BCMB 230 1st Edition Lecture 12 Outline of Last Lecture I Sensory Physiology II Information We Get From Receptors III Sensory Anatomy Outline of Current Lecture I Components of the Inner Ear II Chemosenses III Looking at the Eye IV Muscles Current Lecture Sensory Physiology and Muscle I Components of the Inner Ear Cochlea 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 tuned so 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 fluidfilled 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 in These 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 pitches II Chemosenses Three 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 the tongue 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 taste III 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 adjustable Four 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 use these 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 than rods used to focus during the day visual acuity visual acuity gives you more detail During 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 dark Light 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 in the dark increases sensitivity to light Light 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 reactivated IV Muscles Three 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 smooth Three 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 that sticks 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 myosin to Z proteins holds contractile proteins in place forms sarcomere function unit myofilaments are combined into