BCMB 230 1st Edition Lecture 12 Outline of Last Lecture I.Sensory PhysiologyII.Information We Get From ReceptorsIII.Sensory AnatomyOutline of Current Lecture I.Components of the Inner EarII.ChemosensesIII.Looking at the EyeIV.MusclesCurrent LectureSensory Physiology and MuscleI. Components of the Inner EarCochlea-spiral shaped structure (which can be uncurled) composed of three fluid-filled tubes; middle one has the Organ of Corti in it; basilar membrane is stretched along the cochlea-Organ of Corti: contains hair cells connected to a basilar membrane; membrane is tunedso that different pitches stimulate different sections of it-sound captured by outer ear, directs it into the ear cannel, hits the tympanic membrane (eardrum) causing it to vibrate which causes a series of bones to vibrate and then is transferred to the cochlea through the oval window; vibration then goes along the fluid-filled tubes-stapes-the bone above the oval window-middle ear conducts and amplifies signal-allows us to hear soft sounds-get amplification through the tympanic membrane to oval window (taking information from a large area to a small area)-small bones between act as levers and also contribute to amplification-these small bones can be controlled—has small muscles attached to them-muscles can loosen the connections/adjust the tension across the middle ear to help protect it from loud sound-have to make sure air on both sides of the tympanic membrane is equal so that the ear drum does not get pushed out or inThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.-to relieve pressure on middle ear, open auditory/Eustacian tube (connects the middle ear to the back of the throat)Reasons for loss of hearing: -age: lose elasticity of basilar membranecan no longer hear higher pitches-being around loud low soundscan mess up ability to hear lower pitchesII. ChemosensesThree main sensory modes that are chemosensory: taste, smell, visceral (stomach, gut)Chemoreceptors act the same as receptors for chemical messengers: binding site, specificity, etc.-specificity is fairly broad-taste-5 main types of receptors: sweet, sour, salty, bitter, savory (umami) -receptors are scattered over the tongue, but going to be localized to certain areas of thetongue (most receptors are on the tip of your tongue)-smell-receptors in the nasal cavity, have a similar arrangement but have many more different kinds of receptors; plays a critical role in taste; is a stronger sense than tasteIII. Looking at the eye-three main layers of the eye-schlera-the outer layer-in the front of the eye, the outer layer becomes the cornea which is clear-choroid-middle layer- made up of the lens which has ciliary muscles attached to it-there is another set of muscles (makes up the iris) in front of the lens-the hole in the middle of the iris is the pupil-pupil dilates under sympathetic control, constricts under parasympathetic control-retina-innermost layer-mostly on the back of the eye; contains photoreceptors, blind spot is the optic disc where the optic nerve enters the retina; fovea-function of the eye is to detect light and to focus the light into an image-refraction-bend the light in order to focus it on an image-differences in density bends and curved surface bends the light-lens has curvature with muscles attached to it, so its shape is easily adjustable-cornea has density, is not adjustableFour main categories of photoreceptors in rod cells and cone cells-rods are found outside of fovea along the retina; wider distribution, more sensitive to light; usethese for peripheral vision and in the dark-cones are found inside the fovea; sensitive to narrower wavelengths of color: blue, red, and green; huge concentration of receptors, narrower distribution; less sensitive to light thanrods; used to focus during the day—visual acuity-visual acuity-gives you more detailDuring the signal transduction process, stimulating photochemicals (with light)-generates an action potential; photochemical is inactive-need to hit inactive photochemical with something before it becomes active again-light to an inactive photochemical will not bring about an action potential-can regenerate in the light but happens better in the darkLightactive photochemicalaction potentialinactive photochemical (cannot create action potential until more active photochemicals are generated)Dark adaptation-increase in the number of active photochemicals that increases ability to see inthe dark, increases sensitivity to lightLight adaptation-constantly regenerating the number of active photochemicals, reduce sensitivity to light (to something when you can see better)Photochemicals are constantly regenerating in the light; in bright light, photochemicals are deactivatedturn off the lights, photochemicals reactivatedIV. MusclesThree main kinds of muscles:-skeletal-very long cells, more than one nucleus per cell, have a striped pattern called striations that are due to differing amounts of overlapping protein; typically attached to bone, controlled by somatic motor neurons-smooth- one nucleus, no striation, small cells, controlled by autonomic motor neurons-cardiac-moderate sized cells, do have striations, some have more than one cell; has a combination of characteristics from skeletal and smoothThree main classes of protein:-contractile-actin: round structure with myosin binding site-myosin: golf club structure with actin and ADP/ATP binding sites; has a head thatsticks out from the filament (in three dimension)-myosin head can be in two states:-energized: ATP binding site (ready to spring)-non-energized: ADP binding site (already sprung; energy lost)-no phosphorylation-mysoin has ATPas activity—breaks down ATP-cross bridge: actin and myosin bond-influenced by control proteinsbond can be blocked-both found in myofilaments-ability to connect actin and myosin depends on tropomyosin and troponin -control access to myosin binding sites-when tropomyosin is present, cross bridge cannot be made; when tropomyosin is taken away, cross-bridge is able to be made—move tropomyosin by using troponin which is Ca2+ binding to-tropomyosin: blocks cross bridge formation when muscle is at rest-tropomin: Ca2+ binding proteinmoves tropomyosin out of the way-support/structural-Z proteins-form boundary of sarcomere; actin binds directly to Z proteins-titin-indirectly binds