Transcript Chapter 15
Anatomy and Physiology, Sixth Edition Rod R. Seeley Idaho State University Trent D. Stephens Idaho State University Philip Tate Phoenix College Chapter 15 Lecture Outline* *See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes. 15-1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 15 The Special Senses 15-2 Special Senses • • • • Olfaction Taste Visual system Hearing and balance 15-3 Olfaction • Sense of smell – Olfactory neurons in this epithelium • Bipolar neurons – Olfactory hairs • Cilia which lies in mucous • Odors – Odorants bind to chemoreceptor molecules – Depolarize and initiate action potentials in neurons – Low threshold for odor detection 15-4 Neuronal Pathways of Olfaction 15-5 Taste • Detected by taste buds • Papillae – – – – Vallate Fungiform Foliate Filiform • Histology – Support cells – Gustatory cells • Hairs • Function – Receptors on hairs detect dissolved substances • Taste types – – – – – Sour Salty Bitter Sweet Umami 15-6 Papillae and Taste Buds 15-7 Actions of Major Tastants 15-8 Neuronal Pathways for Taste 15-9 Visual System • Eye • Accessory structures – Eyebrows, eyelids, eyelashes, tear glands – Protect eyes from sunlight and damaging particles • Optic nerve (II) – Tracts – Pathways • Eyes respond to light and initiate afferent action potentials 15-10 Accessory Structures of Eye • Eyebrows – Prevent running perspiration into eyes – Shade • Eyelids or palpebrae – Consist of 5 tissue layers – Protect and lubricate • Conjunctiva – Covers inner eyelid and anterior part of eye • Lacrimal apparatus • Extrinsic eye muscles 15-11 Lacrimal Apparatus • Lacrimal apparatus – Lacrimal Gland: Produces tears to moisten, lubricate, wash • Lacrimal Canaliculi – Collects excess tears • Punctum • Lacrimal Sac • Nasolacrimal duct – Opens into nasal cavity 15-12 Extrinsic Eye Muscles 15-13 Anatomy of the Eye • Three coats or tunics – Fibrous: Consists of sclera and cornea – Vascular: Consists of choroid, ciliary body, iris – Nervous: Consists of retina 15-14 Anatomy of the Eye • Fibrous tunic: Outer – Sclera: White outer layer, maintains shape, protects internal structures, provides muscle attachment point, continuous with cornea – Cornea: Avascular, transparent, allows light to enter eye and bends and refracts light • Vascular tunic: Middle – Iris: Controls light entering pupil; smooth muscle – Ciliary muscles: Control lens shape; smooth muscle • Retina: Inner – Contains neurons sensitive to light – Macula lutea or fovea centralis: Area of greatest visual acuity – Optic disc: Blind spot • Compartments – Anterior: Aqueous humor – Posterior: Vitreous humor • Lens – Held by suspensory ligaments attached to ciliary muscles – Transparent, biconvex 15-15 Functions of the Complete Eye • • • • Eye functions like a camera Iris allows light into eye Lens, cornea, humors focus light onto retina Light striking retina is converted into action potentials relayed to brain 15-16 Light • Visible light: Portion of electromagnetic spectrum detected by human eye • Refraction: Bending of light – Divergence: Light striking a concave surface – Convergence: Light striking a convex surface • Focal point: Point where light rays converge and cross 15-17 Focus and Accommodation • Emmetropia: Normal resting condition of lens • Far vision: 20 feet or more from eye • Near vision: Closer than 20 feet – Accommodation – Pupil constriction – Convergence 15-18 The Retina • Provides black backdrop for increasing visual acuity • Sensory retina and pigmented retina • Photoreceptors – Rods: Noncolor vision • Rhodopsin reduction: Light adaptation • Rhodopsin production: Dark adaptation – Cones: Color vision 15-19 Sensory Receptor Cells 15-20 Rhodopsin Cycle 15-21 Rod Cell Hyperpolarization 15-22 Visual Pathways 15-23 Eye Disorders • Myopia: Nearsightedness – Focal point too near lens, image focused in front of retina • Hyperopia: Farsightedness – Image focused behind retina • Presbyopia – Degeneration of accommodation, corrected by reading glasses • Astigmatism: Cornea or lens not uniformly curved • Strabismus: Lack of parallelism of light paths through eyes • Retinal detachment – Can result in complete blindness • Glaucoma – Increased intraocular pressure by aqueous humor buildup • Cataract – Clouding of lens • Macular degeneration – Common in older people, loss in acute vision • Diabetes – Dysfunction of peripheral circulation 15-24 The Ear • External ear: Hearing; terminates at eardrum • Middle ear: Hearing; contains auditory ossicles • Inner ear: Hearing and balance; interconnecting fluid-filled tunnels and chambers 15-25 The Ear • External ear – Auricle or pinna: elastic cartilage – External auditory meatus • Lined with hairs and ceruminous glands – Tympanic membrane • Vibrated by sound waves • Middle ear – Auditory or eustachian tube • Opens into pharynx, equalizes pressure • Ossicles: malleus, incus, stapes: transmit vibrations • Oval window 15-26 Inner Ear • Labyrinth – Bony • Cochlea: Hearing • Vestibule: Balance • Semicircular canals: Balance – Membranous • -Lymphs – Endolymph • In membranous labyrinth – Perilymph • Space between membranous and bony labyrinth 15-27 Structure of Cochlea 15-28 Auditory Function • Vibrations produce sound waves – Volume or loudness : Function of wave amplitude – Pitch: Function of wave frequency – Timbre: Resonance quality or overtones of sound 15-29 Effect of Sound Waves on Cochlear Structures 15-30 CNS Pathways for Hearing 15-31 Balance • Static – Evaluates position of head relative to gravity – Detects linear acceleration and deceleration – Utricle and saccule • Maculae: Consist of hairs embedded in gelatinous mass containing otoliths • Kinetic – Evaluates movements of head – 3 semicircular canals • Ampulla – Crista ampullaris – Cupula: endolymph moves when head moves 15-32 Structure of the Macula 15-33 Vestibule in Maintaining Balance 15-34 Semicircular Canals 15-35 CNS Pathways for Balance 15-36 Ear Disorders • Tinnitus – Ringing, clicking, whistling in ear due to disorders in middle or inner ear • Motion sickness – Dysfunctions caused by stimulation of semicircular canals during motion • Otitis Media – Infections in the middle ear • Earache – Results from otitis media, dental abscesses, TMJ pain 15-37 Effects of Aging on the Special Senses • • • • Slight loss in ability to detect odors Decreased sense of taste Lenses of eyes lose flexibility Development of cataracts, macular degeneration, glaucoma, diabetic retinopathy • Decline in visual acuity and color perception 15-38