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Chapter 15_ The Special Senses

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					Chapter 15: The Special Senses
The special senses are

   •   __________ = smell
   •   taste =           1) __________, 2)____________, 3)_____________, 4)___________

   •   vision = sight; ______/________(______________of light), ________, _______, _______
   •   hearing
   •   balance

Olfaction - seven primary odors now recognized
              - average person can recognize 4000 different odors (chemicals).
              - perceived by olfactory epithelium
              - dendrites of olfactory neurons have enlarged ends (olfactory vesicles).

Cilia (olfactory _________) of olfactory neuron embedded in mucus.

Odorants ___________ in mucus.

Somehow (mechanism unknown) odorants attach to receptors, cilia ___________ and initiate
action potentials in olfactory neurons.

One receptor may respond to more than one type of odor.

Olfactory epithelium is ______________ as it wears down. Olfactory neurons are replaced by
basal cells every two months. Unique: most neurons are permanent cells (aren't replaced if they
die).

Neuronal Pathways of Olfaction
  • Olfactory sensory pathway: olfactory neurons (bipolar) in the olfactory epithelium pass
            through cribiform plate to olfactory bulbs and synapse with tufted cells or
            mitral cells.
     These extend to the olfactory tract and synapse with ____________ neurons.

   •   Association neurons also receive input from brain, so information can be __________
       before it reaches the brain.

Information goes to olfactory cortex of the frontal lobe _________________________ thalamus
(only major sense that does not go through thalamus).

Three regions in frontal lobe affect conscious perception of smell and interact with limbic system.

- Lateral olfactory area: ____________ perception of smell

- Medial olfactory area: visceral and ______________ reactions to odors
- Intermediate olfactory area: effect modification of incoming information
Taste
- Taste buds located, primarily, on ___________
- Types of papillae
       - Vallate.
               - Largest, least numerous.
               - 8-12 in V along border between anterior and posterior
                      parts of the tongue.

             - _________ taste buds.
      - Fungiform.
             - Mushroom-shaped.
             - Scattered irregularly over the superior surface of tongue.
                    Look like small red dots interspersed among the filiform.

              - ________ taste buds.
      - Foliate.
              - Leaf-shaped.
              - In folds on the sides of the tongue.


               - Contain _______________ taste buds. Decrease in number with age.
      - Filiform.
               - Filament-shaped.
               - Most numerous.

              - ____________ taste buds. (so then, what is their function????????)

Taste bud: supporting cells surrounding taste (gustatory) cells.

Taste cells have microvilli (gustatory hairs) extending into taste pores. Replaced about every 10
days

Five Tastes

sour - ________ aspects of the tongue - response is primarily to H+; sour then is _______

salt - ______ of tongue - shares _____ sensitivity with sweet - anything with Na+ (or other cation)
              causes depolarization

bitter - ________aspect - ________ sensitivity - ______alkaloids are bitter, bitter is then _______

sweet - _____ of tongue - shares ______ sensitivity with salty - sugars, some carbohydrates, and
                    some proteins (NutraSweet: aspartame).

umami (glutamate) - scattered sensitivity - caused by _________

taste
- texture affects the perception of taste (remember tongue and finger tips have highest
                                                                    two point discrimination
- ___________________ affects taste perception (why??????)
   -   very __________ adaptation (why??????), both at level of taste bud and within the central
       nervous system
   -   taste influenced by ____________
           - actually I would say taste is mostly olfaction
           - compare your “taste” when you have a cold to when you do not have one
   -   different tastes have different thresholds
           - bitter is the taste to which we are _________ sensitive.
           - many alkaloids (bitter) are poisonous.
           - I HAVE A CHALLENGE FOR YOU!!! TELL ME ONE BEVERAGE (something we
               drink for PLEASURE) THAT HAS A pH GREATER THAN 7 (basic)
               - no, milk contains lactic ACID, so it is not basic

Neuronal Pathways for Taste (notice the involvement of ________ cranial nerves)
  - Chorda tympani (part of cranial nerve VII):
         carry sensations from anterior one-third of tongue except from circumvallate papillae

   -   Cranial nerves IX and X carry information from _________ one-third tongue
          - circumvallate papillae, superior pharynx, epiglottis
          - TWO cranial nerves handling information from this region, why????????

   -   Information to medulla oblongata
           - decussation takes place
           - information projects from there to the thalamus.
             - then to taste area of cortex (extreme inferior end of the postcentral gyrus)

Visual System: Accessory Structures
       - eyebrows: shade; inhibit sweat
       - eyelids (palpebrae) with conjunctiva.
       - palpebral fissure: space between eyelids.
       - canthi: lateral and medial, eyelids meet.
               - medial canthus has caruncle with modified sweat and sebaceous glands

five layers of tissues including dense __________ tissue tarsal plate that helps maintain lid shape

eyelashes: double/triple row of hairs

ciliary glands (modified ________ glands) empty into hair follicles. Which makes them which kind
of sweat glands??? (remember there are two kinds)

meibomian glands at inner margins produce sebum

conjunctiva: thin __________ mucous membrane
  palpebral conjunctiva: - inner surface eyelids
  bulbar conjunctiva: - anterior surface of eye except over __________

Lacrimal Apparatus
lacrimal gland: produces tears to moisten, _____________, wash.
tears pass through ducts and then over eye.
- lacrimal canaliculi: collect excess tears through openings called puncta.

lacrimal sac to nasolacrimal duct: opens into nasal cavity beneath the inferior nasal conchae.
    - nasolacrimal duct: opens into nasal cavity
   Eye Anatomy
      three layers:
             - fibrous: sclera and cornea
             - vascular: choroid, ciliary body, iris
             - nervous: retina

Fibrous Layer
      Sclera: _______ outer layer.
          – Maintains shape,
          – protects internal structures,

          –   provides _______________________ point,

          –   continuous with _________.

          –   Dense ______________________ tissue with __________ fibers.

         – Collagen fibers are _______ and ___________.
      Cornea:
           - connective tissue matrix containing collagen, elastic fibers and proteoglycans.

              - layer of _____________________ epithelium on the outer surface. (why????)

              - collagen fibers are small, thus ________________.
              - more proteoglycans than sclera,
              - low water content (water would ________________).
              - avascular, transparent, allows light to enter eye;
              - bends and refracts light.

Vascular layer
   - middle layer.
           contains most of the ___________of the eye: branches off the internal carotid arteries.
           - contains melanin.
      - iris: colored part of the eye.
               - controls light entering the pupil.

              - __________ muscle determines size of pupil.
                                - sphincter pupillae: ________________________

                                - dilator pupillae: __________________________
      Ciliary body: produces aqueous humor that fills anterior chamber

      Ciliary muscles: control lens shape; smooth muscle.
      Ciliary processes attached to suspensory ligaments of _________________

      Choroid: associated with sclera. Very thin, pigmented.
Nervous Layer
   two layers
      - ____________________ retina: outer, pigmented layer;

             - pigmented simple _______________ epithelium.
             - pigment of this layer and choroid help to separate sensory cells and
                           reduce light scattering.

       - ________________ retina: inner layer of rod and cone cells sensitive to _________

       Lens focuses light on macula lutea and fovea centralis
          - Macula lutea: small yellow spot

          - Fovea centralis: area of ___________ visual acuity; photoreceptor cells tightly packed

          - Optic disc: ______________. Area through which _______________ enter eye,

                    where nerve processes from sensory retina _________________ eye

anterior compartment: anterior to lens; filled with aqueous humor
   - anterior chamber: between cornea and iris
   - posterior chamber: between iris and lens

   -   helps maintain ___________; supplies _____________ to structures bathed by it;

             contributes to __________________________
                - produced by ciliary process; returned to venous circulation through canal of
                    Schlemm or scleral venous sinus

________________: abnormal increase in intraocular pressure

posterior compartment: posterior to lens.

   -   filled with jelly-like ________________
   -   frequently mentioned in crime shows, like CSI) as a point where _____________________
   -    helps maintain intraocular pressure
   -    holds lens and retina in place

   -   ________________

lens
- held by suspensory ligaments attached to __________muscles

- changes __________ as ciliary muscles contract and relax.

- made of long ________epithelial cells that __________ and produce proteins called crystallines.
- surrounded by a highly elastic, transparent capsule
- transparent, biconvex
Light
- visible light: portion of electromagnetic spectrum detected by human eye

- refraction: __________ of light

- convergence: light striking a _____________ surface

- focal point: point where light rays _____________

- focusing: causing light to ___________
- lens changes shape causing adjustment of _____________ on the retina

Focusing
     - emmetropia: normal resting condition of lens.
                  - ciliary muscle is relaxed.
                  - lens is flat.
                  - far point of vision:
Near Vision
- closer than 20 feet.
     - changes occur in lens, size of pupil, and distance between pupils
  - called accommodation:
         - ciliary muscles contract due to parasympathetic input of cranial nerve III

  - pulls choroid toward lens ___________ tension on suspensory ligaments.

       - lens becomes more ____________ greater refraction of light
       - pupil constriction: varies depth of focus
       - convergence: as objects move close to the eye, eyes are rotated medially.
               - reflex contraction of the medial rectus muscles

Retina Structure and Function
   - sensory retina: three layers of neurons:
          - photoreceptor,
          - bipolar, and
          - ganglionic

Cell bodies form nuclear layers separated by plexiform layers,
                           where neurons of adjacent layers synapse with each other

Pigmented retina: single layer of cells;

      - filled with ______________.
      - with choroid,
- enhances visual acuity by isolating individual photoreceptors, reducing light scattering

Rods - bipolar photoreceptor cells; black and white vision.
  - found over most of retina, but not in fovea centralis.

   -   ___________ sensitive to light than cones.

       - protein rhodopsin changes ________ when struck by light
       - separates into its two components: opsin and retinal
In absence of light, opsin and retinal _____________ to form rhodopsin.
      Retinal originally derived from Vitamin A

Rods are unusual sensory cells:
- when not stimulated they are ______________ ( ________ sensitive)
- light causes them to depolarize.

Depolarization of rods causes
      depolarization of bipolar cells causing
             depolarization of ganglion cells

Light and dark adaptation: adjustment of eyes to changes in light.
       happens because of changes in amount of available _____________.

Light and Dark Adaptation:
Rods:
       bright light,
               - more rhodopsin  Vitamin A than
                       rhodopsin  Vitamin A
               - protects the eye
               - eye less sensitive to light.

       darker conditions,
              - more rhodopsin  Vitamin A          than
                 rhodopsin  Vitamin A
              - eye more sensitive to light.

Pupils: constriction in bright light; dilation in dim light.

Accommodation takes time because of the ______________ changes that must occur.

Cones
- bipolar receptor cells.
- color vision and visual acuity.
- distribution
         - numerous in _______________ and __________________;
         - fewer over rest of retina.
- response
         - light intensity  ability to see color 

visual pigment is iodopsin:
- three types respond to
        - blue
        - red and
        - green light
- receptor response to light ______________
- interpretations of color possible several million colors - just like television
In all areas except the fovea
        - rods and cones synapse with bipolar cells
               - bipolar cells synapse with ganglion cells.
                      - ganglion cell axons converge at optic disc,
                              - exit via optic nerve
                                      - impulses travel to visual cortex

Fovea centralis: highest visual acuity

Rods have ________ summation.
      - one bipolar cell receives input from _________rods,
                    - one ganglion cell receives input from __________ bipolar cells.

Cones exhibit ________________________.
- receptive fields
       - area from which a ganglion cell receives input
       - roughly circular with receptive field center
       - those in fovea centralis smaller than in other parts of retina

two types of receptive fields
- on-center ganglion cells:
       - more action potentials when light is directed ______ the receptive field.

        - respond to ________ of light
- off-center neurons:
        - more action potentials when light is off or when light ______________________ field.

       - respond to __________ in light

Interneurons present in inner layers - _________ signal before signal ___________ retina.
       - enhance borders and contours, increasing intensity at borders

Binocular vision: visual fields partially _____________ yielding _________________

Eye Disorders

- Myopia: ______________ Focal point too near lens, image focused in front of retina

- Hyperopia: ____________ - Image focused behind retina
- Presbyopia - Degeneration of accommodation, corrected by reading glasses

       - lens no longer ________ after being stretched

- Astigmatism: Cornea or lens not ________________
- Strabismus: Lack of parallelism of light paths through eyes
- Retinal detachment -Can result in complete blindness

- Glaucoma -Increased _________________ by aqueous humor buildup

- Cataract - Clouding of lens
- Macular degeneration – Pigmented layer of _________ atrophies and degenerates. Common in
older people, loss in acute vision
- Diabetes - Dysfunction of peripheral circulation

External ear: hearing.
           - terminates at eardrum (tympanic membrane).
           - auricle and external auditory meatus
Middle ear: hearing.
       - air-filled space
       - auditory ossicles
Inner ear: hearing and balance.
           - interconnecting fluid-filled tunnels and chambers

          -   within the ___________ bone

external ear
      - auricle or pinna
      - elastic cartilage covered with skin
      - external auditory meatus:
      - lined with
              - hairs and
              - ceruminous glands.
                      - produce cerumen (__________________)
- tympanic membrane
      - structure
              - thin membrane of two layers of _______________

             - _______________ between
      - sound waves cause it to vibrate
      - forms border between external and middle ear

middle ear
      - separated from the inner air by the oval and round windows
      - two passages for air
             - auditory or ______________ tube: opens into pharynx, _____________________
             - passage to mastoid air cells in mastoid process

      - ossicles: ___________________ from eardrum to oval window
              - malleus
              - incus
              - stapes

oval window
       - connection between middle and inner ear.

      - foot of the ____________ rests on oval window
      - held in place by annular ligament
inner ear labyrinths
       - bony labyrinths : ___________________ in the ______________ bone

              - cochlea: _____________

              - vestibule: ______________

            - semicircular canals: ______________
       - membranous labyrinths : tunnels and chambers in the bony labyrinth
            - called lymphs
                    - endolymph: in membranous labyrinth
                    - perilymph: between membranous labyrinth and periosteum of
                            bony labyrinth

oval window communicates with vestibule
       - vestibule communicates with the scala vestibuli of the cochlea

scala vestibuli extends from oval window to helicotrema at cochlear apex

a second cochlea chamber (scala tympani) from helicotrema to chambers filled with perilymph

Inner Ear
- wall of scala vestibuli is vestibular membrane - oval window communicates with scala vestibuli
- wall of scala tympani is basilar membrane - round window communicates with scala tympani

cochlear duct (scala media): - space between vestibular and basilar membranes
- filled with endolymph

_________________ of basilar membrane increases
     - from 0.04 mm near oval window to 0.5 mm near helicotrema

       - Near oval window basilar membrane responds to high_______________ vibrations

       - Near helicotrema responds to low______________ vibrations

spiral organ (organ of Corti):
- hair cells in cochlear duct with hair-like projections at apical ends
        - microvilli called stereocilia

basilar region of hair cells with synaptic terminals of sensory neurons
       - cell bodies of afferent neurons grouped into cochlear (spiral) ganglion
       - afferent fibers form the cochlear nerve

Hair cells arranged in rows
       - inner hair cells - responsible for _______________

       - outer hair cells - regulate __________ on basilar membrane

Hair bundle: stereocilia of one inner hair cell
       - Tip link (gating spring) attaches tip of stereocilium to side of next longer stereocilium.

       - As stereocilia bend, they open K+ gates (________________________)
Vibrations produce sound waves
- volume or loudness: function of wave ______________

- pitch: function of wave ______________________
- timbre: resonance quality or overtones of sound

sound waves strike the tympanic membrane - membrane vibrates
      vibration of tympanic membrane vibrates three bones of the middle ear
              foot plate of the stapes vibrates in the oval window.
                     causes the perilymph in the scala vestibuli to vibrate.
                             vibration of perilymph displaces basilar membrane

- short waves (high pitch) displace basilar membrane __________ oval window

- longer waves (low pitch) displace basilar membrane __________ oval window.

basilar membrane movement detected by ______________________________

endolymph vibrations in cochlear duct transferred to perilymph of scala tympani.
perilymph vibrations in scala tympani transferred to the round window,
where they are dampened

middle ear ___________________________
- tensor tympani - inserts on malleus - innervated by cranial nerve V
- stapedius - inserts on stapes - innervated by cranial nerve VII

- attenuation reflex: muscles _____________ during loud noises and prevent damaging vibrations

hearing sensitivity
- fine-tuning tension on basilar membrane
- more than 90% of afferent axons of the cochlear ganglion synapse with inner hair cells, 10-30
per hair cell.

a few small-diameter afferent axons synapse with rows of outer hair cells

 afferent axon signal goes to processing center which generates an efferent signal __________
hair cells

outer hair cells receive the efferent input causing them to shorten.
actin filaments in hair cells attach to K+ gated channels
        - can move them along the cell membrane
        - can tighten or loosen the spring.

hair cells are tuned to very specific ____________________

Pitch is localized along the cochlea

afferent cochlear nerve fibers send action potentials to superior olivary nucleus in medulla
oblongata.

The action potentials are compared and strongest is taken as standard.
Efferent action potentials inhibit other action potentials.

Action potentials from maximum vibration go to cortex and are perceived

balance
- static labyrinth
        - utricle and saccule of the vestibule
        - evaluates position of head relative to _________________

        - detects linear ________________________ (as in a car)
- kinetic labyrinth
        - semicircular canals
        - evaluate movement of the head in _______________________________

Static Labyrinth
       Utricle - macula oriented ______________________ to base of skull

       Saccula - macula oriented _________________ to base of skull

       Macula - specialized supporting ____________ epithelium cells
             - hair cells with

                     - numerous stereocilia (______________)
                     - one cilium (kinocilium) embedded in __________ mass weighted by _____
              Gelatinous mass moves in response to gravity bending hair cells and initiating
                            action potentials

Otoliths stimulate hair cells with varying frequencies

Patterns of stimulation translated by brain into specific information about head position or
acceleration

Kinetic Labyrinth
- three semicircular canals filled with endolymph:

       - ____________ plane

       - ____________ plane

      - ____________ plane
Base of each expanded into ampulla with sensory epithelium (crista ampullaris)
Cupula suspended over crista hair cells.
      - acts as a float displaced by fluid __________ within semicircular canals

Displacement of the cupula is most intense when the ____________________,

thus this system detects ________________________________________
hence “Dead Men’s Spiral)

				
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