L30 Special Senses

• Differences far and near point of the eye

  far point : furthest distance - relaxed eye

  near point : nearest distance - accomodate
• where does image focused on retina relating to refraction

  -inverted

  -left to right reversed
• state 3 refractive errors of eye and how it corrected

  -myopia -concave lens

  -hyperopia -convex lens

  -astigmatism -cylindrical lens
• differentiate myopic and hyperopic eye

  myopic : elongated eyeball - thickened lens

  hyperopic : shortened eyeball - thin lens
• give the neural layers

  -photoreceptor

  -bipolar cell

  -ganglion cell
• describe structure of rods and cones

  rod : 120 million, no colour vision, black/white

  cone : 6 million, has colour vision, green/blue/red
• why fovea centralis has the highest visual activity ?

  -there's no bipolar and ganglion cells present

  -it displaced to periphery of fovea centralis

  -increase resolution of vision
• distinguish the functions of rods and cones

  function - rods vs cones

  sensitivity to light - low intensity vs high intensity

  acuity - periphery vs fovea centralis

  dark adaptation - later vs early

  colour vision - black/white vs colour
• differentiate photopigments and rhodopsin

  photopigment - in cones, regenerate quickly, 3 opsins

  rhodopsin - in rods, regenerate slowly, 1 opsin
• briefly describe phototransduction

  -process which light converted into electrical signals

  -light enters eye and detected by rods and cones

  -chemical reaction triggered when light strikes these pigments

  -changes occur in electrical activity of photoreceptor cells

  -signal process passing biolar cells and ganglion cells before optic nerve carries electrical signals to brain

  -electrical signals interpreted as vision
• state the pathway of light until in conversion of electrical energy

  light -> absorb by photopigments -> triggers chemical reaction -> decreased transmitter released -> bipolar and ganglion cells response -> nerve impulses in optic nerve fibres
• differences axons of ganglion cells in temporal half of retina and nasal half of retina which extends to the thalamus

  temporal half retina : on same side

  nasal half of retin : on opposite side
• state the visual pathway

  optic (III) nerve -> opic chiasm -> optic tract -> lateral geniculate -> nucleus of thalamus -> optic radiation -> primary vision area (17) in occipital area
• differences of focus using on distant and near object

  distant vs near

  ciliary muscle - diverge vs converge

  pupil size - dilate vs constrict

  lens shape - thin vs thick
• pathway of accomodation reflex

  visual informatiion -> primary visual cortex -> frontal eye ->. oculomotor nucleus -> third nerve -> muscle of accomodation
• describe how pupil response to light

  -iris regulates amount of light entering the eye

  -iris control by autonomic nervous system

  -pupil dilate : sympathetic nerve

  -pupil constrict : parasympathetic nerve
• Light reflex on one side of the eye

  1. Light strike into one eye

  2. Rods and cones stimulated

  3. Nerve impulse transmitted from optic nerve to optic chiasm

  4. Fibers of optic tract transmit nerve impulse to superior colliculi

  5. Nerve impulse transmitted to lateral geniculate bodies of same site and at thalamus of opposite site

  6. Parasympathetic oculomotor nerve transmit nerve impulse to ciliary ganglion and sphincter pupilae cause pupil constricted

  7. Nerve impulse transmitted to lateral geniculate body opposite site, oculomotor nerve transmit nerve impulse to sphincter pupilae cause opposite pupil constricted
• differences between inner and outer hair cells

  inner - single row, few in number, receptor for hearing, convert mechanical vibrations into electrical signals

  outer - parallel rows, greater in number, not serve as hearing receptors, increase sensitivity of inner hair cells
• differences outer and middle ear

  outer - directs sound waves in auditory canal

  middle air filled cavity which contain tympanic membrane and auditory ossicles (malleus, incus & stapes)
• significance of stapes insert into oval window ?

  -sound wave causes tympanic membrane to vibrate

  -ossicle vibrate, pushing stapes into oval window
• function of hair cells of spiral organ

  convert mechanical vibration (stimulus) into an electrical signal (receptor potential)
• Sound transduction

  1. Sound waves enter the outer ear

  2. Travel down the auditory canal

  3. Strike the eardrum (tympanum), causing it to vibrate

  4. Vibrations transferred to three tiny bones in the middle ear: the malleus, incus, and stapes

  5. Stapes bone vibrates against the oval window of the cochlea in the inner ear

  6. Vibrations in the oval window cause the fluids in the cochlea to move

  7. Movement of the fluids bends tiny hairs on the hair cells

  8. Bending the hair cells triggers the release of chemicals

  9. Chemicals generate electrical signals

  10. Electrical signals travel along the auditory nerve to the brain

  11. Brain interprets the electrical signals as sound
• Cochlea

  • Fluid-filled snail-shaped structure lined with hair cells
• how sound encoded along basiilar membrane ?

  -frequency activating a hair cell depends on the location of hair cell along the basilar membrane

  -base of basilar membrane : respond best to high frequency

  -apex of basilar membrane : reposnd best to low frequency
• name the hearing test and the impairment when hearing is gradually loss?/

  -rinne test

  -presbycusis (with aging >75 years and above)
• state the auditory pathway

  -hair cells of cochlea

  -auditory information conveyed along cochlear branch of vestibulocochlear (VIII) nerve

  -brainstem

  -thalamus

  -cerebral cortex
• equilibriumwhat is vestibular system ?

  receptor organs for equuilibrium
• what happens to macula when head is in an upright position ?

  orientation macula of

  utricle - oriented horizontally

  saccule - oriented vertically
• function of utricle & saccule of vestibule and semicircular ducts of the semicircular canals

  utricle & saccule : detect linear acceleration

  semicircular ducts : detects angular acceleration (rotation)
• content of olfactory epithelium

  -olfactory receptor cells

  -supporting cells

  -basal cells
• state 3 abnormalities of smell and its definition

  -anosmia -inability to smell

  -hyposmia -decreased ability to smell

  -hyperosmia -hypersensitive sense
• Gustatory pathway

  The pathway for the sense of taste
• Taste bud detection

  Taste buds on your tongue contain receptor cells that identify the five basic tastes (sweet, salty, sour, bitter, umami)
• Cranial nerve connection

  1. Facial nerve (VII) - Front 2/3 of tongue (sweet, salty)

  2. Glossopharyngeal nerve (IX) - Back 1/3 of tongue (sour, bitter, umami)

  3. Vagus nerve (X) - Epiglottis (bitter)
• Brainstem relay


  Nerves carry signals to the medulla oblongata in the brainstem
• Thalamus transfer

  Signals project to the thalamus, a sensory relay station
• Gustatory cortex interpretation

  Signals reach the gustatory cortex (frontal & insular lobe) for conscious taste perception
• Smell (olfactory system) and past experiences (limbic system)

  Influence taste perception
• draw and label tongue and its five primary taste

  draw first then label

  A) Bitter

  B) Umami

  C) Sour

  D) Sour

  E) Salt

  F) Salt

  G) Sweet

  
• Describe tastant in gustation

  -tastant is a chemical stimulate the gustatory receptor

  -tastant dissolve in saliva producing nerve impulses

  -different tastants arise different receptor potentials