The Eye

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The Eye

• Photoreception
• Accessory Structures
• Eyebrows
• Eyelids
• Lacrimal caruncle
• Sebaceous sweat glands Sandmans eye sand.
  Epicanthic fold
• Eyelashes
• Innervated with many nerves.

• Conjuctivatransparent membraneover eyelids and
  sclera. Important in lubrication of the eye.
• ConjuctivitisPinkeye.
• Lacrimal Apparatus
• Lacrimal gland
• Nasolacrimal duct
• Tears contain antibodies and lysozyme.

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The Human Eye

• Corneacontains many nerve endings.transplantatio
  n and repair.
• pupil
• iris
• Lens--convex
• suspensory ligaments
• ciliary bodies
• Extrinsic muscles
• retina
• cones and rods
• optic nerve
• Choroid coatWhy is it dark colored?

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Human Eye
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Light and Image Formation

• Electromagnetic Radiation
• Visible light
• Reflection
• Refraction
• Real image
• Convex lens
• Upside down and reversed form left to right.

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Image Formation

• Focal point
• Focal length
• Retina
• Photoreceptors
• Optic disc
• Blind spot
• Optic nerve
• Rods
• cones

• Macula lutea
• Fovea centralis
• Forms a pathway for light to get to the
  photoreceptors.
• Most cones are in the fovea.
• This is where important area for hard focusing.
• Small portion of our field of view.

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Human Eye Defects

• Myopia
• Causes
• Eye too long or lens too convex
• Effects
• Correctionconcave lens.
• Hyperopia
• Causes
• Eye too short or lens too flat
• Effects
• Correctionconvex lens.
• Presbyopia

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Myopia
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Hyperopia
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Eye Disorders

• Diplopiamovements of the extrinsic muscles of
  the 2 eyes are not coordinated. Leads to double
  vision.
• Strabismuscross-eyed Affected eye rotates
  either medially or laterally. Treatments and
  effects.

• Retinal Detachment
• Glaucomaexcessive aqueous humorIntraocular
  pressure.
• Cataractclouding of the lens. May be caused by
  sunlight, diabetes, smoking, vitamin
  deficiencies,, etc
• Astigmatism
• Color blindness
• Night blindness

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Visual Pathways to the Brain

• From the retina, visual impulses travel to
• Optic nerve
• Optic chiasma
• Optic tracts
• Thalamus
• Optic radiation tract
• Primary visual cortex in the optic lobe.

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Hearing

• What is sound?
• Wavelength
• Frequency
• Pitch
• Intensity
• Amplitude
• Loudness
• Decibels
• Above 90 db is dangerous

• Hearing range20 to 20000 Hz

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Hearing

• Mechanoreceptors
• Fluids
• Outer, middle, and inner ear
• Outer ear
• Pinna or auricle
• Are bigger ears better?
• External auditory canal
• Ceruminous glands
• Tympanic membrane

• Middle Ear
• Pharyngotympanic tube
• Eustachian tube
• How does this structure function?
• Ossicles
• Malleus, incus, stapes
• Malleus is attached to the eardrum.
• Stapes is attached to the oval window of the
  inner ear.
• Sound amplification

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Hearing

• Transmit vibrations of the eardrum to the middle
  ear.
• Inner ear
• Bony labyrinth
• Semicircular canals
• Vestibule
• Cochlea
• Membranous labyrinth
• Inside the bony labyrinth

• Filled with fluid
• Vestibuleoval window is attached to this
  structure.
• Contains equilibrium receptors.
• Semicircular canalsposter and lateral to the
  vestibule. Ampullaequilibrium receptors.

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Hearing

• Cochleaanterior to the vestibule.
• Cochlear duct
• Basilar membrane
• Organ of Corti
• Hair cells
• Cochlear nerve
• Thalamus
• Auditory cortex in temporal lobes

• Disorders of the Ear
• Otitis Media
• Deafness
• Conduction Deafness
• Otosclerosisstapes becomes fused to oval window.
• Sensorineural deafnessdamage to hair cells or
  neural pathways.
• Cochlear implants
• Tinnitus

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Equilibrium

• Importance of head movements.
• Inputs from the inner ear, eyes, and stretch
  receptors
• Vestibular apparatus
• Vestibulestatic equilibrium
• Semicircular canalsdynamic equilibrium

• Maculaerespond to straight line changes in speed
  and direction, not to rotation
• Hairs cells
• Vestibular nerve
• Respond only to changes in velocity or
  acceleration.

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Equilibrium

• Crista ampullaris
• Semicircular canals
• Respond to rotation
• Changes in rotation
• Hair cells
• To balance centers in the brain stem or the
  cerebellum
• Motion sickness
• Sensory input mismatch

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Taste

• Chemoreceptors
• Aqueous chemicals
• Taste buds
• Most on the tongue
• Papillaeprojections of the surface of the
  tongue.
• Gustatory and taste cellstaste receptors

• Taste pore
• Gustatory hairs
• Replaced every 7 to 10 daystaste buds
• 4 basic tastes
• Sweet, salty, bitter, sour
• Sweetsugars, alcohols, amino acids
• Souracids
• Saltymetal ions
• Bitteralkaloids poisons

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Taste

• Impulses travel from taste receptors to
• Either the facial nerve or glossopharyngeal nerve
  or vagus nerve to
• Medulla to
• Thalamus to
• Gustatory cortex in the parietal lobes
• There are also branches to the limbic system
• Triggers digestive reflexes.

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Smell

• Olfaction
• Olfactory epithelium in the roof of the nasal
  cavity.
• Olfactory receptor cells
• Olfactory cilia
• Mucous covered
• Life span of 60 days.

• Olfactory receptors to
• Olfactory nerves to
• Olfactory bulbs to
• Olfactory tract to
• Thalamus to the olfactory cortex and the frontal
  lobe and to the hypothalamus, amygdala, and other
  parts of the limbic system.
• Anosmias
• Zinc deficiencies

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