KIN 1223 Unit 5 Lecture 5 Inner Ear Equilibrium Orientation Two kinds of equilibrium changes in position Structures vestibular apparatus other o Static maintenance of body position head with respect to gravity o Dynamic maintenance of body position head in response to acceleration or o 3 Semicircular Canals channels in bone positioned at nearly right angles to each Osseous labyrinth filled with perilymph Membranous labyrinth semicircular duct within semicircular canals filled with endolymph Designated as Anterior Frontal plane and Posterior Saggital plane o Positioned vertically at right angles to each other o Viewed together Plane of right anterior and left posterior Nearly parallel to each other Lateral Transverse plane o Positioned horizontally o At nearly a right angle to the anterior and posterior Ampulla Enlargement at end of each semicircular duct Contains the crista ampullaris equilibrium receptor o Small elevation containing hair cells and supporting cells o Covered by cupula mass of gelatinous material Hair cells have hairs extending into gelatinous material of cupula o Utricle Saccule Enlargements of membranous labyrinth located in vestibule Utricle connected to semicircular ducts Saccule Saccule connected to utricle and cochlear duct Both filled with endolymph Both contain a macula thickened region in walls of utricle and saccule Supporting epithelial cells Receptor hair cells with 2 types of projections o Stereocilia long microvilli o Kinocilium true cilium Many stereocilia but only one kinocilium per hair cell Otolithic membrane o Gelatinous membrane above hair cells o Stereocilia and kinocilium are embedded in the otolithic membrane o Otoliths increase weight or mass and inertia of otolithic membrane Head in upright position Macula of utricle is horizontal hair cells are vertical Macula of saccule is vertical hair cells are horizontal o Vestibular function Vestibular apparatus responds to changes in head position Head stationary vestibular apparatus not stimulated Utricle and saccule provide information when head is moving in a straight line Horizontally or vertically linear acceleration Starting stopping head movement Starting head movement causes otoliths to lag behind o Drags otolithic membrane with them due to greater mass o Bend stereocilia and kinocilium embedded in otolithic membrane Stopping head movement o Otoliths continue moving due to inertia o Also bends stereocilia and kinocilium in opposite directions Movement of hair cells towards the kinocilium causes depolarization away causes hyperpolarization Utricle stimulated by movement in transverse plane running Saccule stimulated by movement in vertical plane elevator Semicircular canals function when head experiences rotational acceleration As head turns inertia o Endolymph is semicircular ducts lags behind due to its o Causes movement or bending of cupula o Bends hair cells of crista ampullaris depolarizes or hyperpolarizes When head stops o Fluid continues to move continuing stimulation of hair cells Have sensation that head is still turning o Movement at constant velocity no stimulation o Respond to changes in motion acceleration Eye Vision Eye detection of electromagnetic radiation o Photochemical reaction Photon adds energy to an atom electron When rhodopsin absorbds light it is converted fron the bent shape cis retinal to the straight trans retinal form as it is bleached Takes 5 minutes to regenerate 50 of rhodopsin Photoreceptor cells Rod night vision o Nocturnal vertebrates only have rods o Discs with Rhodopsin pigment 2 major parts to rhodopsin Protein called opsin Vitamin A derivative called retinal Contain single kind of rhodopsin with absorption peak at wavelength of 500nm o cGMP amplifies 1000x o 600 rods to 1 nerve cell o Generating visual signal in the dark Rods produce steady ion flow in the dark that causes an IPSP that produces no signal in optic nerve Cones color vision day o Photopsin pigments blue green red Opsin moieties contain different amino acids that determine which wavelengths of light are absorbed o Fovia is all cones 1 cone to 1 nerve cell o Primates good color vision o Perception of color based on mixture of nerve signals o Color blindness lack one photopsin hereditary Red green is common lack either red or green cones Incapable of distinguishing red from green o Generating visual signal in the light When rod absorbs light dark current ceases and no inhibition occurs so EPSP occurs in optic nerve Pigments absorb light altering their shape producing nerve signals o Protection Eyelids Palpebrae protect moisten Conjunctiva Inside eyelids covering the globe mucous membrane o Innervated vascular bloodshot eyes Lacrimal glands tear gland moisten Conjuctiva o Superior to Orbit o Help diffusion of O2 CO2 o Lysozyme Eyelashes Eyebrows Supercilia Tunics Outer o Cornea anterior transparent o Sclera posterior white of eye Dense connective tissue Middle o Iris colored part controls pupil size Chromatophore cells contain melanin o Pupil dark circle opening for light o Choroid vascular layer over retina Nourish retina o Ciliary body muscles change shape of lens Attached to lens by Suspensory Ligaments o Retina focusing point for images Eye pressures hold retina in place o Eye fluids Aqueous humor fluid between iris and lens Vitreous humor clear gel inside eye Inner o Eye muscles 6 Extrinsic that move the eyeball Superior Rectus Medial Rectus Lateral Rectus Inferior Rectus Superior Oblique Inferior Oblique o Eye function Lens refract light focus Cataract lens clouding Light projected onto area of retina Posterior aspect of eye Macula Lutea patch of receptor cells o Fovea Centralis most detailed images Optic Disc where optic nerve leaves eye blind spot o Accommodation Ciliary muscle relaxed pupil dilates Tension on Suspensory Ligaments Flatten Lens Ciliary muscle contracts pupil constricts Release tension on Suspensory Ligaments Convex Lens more round Hyperopia farsighted eyeball too short Myopia nearsighted eyeball too long o Image pathway Rods cones stimulated not nerve cells Bipolar nerve cells Retinal ganglion cells axons optic nerve Optic chiasm Optic tracts Thalamus Occipital lobe of Cerebrum