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Understanding the Special Senses: Taste, Smell, and Vision

Learn about the important role of taste, smell, and vision in our perception and experience of the world. Explore the anatomy and functions of the tongue, taste buds, olfactory system, and the eye. Discover how these senses work together and their impact on our daily lives.

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Understanding the Special Senses: Taste, Smell, and Vision

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  1. Special Senses Ch 17

  2. Taste Taste and smell are involved with specific receptor cells called chemoreceptors   respond to chemicals in an aqueous solution like mucus food dissolved in saliva airborne chemicals dissolved in mucous membrane

  3. The Tongue

  4. Taste Buds Filiform papilla Fungiform papilla Circumvallate Papilla Tongue epithelium Connective tissue

  5. Taste Buds

  6. Taste Buds

  7. Five Basic Tastes Why are they important? Salty- metallic ions Umami- savory/meaty Bitter- alkaloid Sour- H+ Sweet- sugar

  8. Gustatory pathway Facial nerve (afferent) 2/3 anterior portion of tongue Glossophyngeal posterior 1/3 of tongue Vagus nerve- few taste buds on epiglottis an pharynx These afferent fibers synapse in medullathalamus gustatory cortex in parietal lobes and fibers to hypothalamus in limbic system

  9. Tastetriggers reflex involved in digestion; causes an increase of saliva in mouth (amylase) and gastric juice in stomach acids cause strong salivary reflex bad tasting food causes gagging or reflexive vomiting taste can change over time taste is 80% smell Mouth also contains: Thermoreceptors Mechanoreceptors Nociceptors- sensitive nerve fibers that are aware of painful stimuli

  10. Olfaction Olfactory epithelium Olfactory tract Olfactory bulb Nasal conchae Route of inhaled air (a) Figure 15.21a

  11. Olfaction Mitral cell (output cell) Olfactory tract Glomeruli Olfactory bulb Cribriform plate of ethmoid bone Filaments of olfactory nerve Lamina propria connective tissue Olfactory gland Axon Basal cell Olfactory receptor cell Olfactory epithelium Supporting cell Dendrite Olfactory cilia Mucus Route of inhaled air containing odor molecules (b) Figure 15.21a

  12. sclera tear drainage canal iris pupil The Eye palpabre cornea Lacrimal caruncle lateral commisure Medial commisure palpabre

  13. Pupil bright light normal light dim light

  14. Lacrimal Apparatus FLOW OF TEARS Lacrimal gland Lacrimal ducts Sup. or inf. lacrimal canal Lacrimal sac Nasolacrimal duct Nasal cavity

  15. Extrinsic Eye Muscles Superior oblique Superior rectus opticnerve Medial rectus Inferior oblique Lateral rectus Inferior rectus

  16. Fibrous Tunic Fibrous tunic- sclera and cornea (outer most layer) Composed of dense avascular connective tissue

  17. Vascular Tunic • Vascular tunic- uvea: choroid, cilliary body, iris, pupil (middle layer) • Choroid- rich vascular nutritive layer; contains a dark pigment • that prevents light scattering within the eye • Cilliary body- lens is attached; contains muscles that change the • lenses shape • Iris- pigmented ring of muscular tissue composed of circular • and radial muscles • reflex contraction of circular muscle in bright light (small dia of pupil) • reflex contraction of radial muscle in dim light (large dia of pupil) • Pupil- central hole in iris 

  18. Sensory Tunic • Sensory tunic- retina (inner most layer) • Photoreceptors: • rods (dim light, contains pigment rhodopsin) and • Cones (color vision, not evenly distributed, concentrated in fovea) • Optic disc- blind spot because its where optic nerve leaves the eyeball (no rods or cones) • Macula lutea- yellow spot, area of high cone • Fovea centralis- in center of macula lutea, contains only cones, area of greatest visual acuity

  19. Eye Interior

  20. Vitreous Humor • Vitreous humor- behind lens, gel-like substance with fine collagenic fibrils imbedded in as viscous ground substance- binds with water • transmits light • supports the posterior surface of the lens and holds the neural retina firmly against pigmented layer • contributes to intraoccular pressure, helping to counter act the pulling force of the extrinsic eye muscles

  21. Aqueous Humor • Aqueous humor- in front of lens, anterior segment, watery fluid • Supplies cornea and lens with nutrients • Helps to maintain the shape of the eye • Produced and renewed every 4 hrs by the cilliary body

  22. Aqueous Humor

  23. Lens • Lens- transparent biconvex structure, flexible • Attached by suspensory ligaments to ciliary body • focuses image onto retina • changes lens thickness to allow light to be properly focused onto retina

  24. Focusing the Image • Coarse Fixed Focusing • Cornea Shape • Accommodation- adjust configuration of • Lens Shape • Pupil Size

  25. Accomodation Focusing on a Near Object

  26. Accomodation Focusing on a Far Object

  27. Refraction Abnormalities • Emmetropia- normal 20:20 • Hyperopia- farsighted • Myopia-near sighted • Presbyopia- mature eyes • Astigmatism 20 ft:20 ft You see Normal vision

  28. Snellan Eye Chart What condition does this person have? What condition does this person have? 20/10

  29. Vision & Corrective Lenses

  30. Vision & Corrective Lenses

  31. Cataract Clouding of lens (hardening or thickening causes: diabetes mellitus, smoking, UV damage

  32. Glaucoma

  33. The Retina blind spot macula

  34. Optic Nerve

  35. Retina

  36. Retina Rod cell membrane photoreceptors

  37. Primary Visual Pathway Binocular vision

  38. Primary Visual Pathway

  39. Illusions Geometrical illusions

  40. Illusions Successive contrast : afterimages ... fixate the black dot in the center for 60 seconds ... … and then look at a the black dot in the right panel !   what do you see?

  41. Auditory System

  42. Outer Ear Outer ear- pinna (auricle), lobule, external auditory canal; elastic cartilage External auditory canal has: ceruminous glands- wax secreting glands- protects delicate lining of meatus and helps prevent microorganisms from entering the ear Tympanic membrane- membrane that vibrates in response to sound waves

  43. Outer & Middle Ear

  44. Middle Ear Middleear- Includes 3 small bones (ossicles)- hammer (mallus), anvil (incus), stirup (stapes) Pharyngeotympanic auditory tube (Eustachian tube)- equalizes pressure; connects middle ear to pharynx. Oval window- found on cochlea; stirrup presses against cochlea Round window- pressure window on cochlea Otis media- inflammation of the middle ear; due to bacteria or allergies, common in children whose auditory tubes are short and horizontal

  45. Middle Ear malleus stapes incus oval window round window external auditory canal tympanic membrane Auditory tube

  46. Inner Ear Inner ear- bony labyrinth filled with perilymph fluid (similar to CFS) and membranous labyrinth filled with endolymph fluid (similar to K+ rich intracellular fluid); these fluids conduct sound vibrations Bony labyrinth (includes vestibule, semicircular canal, and cochlea) Vestibule- posterior to cochlea and anterior to the semicircular canals Perilymph fluid suspends 2 membranous sacs: utricle and sacule-- they house equilibrium receptors called maculae that respond to the pull of gravity

  47. Inner Ear Semicircular canal- contains endolymph fluid; anterior, posterior, and lateral canal; contains equilibrium receptors (ampulla) Cochlea- filled with perilymph fluid Organ of Corti- rests a top basilar membrane; has long row of hair cells

  48. Inner Ear

  49. semicircular canals cochlea Inner Ear Biology 100 Human Biology vestibulochoclear nerve

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