Special Senses

Vision
1. Function
2. Accessory Structure
  1. Conjunctivita
    1. Thin protective mucous membrane
    2. Lines inner aspect of the eyelids and onto surface of the eyeball over sclera
  2. Lacrimal Apparatus
    1. Lacrimal Gland
    2. Lacrimal Duct
    3. Lacrimal Puncta
    4. Lacrimal Sac
    5. Inferior Lacrimal Canal
    6. Nasolacrimal duct
    7. Superior lacrimal canal
    8. Tears (1ml a day)
      1. Contains Lysozome
      2. Protects eye
      3. leans and lubricates and moistens
3. Eye Muscle
  1. Superios Rectus
    1. Superiorly
    2. Medially
    3. Rotates Medially
    4. Occulomotor (III)
  2. Medial Rectus
    1. Medially
    2. Occulomotor (III)
  3. Superios Oblique
    1. Inferiorly
    2. Laterally
    3. Rotates Laterally
    4. Trochlear (IV)
  4. Lateral Rectus
    1. Laterally
    2. Abducens (VI)
  5. Inferior Rectus
    1. Inferiorly
    2. Medially
    3. Rotates Medially
    4. Occulomotor (III)
  6. Inferior Oblique
    1. Superiorly
    2. Laterally
    3. Rotates Laterally
    4. Occulomotor (III)
4. Anatomy/Strucure
  1. Tunics (Layers)
    1. Fibrous Tunic
      1. Cornea
        Transparent
        Helps focus light onto the retina
      2. Sclera (White)
        Shape and support
        Posteriorly pierced by Optic Nerve (CNII)
    2. Vascular Tunic
      1. Choroid
        melanin absorbs scattered light = maintan clear , sharp image
      2. Cilliray Body
        Processes = Secretes aqueos humur
        muscle = alters shape of lens
      3. Suspensary Ligament
        attaches lens to ciliary muscle
        controls tension on ligaments = alter shape of lens (accomodation)
      4. Lens
        Avascular
        Posterior to pupil and Iris
        Lens fine tunes focusing of light rays to fovea od the retina = clear vision
      5. Iris
        Coloured part of eye (depends on melanin)
        Circular and radial smooth muscles
        Function = regulate amount of light entering eye
        Muscles around the iris control the size = amount of light that gets in
      6. Pupil
        Hole in centre of iris
        Light enter in eye
    3. Retina
      1. Photoreceptors = Rods and Cones
        Rods = rod shaped.Black and white vision. Shapes and movements. Around periphery of retina
        Cones = cone shaped. sharp and colour vision. Densely packed in Central Fovea
      2. Optic disc (where optic nerve exits eyeball)
      3. Retinal Blood supply
      4. Macula Lutea - centre of posterior retina
      5. Fovea Centralis
        Centre of Macula Lutea
        Highest visual acuity/resolution
        Only has cones
        Colour and focusing
5. Physiology
  1. Refraction
  2. Accommodation
    1. In Vascular Tunic = Suspensory ligament)
  3. Pupillary Constriction
6. Receptors and Neurons
  1. Nerve impulses
    1. 1)Leave eyeball via optic nerve
    2. 2)Pass through the optic chiasm
    3. 3)Axons now form the optic tract
    4. 4)Pass through the thalamus
    5. 5) Primary visual area
Hearing
1. Function
2. Anatomy
  1. Tympanic Membrane
  2. Round window
  3. Malleus
  4. Incus
  5. Stapes
  6. Oval window
  7. Ossicles
  8. Cochlea
  9. Organ of Corti
  10. Vestibule
  11. Semicircular canals
  12. Auditory tube
3. Physiology
  1. 1) Sound waves vibrate the Tympanic Membrane that is in the Inner ear cavity
  2. 2) Vibration of ossicles transfers and AMPLIFIES the vibratory motion to oval window
  3. 3) Vibrations fof oval window = pressure waves in perilymph cochlea
  4. 4) Pressure waves travels through perilymph --> through the Vestibular Membrane and into Endolymph (in membranous labyrinth
  5. 5) Pressure waves in Endolymph cause Basilar membrane to vibrate = moves hair cells = action potential (nerve impulse)
  6. The nerve that carries the nerve Impulses = Vestibulocochlear (VIII) nerve ( Cochlea branch )
Differences when ageing
1. Vision
  1. Lost of elasticity in lens = cannot change shape easily = decreased accomodation
  2. Lost of transparency = cataracts
  3. weakened circular and radial muscles = slow pupillary reactions = lower adaptation to dark areas
  4. Sharp vision decreased = colour and depth perception reduced
  5. Retinal damage = Macular degeneration
  6. Decreased tear production = dry eyes
  7. Loss of elasticity in eyelids, less adipose tissue = sunken eyes
2. Hearing
  1. Loss of hearing
Sensation
1. Sensory Neurons oly carry information specific for their function

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