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Objective: Describe and observe how taste and smell are related to one another Describe different sensory receptors found in the body Journal: What are your five senses? Ability to sense changes in the environment is necessary for maintaining homeostasis All sense organs must be able to detect a stimulus in the environment Depending on the stimulus, a different receptor will be activated Signal is transmitted over a nervous system “pathway” to brain Photoreceptors – stimulated by light, in eye Chemoreceptors – stimulated by chemicals, in tongue and nose Pain receptors – stimulated by physical damage Thermoreceptors – stimulated by change in temperature Mechanoreceptors – stimulated by change in position Taste and smell: Receptors are chemoreceptors Associated with food intake, influence flow of digestive juices, and affect appetite Chemoreceptors in taste buds in mouth and throat Taste bud consists of Taste pore ▪ Opening through which fluids in mouth come into contact with surface of receptor cells Taste receptor cells ▪ Modified epithelial cells with surface folds called microvilli that contain chemical receptors Located on papillae (bumps on your tongue and throat) Two Types: Fungiform papillae ▪ Small, all over the top and sides of the tongue Circumvallate Papillae ▪ Large, on the back of the tongue Taste buds consist of: ~50 receptor cells surrounded by supporting cells Basal cells develop into supporting cells then receptor cells ▪ Gustatory hairs project through the taste pore Four kinds of tastes caused by different chemical stimuli: Sweet, Sour, Bitter, and Salty Chemoreceptors that allow for smell are called olfactory receptors Located in the nasal cavity Olfactory neurons Located in the olfactory epithelium and sense changes in smell through the olfactory hairs Connect to olfactory nerve tract Supporting Cells Metabolic and physical support cells for the olfactory neurons The physical stimuli are chemical substances carried in the air that are dissolved in the mucus in the nose. Pathway: Olfactory Hairs Olfactory Neurons Olfactory Nerve in the Brain Neurons connect directly into the brain from the nasal epithelium through the cribriform plate Journal: Explain why ice cream tastes different than a lemon. Two functions: Hearing and Equilibrium Physical forces from sound and movements stimulate the mechanoreceptors Three parts of the ear: External ear, Middle ear, Inner ear Made up of: Auricle (aka Pinna) – appendage on side of head External auditory canal – curving tube, about 1 in long ▪ Ends at ear drum (aka Tympanic membrane) ▪ Separates external and middle ear ▪ Auditory canal lined with hair and contains ceruminous glands ▪ Produces cerumen (ear wax) to protect inner ear ▪ Sound waves travel thru canal, strike the tympanic membrane and cause it to vibrate Tiny cavity hollowed out of temporal bone Also connects to the throat by Pharyngotympanic tube Sore throat could spread to ear, causes middle ear infection Contains three small bones called ossicles Names describe shape: ▪ Malleus (hammer), Incus (anvil), Stapes (stirrup) Malleus attached to tympanic membrane and incus Incus attached to stapes Stapes presses against a membrane that covers the oval window (small opening in inner ear) Sounds cause tympanic membrane to vibrate, which is then transmitted and amplified by ossicles Causes movement of fluid in inner ear Mechanoreceptors found in fluid-filled chambers known as the membranous labyrinth Endolymph – thick fluid Bony labyrinth covers membrane labyrinth to provide protection Perilymph – watery fluid between bony and membranous labyrinth Bony labyrinth divided into three parts: Cochlea (hearing)– snail-like shape, contains organ of Corti which is covered in hairs Surrounded by endolymph, sound waves causes liquid to move, which moves hairs ▪ Nerve impulse stimulated when hairs are bent Semicircular Canal (balance) – 3 half-circle canals Endolymph surrounds receptors (crista ampullaris) which are covered in hair ▪ Nerve impulse stimulated by rotation of head Vestibule (sense gravity) – btw cochlea and s. canal In US – over 6 million people with a hearing deficit CONDUCTIVE DEAFNESS Conditions in outer or middle ear blocks vibrations External auditory canal blocked with wax, water Scarring of eardrum NERVE DEAFNESS Problem in cochlea or auditory pathway to brain Receptors in organ of Corti can’t interpret sounds Correction - chochlear implant Nerve impulse doesn’t make it to brain http://www.youtube.com/watch?v=Go9pONJ Bffk Frequency 8 kHz 10 kHz 12 kHz 14 kHz 15 kHz 16 kHz 17 kHz 18 kHz 19 kHz 20 kHz 21 kHz 22 kHz Heard? Could you hear all the frequencies? What is your hearing threshold? How do dog whistles work? Does the frequency of sound you can hear change as you age? Objective: Label and describe the structures of the eye Explain how the eye allows you to see Journal: List and explain the difference between the two types of deafness. The eye is covered with three layers of tissue: sclera, choroid, retina SCLERA (aka “whites of the eyes”) Made up of tough, fibrous tissue Front has a transparent portion – Cornea ▪ Covers iris – colored portion of eyes Conjuntiva – mucous membrane keeps eye moist Lacrimal Gland – produces tears CHOROID Middle layer of eyeball Contains dark pigment to prevent scattering of incoming rays of light Made up of 2 involuntary muscles: Iris and ciliary ▪ Pupil is actually a hole in the center of the iris muscle ▪ 2 kinds of muscles in iris: circular – constricts pupil, lateral – dilates pupil ▪ Ciliary muscle helps to focus on objects ▪ Relaxed for distance, contracted for close RETINA Contains microscopic photorecepotors: ▪ Rods – nightime vision, black and white ▪ Cones – daytime vision, color ▪ 3 types detect color – red, green, blue Macula Lutea – yellowish area near center of retina Surrounds fovea centralis – a depression that contains the most cones Visual sharpness is obtained by focusing the image on the fovea centralis Fluid maintains intraocular pressure of eyeball Fluid refracts light rays to focus on retina Aqueous Humor – fluid in front of lens Vitreous Humor – Jellylike material in the posterior cavity Lens – directly behind pupil Held in place by ligament Elastic to allow change of shape Light stimulates photoreceptors Light enters the eye at the pupil, and is refracted by lens to focused on retina Nerve impulses created by rods and cones are collected and exit with the optic nerve No rods cones are present where optic nerve exists which is known as the blind spot Myopia - Image focuses in front of retina, distant objects blurry Hyperopia - Image focuses behind retina, close objects blurry Astigmatism – Abnormal curvature of cornea or lens, fails to refract light properly CATARACTS Lens of eye becomes cloudy so less light enters the eye If completely opaque, person will be blind CORRECTION – surgery to replace lens GLAUCOMA Aqueous humor not drained properly, intraocular pressure builds up Distorts soft tissue of the eye and can cause blindness CORRECTION - surgery to drain fluid, drugs to increase drainage Unable to distinguish certain colors Caused by a recessive gene on the X chromosome Men more likely to be colorblind Occurs when cones are nonfunctional Most common – red cones missing Can’t distinguish red from green https://www.youtube.com/watch?v=ea_xOq NvntA
