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8.UC Loyalty Oathmade to make people affirm that they weren't communists, there was a Supreme Court case about it but a CA constitution amendment still says everyone has to sign it
12 Lecture 6
13 After sodium and potassium channels are triggered, they require a few seconds before they can be triggered again. • action potential propagation along axon: Each opening sodium channel activates the one next to it. Goes in the direction of the hillock to the terminus. • axon hillock: Area with a high concentration of sodium and potassium channels, immediately adjacent to the cell soma. • myelin: Coating on the axon exterior of certain neurons that causes action potentials to propagate faster. White myelinated neurons. Mixture of proteins and phospholipids. The bodies of oligodendrocytes in the brain and schwann cells in the peripheral nervous system. • oligodendrocytes: Large flattened cells that make up myelin in the brain. (CNS) • nodes of Ranvier: The nodes of ranvier are the gaps in the myelin that allow sodium and potassium to enter the gates every few hundred micrometers (myelin blocks the voltage gated ion channels otherwise). • saltatory conduction: The mode of the propagation of the action potential in myelinated axons. Lecture 7 Na+ channel densities per square micrometer for: ●Unmyelinated: ~100 ●Myelinated: ~ >10,000 ●Brain has both, but myelinated nerves have some special properties (see below) Myelin speeds up nerve impulse propagation via saltatory conduction (<10 meters per second vs 100 meters per second!) Multiple Sclerosis:
14 ●Auto-immune (body attacking itself) damage to myelin ●Nerve conduction is impaired ●Motor and/or sensory symptoms; variable symptoms Golgi’s “reticular theory” versus Santiago Ramon y Cajal’s “neuron theory” ●The two theories: ○Former is more of the web-like structure and chaotic firing ○Latter (Cajal’s) aligns itself with discrete units and directional firing ●