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Special Senses. Utilize distinct receptor cells as receptors. Chemical senses. Taste (gustation) Smell (olfaction). Taste. Taste buds. Most are on the tongue. Papillae. Filiform - rough, conical shape, few taste buds Fungiform – scattered; most numerous on sides and tips

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special senses

Special Senses

Utilize distinct receptor cells as receptors

chemical senses
Chemical senses
  • Taste (gustation)
  • Smell (olfaction)
taste
Taste
  • Taste buds.
    • Most are on the tongue.
    • Papillae.
      • Filiform - rough, conical shape, few taste buds
      • Fungiform – scattered; most numerous on sides and tips
      • Circumvallate –largest; least numerous; back of tongue
structure of a taste bud
Structure of a taste bud.
  • Supporting cells – form bulk, insulate
  • Receptor (Gustatory or Taste) cells – contain gustatory hairs that extend through surface
  • Basal cells - stem cells that divide giving rise to new gustatory cells
taste sensation
Taste sensation
  • Sour – stimulated by acids
  • Sweet – stimulated by sugars, alcohols, some amino acids
  • Bitter – stimulated by bases
  • Salty – stimulated by metal ions
sensitivity of the taste buds in different locations
Sensitivity of the taste buds in different locations.
  • Anterior tongue is more sensitive to sweet and salty substances
  • Posterior tongue is more sensitive to bitter substances.
  • Lateral tongue is more sensitive to sour substances.
physiology of taste
Physiology of taste.
  • Chemical comes in contact with gustatory hair cells on receptor cells.
  • Depolarization of taste cells results in generation of action potentials in associated sensory neurons.
  • Relayed to the gustatory cortex.
  • Other sensations
    • Taste is 80% smell
    • Affected by temperature; texture; heat
smell
Smell
  • Localization and structure of olfactory receptors
  • Detects chemicals in solution
  • Olfactory epithelium - Contains the olfactory receptors and is located in the roof of the nasal cavity.
structure of olfactory receptors
Structure of olfactory receptors.
  • Supporting cells –
  • Basal cells –
  • Olfactory receptor cells –
specificity of the olfactory receptors
Specificity of the olfactory receptors –
  • Can distinguish 10,000 chemicals
  • Not clearly understood
  • May be 1000 odorant binding proteins that act in combinations
activation of olfactory receptors
Activation of olfactory receptors.
  • Chemical comes in contact with the olfactory hair cells on the receptor cells.
  • Depolarization of the receptor cells results in the generation of action potentials.
homeostatic imbalances of the chemical senses
Homeostatic imbalances of the chemical senses
  • Anosmias – without smell
  • Uncinate fits – temporary distortions of smell due to brain damage, psychological disorders, or even seizures
vision
Vision
  • Accessory structures of the eye
    • Eyebrows
    • Eyelids “palpebrae”
      • Canthi – angles of the eyelids
      • Epicanthic fold – found in Asians
      • Lacrimal Caruncle – fleshy elevation found at medial canthus
slide17
Meibomian glands – Modified sebaceous glands in eyelid
      • Infection of these called Chalazion
  • Ciliary glands – between hair follicles of eyelashes
      • Infection of these called a Sty
  • Conjunctiva – mucus membrane covering eye (infection called conjunctivitis or pinkeye
accessory structures of eye
Accessory Structures of Eye
  • Lacrimal apparatus
    • Lacrimal glands – secrete tears
    • Lacrimal secretions – contains mucus, antibodies, & lysosozyme
      • Cleanses, protects, & lubricates eye
extrinsic eye muscles
Extrinsic eye muscles
  • Medial rectus –
  • Superior rectus -
  • Lateral rectus -
  • Inferior rectus -
  • Superior oblique -
  • Inferior oblique –
fibrous tunic coat outermost layer
Fibrous tunic (coat) – outermost layer
  • Sclera – whites of the eye
  • Cornea – clear portion in front of eye
vascular tunic coat middle layer uvea
Vascular tunic (coat) – middle layer (uvea)
  • Choroid – vascular brown membrane
  • Ciliary body – encircles lens forming the:
    • Ciliary muscles – control lens shape
    • Ciliary processes - contain capillaries that secrete fluid
    • Suspensory ligaments –
  • Iris – colored portion
  • Pupil – opening in iris
sensory tunic retina innermost layer
Sensory tunic (Retina) – innermost layer
  • Pigmented layer – absorbs light
  • Neural layer – contains photorecptor cells
  • Cells of the retina.
    • Ganglionic cells – generate action potentials
    • Bipolar cells – transfer energy from receptors to ganglionic cells
    • Photoreceptors - sensitive to light
slide25
Rods – dim-light, no color, and peripheral vision
  • Cones – bright light, color vision
  • Macula lutea – “yellow spot” directly behind pupil
  • Fovea centralis – minute pit in center of macula lutea
  • Contains cones only
  • Macular degeneration - linked to nutritional deficiencies
  • Optic disc (blindspot) – location of junction with optic nerve
internal chambers and fluids
Internal chambers and fluids
  • Posterior segment - behind lens
    • Vitreous humor - clear gel
  • Anterior segment - in front of lens
      • Anterior chamber - in front of iris
      • Posterior chamber - between iris and lens
slide27
Aqueous humor - clear liquid filling anterior segment
  • Scleral venous sinus (Canal of Schlemm) - drains aqueous humor back into veins; located at corneal / scleral junction
  • Glaucoma - elevated pressure of the aqueous humor
slide28
Lens
  • Biconvex; transparent; held in place by suspensory ligaments
  • Lens epithelium - outer covering
  • Lens fibers - inner bulk of lens
    • made of folded proteins called crystallins
  • Cataracts - clouding of the lens
    • Age related hardening and thickening; diabetes; inadequate delivery of nutrition to lens
physiology of vision
Physiology of vision
  • Photons - packets of light
  • Wavelength
    • Electromagnetic spectrum - all wavelengths
    • Visible spectrum - 400-700 nanometers
      • nanometer = 1 billionth of a meter
    • Color - reflection of different wavelengths
      • Red, Orange, Yellow, Green, Blue, Indigo, Violet
refraction and lenses
Refraction and lenses
  • Reflection - light bounces off a surface
  • Refraction - light bends as it passes through one substance to another with a different density
  • Lens - a transparent material curved at one or both surfaces
    • Convex - thicker in the center; light converges
    • Concave - thicker at the edges; light spreads
focusing of light on the retina
Focusing of light on the retina.
  • Light is refracted three times
    • Cornea
    • Entering the lens
    • Exiting the lens
focusing for distance vision
Focusing for distance vision.
  • Eye are fixed (preset) on an object 20 feet or more away.
  • Ciliary muscles are completely relaxed.
  • Lens is stretched as thin as it can get.
focusing for close vision
Focusing for close vision.
  • Accommodation of the lens.
      • Ciliary muscles contract.
      • Lens bulges.
  • Constriction of the pupils -
  • Convergence of the eyeballs -
homeostatic imbalances of refraction
Homeostatic imbalances of refraction.
  • Myopia - Nearsightedness
    • Eyeball is too long
    • Image is focused in front of retina
  • Hyperopia - Farsightedness
    • Eyeball is too short
    • Image is focused behind the retina
  • Astigmatism - caused by unequal curvature in different parts of the lens
photoreception
Photoreception.
  • Functional anatomy of the photoreceptors
    • Outer segment.
    • Inner segment
the chemistry of visual pigments
The chemistry of visual pigments.
  • Retinal - a light absorbing pigment
    • made from vitamin A
    • combines with opsonins forming
      • Rhodopsin - “purple” visual pigment of Rods
      • Light stimulation separates retinal from the opsins
      • Retinal will be re-joined with the opsins to regenerate rhodopsin later
different types of opsins in cones
Different types of opsins in cones.
  • 3 Different types of Cones
    • Blue - absorbs blue wavelengths best
    • Green - absorbs green wavelengths best
    • Red - absorbs red wavelengths best
  • Cone wavelengths overlap
  • Stimulation of various cones in different amounts creates different shading and coloration
color blindness
Color blindness -
  • Sex-linked, genetic trait
  • Lack specific types of cones, usually red or green
light transduction in photoreceptors
Light transduction in photoreceptors.
  • Generation of electrical current
  • Photoreceptors depolarize in dark and hyperpolarize in light
  • Produce graded potentials (local)
  • Action potentials produced by Ganglion cells
light and dark adaptation
Light and dark adaptation -
  • Light adaptation - from dark to light (5-10 minutes)
  • Dark adaptation - from light to dark (20-30 minutes)
binocular vision and stereopsis
Binocular vision and stereopsis
  • Anterior placement of eyes results in greater depth perception or three-dimensional vision
hearing and balance
Hearing and balance
  • Structure of the ear
    • Outer (External) ear.
      • Auricle (pinna)
      • External auditory canal (meatus)
        • Ceruminous glands - wax glands
      • Tympanic membrane - “eardrum”
        • boundary between outer and middle ear
middle ear tympanic cavity
Middle ear (Tympanic cavity)
  • Mastoid antrum - canal leading to mastoid process
  • Pharyngotympanic (auditory or eustachian) tube - equalizes pressure on eardrum
  • Ear ossicles.
    • Malleus (hammer) -
    • Incus (anvil) -
    • Stapes (stirrup) -
    • Ear muscles: Tensor tympani & Stapedius
inner internal ear
Inner (Internal) ear
  • Bony (Osseous) labyrinth.
    • Cochlea - “snail” ; hearing
    • Semicircular canals - balance
    • Vestibule - central cavity
  • Membranous labyrinth.
    • Perilymph - surrounds membrane structures
    • Endolymph - fills membrane structures
vestibule
Vestibule
  • Saccule - smaller sac nearer cochlea
  • Utricle - larger sac nearer semicircular canals
  • Maculae - receptors for balance and head position
semicircular canals anterior posterior lateral
Semicircular canals. anterior, posterior, lateral
  • Semicircular ducts - connect canals to utricle
  • Ampulla - swollen base of canals; houses:
    • Crista ampullaris - receptors for head movement
mechanisms of equilibrium
Mechanisms of equilibrium
  • Static equilibrium = head position
  • Maculae - receptors for static equilibrium
    • Supporting cells contain hair cells embedded in gel-like otolithic membrane
      • Otoliths -crystals that make membrane heavier, increase inertia
      • Utricle’s macula is horizontal for linear acceleration stimuli -
      • Saccule’s macula is vertical and responds to vertical movements
dynamic equilibrium
Dynamic equilibrium.
  • Crista ampullaris -- located in the ampulla
    • Supporting cells -
    • Hair cells -
    • Cupula - gelled mass resembling a pointed cap
  • Responds to rotational stimuli -
cochlea
Cochlea.
  • Modiolus -
    • bony pillar at center
  • Cochlear duct -
    • wedge-shaped duct containing Organ of Corti
    • Organ of Corti - receptor for hearing
scalas chambers
Scalas “chambers”
    • Scala vestibuli - connects to vestibule at oval window
    • Scala media = cochlear duct
    • Scala tympani - connects to vestibule at round window
  • Vestibular membrane - roof of cochlear duct
  • Basilar membrane - floor of cochlear duct
sound and mechanisms of hearing
Sound and mechanisms of hearing
  • Properties of sound.
    • Frequency - measured in hertz
    • Amplitude - measured in decibels (dB) -
      • logarithmic (exponents of ten)
      • 0 dB = hearing threshold
      • 50 dB = normal conversation
      • 90 dB = danger zone
      • 120 dB = Rock concert
      • 130 dB = Pain threshold
transmission of sound to the inner ear
Transmission of sound to the inner ear -
  • Vibrations transferred from air to tympanic membrane to malleus, incus, stapes, to oval window, to cochlear fluid causing resonance of the basilar membrane -
  • Basilar membrane contains fibers of different lengths that resonate to different frequencies from high to low
excitation of hair cells in the organ of corti
Excitation of hair cells in the organ of Corti.
  • Organ of Corti - rests atop the basilar membrane
  • contains approx. 16,000 cochlear hair cells
auditory processing
Auditory processing.
  • Perception of pitch - specific hairs in specific sections of basilar membrane identify pitch
  • Detection of loudness - some hair cells for a certain frequency require stronger stimulation; more stimulation = more hair cells = louder perception
  • Localization of sound -identified by timing and intensity
homeostatic imbalances of hearing
Homeostatic imbalances of hearing.
  • Deafness.
    • Conduction deafness -
      • possible causes include: ear wax, perforated eardrum, inflamation, otosclerosis
    • Sensineural deafness - nerve damage
  • Tinnitus - ringing in the ear
  • Meniere's syndrome - attacks of dizziness, nausea, caused by excess endolymph in the membranous labyrinth