ch. 15

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ch. 15
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ch. 15 notecards special senses
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  1. what are the five special senses
    • vision
    • taste
    • smell
    • hearing
    • equilibrium
  2. 70'5 of the body's sensory receptors are where
    in the eye
  3. what is most of the eye protected by
    cushion of fat and bony orbit
  4. what are the accessory structure of the eye
    • eyebrows
    • eyelids (palpebrae)
    • conjuctiva
    • lacrimal apparatus
    • extrinsic eye muscles
  5. eyebrow function
    • shade eye form sunlight
    • prevent perspiration from reaching eye
  6. eyelid function
    • protect eye anterioly
    • separated at palpebral fissure
    • meet at medial and lateral commissures
    • lacrimal caruncle: at medial commissure, contains oil and sweat glands
    • tarsal plates: supporting connective tissue
  7. eyelid muscles
    levator palpebrae superioris: gives upper eyelid mobility
  8. how often do you blink
    every 3-7 seconds
  9. eyelash function
    nerve endings of follicles initiate reflex blinking
  10. tarsal (meibomian) glands
    • modified sebaceous glands
    • oily secretion lubricates lid and eye
  11. ciliary glands
    • between hair folicles
    • modified sweat glands
  12. conjunctiva
    • transparent mucous membrane that produces a lubricating mucous secretion
    • palpebral conjuctiva: lines eyelid
    • bulbar conjunctiva: covers white of eyes
    • cojunctival sac: between palpebral and bulbar conjunctiva where the lens rests
  13. lacrimal apparatus
    • lacrimal gland and ducts that drain into nassal cavity (crying)
    • lacrimal gland: in orbit above lateral end of eye
    • lacrimal secretion (tears): dilute saline solution containing mucus antibodies, lysozyme; blinking spreads tears toward medial commissure; tears enter lacrimal canaliculi then drain into lacrimal sac and nasolacrimal duct
  14. extrinsic eye muscles
    • six straplike extrinisic eye muscles: originate form bony orbit, insert on eyeball and enable the eye to follow moving objects
    • four rectus muscles: originate from common tendious ring (superior, inferior, lateral and median rectus muscles)
    • two oblique muscles: move eye in vertical plane and rotate eyeball (superior and inferior oblique muscles)
  15. what cranial nerve moves the lateral rectus
    abducens VI
  16. what cranial nerve moves the superior rectus, medial rectus, inferior rectus and inferior oblique
    oculomotor III
  17. which cranial nerve moves the superior oblique
    trochlear IV
  18. what are the three layers of the wall of the eyeball
    • fibrous
    • vascular
    • inner
  19. internal cavity is filled with fluids called
    humors
  20. lens separates internal cavity into
    anterior and posterior segments
  21. fibrous layer
    • outermost layer
    • dense avasular connective tissue
    • two regions: schlera and cornea
  22. schlera
    • opaque posterior region
    • protects, shapes eyeball, anchors extrinisic eye muscles
    • continuous with dura mater of brain posteriorly
  23. cornea
    • transparent anterior 1/6 of fibrous layer
    • bends light as it enters eye
    • sodium pumps of corneal endothelium on inner face help maintain clarity of cornea
    • numerous pain receptors contribute to blinking and tearing reflexes
  24. vascular layer (uvea)
    • middle pigmented layer
    • three regions: choroid, ciliary body and iris
  25. choroid
    • posterior portion of uvea
    • supplies blood to all layers of eyeball
    • brown pigment absorbs light to prevent light scattering and visual confusion
  26. ciliary body
    • ring of tissue surround lens
    • smooth muscles bundles control lens shape
    • capillaries of ciliary processes sescrete fluid
    • ciliary zonule holds lens in position
  27. iris
    • colored part of the eye
    • pupil: central opening that regulates amount of light entering the eye; changes for close vision, distant vision and emotional state
  28. the inner layer is
    the retina
  29. the retina
    • originates as outpocketing of brain
    • delicate two layered membrane: pigmented layer and inner neural layer
  30. pigmented layer (retina)
    • single cell thick lining
    • absorbs light and prevents its scattering
    • phagocytize photoreceptor cell fragments
    • store vitamin A
  31. neural layer (retina)
    • transparent
    • composed of three main types of neurons (photoreceptors, bipolar cells, ganglion cells)
    • signals spread from photoreceptors to bipolar cells to ganglion cells
    • ganglion cell axons exit eye as optic nerve
  32. optic disc
    • your blind spot
    • site where optic nerve leaves eye
    • lacks photoreceptors
  33. what are the two types of photoreceptors
    rods and cones
  34. rods
    • dim light
    • peripheral vision receptors
    • more numerous, more sensitive to light than cones
    • no color vision or sharp images
    • numbers greatest at periphery
  35. cones
    • vision receptors for bright light
    • high resolution color vision
    • macula lutea: exactly at posterior pole
  36. fovea centralis
    tiny pit in center of macula with all cones; your best vision
  37. what are the two sources of blood supply to the retina
    • choroid: supplies outer third (photoreceptors)
    • central artery and vein: supply inner two thirds and enter/exit through optic nerve
  38. the lends and ciliary zonule separate eye into
    anterior and posterior segments
  39. posterior segment
    • vitreous humor
    • transmits light
    • supports posterior surface of lens
    • holds neural layer of retina firmly against pigmented layer
    • contributes to intraocular pressure
    • forms in embryo and lasts a lifetime
  40. anterior segment
    • has 2 chambers
    • contains aqueous humor
    • plasma like fluid continously formed by capillaries of ciliary processes
    • drains via scleral venous sinus
    • supplies nutrients and oxygen mainly to lens and cornea but also to retina and removes wastes
    • anterior chamber: between cornea and iris
    • posterior chamber: between iris and lens
  41. glaucoma
    blocked drainage of aqueous humor increases pressure and causes compression of retina dn optic nerve leading to blindness
  42. lens
    • biconvex, transparent, flexible, and avascular
    • changes shape to precisely focus light on retina
    • two regions: lens epithelium (anterior) and lens fibers
  43. cataracts
    • clouding of the lens
    • consequence of aging, diabetes, heavy smoking, overexposure to sunlight
  44. what is the pathway of light entering the eye
    cornea, aqueous humor, lens, vitreous humor, entire neural layer of retina, photoreceptors
  45. light is refracted how many times when it enters the eye
    • 3;
    • entering the cornea
    • entering lens
    • leaving lens
  46. eyes are best adapted for what kind of vision
    distant
  47. ciliary muscles are contracted or relaxed for distant vision
    relaxed
  48. presbyopia
    loss of accomodation over age 50
  49. convergence
    medial rotation of eyeballs toward object being view
  50. constriction
    accomodation pupillary reflex constricts pupils to prevent most divergent light rays form entering eye
  51. myopia
    • nearsightedness
    • focal point in front of retina e.g. eyeball too long
    • corrected with a concave lens
  52. hyperopia
    • farsightedness
    • focal point behind retina .e.g eyeball too short
    • corrected with a convex lens
  53. astigmatism
    • unequal curvatures in different parts of cornea or lens
    • corrected with cylindrically ground lenses or laser procedures
  54. what are the receptive regions of rods and cones called
    outer segments: contain visual pigments where molecules change shape as absorb light
  55. photoreceptor cells
    • vulnerable to damage
    • degenerate if retina detached
    • destroyed by intense light
    • outer segment renewed every 24 hours
  56. functional characteristics of rods
    • very sensitive to light
    • best suited for night vision or peripheral vision
    • contain a single pigment (perception in gray tone only)
    • pathways converge, causing fuzzy, indistinct images
  57. functional characteristics of cones
    • need bright light for activation (low sensitivity)
    • react more quickly
    • have one of three pigments for colored view
    • nonconverging pathways create detailed high resolution images
  58. colorblindness
    lack of one or more cone pigments
  59. cones vs rods
    • rods:
    • noncolor vision
    • high sensitivity; dim light
    • low acuity
    • more numerous
    • mostly in peripheral

    • cones:
    • color vision (3 pigments)
    • low sensitivity; bright light
    • high acquity
    • less numerous
    • mostly in central retina
  60. processing in the retina
    • photoreceptors and bipolar cells only generate graded potentials (EPSPS IPSPS)
    • when light hyperpolarizes photoreceptor cells: stop releasing inhibitory NT glutamate, bipolar cells depolarize and release NT into ganglion cells, ganglion cells generate APs transmitted in optic nerve to brain
  61. light adaptation
    • move from darkness into bright light
    • both rods and cones trongly stimulated and pupils constrict
    • large amounts of pigments broken down instantaneously producing glare
    • visual acquity improves over 5-10 minutes as rod system turns off, retinal sensitivity decreases, and cones and neurons adapt
  62. dark adaptation
    • move from bright light into darkness
    • cones stop functioning in low intensity light
    • rod pigments bleached; system turned off
    • rhodopsin accumulates in dark
    • transducin returns to outer segments
    • retinal sensitivity increases within 20-30 minutes
    • pupils dilate
  63. nyctalopia
    • night blindess
    • rod degeneration
    • commonly caused by vitamin A deficiency
    • or retinitis pigmentosa
  64. visual pathway to the brain
    • axons of retinal ganglion cells form optic nerve
    • medial fibers of optic nerve decussate at optic chiasma
    • most fibers of optic tracts continue to lateral geniculate body of thalamus
    • fibers from thalamic neurons form optic radiation and project to primary visual cortex in occipital lobes
  65. visual pathway
    • fibers from thalamic neurons form optic radiation
    • optic radiation fibers connect to primary visual cortex in occipital lobes
    • other optic tract fibers send branches to midbrain, ending in superior colliculi
    • a small subset of ganglion cells in retina contain melanopsin (circadian pigment)
  66. depth perception
    • both eyes view same image form slightly different angles
    • depth perception results from cortical fusion of slightly different images
    • requires input from both eyes
  67. visual processing
    • retinal cells split input into channels
    • color brightness angle direction, speed of movement
    • job of amacrine and horizontal cells
    • lateral geniculate nuclei of thalamus: process for depth perception, cone input, contrast sharpened
    • primary visual cortex: neurons respond to dark and bright edges and object orientation, provide form, color, motion inputs to visual association areas
  68. cortical processing
    • occipital lobe centers continue processing of form color and movement
    • complex visual processing extends to other regions
    • what: ventral temporal lob
    • where: parietal cortex to postcentral gyrus
    • output from both passes to frontal cortex for direct movements
  69. what type of receptors respond to chemicals in aqueous solution for smell and taste
    chemoreceptors
  70. olfactory epithelium
    • in roof of nasal cavity
    • covers superior nasal conchae
    • contains olfactory sensory neurons
    • olfactory stem cells lie at base of epithelium
    • bundles of nonmyelinated axons of olfactory receptor cells form olfactory nerve
  71. olfactory sensory neurons
    • unusual bipolar neurons
    • thin apical dendrite terminates in knob
    • long, nonmotile cilia radiate from know¬†
    • olfactory stem cells differentiate to replace them
  72. humans can distinguish how many different odors
    10000
  73. 400 smell genes active only in one nose
    • each encodes unique receptor protein which responds to one or more odors
    • each odor binds to several different receptors
    • each receptor has one type of receptor protein
  74. does the nasal cavity have pain and temperature receptors
    yes
  75. physiology of smell
    • gaseous odorant must dissolve in fluid of olfactory epithelium
    • activation of olfactory sensory neurons: dissolved odorants bind to receptor proteins in olfactory cilium membranes
  76. smell transduction
    • odorant binds to receptor and activates G protein
    • G protein uses a second messenger for synthesis
    • Na+ and Ca2+ channels open causing Na+ influx
    • depolarization occurs with impulse transmission
    • Ca2+ influx creates the olfactory adaptation (decreased response to sustained stimulus)
  77. olfactory pathway
    • olfactory receptor cells synapse with mitral cells in glomeruli of olfactory bulbs
    • axons form neurons with same receptor type converge on given type of glomerulus
    • mitral cells amplify, refine, and relay signals
    • amacrine granule cells releases GABA to inhibit mitral cells
    • impulses form activated mitral cells travel to piriform lobe of olfactory cortex
    • some info to frontal lobe, some to the hypothalamus, amygdala, and other regions of limbic system (emotional responses to odor)
  78. taste buds are
    receptor ogans
  79. most of 10000 taste buds are where
    • on tongue papillae
    • on tops of gungiform papillae, or side walls of foliate and circumvallate papillae
  80. a few tastebuds are located where
    soft palate, cheeks, pharynx, epiglottis
  81. structure of a taste bud
    • 50-100 flask shaped epithelial cells of 2 types
    • gustatory epithelial cells:
    • basal epithelial cells:
  82. gustatory epithelial cells
    • microvilli (hairs) are receptors
    • three types: one releases serotonin, one releases ATP
  83. basal epithelial cells
    dynamic stem cells that divide every 7-10 days
  84. what are the five basic taste sensations
    • sweet: sugars, alcohol, amino acids, lead salts
    • sour: hydrogen ions in solution
    • salty: metal ions
    • bitter: alkaloids, nicotine, aspirin
    • umami: amino acids glutamate and aspartate
  85. what is the possible sixth sense
    that humans can taste long chain fatty acids form lipids
  86. in order to taste, chemicals must
    • be dissolved in saliva
    • diffuse into taste pore
    • contact gustatory hairs
  87. activation of a taste receptor
    • binding of food chemical depolarizes taste cell membrane so NT releases which initiates a generator potential which elicits an action potential
    • different thresholds for activation
    • all adapt in 3-5 seconds; complete adaptation 1-5 minutes
  88. which taste receptor is most sensitive
    bitter
  89. taste transduction
    • gustatory cell depolarization caused by:
    • salty: taste due to Na+ influx (depolarization)
    • sour: H+ opening cation channels
    • unique receptors for sweet, bitter, umami coupled to G protein gustducin: stored Ca2+ release opens cation channels, depolarization then ATP release
  90. gustatory pathway
    • cranial nerves VII and IX carry impulses from taste buds to solitary nucleus of medulla
    • impulses then travel to thalamus and from there fibers branch to gustatory cortex, hypothalamus and limbic system
    • vagus nerve transmits from epiglottis and lower pharynx
  91. role of taste
    • triggers reflexes involve din digestion
    • increase secretion of saliva into mouth
    • increase secretion of gastric juice into stomach
    • may initiate protective reactions (gagging, vomitting)
  92. what percentage of taste is smell
    80%
  93. what types of receptors in the mouth influence taste
    • thermoreceptors
    • mechanoreceptors
    • nociceptors
  94. what are the three major areas of the ear
    • external ear :hearing only
    • middle year (tympanic cavity): hearing only
    • internal ear: hearing and equilibrium
  95. are receptors for hearing and balance activated dependently
    no, activated independently
  96. auricle
    • pinna
    • composed of helix (rim) and lobule (earlobe)
    • funnels sound waves into auditory canal
  97. external acoustic meatus
    • auditory canal
    • short curved tube lined with skin bearing hairs, sebaceous glands and ceruminous glands
    • transmits sound waves to eardrum
  98. external ear consists of what
    • auricle
    • external acoustic meatus
    • tympanic membrane (eardrum)
  99. tympanic membrane
    • eardrum
    • boundary between external and middle ears
    • connective tissue membrane that vibrates in response to sound
    • transfers sound energy to bones of middle ear
  100. middle ear
    • tympanic cavity
    • small air filled mucose lined cavity in temporal bone
    • blanked laterally by eardrum
    • blanked medially by bony wall containing oval (vestibular) and round (cochlear) windows
  101. parts of the middle ear
    • epitympanic recess
    • mastoid antrum
    • pharyngotympanic (auditory) tube
  102. epitympanic recess
    superior portion of middle ear
  103. mastoid antrum
    canal for communication with mastoid air cells
  104. pharyngotympanic (auditory) tube
    • connects middle ear to nasopharynx
    • equalizes pressure in middle ear cavity with external air pressure
  105. otitis media
    • middle ear inflammation
    • common in children
    • most frequent cause of hearing loos in children
    • treated with antibiotics
  106. ear ossicles
    • three small bones in tympanic cavity
    • malleus, incus, and stapes
    • suspended by ligaments and joined by synovial joints
    • transmit vibratory motion of eardrum to oval window
    • tensor tympani and stapedius muscles contrat reflexively in response to loud sounds to prevent damage to hearing receptors
  107. what are the two major divisions of internal ear
    bony labyrinth and membranous labyrinth
  108. bony labyrinth
    • tortuous channels in temporal bone
    • three regions: vestibule, semicircular canals, cochlea
    • filled with perilymph- similar to CSF
  109. membranous labyrinth
    • series of membranous sacs and ducts
    • filled with potassium rich endolymph
  110. vestibule
    • central egg shaped cavity of bony labyrinth
    • contains two membranous sacs: saccule and utricle
    • these sacs house equilibrium receptor regions (maculae)
    • respond to gravity and changes in position of head
  111. saccule
    • continuous with the cochlear duct
    • membranous sac
  112. utricle
    • continuous with semicircular canals
    • membranous sac
  113. semicircular canals
    • three canals (anterior, lateral, posterior) each define 2/3 circle
    • membranous semicircular ducts line each canal and communicate with utricle
    • ampulla of each canal houses equilibrium receptor region called the crista ampullaris (receptors respond to rotational movements of head)
  114. cochlea
    • spiral, conical, bony chamber
    • size of split pea
    • extends from vestibule
    • coils around bony pillar (modiolus)
    • contains cochlear duct, which houses spiral organ and ends at cochlear apex
    • divided into 3 chambers: scala vestibuli, scala media, scala tympani
  115. scala vestibuli
    abuts oval window, contains perilymph
  116. scala media
    • cochlear duct
    • contains endolymph
  117. scala tympani
    • terminates at round window
    • contains perilymph
  118. scalae tympani and vestibuli are continuous with each other at
    helicotrema (apex)
  119. what is the roof ot he cochlear duct
    vestibular membrane
  120. what is the floor of cochlear duct composed of
    • bony spiral lamina
    • basilar membrane
  121. the cochlear branch of nerve VIII runs from spiral organ to the
    brain
  122. sound is
    pressure disturbance produced by vibrating object
  123. sound wave
    • moves outward in all directions
    • illustrated as an S shaped curve or sine wave
  124. frequency
    • number of waves that pass given point in given time
    • pure town has repeating crest and troughs
  125. wavelength
    • distance between two consecutive crests
    • shorter wavelength=higher frequency of sound
  126. pitch
    • perception of different frequencies
    • normal range 20-20000 hz
    • higher frequency=higher pitch
  127. quality of sound
    • most sounds mixtures of different frequencies
    • richness and complexity of sounds (music)
  128. amplitude
    • height of crests
    • perceived as loudness
    • subjective to interpretation of sound intensity
    • normal range 1-120 db
    • hearing loss occurs with prolonged exposure to above 90 db
  129. transmission of sound to the internal ear
    • sound waves vibrate tympanic membrane
    • ossicles vibrate and amplify pressure at oval window
    • cochlear fluid set into wave motion
    • pressure waves move through perilymph of scala vestibule
    • waves with frequencies below threshold of hearing travel through helicotrema and scali tympani to round window
    • sounds in hearing range go through cochlear duct, vibrating basilar membrane at specific location according to frequency of sound
  130. resonance of basilar membrane
    • fibers near oval window short and stiff: resonate with high frequency pressure waves
    • fibers near cochlear apex longer and floppy: resonate with lower frequency pressure waves
    • *this mechanically processes sound before signals reach receptor
  131. excitation of hair cells in the spiral organ
    cells of spiral organs: supporting cells, cochlear hair cells
  132. cochlear hair cells
    • one row of inner hair cells
    • three rows of outer hair cells
    • have many sterocilia and one kinocilium
  133. afferent fibers of cochlear nerve coil about the bases of______
    hair cells
  134. steriocilia
    • protrude into endolymph
    • longest enmeshed in gel like tectorial membrane
    • sound bending these toward kinocilium:
    • opens mechanically gated ion channels, K+ and Ca2+ influx causes graded potential and NT glutamate is released causing cochlear fibers to transmit impulses to the brain
  135. auditory pathways to the brain
    • impulses from cochlea pass via spiral ganglion to cochlear nuclei of medulla
    • from there, impulses sent to superior olivary nucleus, via lateral lemniscus to inferior colliculus
    • from there, impulses pass to medial geniculate nucleus of thalamus, then to primary auditory cortex
    • auditory pathways decussate so that both cortices receive input from both ears
  136. auditory processing
    • pitch perceived by impulses from specific hair cells in different positions along basilar membrane
    • loudness detected by increased numbers of action potentials that result when hair cells experience larger deflections
    • localization of sound depends on relative intensity and relative timing of sound waves reaching both ears
  137. equilibrium and orientation
    vestibular apparatus: equilibrium receptors in semicircular canals and vestibule, vestibular receptors monitor static equilibrium, semicircular canal receptors monitor dynamic equilibrium
  138. maculae
    • sensory receptors for static equilibrium
    • one in each saccule wall and one in each utricle wall
    • monitor the position of head in space, necessary for controlling posture
    • respond to linear acceleration forces, not rotation
    • contain supporting cells and hair cells
    • sterocilia and kinocilia are embedded in the otolith membrane studded with otoliths
  139. maculae in utricle respond to
    horizontal movements and tilting head side to side
  140. maculae in saccule respond to
    vertical movements
  141. the hair cells of maculae synapse with
    vestibular nerve fibers
  142. activating maculae receptors
    • hair cells release NT continuously: movement modifies amount released
    • bending of hairs in direction of kinocilia: depolarizes hair cells, increases amount of NT released, more impulses travel up vestibular nerve to brain
    • bending away from kinocilium: hyperpolarizes receptors, less NT released, reduces rate of impulse generation
    • lets the brain know the head is changing position
  143. crista ampullares
    • sensory receptor for rotational acceleration: one in ampulla of each semicircular canal; major stimuli are rotational movements
    • each crista has supporting cells and hair cells that extend into gel like mass called ampullary cupula
    • dendrites of vestibular nerve fibers encircle base of hair cells
  144. ampullary cupula
    gel like mass of supporting cells and hair cells
  145. what are the only two receptors that don't adapt
    pain and joint
  146. activating crista ampullaris receptors
    • cristae respond to changes in velocity of rotational movements of the head
    • bending of hairs in cristae causes depolarizations, and rapid impulses reach brain at faster rate
    • bending of hairs int he opposite direction causes hyperpolarizations and fewer impulses reach the brain
    • thus brain informed of rotational movement
  147. vestibular nystagmus
    • strange eye movements during and after rotation (usually with vertigo)
    • eyes continue to rotate in direction of spin then jerk rapidly in opposite direction due to CNS compensation
  148. equilibrium pathway to the brain
    • equilibrium info goes to reflex centers in rain stem: allows fast reflexive responses to imbalance
    • impulses travel to vestibular nuclei in brain stem or cerebellum
    • three modes of input for balance and orientation: vestibular receptors, visual receptors, somatic receptors
  149. motion sickness
    • sensory input mismatches; visual input differs from equilibrium input
    • warning signs: excess salivation, sweating, rapid breath
    • treatment: anti motion drugs

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