Special Senses

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  1. 3 Basic layers of the eye
    • Fibrous: outermost
    • Vascular: Middle layer
    • Neurolayer: inner layer (also called sensory layer)
  2. fibrous layer structures
    • sclera: white of eye, protects and shapes the eye
    • cornea: transparent front part, continuous with sclera, bends the light waves from the object you are looking at to help focus it on the retna
  3. structures of the vascular layer
    • uvea
    • choroid
    • pigments
    • ciliary body
    • lens
    • iris
  4. uvea
    contains blood vessels
  5. choroid
    blood vessels to nourish the eye
  6. pigments
    prevent light scattering
  7. ciliary body
    • smooth muscle with suspensory ligaments attached that attach to the lens
    • when this muscle contracts it will change the shape of the lens and the shape will adjust for near and far vision (accomodation)
  8. lens
    bends the light rays to focus on the retina (like the cornea but it can be adjusted)
  9. iris
    • smooth muscle
    • colored part
    • central canal opening is the pupil- regulates the amount of light entering the eye and reaching the retina
  10. Structures in the neurolayer
    • retina
    • optic nerve fibers
    • optic disc
    • fovea centralis
  11. retina
    • contains the visual receptor cells- they are photoreceptors bc they are sensitive to light as the stimulus- called rods and cones
    • optic nerve fibers originate in the retina
  12. optic disc
    • blind spot
    • no receptors 
    • retinal fibers pulled into optic nerve
  13. fovea centralis
    • part of the retina with the most accurate vision bc it has the highest concentration of cones
    • located in the middle of the macula lutea (yellow spot)
  14. Focus of light waves on the retina order of parts of eye
    • the substances and structures have different densities and they will refract (or bend) the light rays 
    • order: cornea
    • aqueous humor- watery substance between the cornea and lens
    • lens- only part that can make adjustments for near + far vision
    • vitreous humor- a jelly like material behind the lens and filling the whole space in the back, supports retina
  15. muscle associated with the eye
    • extrinsic muscles
    • intrinsic muscles
  16. extrinsic muscles
    • on the outside of the eye, they are skeletal muscles and move the eye
    • supereior, inferior, lateral and medial rectus
    • superior and inferior obliques
    • all these muscles are regulated by somatic nerve fibers of cranial nerves oculomotor, trochelar and abducans
  17. intrinsic muscles
    • inside the eye, smooth muscle
    • iris: regulates the amount of light coming in
    • ciliary muscle (of the ciliary body): regulates lens to focus 
    • these muscles are regulated by the autonomic nerve fibers of the oculomotor nerve
  18. protection of the eye
    • conjunctiva
    • accessory structures
    • location of the eyes in orbits of the skull- bone protects the eyeballl
  19. conjunctiva
    • a mucous membrane on the surface of the eyeball and lining the eyelid
    • keeps the eye moist and protects it
    • conjunctivitis- infection of the conjunctiva
  20. accessory structures that protect the eye
    • eyelids (palpabrae)
    • eyelashes
    • eyebrows
    • lacrimal apparatus- the structures making and circulating tears (lacrimal fluid)
    • tears- lubricate, protect and clean the eye, contain water, salts, mucous, some antibodies, and and enzymes that kill bacteria
  21. 3 layers of cells in the retina
    • ganglion neurons (outer)
    • bipolar neurons (middle)
    • cones and rods (deepest in- these need to be stimulated by the light)
  22. How do impulses travel relative to light?
    • the impulses go in the opposite direction of the light
    • light stimulates rods and cones and an impulse is generated and sent to the bipolar neurons which send impulses to the ganglion neurons which have axons in the optic nerve
  23. what stimulates rods and cones
    light but they have different functions
  24. cones
    • bright light daytime vision and color vision
    • they need a lot of light as a stimulus (100x the amount the rods need)
    • the distribution in the retina is most concentrated in the fovea and less as you go farther from it
  25. rods
    • dim light, night vision
    • more sensitive to small amounts of light
    • distribution- absent from the fovea and more concentrated as you move away from the fovea
  26. vision
    formation of the image on the retina and impulses going to the brain you need 4 processes for vision to occur
  27. 4 processes needed for vision to occur
    • 1. Refraction- bending of light rays
    • 2. Accomodation of the lens for near and far vision (far- lens is flattented by symp NS; near- lens bulges from parasymp NS regulating the ciliary muscle attached to the lens)
    • 3. Adjust the amount of light 
    • 4. Convergence of the eyes
  28. adjusting the amount of light
    • iris controls pupil- when it is dialated (wider) it lets more light in- sympathetic NS dilates
    • dim light- we need more light to see something far
    • constriction- when there is bright light it protects the retina from too much light and for near vision
  29. convergence of the eyes
    involves coordination of both eyes working together to see one image- not 2, due to intrinsic muscles
  30. stimulation of photoreceptors
    • rods contain a photosensitive pigment- a chemical that responds to light (called Rhodopsin)
    • with light rhodopsin will create impulses in rods and will also do bleaching reaction (chemically break down) into opsin and retinine (made from vitamin A) which in darkness remakes more rhodopsin
  31. Vitamin A in synthesis of rhodopsin
    • critical for vision in dim light
    • also used for maintenance of membranes such as the conjunctiva
    • stored in the eye in the pigmented epithelium of the retina (this layers function is similar to the choroid)
  32. deficiency of vitamin A
    • the first sign is night blindness bc its needed for more rhodopsin
    • extreme deficiency causes blindness and sores on eye
  33. pigmented epithelium of the retina
    prevents the scattering of light like the choroid
  34. age related macula degeneration (macula lutea)
    • source of vision loss at age 65 and on
    • 2 types : wet and dry
  35. wet age related macula degeneration
    • blood vessels from the choroid leak causing a detatched retina from the choroid
    • can be treated by slowing the progress with lasers and drugs
  36. dry age related macula degeneration
    • increase of pigment (more than needed) can destroy photoreceptors in the macula and cells in the epithelium, decreasing vision
    • cant treat 100% but you can use vitamins and zinc to decrease the progress
  37. Pigments in the cones (rods had rhodopsin)
    • contain photosensitive pigments such as iodopsin
    • 3 kinds of cones- sensitive to different wavelengths of light- red green and blue
  38. Nervous pathway for vision (main pathway)
    • begin at the retina-- optic nerve from both eyes (the ganglion axons are in the eye), impulse travels through the optic chiasma and throught the optic tracts to have a synapse in the lateral geniculate body of the thalmus to the occipital lobe of the cerebral cortex
    • 1/2 the medial fibers (only, not the lateral ones) in the optic chiasma from both eyes cross over to the other side of the brain meaning both sides of the brain get info from both eyes to maximize vision
  39. visual field
    • the visual field of each eye is the area seen by the eye
    • the visual field of the 2 eyes overlaps in the middle giving you maximum vision and sending more info to the brain
  40. emmetropia
    • normal vision
    • image focuses on the retina
  41. myopia
    • image focused on front of retina instead of directly on it
    • lens to thick or eyeball too long- error of refraction
    • nearsighted
    • treated with corrective lens- concave- lessens refraction
  42. hypermetropia
    • image focused in back of retina, lens to thin or eyeball to short- error of refraction
    • farsighted
    • treated by corrective lens- convex- increase refraction
  43. presbyopia
    • lens with decreased elasticity, as in aging-error of refraction
    • farsighted as you get older
    • treated with corrective lens- convex, bifocals if myopic
  44. astigmatism
    • irregular cornea or lens- error of refraction
    • blurred or distorted vision
    • treated with corrective lens
  45. retinal detachment
    • complete or partial separation of retina from choroid (may follow trauma, tumors, choroid hemmorrage)
    • loss of vision where detached (ex- curtain like vision)
    • treatment- surgery
  46. cataracts
    • opacity of lens and/or its capsule (most common in aging)
    • progress from cloudy to swelling then shrinkin of lens with lens becoming opaque-loss of vision
    • treatment- remove lens and replace with fake one
  47. glaucoma
    • eye disease with intraocular pressure, which may lead to shrinking of optic nerve and blindness- closing of canal of schlemm the exit duct of aqueous humor
    • blurred vision, pain partial or complete blindness, eyeball hardens
    • treatment- drugs to dialate canal or surgery treat any associated diseases like diabetes
  48. Eye receptors
    • rods and cones
    • located in retina of the eye
  49. olfactory epithelium
    upper part of the nasal cavity of the nose
  50. smell cell types (olfactory)
    • supporting cells: support the receptor cells and try to detoxify chemicals
    • basal cells: divide to form receptor cells
    • olfactory receptor cells
  51. olfactory receptor cells
    • nervous sells
    • have cillia in mucous
    • sense of smell is better if you sniff something into the mucous
    • the axons of these cells are in the olfactory nerves (the fiber travels through the ethmoid bone to get there and to the olfactory bulb)
    • the olfactory bulb contains the synapse and the cells magnify the sense of smell when the impulse gets to the olfactory bulb- mitral cells
  52. where are the axons of mitral cells
    olfactory tracts
  53. smell stimulus
    • odorants- chemicals
    • we can smell thousands of odorants
    • these chemicals have to be volitile (in gas form) and they dissolve in the mucous
    • oflactory receptors (in the upper nasal cavity of nose) are very sensitive to chemicals (you only need a few molecules to detect them) but they adapt easily
  54. adaptation- smell
    due to granule cells in the olfactory bulbs that release GABA which inhibits the mitral cells which allows you to get used to a smell and not detect it anymore
  55. Main pathway of smell
    start in nose, olfactory receptr cells have axons in the olfactory nerve, impulse goes to olfactory bulb and by the way of the olfactory tract there is a synapse in the thalmus, impulse travels to temporal lobe of cerebral cortex (some go to frontal)
  56. Secondary pathway of smell
    • same until the impulse reaches the olfactory tract, then it goes from there to the limbic system (cerebrum + diencephalon)
    • this secondary pathway associates smells with emotions
  57. what happens if danger is associated with a smell
    it can trigger a sympathetic nervous system response through the hypothalmus which controls the symp and parasymp
  58. how can smells stimulate reflexes
    • sneezing- if you smell an irritant
    • increase in saliva- if you smell appealing food, can also increase stomach secretions
  59. anosmia
    • lack of sense of smell
    • can be a disorder but is usually due to some sort of trauma (head injury, inflammation, etc) in the part of the brain invovled in smell or damage to the nerves
  60. Taste
    also called gustation
  61. taste receptors
    • gustatory receptors located in taste buds on the upper surface of toungue, mouth, pharynx, and larynx
    • gustatory cells have gustatory hairs
  62. lingual papillae
    bumps on toungue, some contain taste buds on the side
  63. Taste buds
    • contain gustatory cells with growing hairs 
    • cells arranged on the surface, pre opening access to saliva
    • taste receptors replaced through the basal cells in the taste bud (they only live about 10 days) basal cells act like stem cells
  64. taste stimulus
    chemical- must be in solution (saliva or other liquid)
  65. chemicals we taste
    • only taste these or a combination of them
    • sweet
    • sour (acid)
    • salty (sodium)
    • bitter
    • umani (beefy flavor-asparate and glutamate amino acids- protein in these foods stimulates)
  66. protective function of taste
    • we are more sensitive to some tastes than others
    • ex- bitter you can taste in very low conc but sugary you need much more
    • like smell, taste receptors adapt quickly
  67. factors that affect taste (7)
    • 1. chemicals must be in solution- bathe receptor cells
    • 2. sense of smell- if you cant smell you cant taste well
    • 3. texture of food
    • 4. temperature of food
    • 5. zinc- deficiency will decrease sense of taste- found in high protein food
    • 6. aging- decreases sense of taste and sometimes smell
    • 7. damage to nerves and the brain
  68. cranial nerves in taste
    • facial: most important- covers anterior 2/3 of tongue
    • glossopharangeal: 1/3 of tongue and pharynx
    • vagus: lower pharynx and larynx (epiglottis flap)
  69. Pathway of taste (main pathway)
    gustatory receptors have axons in cranial nerves 7,9 and 10 impulse travels to solitary nucleus in medulla then to ventral posteriomedial nucleus in thalmus then to parietal lobe and insula of cerebral cortex
  70. secondary pathway of taste
    same until the impulse reaches the medulla, it then travels to the limbic system (diencephalon and cerebrum) associates taste with an emotion
  71. the ear
    vestibulocochlear system
  72. functions of the ear
    • equilibrium: vestibulo- inner ear involved
    • hearing: cochlear- whole ear involved
  73. receptors of the ear
    • hair cells of the organ of corti
    • located in the cochlea of ear
  74. hearing stimulus
    sound waves
  75. external ear (structures in it included)
    • aracle: (also called pinna) outer part
    • external acoustic meadis: (external auditory canal) the ear canal
    • external ear collects and guides soundwaves to the more internal parts mainly the tympanic membrane (ear drum)
  76. tympanic membrane
    • separates external and middle ear
    • projects soundwaves internally bc there are receptors in the inner ear and protects the internal structures
  77. middle ear (structures included)
    • located in the temporal lobe
    • lined with mucous membrane which helps to lubricate and protect the structures of the middle ear, also covers the ear bones
    • contains autitory ossicles- ear bones
    • pharyngotympatic tube (auditory tube)- equalizes pressure on both sides of the tympanic membrane, important for sound projection
  78. auditory ossicles (from closes to tympanic membrane to most inner to ear)
    • malleus
    • incus
    • stapes- articulates with oval window of the vestibule of inner ear by going in and out of it to move fluid
    • these transmit sound vibrations to the inner ear
  79. Inner ear
    • also located in temporal bone (like middle ear)
    • made of 2 laberinths
  80. 2 laberyinths of the inner ear
    • outer bony labrynth
    • inside membranous labyrinth that parralles the whole thing (ducts and sacs with fluid both in and out of them)
  81. parts of the laberynth
    • cochlear, vestibule and 3 semicircular canals
    • endolymph: innermost fluid (in the sac)
    • perilymph: fluid outside the sac
  82. functions of the inner ear
    • chochlea (and cochlear branch of the vestibulocochlear nerve): hearing 
    • vestibule (and semicircular canals and vestibular branch of vestibulocochlear nerve): equilibrium and propriosection of the head (sense of position and movement)
  83. vestibular apparatus
    • vestibule and semicircular canals 
    • interconnecting sacs and tubules with endolymph
    • branches of vestibulocochlear nerve- both vestibule canals
  84. vestibule
    • has 2 sacs: utrical and sacule with sensory receptors 
    • senses position of head relative to gravitiy- static equilibrium
    • senses movement of head in horizontal or vertical postion (not twirling or angular) called linear acceloration
  85. semicircular canals
    • will fell angular movement of head such as twirling around- rotational acceleration; dynamic equilibrium
    • have 3 angles
    • at the end of each theres a wider part called the ampula- contains receptor cells
    • contains crista ampularis: gelatinous structure with cupula which contains the hair cells which are receptor cells with axons in the vestibulocochlear nerve
  86. macula
    • unit in the saccule and utricle sacs with the receptors
    • a gel with little calcium carbonate stones called otoliths
    • there are also hair cells- receptors
    • change in postion of the head causes the stones to pull the gel and stimulate the ear cells which create impulses, you disturb the cells relative to gravity
  87. Nervous pathway of the ear (important part of brain)
    cerebellum is more important than cerebrum- for balance and proprioception in addtion ot ears- eyes and muscle also important
  88. ear infections
    • most common in middle ear- otitis media- ear ache
    • usually bacteria through the auditory tube
    • bulging red tympanic membrane
    • young people more susceptable bc tube is shorter and has a different angle
    • often a secondary infection to a cold (virus) mucus membrane swells and bacteria flourish
    • chronic infections can affect a persons hearing
  89. less common ear infections
    • inner ear infection- dizzyness
    • swimmers ear-external ear infection from bacteria or fungus coming from outside, happens especially when ear is moist
  90. protection of the ear
    • cerumen- ear wax from the ceruminous glands
    • hair
    • temporal bone protects middle and inner ear
Card Set
Special Senses
Quiz of 11/19
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