The Special Senses Ch. 17
Part 1 Objectives • Describe the olfactory receptors.
Part 1 – Olfaction: Sense of Smell • Anatomy • 3 types of cells • Olfactory receptors – detect the smell and initiate the signal to the brain • Supporting cells – provide physical support, nourishment, and insulation for receptors • Basal cells – make supporting cells • Bowman’s glands • Secrete mucus that moistens olfactory area (boogers)
Hyposmia • Reduced ability to smell • Affects half of people over age 65 and 75% of people over age 80 • Women smell better than men, especially during ovulation • Smoking can impair the sense of smell
Part 2 Objectives • Describe the gustatory receptors.
Part 2 – Gustation: Sense of Taste • Only 5 primary tastes • Sour, sweet, bitter, salty, umami (meaty or savory) • all flavors are combinations of these tastes • Olfactory and gustatory senses are closely linked – like when you have a cold and food doesn’t taste the same • It is your smell that actually isn’t working properly
Gustation Anatomy – p. 470 • Taste bud – oval body consisting of cells • Papillae – covered in taste buds • Vallate papillae – 12 very large, circular areas • Fungiform papillae – mushroom-shaped elevations scattered over area of tongue • Foliate papillae – small trenches on tongue – most taste buds are gone by childhood • Filiform papillae – no taste buds – just add friction to tongue making chewing and moving food easier
Part 3 Objectives • List and describe the accessory structures of the eye and the structural components of the eyeball. • Discuss image formation by describing refraction and accommodation. • Describe vision abnormalities.
Accessory Structures of Eye • Eyelids • Eyelashes • Eyebrows • Lacrimal apparatus • Extrinsic eye muscles
Accessory Structures of Eye • Eyelids – palpebrae • Functions: • Shade eyes during sleep • Protect eyes from light • Protect eyes from foreign objects • Spread lubrication over eyeballs • upper eyelid is more moveable – levatorpalpebraesuperioris muscle • Where eyelids meet is called commissure – lateral and medial • Lacrimalcaruncle – reddish bump in medial commissure that secretes oil and sweat – causes “sleep” in your eyes
Infections • Sty – infection in oil gland of eyelash follicle • Chalazion – infection in tarsal glands of eyelid • Tarsal glands secrete fluid onto eye for lubrication
Accessory Structures of Eye • Lacrimal apparatus • Produces and drains lacrimal fluid or tears • Eye muscles
Anatomy of the Eyeball • 2.5 cm in diameter • 3 anatomical layers • Fibrous tunic • Vascular tunic • Retina
Tunic Layers • Outer layer – fibrous • Cornea – transparent, focuses light rays • Sclera – white of the eye • Optic nerve – transmits info to brain • Middle layer – vascular • Choroid coat – contains blood vessels • Ciliary body – holds the lens in place • Lens – focusing • Aqueous humor – fluid surrounding lens • Pupil – opening for light to enter
Tunic Layers • Inner layer • Retina – visual receptor cells • Vitreous humor – fluid supports internal structures
Retina • Made of cells that are light receptors – photoreceptors • Rods and cones • Rods – black and white • Cones - color • Color blindness • Lack of cones
Colorblindness A genetic trait that affects boys more than girls. The location of the gene is on the X chromosome
Image Formation • Seeing is like taking a picture • The object must be focused on a “film” – retina • The correct amount of light must be present – pupil Light bends - refraction
Refraction • When light bends as it moves between two mediums – air and water • Images on the retina are upside-down and have right-to-left reversal
Image Formation Process • Light hits the cornea and is bent • Light leaves the cornea and is bent again • Light enters the lens where it is focused on the retina • So why don’t we see everything upside-down? • Very early on the brain “learns” how to coordinate the images and make them correct
Accommodation • Most of the focusing is done by the cornea • 25% must be done by the lens • Our lens is convex on both sides in order to produce clear images • The lens will increase its curvature in order to focus all images exactly
Animations • http://www.bbc.co.uk/science/humanbody/body/factfiles/sight/sight_animation.shtml • http://www.biologymad.com/resources/eye.swf
Abnormalities and Changes • Presbyopia – lens loses elasticity with age • Around age 40 the lens can’t focus near images and people need glasses • Normal eye – emmetropic – can reflect images perfectly of objects 20 ft away • Myopia - near-sightedness • Eyeball is too long for the focusing power of the lens or lens is thicker than normal • Hyperopia – far-sightedness • Eyeball is too short for the focusing power of the lens or lens is thinner than normal
Part 4 Objectives • Describe the anatomy of the structures in the three main regions of the ear. • List the major events in the physiology of hearing.
Part 4 – Hearing • Anatomy of the ear • External ear • Collects sound waves and channels them inward • Middle ear • Conveys sound vibrations to the oval window • Inner ear • Houses the receptors for hearing and equilibrium
Outer Ear • Auricle (pinna) – flap of elastic cartilage shaped like a trumpet • External auditory canal – curved tube that lies in the temporal bone and leads from the auricle to the eardrum • Eardrum (tympanic membrane) – thin, semitransparent partition between the external auditory canal and the middle ear • Ceruminous glands – produce wax to protect ear from dust and foreign objects
Middle Ear • Small, air-filled cavity • Contains 3 smallest bones in the body • Auditory ossicles • Malleus, incus, and stapes • contains auditory tube (eustachian tube) – connects middle ear to the throat and nasal cavities • Helps maintain air pressure • Can lead to ear pain during sore throats
Inner Ear • Labyrinth – communicating chambers and tubes • Contains • Semicircular canals – sense of equilibrium • Cochlea – sense of hearing • Organ of Corti – contains hearing receptors, hair cells detect vibrations
Hearing • Pinna directs sound waves into auditory canal • Sound waves strike ear drum and it vibrates • Auditory ossicles amplify vibrations to cochlea • Organs of Corti contain receptor cells (hair cells) that deform the vibrations • Impulses sent to nerves • Temporal lobe interprets sensory impulses
Part 5 Objectives • Identify the receptor organs for equilibrium, and describe how they function.
Part 5 - Equilibrium • Balance – 2 types • Static – maintenance of body relative to gravity • Dynamic – maintenance of body in response to sudden movements like rotation, acceleration, and deceleration • Organs that control this are called the vestibular apparatus – all lined with hairs • Sacculeand utricle • Semicircular ducts (canals)
Equilibrium • The hair cells send signals to the brain that tell it the position of the head • As the hair cells move, the brain can interpret and fix balance