BILD 2 Chapter Notes - Chapter 37: Hyperkalemia, Extracellular Fluid, Resting Potential
8 Dec 2015
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In myelinated axons, vg na+ channels are restricted to nodes of ranvier (ec fluid is only in contact with axon membrane here). Ap"s not generated between the nodes (only current flow here). The rise in ca2+ concentration causes some synaptic vesicles containing neurotransmitters to fuse with the presynaptic membrane, releasing neurotransmitter into the synaptic cleft. Then, the neurotransmitter binds to ligand-gated ion channels in the postsynaptic membrane. Na+ opens, the membrane potential depolarizes toward a value midway between ek and ena. It brings membrane potential toward the threshold; depolarization graded potential. Ipsp - selectively permeable ion channels for k+ or cl- opening causes hyperpolarization moving membrane potential away from the threshold. Synaptic cleft - gap separates presynaptic neuron from postsynaptic cell. Hyperkalemia is a condition by which increased reabsorption of potassium ions by the kidney leads to a considerable increase in potassium ions in the extracellular fluid.
