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Download Senses PPT - Effingham County Schools
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SPECIAL SENSES 1 Special Senses General Senses • receptors that are widely distributed throughout the body • skin, various organs, and joints • receive stimulation of touch, temperature, pain Special Senses • specialized receptors confined to structures in the head • eyes and ears •Allow vision, hearing, equilibrium, taste, and smell 2 Senses Sensory Receptors • specialized cells or multicellular structures that collect information from the environment • stimulate neurons to send impulses along sensory fibers to the brain Sensation • a feeling that occurs when brain becomes aware of sensory impulse Perception • a person’s view of the stimulus; the way the brain interprets the information 3 Receptor Types Chemoreceptors • respond to changes in chemical concentrations Pain receptors (Nociceptors) • respond to tissue damage • respond to intense stimuli of any kind Thermoreceptors • respond to changes in temperature Mechanoreceptors • respond to mechanical forces • touch/pressure Photoreceptors • respond to light 4 Referred Pain • May occur due to sensory impulses from two regions following a common nerve pathway to brain 5 Special Senses • Sensory receptors are within large, complex sensory organs in the head • smell in olfactory organs • taste in taste buds • hearing and equilibrium in ears • sight in eyes 6 Sense of Smell Olfactory Receptors • chemoreceptors • respond to chemicals dissolved in liquids Olfactory Organs • contain olfactory receptors and supporting epithelial cells • cover parts of nasal cavity, superior nasal conchae, and a portion of the nasal septum Sensory Adaptation • when an odor seems to fade away after you have been exposed to it 7 Olfactory Receptors 8 Sense of Taste-Gustatory Senses Taste Buds • organs of taste • located on papillae of tongue, roof of mouth, linings of cheeks, and walls of pharynx Taste Receptors • chemoreceptors • taste cells – modified epithelial cells that function as receptors • taste hairs – microvilli that protrude from taste cells; sensitive parts of taste cells 9 Gustatory Sense Organs 10 Tongue Map 11 Taste Receptors 12 Taste Sensations Four Primary Taste Sensations • sweet – stimulated by carbohydrates • sour – stimulated by acids • salty – stimulated by salts • bitter – stimulated by many organic compounds Spicy foods activate pain receptors 13 Hearing Ear – organ of hearing Three Sections • External • Middle • Inner 14 External Ear • Auricle • Collects sounds waves • Flap on the side of the head • External auditory meatus • Ear canal • Carries sound to tympanic membrane • Terminates with tympanic membrane • Tympanic membrane • Ear drum • Vibrates in response to sound waves • Separates external from middle ear 15 Middle Ear • Tympanic cavity • Air-filled space in temporal bone • Three auditory ossicles • Vibrate in response to tympanic membrane • Malleus, incus, and stapes • Oval window • Opening in wall of tympanic cavity • Stapes vibrates against it to move fluids in inner ear 16 Auditory Tube • Eustachian tube • Connects middle ear to throat • Helps maintain equal pressure on both sides of tympanic membrane • Usually closed by valvelike flaps in throat • Pathway for infection 17 Inner Ear Three Parts of Labyrinths • Cochlea • Functions in hearing • Semicircular canals • Functions in equilibrium • Vestibule • Functions in equilibrium Range of Human Hearing • 20 – 20,000 vibrations per second 18 Sight Visual Accessory Organs • Eyelids • Lacrimal apparatus • Extrinsic eye muscles 19 Eyelid • Palpebra • Composed of four layers • skin • muscle • connective tissue • conjunctiva • Orbicularis oculi - closes • Levator palperbrae superioris – opens • Tarsal glands – secrete oil onto eyelashes • Conjunctiva – mucous membrane; lines eyelid and covers portion of eyeball 20 Lacrimal Apparatus • Lacrimal gland • lateral to eye • secretes tears • Canaliculi • collect tears • Lacrimal sac • collects from canaliculi • Nasolacrimal duct • collects from lacrimal sac • empties tears into nasal cavity 21 Coats of the Eyeball - Outer Tunic Cornea • anterior portion • transparent • No blood vessels Sclera • posterior portion • opaque • protection 22 Middle Tunic Iris • anterior portion • pigmented • controls light intensity Ciliary body • anterior portion • pigmented • holds lens • moves lens for focusing Choroid coat • provides blood supply • pigments absorb extra light 23 Anterior Portion of Eye • Filled with aqueous humor (thick watery substance) 24 Lens • transparent • biconvex • lies behind iris • largely composed of lens fibers • elastic • held in place by suspensory ligaments of ciliary body 25 Accommodation • changing of lens shape to view objects 26 Iris • composed of connective tissue and smooth muscle • pupil is hole in iris • dim light stimulates radial muscles and pupil dilates • bright light stimulates circular muscles and pupil constricts 27 Inner Tunic • Retina • contains visual receptors - Rods and Cones • continuous with optic nerve • ends just behind margin of the ciliary body • composed of several layers 28 Posterior Cavity • Contains vitreous humor – thick gel that holds retina flat against choroid coat 29 Layers of the Eye 30 Visual Receptors Rods • long, thin projections • contain light sensitive pigment called rhodopsin • hundred times more sensitive to light than cones • provide vision in dim light • produce colorless vision • produce outlines of objects Cones • short, blunt projections • contain light sensitive pigments called erythrolabe, chlorolabe, and cyanolabe • provide vision in bright light • produce sharp images • produce color vision 31 Rods and Cones 32
