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Presentation on theme: "SPECIAL SENSES."— Presentation transcript:


2 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

3 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

4 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

5 Referred Pain May occur due to sensory impulses from two regions following a common nerve pathway to brain

6 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

7 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

8 Olfactory Receptors

9 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

10 Gustatory Sense Organs

11 Tongue Map

12 Taste Receptors

13 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

14 Hearing Ear – organ of hearing Three Sections External Middle Inner

15 External Ear Auricle External auditory meatus Tympanic membrane
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

16 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

17 Auditory Tube Eustachian tube Connects middle ear to throat
Helps maintain equal pressure on both sides of tympanic membrane Usually closed by valve-like flaps in throat Pathway for infection

18 Inner Ear Three Parts of Labyrinths Cochlea Semicircular canals
Functions in hearing Semicircular canals Functions in equilibrium Vestibule Range of Human Hearing 20 – 20,000 vibrations per second

19 Sight Visual Accessory Organs Eyelids Lacrimal apparatus
Extrinsic eye muscles

20 Eyelid Palpebra Composed of four layers Orbicularis oculi - closes
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

21 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

22 Coats of the Eyeball - Outer Tunic
Cornea anterior portion transparent No blood vessels Sclera posterior portion opaque protection

23 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

24 Anterior Portion of Eye
Filled with aqueous humor (thick watery substance

25 Lens transparent biconvex lies behind iris
largely composed of lens fibers elastic held in place by suspensory ligaments of ciliary body

26 Accommodation changing of lens shape to view objects

27 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

28 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

29 Posterior Cavity Contains vitreous humor – thick gel that holds retina flat against choroid coat

30 Layers of the Eye

31 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

32 Rods and Cones

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