Vision

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Three Tunics of the Eye. 1. Tunica fibrosa - fibrous or avascular tunic2. Tunica vasculosa- vascular tunic or uvea3. Tunica interna or nervous tunic or retina. Fibrous or Avascular Tunic. a. scleraposterior 5/6dense connective tissue with collagen and elastic fibersmaintains the shape of the eyecalled _______________ anteriorlycontains insertion of 6 extrinsic eye muscles.

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Vision

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1. Vision eye can sense 10 million gradations of light intensity 7 million different shades of color eyes are responsible for 80% of all knowledge assimilated eye contains 70% of all sensory receptors optic nerve carries 1/3 of all afferent neurons see only 1/70 of the electromagnetic spectrum between 400 and 750 nm

2. Three Tunics of the Eye 1. Tunica fibrosa - fibrous or avascular tunic 2. Tunica vasculosa- vascular tunic or uvea 3. Tunica interna or nervous tunic or retina

3. Fibrous or Avascular Tunic a. sclera posterior 5/6 dense connective tissue with collagen and elastic fibers maintains the shape of the eye called _______________ anteriorly contains insertion of 6 extrinsic eye muscles

4. Fibrous or Avascular Tunic b. cornea clear, dense connective tissue outer layer of stratified squamous epithelium continuous with __________________ 95% transplantation success because has no blood vessels

5. Vascular Tunic or Uvea a. choroid lines most (2/3) of internal region of sclera darkly pigmented with concentrations of ______________ contains many blood vessels delivers oxygen and nutrients to retina

6. Vascular Tunic or Uvea b. ciliary body thickened region around edge of cornea contains two regions 1. ciliary body or processes folds on internal surface where cells secrete _______________ humor suspensory ligaments attach to these processes 2. contains smooth muscles called ciliary muscles

7. Vascular Tunic or Uvea c. iris continuation of choroid, highly vascular thin, muscular diaphragm pupillary constrictor muscles pupillary dilator muscles contains the pigment _______________ causes eye color regulates the size of pupils

8. Nervous Tunic or Retina a. outer pigmented layer simple cuboidal epithelium abuts choroid, provides nutrition for nervous layer acts as phagocytes, absorbs vitamin A b. inner nervous tissue layer photoreceptors rods cones two layers are close together but not fused can separate -- _____________ retina

9. Nervous Tunic or Retina neurons horizontal cells & amacrine cells bipolar cells & ganglion cells optic disc where optic nerve leaves rear of retina no photoreceptors, called ______________ macula lutea no rods where visual image arrives _____________ -highest concentration of cones at center of macula lutea

10. LENS avascular like the cornea dense fibrous capsule covers entire lens filled with transparent proteins called crystallins stable proteins that remain intact and functional for a lifetime without need for replacement held by a fibrous suspensory ligament attaches to ciliary body normally pulls lens flat at rest

11. LENS CATARACTS lens hardens and thickens crystallin unfolds and becomes cloudy causes drug reactions, injuries radiation, aging lens turns yellow, may go completely opaque treatment removal of lens or piece of lens

12. ANTERIOR CAVITY anterior to lens and iris divided into two chambers 1. anterior chamber before the iris 2. posterior chamber in between iris and lens aqueous humor clear fluid similar to cerebrospinal fluid secreted by epithelium of ciliary processes into posterior chamber 5 to 6 ml per day maintains a pressure between 12 - 21 mm drains into the Canal of ___________ (venous sinus)

13. GLAUCOMA drainage of aqueous humor into Canal of Schlemm impaired increasing pressure on weak point- optic nerve 2% of population over 25 treatments drugs - constrict pupil and tenses edge of iris laser surgery to perforate wall of anterior chamber

14. POSTERIOR CAVITY 80% of the cavities vitreous humor jellylike substance network of fine collagenous fibers embedded in a viscous connective matrix (proteoglycans) not replaced

15. ACCESSORY STRUCTURES 1. eyelids continuation of skin contain skeletal muscles blink 20-30 times per minute 2. eyelashes 200 prevent foreign matter from reaching surface of eye

16. ACCESSORY STRUCTURES 3. sebaceous and sweat glands meibomian or tarsal glands embedded in tarsal plate modified sebaceous glands oily secretions keep eyelids from adhering to each other

17. ACCESSORY STRUCTURES 4. lacrimal caruncle at the medial canthus small papillary projection includes sebaceous and sweat glands produces the white material of the eye 5. conjunctiva mucous membrane lines inside of eyelids and anterior surface of the eye thin layer of stratified squamous epithelium inflammation called _______________ or pink eye viral or bacterial

18. ACCESSORY STRUCTURES 6. lacrimal apparatus or gland superior and lateral region of the orbit 6 to 12 ducts components lacrimal gland lacrimal punctum lacrimal canaliculi lacrimal sac nasolacrimal duct

19. ACCESSORY STRUCTURES 6. lacrimal apparatus or gland produces tears which it releases when you blink components of tears - water, mucin, salt and lysozymes functions cleans, lubricates and moistens eye production an average of 1 ml produced per day drains into inferior meatus

20. FOCUSING IMAGES light is bent ( refraction) 3 times 1. cornea 2. entering lens 3. leaving lens three basic processes to focusing 1. refraction of light 2. accommodation of lens 3. constriction of pupil

21. FOCUSING IMAGES - LENS when ciliary muscles contract when they contract (parasympathetic stimulation) ciliary body moves toward lens relaxes the tension on the suspensory ligament allows the lens to assume a more spherical shape when ciliary muscle relax tension in suspensory ligament tightens the capsule causes lens to form a more flattened shape accommodation ability of lens to change shape

22. FOCUSING IMAGES - IRIS 2 sets of smooth muscles 1. circular muscle (pupillary constrictor muscle) constricts the pupils stimulated by the _____________ nervous system 2. radial muscle (pupillary dilator muscle) dilates pupils stimulated by the _______________ nervous system

23. ACCOMMODATION PROBLEMS a. myopia or nearsightedness distant objects are focused in front of the retina lens is too thick or eyeball is too long correction - concave or biconcave lens b. hyperopia or farsightedness image is focused behind the retina lazy lens (poor refractory period) or eyeball that is too short correction - biconvex lens

24. ACCOMMODATION PROBLEMS c. astigmatism unequal curvature of the lens or cornea d. presbyopia lens tends to lose its elasticity and ability to accommodate

25. ANATOMY OF RODS AND CONES a. synaptic body or ending connects to bipolar neurons releases the neurotransmitter b. soma or nerve cell body contains the _____________ c. inner segment contains mitochondria makes ________________

26. ANATOMY OF RODS AND CONES d. outer segment composed of shelves of membranes or discs made up of about 1000 discs contains the visual pigments rhodopsin - rods iodopsin - cones embedded in the pigmented layer of the retina

27. RODS more numerous than cones, 130 million per retina detects presence or absence of photons without regard to wavelength night vision and peripheral vision perceive as gray rhodopsin ------> scotopsin + retinene or retinal retinal is derived from vitamin A takes 5 minutes to regenerate 50% of bleached rhodopsin in rods rod stimulation is believed to occur at the very instant that rhodopsin becomes excited by light

28. PHOTORECEPTION - RODS unexcited - dark current inner segment continually pumps Na+ to outside creating a negative potential inside the cell (- 40 mV) outer segment is in an unexcited state and is very leaky to Na+ Na+ continually leaks back inside neutralizing much of the negativity on the inside of the cell rods in the dark releases the neurotransmitter ___________ at a constant rate

29. PHOTORECEPTION - RODS excited - exposed to light when rhodopsin is exposed to light in the outer segment it begins to break down decreases the leakage of Na+ into the rods Na+ continues to be pumped out see a net loss of Na+ called ___________________ (-40 mV to -70 mV) hyperpolarization causes the rods to _____________release of neurotransmitter glutamate inhibition of rod causes depolarization of bipolar neuron excites ganglion cells

30. LIGHT AND DARK ADAPTATION after 30 minutes in dark, almost all visual pigments will be fully receptive to stimulation - dark- adapted state a single rod will hyperpolarize in response to a single photon of light when lights come on, tremendous amount of bleaching occurs sensitivity changes 25,000 times night blindness - lack of vitamin A

31. PHOTORECEPTION - CONES color and clear vision 6.5 million cones per one retina photochemical in cones have almost exactly the same chemical composition as that of rhodopsin in rods protein portion is photopsin instead of scotopsin in rods iodopsin ------> photopsin + retinal takes 90 seconds to regenerate 50% of iodopsin in cones 3 different types of photochemicals in cones red (erythrolobe)- 74% - 558 nm green (chlorolobe)- 10% - 531 nm blue (cyanolobe)- 16% - 420 nm

32. PHOTORECEPTION - CONES color vision orange light red cones 99% blue cones 0 green cones 42% blue light red cones 0 blue cones 97% green cones 0 white light equal stimulation of all three cones

33. PHOTORECEPTION - CONES colorblindness 8% of all men 0.5% of all women most common is red-green genes found on X chromosome deficiency of either red or green cones reds and greens are seen as the same color

34. PHOTORECEPTION - CONES visual acuity fovea centralis 4000 cones converge on 4000 bipolar cells peripheral to fovea 600 rods converge on one bipolar cell blindspot where the optic nerve leaves the retina has no rods or cones

35. ANATOMY OF THE EAR 1. external ear pinna or auricle elastic cartilage external auditory canal or ear canal curved passageway 3 cm long lined with skin and near entrance are fine hairs and sebaceous glands ceruminous glands produce cerumen slows growth of microorganisms ends at the ______________ membrane

36. ANATOMY OF THE EAR 2. middle ear- small air-filled cavity tympanic membrane at junction of middle and outer ear semitransparent fibrous connective tissue hole in tympanic membrane is a perforated eardrum oval and round windows mastoid sinus separated from brain by only thin bony partition

37. ANATOMY OF THE EAR 2. middle ear eustachian or auditory tube 4 cm long and opens into nasopharynx can open passageway by yawning or swallowing equalizes air pressure infections may travel along this passageway

38. ANATOMY OF THE EAR 2. middle ear middle ear bones a. malleus or hammer connects to tympanic membrane b. incus or anvil c. stapes or stirrup connects to oval window

39. ANATOMY OF THE EAR 3. inner ear labyrinth, two divisions a. bony labyrinth divided into three areas a. semicircular canals b. vestibule c. cochlea lined with periosteum and filled with perilymph similar to cerebrospinal fluid

40. ANATOMY OF THE EAR 3. inner ear b. membranous labyrinth lined with epithelium and contains a fluid called endolymph different from those of typical body fluids 3 parts to bony labyrinth 1. cochlea spiral canal that resembles a snail's shell makes almost 2.5 turns

41. ANATOMY OF THE EAR 3. inner ear bony labyrinth 2. vestibule oval central portion of bony labyrinth contains a membranous labyrinth consisting of two sacs a. utricle b. saccule 3. semicircular canals three - one in each plane one end of each canal enlarges into a swelling called the ampulla

42. VESTIBULE two sacs a. utricle b. saccule equilibrium sensations whether body is moving or not macula - small thickened area contains hair and supporting cells each cell has 40 - 70 stereocilia (microvilli) and one kinocilium imbedded in a gelatinous substance are particles of calcium called the otolith

43. VESTIBULE concerned with static and dynamic equilibrium movement of stereocilia initiates depolarizing or hyperpolarizing receptor potentials static equilibrium - position of head dynamic equilibrium - linear acceleration

44. SEMICIRCULAR CANALS respond to rotational movements of the head anterior, posterior and lateral semicircular ducts are continuous with the utricle each duct has an expanded regions called the ampulla inside ampulla are many hair cells with their kinocilium and sterocilia embedded in a gelatinous mass called the cupula crista contains group of hair cells and supporting cells

45. MOTION SICKNESS temporary disturbance in functioning of semicircular canals results in headache, sweating, nausea and vomiting results from repetitive changes in rate and direction of movement and from conflicting vestibular and visual signals treatment dramamine - depresses activity at the vestibular nuclei

46. MENIERE’S DISEASE caused by irritation or damage to inner ear leads to accumulation of excess endolymph if semicircular canals are affected dizziness and loss of equilibrium if cochlea is affected tinnitus

47. COCHLEA - STRUCTURE modiolus bony core of cochlea three passageways 1. scala vestibuli 2. scala tympani 3. scala media or cochlear duct contains endolymph scala vestibuli and tympani are continuous both contain perilymph

48. COCHLEA - STRUCTURE other structures helicotrema opening which connects scala vestibuli and tympani vestibular membrane separates cochlear duct from scala vestibuli

49. COCHLEA - STRUCTURE basilar membrane separates cochlear duct from the scala tympani contains 20,000 to 30,000 basilar fibers elastic and reedlike and can vibrate like reeds of an harmonica lengths of basilar fibers increase from 0.04 mm near the windows to 0.5 mm at the helicotrema 12 fold increase in length diameters of fibers decrease from the windows to the helicotrema

50. COCHLEA - STRUCTURE basilar membrane short, stiff fibers near windows vibrate at higher frequencies long, limber fibers near helicotrema vibrate at lower frequencies organ of corti or spiral organ sits on the basilar membrane contains a coiled sheet of epithelial cells supporting cells and about 20,000 hair cells in 4 rows lack kinocilia but stereocilia are in contact with overlying tectorial membrane not neurons

51. COCHLEA - STRUCTURE organ of corti hair cells are receptors for auditory sensations two groups of hair cells with supporting cells a. inner- single row b. outer- several rows when portion of basilar membane vibrates, the sterocilia of the hair cells are pressed against the tectorial membrane and become distorted

52. PATHWAY OF SOUND 1. auricle directs sound waves into external auditory canal 2. sound waves cause the tympanic membrane to vibrate tympanic membrane has 18X the surface area of the oval window central areas of tympanic membrane connects to the malleus which also starts to vibrate

53. PATHWAY OF SOUND 3. vibration continues to the incus and stapes as stapes moves back and forth, it pushes the membrane of the oval window in and out energy is magnified 18X to the oval window movement of oval window sets up fluid pressure waves in the perilymph of the cochlea

54. PATHWAY OF SOUND 4. as oval window bulges in, it pushes on the perilymph of the scala vestibuli pressure waves are transmitted from scala vestibuli to scala tympani pressure waves eventually hit the round window which bulges outwards

55. PATHWAY OF SOUND 5. as pressure waves deform the walls of the scala vestibuli and scala tympani they also push the vestibular membrane back and forth pressure of endolymph inside the cochlear duct increases and decreases 6. pressure fluctuations of the endolymph move the basilar membrane slightly

56. PATHWAY OF SOUND 7. when the basilar membrane vibrates, the hair cells of the spiral organ move against the tectorial membrane bending of the hairs opens ion channels and produces receptor potentials that lead to the generation of nerve impulses 8. pressure changes in the scala tympani cause the round window to bulge outward into the middle ear

57. SOUND a. pitch determined by frequency of vibrations higher frequency (short wavelength) stimulates window end of basilar membrane lower frequency (long wavelength) stimulates helicotrema end of basilar membrane human ear is sensitive to a range from 20 - 20,000 hertz (Hz) or cycles per second (cps)

58. SOUND b. intensity three ways 1. amplitude of vibration increases 2. number of hair cells vibrating increases 3. some hair cells have different thresholds can discriminate a 100 trillion fold difference in sound from a whisper to the loudest noise sound intensity is expressed in decibels 1 decibel = actual increase in intensity of 1.26 times

59. SOUND b. intensity 20 decibels - ticking watch 45 decibels -normal conversation 60 decibels - crowd noise 80 decibels - alarm clock at 2 feet, subway damage at 8 hours 100 decibels - chain saw, pneumatic drill damage at 2 hours 120 decibels - sandblasting, rock concert damage immediate 140 decibels - gunshot, jet plane 160 decibels - rocket launching pad

60. ATTENUATION REFLEX muscles in middle ear pull malleus and stapes to make ossicles rigid can reduce sound by 30-40 decibels but is a relatively slow reflex - 40 msec

61. DEAFNESS 1. conduction deafness a. ear wax buildup b. otosclerosis c. destruction of tympanic membrane

62. DEAFNESS 2. nerve deafness damage to receptors or nerve fibers - cochlea, auditory nerve causes a. low frequency sounds excessive and prolonged exposure to very loud sounds like rock band, jet engine b. all frequency sounds drug sensitivity of organ of corti to some antibiotics like neomycin and gentamicin

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