Activated rhodopsin triggers a signal transduction cascadeReminder on Ion Distribution and Transport in CellsIon Channels and Transient PermeabilityMwc models of ligand-gated channelsLight-induced hyperpolarization of the rod cell membraneElectrical consequences of illuminationSynapse diffusionOther examples of synaptic communicationSlide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Activated rhodopsin triggers a signal transduction cascadeReminder on Ion Distribution and Transport in CellsCells (eukaryotes) divided into a number of membrane-bound compartments.Concentrations in different compartments can be orders of magnitude different.Proteins (ion channels, transporters) mediate these concentration gradients.Membrane proteins central to huge range of processes – cell signaling, nerve impulses, nutrient transport, etc.Ion Channels and Transient PermeabilityChannels open in response to a variety of different stimuli.Key mechanisms are voltage gating, ligand binding-induced gating and mechanical tension in the membrane.Mwc models of ligand-gated channelsLight-induced hyperpolarization of the rod cell membraneHydrolysis of cGMP causes cation channels to closeRod cell membrane hyperpolarizescGMPElectrical consequences of illuminationhttp://www.d.umn.edu/~jfitzake/Lectures/DMED/Vision/Retina/ReceptorPotential.htmlEach dot in the figure below represents delivery of a very dim pulse of light containing only a few quanta. Voltage responses appear to come in 3 sizes: none, small, and large, representing the detection of 0, 1 or 2 quanta in each flash. The granularity of response to dim light stimuli is evident.http://webvision.med.utah.edu/book/part-ii-anatomy-and-physiology-of-the-retina/photoreceptors/Synapse diffusionhttp://www.colorado.edu/intphys/Class/IPHY3430-200/008sensory.htmOther examples of synaptic communicationOther examples of synaptic communicationOther examples of synaptic communicationOther examples of synaptic communicationOther examples of synaptic communicationOther examples of synaptic communicationOther examples of synaptic communicationOther examples of synaptic communicationOther examples of synaptic
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