BMS107 Chapter 19 Outline
Outlines | Home
STIMULI AND RECEPTORS
  1. general sense receptors - are housed in the skin, musculoskeletal organs, and viscera
  2. special senses: vision, hearing, equilibrium, olfaction, gustation
  3. receptors act as transducers that transform the energy in a stimulus into electrical (nerve) signals
VISION
  1. accessory structures
    1. conjunctiva (mucous membrane) - ocular conjunctiva, palpebral conjunctiva
    2. lacrimal apparatus
      1. lacrimal gland - produces lacrimal fluid
      2. nasolacrimal duct - receives fluid; fluid drains to nasal cavity
  2. fibrous tunic
    1. cornea - avascular, convex, refracts (bends) light rays
    2. sclera - dense irregular connective tissue, provides shape and protection (skleros = hard)
  3. vascular tunic ("uvea")
    1. choroid - cells are filled with melanin to absorb extraneous light
    2. ciliary body
      1. in anterior portion of vascular tunic
      2. ciliary muscle - four bands of smooth muscle organized into a ring
      3. ciliary processes - extensive folds of ciliary body
      4. aqueous humor - fluid produced by epithelium of ciliary body
      5. suspensory ligaments extend from ciliary processes and attach to lens capsule
        • lens is strong yet deformable
        • ciliary body and suspensory ligaments determine shape and position of lens
      6. for far vision
        • ciliary muscle relaxes
        • tension on suspensory ligaments increases
        • causes lens to flatten ("default" position)
      7. accommodation for near vision
        • ciliary muscle contracts
        • ciliary body moves anteriorly
        • reduces tension in suspensory ligaments
        • lens becomes more spherical and the degree of refraction increases
    3. iris
      1. continuous with ciliary body
      2. pupil - hole in center of iris
      3. iris contains pigment-forming cells and two groups of smooth muscle fibers
      4. sphincter pupillae muscle (pupillary constrictor) - arranged in concentric circles; innervated by parasympathetic division of ANS
      5. dilator pupillae muscle (pupillary dilator) - organized in radial pattern; controlled by sympathetic division of ANS
  4. neural tunic (retina)
    1. pigmented layer
    2. neural layer - contains photoreceptors
    3. ora serrata - jagged margin of retina
  5. organization of neural retina (know locations & sequence of layers)
    1. photoreceptor cells
      • rods - more than 100M per eye; function in dim light; relatively high degree of convergence with bipolar cells
      • cones (require high intensity light)
        • low degree of convergence with bipolar cells provides visual acuity
        • color vision - based on three types of cones with varying sensitivities ("blue cones," "green cones," "red cones")
      • macula lutea - "yellow spot"
      • fovea centralis - "central pit" - on visual axis; contains high proportion of cones (almost no rods)
    2. bipolar cells - form synapses with bipolar cells
    3. ganglion cells - axons from ganglionic cells extend through the optic disc and form optic nerve (no photoreceptors at optic disc)
VISUAL PATHWAY
  1. retina
  2. optic nerves
  3. optic chiasm - medial axons cross (Figs. 15.8, 17.11, 19.18)
  4. optic tracts
  5. in brain, optic tract axons extend to
    1. thalamus (lateral geniculate nucleus)
    2. midbrain (for coordination of eye, head, and neck movements)
  6. projection fibers (optic radiations) project from thalamus to occipital lobes
CAVITIES OF THE EYE
  1. anterior cavity
    1. posterior to cornea / anterior to lens
    2. chambers
      1. anterior chamber - between iris and cornea
      2. posterior chamber - between iris and lens
    3. contains aqueous humor
      • secreted into posterior chamber; flows through pupil into anterior chamber
      • maintains chemical environment & creates intraocular pressure
      • continually reabsorbed into scleral venous sinus then conducted to veins
  2. posterior cavity
    1. posterior to lens / anterior to retina
    2. occupied by transparent, gelatinous vitreous body (between lens and retina)
    3. vitreous body helps maintain eye shape and supports retina
EXTERNAL EAR
  1. auricle - directs sound waves into...
  2. external auditory canal, which terminates at...
  3. tympanic membrane ("eardrum")
    1. partition between external and middle ear
    2. medial surface is lined by a mucosa
    3. vibrates in response to sound waves

MIDDLE EAR
  1. contains air-filled tympanic cavity
  2. auditory tube (pharyngotympanic tube, Eustachian tube)
    • opens into nasopharynx from middle ear
    • air can move through tube for pressure equalization between tympanic cavity and atmosphere
  3. auditory ossicles
    • malleus - attached to medial surface of tympanic membrane
    • incus
    • stapes - footplate fits into oval window (lateral wall of inner ear)
    • ossicles vibrate along with tympanic membrane
    • movement of stapes initiates pressure waves in fluid within inner ear
    • tympanic membrane is approximately twenty times greater in diameter than the footplate of the stapes (concentrates force of vibrations)
    • stapedius & tensor tympani - skeletal muscles; restrict ossicle movement when loud noises occur (protect inner ear)

INNER EAR
  1. membranous labyrinth - fits within bony labyrinth (in petrous portion of temporal bone)
  2. perilymph - fluid between membranous labyrinth and wall of bony labyrinth
  3. endolymph - fluid within membranous labyrinth
  4. regions of bony labyrinth / membranous labyrinth
    1. vestibule (of bony lab.) - contains utricle and saccule (of memb. lab.)
    2. semicircular canals (of bony lab.) - contain semicircular ducts (of memb. lab.)
    3. cochlea (of bony lab.) - contains cochlear duct (of memb. lab.)
  5. vestibular complex = vestibule + semicircular canals
  6. hair cells
    1. receptors for both hearing and equilibrium
    2. stimulated by mechanical forces (stretch/compression/distortion)
  7. hearing
    1. cochlear duct - runs through cochlea
    2. basilar membrane - floor of cochlear duct
    3. spiral organ - consisting of hair cells and supporting cells
    4. hair cells extend stereocilia into tectorial membrane
    5. movement of basilar membrane distorts hair cells (leads to stimulation of sensory neurons in cochlear nerve)
    6. auditory pathway
      1. cochlear nerve axons terminate in cochlear nuclei in brainstem
      2. secondary neurons project to thalamus, midbrain, etc.
      3. some axons extend from thalamus to auditory cortex
  8. equilibrium
    1. receptors in utricle and saccule detect position/acceleration of head
      • tilt of head > otolithic membrane shifts > distortion of hair cells stimulates sensory neurons
    2. receptors in semicircular canals detect rotation of the head
      • rotation of head > endolymph moves / pushes against cupula > distortion of hair cells stimulates sensory neurons
    3. vestibular sensation pathways
      1. vestibular branch of CN VIII
      2. vestibular nerve axons project to vestibular nuclei in brainstem
      3. vestibular nuclei integrate signals and send impulses to cerebellum, thalamus, spinal cord, other brainstem nuclei, etc.
Chapter 19 Questions
    In Textbook, Second Edition
  • What Did You Learn? - 10, 11, 13, 14
  • What Do You Think? - 4
  • Matching - 1, 2, 3, 5, 6, 8
  • Multiple Choice - 4, 6
  • Content Review - 5, 6, 7, 8, 9
At Publisher's Web Site Simple Multiple Choice - 2, 3, 4, 5, 6, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 27, 28, 29, 30
Difficult Multiple Choice - 1, 10, 20, 21, 22
Challenge Yourself - 1, 2, 3, 4, 6, 8, 9, 10
Outlines | Home
Spring 2009