Special Senses: Olfaction, Taste and Vision Exercise 26, 25, 24 in the lab book Types of Sensory Receptors I. Chemoreceptors – detect chemical cues Ex: taste and smell II. Mechanoreceptors – detect stimuli via a mechanical distortion of a cell membrane Ex: hearing and touch III. Photoreceptors – detect light Ex: vision Smell (Olfaction) Chemoreceptors in the olfactory epithelium respond to chemicals Olfactory Nerve Olfactory Epithelium Taste The tongue’s surface is covered by small projections called papillae Papillae contain the taste buds There are 10,000 taste buds on the human tongue Each taste bud has ~100 taste cells Taste Pore Taste Chemicals in food are detected by taste cells located in the taste buds Taste Cells Taste Bud Taste Activities Locate the papillae on your tongue – Pg. 399 Do Activity 3: Stimulating the taste buds Can you taste the sugar? The Distribution of Taste Sweet, Sour, Salty, and Bitter There is now 5th “taste” Umami is the distinctive taste found in meat and cheese Led to the creation of MSG as a seasoning/preservative Plotting Taste Bud Distribution Does YOUR tongue match this pattern? Hi, I am Kikunae Ikeda. I discovered Umami in 1907. You can blame MSG on me. Taste Activities Do Activity 4: Effect of smell on taste Fill out the table on Pg. 401 Do Activity 5: Importance of taste and olfaction on odor identification Fill out the table on Pg. 402 Hearing Outer Ear Middle Ear Inner Ear Middle Ear Bones: Malleus, Incus, and Stapes Tympanum Semicircular Canals Cochlea Auricle (Pinna) External Acoustic Meatus Auditory Tube (Eustacean Tube) Hearing Hearing involves mechanoreceptors in the ear Sound waves vibrate the tympanum (eardrum) Ear Infection (Otitis Media) Inflammation of the mucosal membrane in the middle ear Commonly caused by bacteria from a sore throat middle ear & throat are connected by the auditory tube Sensory Adaptation • All senses “adapt” to stimuli • Test with sound pupil Sclera Iris Pupil Cornea The pupil will change size with light condition The Rods and Cones These are the photoreceptors of the eye They occur in the retina of the eye 120 million rods and 6 million cones in each retina Rods are specialized for low light conditions Cones are specialized for color vision under high light intensity The Blind Spot Do Activity 5: Demonstrating the Blind Spot Why do you have a blind spot? The Causes of Near/Far Sightedness 1. Lens over or under compensates when focusing 2. Eyeball is too long or too short for proper focusing 3. Cornea or lens has improper curvature Cataract Lens is hard and opaque Causes problems for focusing light on the retina Glaucoma Aqueous humor is constantly being created and drains from the eye Blockage stops drainage, putting pressure on the retina & optic nerve Astigmatism Irregular curvature to the cornea or lens causes focusing problems Other vision tests: Do Activity 8: Astigmatism Binocular Vision Testing for Astigmatism Do Activity 10: Testing for Binocular Vision Color Blindness Normal Vision Color Blind What Causes Color Blindness? There are 3 Types of Cones in the Human Eye: Red Cones for red wavelengths of light Blue Cones for blue wavelengths of light Green Cones for green wavelengths of light Color Blindness occurs when one or all of these cone types are not sensitive to the correct wavelengths of light Occurs in 6% of men and 0.5% of women Testing for Color Blindness Color Blindness Test Processing Sensory Information • Sensory register – memory system that records information received by receptor cells (stored as a sensory trace) – Specific to each sense • Why need a sensory register? • Size of the sensory register? – Change Blindness Test Dissection of the Cow Eye Blue Book: Yellow Book: Pg. 368-369 Pg. 270-271 Find the structures on your handout What is the tapetum lucidum? Do you have a tapetum lucidum?