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. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Chapter 15 The Special Senses

Special Senses Olfaction Taste Visual system Hearing and balance

Olfaction Sense of smell Odors 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

Neuronal Pathways of Olfaction

Taste Detected by taste buds Function Papillae Taste types Histology Vallate Fungiform Foliate Filiform Histology Support cells Gustatory cells Hairs Function Receptors on hairs detect dissolved substances Taste types Sour Salty Bitter Sweet Umami

Papillae and Taste Buds

Actions of Major Tastants

Neuronal Pathways for Taste

Visual System Eye Accessory structures Optic nerve (II) 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

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

Lacrimal Apparatus Lacrimal apparatus Lacrimal Canaliculi Punctum Lacrimal Gland: Produces tears to moisten, lubricate, wash Lacrimal Canaliculi Collects excess tears Punctum Lacrimal Sac Nasolacrimal duct Opens into nasal cavity

Extrinsic Eye Muscles

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

Anatomy of the Eye Retina: Inner Fibrous tunic: Outer Compartments 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 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

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

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

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

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

Sensory Receptor Cells

Rhodopsin Cycle

Rod Cell Hyperpolarization

Visual Pathways

Eye Disorders Myopia: Nearsightedness Retinal detachment Glaucoma 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

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

The Ear External ear Middle ear Oval window 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

Inner Ear Labyrinth -Lymphs Bony Membranous Endolymph Perilymph Cochlea: Hearing Vestibule: Balance Semicircular canals: Balance Membranous -Lymphs Endolymph In membranous labyrinth Perilymph Space between membranous and bony labyrinth

Structure of Cochlea

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

Effect of Sound Waves on Cochlear Structures

CNS Pathways for Hearing

Balance Static Kinetic 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

Structure of the Macula

Vestibule in Maintaining Balance

Semicircular Canals

CNS Pathways for Balance

Ear Disorders Tinnitus Motion sickness Otitis Media Earache 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

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