1 / 65

Special Senses

Special Senses. Utilize distinct receptor cells as receptors. Chemical senses. Taste (gustation) Smell (olfaction). Taste. Taste buds. Most are on the tongue. Papillae. Filiform - rough, conical shape, few taste buds Fungiform – scattered; most numerous on sides and tips

hiero
Télécharger la présentation

Special Senses

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Special Senses Utilize distinct receptor cells as receptors

  2. Chemical senses • Taste (gustation) • Smell (olfaction)

  3. Taste • Taste buds. • Most are on the tongue. • Papillae. • Filiform - rough, conical shape, few taste buds • Fungiform – scattered; most numerous on sides and tips • Circumvallate –largest; least numerous; back of tongue

  4. Structure of a taste bud. • Supporting cells – form bulk, insulate • Receptor (Gustatory or Taste) cells – contain gustatory hairs that extend through surface • Basal cells - stem cells that divide giving rise to new gustatory cells

  5. Taste sensation • Sour – stimulated by acids • Sweet – stimulated by sugars, alcohols, some amino acids • Bitter – stimulated by bases • Salty – stimulated by metal ions

  6. Sensitivity of the taste buds in different locations. • Anterior tongue is more sensitive to sweet and salty substances • Posterior tongue is more sensitive to bitter substances. • Lateral tongue is more sensitive to sour substances.

  7. Physiology of taste. • Chemical comes in contact with gustatory hair cells on receptor cells. • Depolarization of taste cells results in generation of action potentials in associated sensory neurons. • Relayed to the gustatory cortex. • Other sensations • Taste is 80% smell • Affected by temperature; texture; heat

  8. Smell • Localization and structure of olfactory receptors • Detects chemicals in solution • Olfactory epithelium - Contains the olfactory receptors and is located in the roof of the nasal cavity.

  9. Structure of olfactory receptors. • Supporting cells – • Basal cells – • Olfactory receptor cells –

  10. Specificity of the olfactory receptors – • Can distinguish 10,000 chemicals • Not clearly understood • May be 1000 odorant binding proteins that act in combinations

  11. Activation of olfactory receptors. • Chemical comes in contact with the olfactory hair cells on the receptor cells. • Depolarization of the receptor cells results in the generation of action potentials.

  12. Homeostatic imbalances of the chemical senses • Anosmias – without smell • Uncinate fits – temporary distortions of smell due to brain damage, psychological disorders, or even seizures

  13. Vision • Accessory structures of the eye • Eyebrows • Eyelids “palpebrae” • Canthi – angles of the eyelids • Epicanthic fold – found in Asians • Lacrimal Caruncle – fleshy elevation found at medial canthus

  14. Meibomian glands – Modified sebaceous glands in eyelid • Infection of these called Chalazion • Ciliary glands – between hair follicles of eyelashes • Infection of these called a Sty • Conjunctiva – mucus membrane covering eye (infection called conjunctivitis or pinkeye

  15. Accessory Structures of Eye • Lacrimal apparatus • Lacrimal glands – secrete tears • Lacrimal secretions – contains mucus, antibodies, & lysosozyme • Cleanses, protects, & lubricates eye

  16. Extrinsic eye muscles • Medial rectus – • Superior rectus - • Lateral rectus - • Inferior rectus - • Superior oblique - • Inferior oblique –

  17. Structures of the eyeball

  18. Fibrous tunic (coat) – outermost layer • Sclera – whites of the eye • Cornea – clear portion in front of eye

  19. Vascular tunic (coat) – middle layer (uvea) • Choroid – vascular brown membrane • Ciliary body – encircles lens forming the: • Ciliary muscles – control lens shape • Ciliary processes - contain capillaries that secrete fluid • Suspensory ligaments – • Iris – colored portion • Pupil – opening in iris

  20. Sensory tunic (Retina) – innermost layer • Pigmented layer – absorbs light • Neural layer – contains photorecptor cells • Cells of the retina. • Ganglionic cells – generate action potentials • Bipolar cells – transfer energy from receptors to ganglionic cells • Photoreceptors - sensitive to light

  21. Rods – dim-light, no color, and peripheral vision • Cones – bright light, color vision • Macula lutea – “yellow spot” directly behind pupil • Fovea centralis – minute pit in center of macula lutea • Contains cones only • Macular degeneration - linked to nutritional deficiencies • Optic disc (blindspot) – location of junction with optic nerve

  22. Internal chambers and fluids • Posterior segment - behind lens • Vitreous humor - clear gel • Anterior segment - in front of lens • Anterior chamber - in front of iris • Posterior chamber - between iris and lens

  23. Aqueous humor - clear liquid filling anterior segment • Scleral venous sinus (Canal of Schlemm) - drains aqueous humor back into veins; located at corneal / scleral junction • Glaucoma - elevated pressure of the aqueous humor

  24. Lens • Biconvex; transparent; held in place by suspensory ligaments • Lens epithelium - outer covering • Lens fibers - inner bulk of lens • made of folded proteins called crystallins • Cataracts - clouding of the lens • Age related hardening and thickening; diabetes; inadequate delivery of nutrition to lens

  25. Physiology of vision • Photons - packets of light • Wavelength • Electromagnetic spectrum - all wavelengths • Visible spectrum - 400-700 nanometers • nanometer = 1 billionth of a meter • Color - reflection of different wavelengths • Red, Orange, Yellow, Green, Blue, Indigo, Violet

  26. Refraction and lenses • Reflection - light bounces off a surface • Refraction - light bends as it passes through one substance to another with a different density • Lens - a transparent material curved at one or both surfaces • Convex - thicker in the center; light converges • Concave - thicker at the edges; light spreads

  27. Focusing of light on the retina. • Light is refracted three times • Cornea • Entering the lens • Exiting the lens

  28. Focusing for distance vision. • Eye are fixed (preset) on an object 20 feet or more away. • Ciliary muscles are completely relaxed. • Lens is stretched as thin as it can get.

  29. Focusing for close vision. • Accommodation of the lens. • Ciliary muscles contract. • Lens bulges. • Constriction of the pupils - • Convergence of the eyeballs -

  30. Homeostatic imbalances of refraction. • Myopia - Nearsightedness • Eyeball is too long • Image is focused in front of retina • Hyperopia - Farsightedness • Eyeball is too short • Image is focused behind the retina • Astigmatism - caused by unequal curvature in different parts of the lens

  31. Photoreception. • Functional anatomy of the photoreceptors • Outer segment. • Inner segment

  32. The chemistry of visual pigments. • Retinal - a light absorbing pigment • made from vitamin A • combines with opsonins forming • Rhodopsin - “purple” visual pigment of Rods • Light stimulation separates retinal from the opsins • Retinal will be re-joined with the opsins to regenerate rhodopsin later

  33. Different types of opsins in cones. • 3 Different types of Cones • Blue - absorbs blue wavelengths best • Green - absorbs green wavelengths best • Red - absorbs red wavelengths best • Cone wavelengths overlap • Stimulation of various cones in different amounts creates different shading and coloration

  34. Color blindness - • Sex-linked, genetic trait • Lack specific types of cones, usually red or green

  35. Light transduction in photoreceptors. • Generation of electrical current • Photoreceptors depolarize in dark and hyperpolarize in light • Produce graded potentials (local) • Action potentials produced by Ganglion cells

  36. Light and dark adaptation - • Light adaptation - from dark to light (5-10 minutes) • Dark adaptation - from light to dark (20-30 minutes)

  37. Binocular vision and stereopsis • Anterior placement of eyes results in greater depth perception or three-dimensional vision

  38. Hearing and balance • Structure of the ear • Outer (External) ear. • Auricle (pinna) • External auditory canal (meatus) • Ceruminous glands - wax glands • Tympanic membrane - “eardrum” • boundary between outer and middle ear

  39. Middle ear (Tympanic cavity) • Mastoid antrum - canal leading to mastoid process • Pharyngotympanic (auditory or eustachian) tube - equalizes pressure on eardrum • Ear ossicles. • Malleus (hammer) - • Incus (anvil) - • Stapes (stirrup) - • Ear muscles: Tensor tympani & Stapedius

  40. Inner (Internal) ear • Bony (Osseous) labyrinth. • Cochlea - “snail” ; hearing • Semicircular canals - balance • Vestibule - central cavity • Membranous labyrinth. • Perilymph - surrounds membrane structures • Endolymph - fills membrane structures

More Related