimulated (depolarized), a neuron must release the chemical. * When a chemical is released, it must act on a post-synaptic receptor and cause a biological effect (alter the physiology of that cell). * After a chemical is released, it must be inactivated. Inactivation can be through a reuptake mechanism or by an enzyme that stops the action of the chemical. * If the chemical is applied on the post-synaptic membrane, it should have the same effect as...
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