Docstoc

THE SENSES

Document Sample
THE SENSES Powered By Docstoc
					THE SENSES
  Chapter 12
                  GENERAL IDEA
   RECEPTOR STIMULATION  SENSORY NERVES  AREAS OF
    BRAIN
   TYPES OF RECEPTORS:
    – CHEMORECEPTORS – CHEMICAL STIMULI
          SMELL/ TASTE
          BLOOD CONC. OF O2, CO2, GLUCOSE, H+ IONS
    – PAIN – TISSUE DAMAGE
    – THERMORECEPTORS – TEMPERATURE
          NOCICEPTORS: COLD AND HOT
    – MECHANORECEPTORS – MECHANICAL (MOVEMENT)
          PROPRIOCEPTORS (TENSION OF MUSCLES/TENDONS)
          BARORECEPTORS (BLOOD PRESSURE)
          STRETCH RECEPTORS
    – PHOTORECEPTORS – LIGHT
          RODS AND CONES
   SENSATION – THE ACTUAL PERCEPTION WHEN BRAIN
    INTERPRETS SENSORY INFORMATION
    – DEPENDS ON PART OF BRAIN INFORMATION IS SENT TO
    – PROJECTION – PINPOINT AREA OF STIMULATION
    – SENSORY ADAPTATION – NERVES BECOME LESS SUSCEPTIBLE TO
      STIMULATION IF STIMULUS IS CONSTANT
             SOMATIC SENSES
   PURPOSE:
    – BODY SURFACE
    – BODY POSITION
    – VISCERA
   TOUCH AND PRESSURE
    – SENSORY NERVE FIBERS
         EPITHELIAL TISSUE
         FREE NERVE ENDINGS
    – MEISSNER’S CORPUSCLES
         OVAL SHAPED, FLATTENED C.T. CELLS
         LIGHT TOUCH, TEXTURE
         LIPS, FINGERTIPS, PALMS, SOLES, NIPPLES, GENITALS
    – PACINIAN CORPUSCLE
         LARGE, ELLIPSOIDAL STRUCTURES
         DEEPER, SUBCUTANEOUS TISSUES – HANDS, FEET,
          PENIS, CLITORIS, URETHRA, BREASTS, TENDONS,
          LIGAMENTS
              SOMATIC SENSES
   TEMPERATURE
    – FREE NERVE ENDINGS
    – HEAT RECEPTORS (>25 oC/ 77oF)
          > 45 oC (113 oF)  BURNING
    – COLD RECEPTORS (<10 oC; 50 oF)
          < 10 oC  FREEZING
    – ADAPTATION
   PAIN
    – FREE NERVE ENDINGS; WIDELY DISPERSED (EXPECPT
      BRAIN)
    – MORE LIKELY TO BE STIMULATED BY WIDESPREAD
      MECHANICAL STIMULI
    – REFERRED PAIN – PROJECTED TO DIFFERENT AREA
          FIGURE 12.3
               SOMATIC SENSES
   PAIN PATHWAYS
    – ACUTE PAIN FIBERS
           SHARP PAIN, SHORT LASTING, PINPOINT
           FASTER
    – CHRONIC PAIN FIBERS
           DULL, LONG-LASTING, WIDESPREAD
           SLOWER
   REGULATION
    – First aware when impulse reaches thalamus
           Cerebral cortex – intensity and location
    – Biochemical help – natural pain killers
           Enkaphalin – block pain
              – Serotonin – cause neurons to release more enkaphalins
           Endorphins – morphine-like chemical
              – Pituitary gland and thalamus
   STRETCH RECEPTORS – Proprioceptors
    – No sensation perceived
    – Muscle Spindles – in skeletal muscle
           Cause muscles to contract when stretched
    – Golgi tendon organs – tendons and close to attachments
           Inhibit contraction when stretched
OLFACTORY SENSE - SMELL
   CHEMORECEPTORS
    – DISSOLVED IN WATER
    – STIMULATED BY SPECIFIC CHEMICALS
    – CLOSELY RELATED TO TASTE
   OLFACTORY ORGANS
    – CONTAIN LARGE AMOUNTS OF OLFACTORY RECEPTORS
          SPECIAL NEURONS
          DENDRITES HAVE CILIA
          AXONS  CRIBRIFORM PLATE  OLFACTORY BULBS
    – HIGH IN NASAL CAVITY
   PATHWAY:
    – OLFACTORY ORGAN  OLFACTORY BULBS 
      OLFACTORY TRACT  LIMBIC SYSTEM
    – OLFACTORY CODE
   LOSE NEURONS OVER TIME
    – SMOKING INCREASES LOSS
    – NOT REPLACED
    GUSTATORY SENSE - TASTE
   CHEMORECEPTORS
    – NEED TO BE DISSOLVED
    – 4 KINDS: SWEET, SOUR, BITTER, SALTY
   TASTE BUDS – ORGANS OF TASTE
    – PAPILLAE – RAISED PORTIONS
    – TASTE CELLS AND SUPPORTING CELLS
          TASTE PORE, TASTE HAIRS
    – 4 TYPES CONCENTRATED ON DIFFERENT AREAS OF THE
      TONGUE
   TASTE SENSATIONS
    – SWEET – CARBOHYDRATES; HIGH ENERGY
          TIP OF TONGUE
    – SOUR – ACIDS, H+ IONS
          ALONG MARGINS
    – BITTER – BASES; POISONS
          BACK OF TONGUE
    – SALTY – ELECTROLYTES; + IONS FROM INORGANIC
      SALTS
          UPPER FRONT PORTION
                 SENSE OF SIGHT
   Structure of the Eye:
    – Accessory Structures
        Eyelids,eye lashes, eyebrows
        Conjuctiva
        Lacrimal apparatus
          – Tears – lubrication & lysozyme (antibacterial)
          – Connected to nasal cavity
        Extrinsic   Eye Muscles (6 on each eye)
          – Superior rectus, inferior rectus, medial rectus, lateral
            rectus, superior oblique, inferior oblique
          – Strabismus – lazy eye
    – Fibrous Tunic – outer layer
        Cornea     – transparent
          – No blood vessels, highly innervated (pain)
        Sclera   – white portion
          – Opaque
        Optic   Nerve
           SENSE OF SIGHT
– Vascular Tunic – Middle layer
   Choroid    Coat – heavily pigmented, lots of
   vessels
     – Keeps eye dark
   Ciliary   Body – muscle ring around front of
   eye
     – Suspensory ligaments – connect to lens
     – Accomodation – change thickness
          Relaxed – far vision; lens thin
          Contract – near vision; lens thick
     – Lens – refracts light to focus
          cataracts

   Iris   – colored portion of eye
     – Opaque
     – Pupil – hole in center of iris
         Regulates light
             SENSE OF SIGHT
      Aqueous humor – anterior cavity
        – Watery fluid
        – Nutrients and shape of eye
        – Glaucoma
      Eyesight problems
        – Myopia – near sighted
             Eye too long
             Concave corrective lens
        – Hyperopia – near sighted
             Eye too short
             Convex corrective lens
        – Astigmatism – bowl shaped curve on lens
– Nervous Tunic – innermost layer
      Retina – photoreceptors, bipolar neurons and ganglion cells
        – Macula lutea, fovea centralis  sharpest vision
        – Optic Disk – ganglion cells leave to optic nerve
             Blind spot

      Vitreous humor – posterior cavity
        – Jelly-like fluid
        – Maintain shape of eye
                   Photoreceptors
   Rods – sensitive to                Cones – sensitive to
    light                               color
    – General outlines,                 –   Sharp images
      colorless                         –   Need brighter light
    – Dim light                         –   Short and blunt
    – Long and thin                     –   Fovea centralis
    – Peripheral part of eye            –   Pigments stimulated by
    – Pigment absorbs light                 different wavelengths of
          Stores Vit. A                    light
          Rhodopsin – visual                   Red
           purple                               Green
            –  opsin and retinal               Blue
              with light
                                                Combination and
            – Darkness converts
              back                               intensities give spectra
            – Light adaptation                     – All = white
                                                   – None = black
                     Visual Pathway
   Stereoscopic Vision – binocular
    – Two separate, slightly different images from each eye
    – Relative sizes also help
   Nerve Pathways
    – Optic nerve  optic Chiasma
           Medial fibers cross to contralateral sides of brain
           Lateral fibers stay travel to ipsilateral sides of brain
    – Thalamus, optic reflex centers
    – Visual cortex in occipital lobe – visual perception




    .
           SENSE OF HEARING
   Structure of the Ear
    – External Ear
        Auricle(pinna) – external funnel
        External auditory meatus – ear canal
          – Ceruminous glands  ear wax
               Waterproof, insect repellent  protection
        Tympanic    membrane (ear drum)
          –   Air-tight membrane
          –   Boundary to middle ear
          –   Vibrations from sound waves
          –   Connected to ear bones in middle ear
    – Middle Ear
        Tympanic    cavity – air filled space
          – Equal air pressure with outside
          – Auditory (eustacian) tube – connected to oral cavity
               Yawn, chew gum
               infections
      SENSE OF HEARING
   Auditry   ossicles – ear bones
     –   Malleus (hammer) – connected to ear drum
     –   Incus (anvil) – middle bone
     –   Stapes (stirrup) – transmits to oval window
     –   Vibrations transmitted and amplified to inner ear
     –   Tympanic Reflex – loud noises
            2 muscles (tensor tympani, stapedius)
            Contract to limit vibrations

   Oval   window – membrane “piston” of inner ear
– Inner Ear
   Labrynth   – interconnected chambers
     – Osseous – temporal bone
     – Membranous – within osseous labrynth
   Semicircular canals (equilibrium);      vestibule and
    cochlea - hearing
              SENSE OF HEARING
          Cochlea – snail shell; organs for hearing receptors
            – Filled w/ perilymph from oval window to apex to round
              window
            – 3 compartments: scala vestibule, cochlear duct, scala
              tympani
            – Organ of corti – hearing receptor cells (hair cells)
                  Upper surface of basilar membrane (bottom of cochlear
                   duct0
                  Tectorial membrane – connects tips of hair cells
                  React differently to different frequencies and intensities
            – Decibels – units of loudness
                  0 – lowest for human ear
                  Logarithmic – each 10 is 10X’s as intense
                  90 can cause damage

   Nerve Pathways
    – Hair cells (mechanoreceptors)  cochlear branch of
      vestibulocochlear nerve
    – Medulla oblongata  midbrain  thalamus
    – Auditory cortices of temporal lobe
          Some fibers cross over
      SENSE OF EQUILIBRIUM
   Equilibrium – balance
    – Static – body position
    – Dynamic – movement
   Static Equilibrium
    – Organis in vestibule
    – Small patches of hair cells
           Macula – supporting cells
    – Utricle – verticle
    – Saccule – horizontal
           Otolithic membranes moves when head changes position
              – Calcium carbonate crystals  weight
   Dynamic Equilibrium
    – 3 semicircular canals – right angles for 3-D
    – Ampulla – enlarged ends of canals
    – Crista ampullaris – balance organs
   Other nerve receptors help
    – Eyes
    – Joints in neck, head and back

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:10
posted:8/21/2011
language:English
pages:20