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Special Senses

Special Senses. Special Senses. Gustation Olfaction Vision Equilibrium Hearing Receptors are specialized structures that detect specific stimuli Receptors transform stimuli into electrical energy. 1. Gustation. Sense of taste Gustatory receptors are taste buds .

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Special Senses

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  1. Special Senses

  2. Special Senses • Gustation • Olfaction • Vision • Equilibrium • Hearing • Receptors are specialized structures that detect specific stimuli • Receptors transform stimuli into electrical energy

  3. 1. Gustation • Sense of taste • Gustatory receptors are taste buds. • Taste buds are located deep to raised areas on the surface of the tongue called papillae (papilla, sng.).

  4. Types of Papillae

  5. Structure of Taste Bud

  6. Taste Sensations • There are 5 basic taste sensations that the human tongue can detect: 1. 2. 3. 4. 5.

  7. Nerve impulses from taste buds in anterior 2/3 of tongue transmitted by VII (facial) • Nerve impulses from taste buds in posterior 1/3 of tongue transmitted by IX (glossopharyngeal)

  8. 2. Olfaction • Sense of smell • Olfactory receptors are single neurons imbedded in the lining of the superior nasal cavities. • These cells possess olfactory hairs where receptors for specific airborne molecules reside.

  9. Olfactory Receptors Cranial nerve I

  10. 3. Vision • Sense of detecting light, color and movement • The receptors are found within the retina of the eye. • These are photoreceptors: rods and cones

  11. Accessory Structures of the Eye • Superficial covering over the anterior exposed surface of the eye • Prevents foreign objects from coming into contact with the eye. • Keeps exposed anterior surface moist, clean and lubricated

  12. External Anatomy of Eye 1. Eyelashes 2. Eyelids (palpebrae) 3. Eyebrows

  13. External Anatomy of Eye 1. Tarsal glands (Meibomian glands)

  14. Lacrimal Gland 1. Lacrimal gland 2. Nasolacrimal duct

  15. Conjunctiva • Stratified squamous epithelium • Lines the internal surface of the eyelids • Lines the anterior surface of the eye….but NOT the cornea • Contains many small blood vessels to provide nutrients to the outer layer of the eye

  16. Note the lack of blood vessels over the cornea.

  17. Conjunctivitis • Most common non-traumatic eye injury complaint seen by physicians etc. • Inflammation and reddening of the conjunctiva (pinkeye) • An irritant (virus, bacteria, allergens) causes dilation of blood vessels

  18. Structure of the Internal Eye • About the size of a ping pong ball • Mostly protected by the bony orbit • Wall of the eye consists of 3 layers (outside to inside): • Fibrous tunic • Vascular tunic • Neural tunic

  19. Three Layers of Eye Wall

  20. Fibrous Tunic • Outermost layer • Comprised of: • Cornea (anterior center) • Sclera (everything else)

  21. A. Cornea • Transparent and avascular (without blood vessels) • Receives nutrients and oxygen from lacrimal gland fluid • Contact lenses, if worn very long periods of time, can interfere with nutrition to the cornea

  22. B. Sclera • Forms the majority of the fibrous tunic • White of the eye • Composed of dense CT • Connects extrinsic eye muscles to eyeball

  23. 2. Vascular Tunic • Middle layer • Comprised of 3 distinct regions: A. Choroid B. Ciliary body C. Iris

  24. A. Choroid • Largest and most posterior region of the vascular tunic • Vast network of capillaries • Supplies the retina with nutrients and oxygen

  25. B. Ciliary Body • Located in the anterior portion of the vascular tunic • Contains smooth muscles and ligaments that attach to the lens and determines the shape of the lens (accommodation) for focusing far and near distance

  26. C. Iris • Most anterior region of the vascular tunic • The colored disc • Center of the iris is the pupil Pupil Iris

  27. C. Iris • Iris controls the amount of light that enters the internal eye by controlling the size of the pupil • Iris contains pupillary dilating smooth muscles and pupillary constricting smooth muscles….both under ANS control.

  28. C. Iris

  29. 3. Neural Tunic • Inner layer….the retina • Contains the light-sensitive rods and cones. These cells are the photoreceptor cells • The retina contains 3 distinct layers: • Photoreceptors • Bipolar cells • Ganglion cells

  30. Retina Axons of ganglion cells Light

  31. Retina • Optic nerve • Blind spot • Axons leave • Blood vessels enter and leave

  32. Internal View of Retina • Blind spot is the optic disc….no photoreceptors (rods and cones) • Fovea centralis….area of retina with sharpest vision….most photoreceptors

  33. Blind Spot See Figure 19.16 (p. 588).

  34. Cavities of the Eye

  35. Cavities of the Eye • The internal eye is divided into two cavities • Anterior and posterior cavities • Separated by the lens

  36. Cavities of the Eye • Anterior cavity is between the cornea and the lens • Posterior cavity is between the lens and the retina

  37. Cavities of the Eye • Anterior chamber filled with aqueous humor • Posterior chamber filled with vitreous humor

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