Sense Organs

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Sense Organs
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Chemoreceptors

• Taste and smell sensory receptors
• Most primitive sense, all animals have it
• Important in finding food, locating a mate and
  detecting chemicals
• Location varies by animal
• Jacobsens organ - snakes

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Taste

• 4 primary types of taste
• Sweet, sour, salty, bitter,
• umami? Cheeses, broth, seafood, Asian foods
• Microvilli of taste cell has receptor proteins
  for food molecules

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Smell

• 10 20 million olfactory cells!! (modified
  neurons)
• Declines with age
• Located on roof of nasal cavity
• Olfactory bulb (extension of brain) has direct
  connection with limbic system (emotions and
  memory)
• Smell and taste work together in cerebral cortex
• Sometime molecules from smell travel to mouth and
  you taste it

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Vision

• Photoreceptors sensitive to light
• Some animals have eye spots, some have image
  forming eyes
• Insects have color vision, shorter spectrum but
  includes ultraviolet light
• Some fish, all reptiles, most birds
• monkeys, apes and humans only mammals
• Stereoscopic vision (binocular in front)
• Panoramic vision eyes on side, prey

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Human Eye
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Human eye

• 3 layers
• Sclera clear outer layer
• Cornea refracts light rays
• Conjunctive moistens
• Pupil light enters
• Choroid middle, includes blood vessels
• iris color of eye, regulates light entrance
• Ciliary muscle holds lens in place
• Retina inner layer, metallic
• Rods sensitive to light, black and white, night
  vision
• Cones color vision
• Fovea centralis acute vision

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Eye

• Lens
• Refracts and focuses light, can be replaced
• Aqueous humor
• Water solution, anterior of eye, behind lens
• Glaucoma pressure builds up
• Vitreous humor
• Gel material in posterior of eye
• Stabilizes the shape of eye, support retina
• Optic nerve sends info to brain
• Blind spot optic nerve exits the retina, no
  rods or cones

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Disorders of eye

• Presbyopia old-sightedness
• lens loses its ability to accommodate near
  objects
• Nearsighted (myopia)
• Elongated eyeball, image in focus in front of
  retina
• Farsighted (hyperopia)
• Shortened eyeball, image focused behind the
  retina
• Astigmatism
• Cornea or lens is uneven, image is fuzzy
• Cataract aging, exposure to sun, lens is milky
  and cannot transmit light rays

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Hearing and balance The Ear

• Mechanoreceptors
• sensitive to pressure, sound waves and gravity
• Outer ear pinna flap, auditory canal
• Middle ear tympanic membrane (ear drum)
• Ossicles stapes (stirrup), incus (anvil),
  malleus (hammer)
• Eustachian tube equalization of pressure
• Inner ear contains fluid
• Semicircular canals, vestibule equilibrium
• Cochlea - hearing

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Sound

• Auditory canal? tympanic membrane? malleus?
  incus? stapes? oval window ? endolymph in cochlea
  ? hair cells of cochlea ? synapse with nerve
  fibers of auditory nerve ?basilar membrane organ
  of corti? nerve impulse travels to brain stem ?
  auditory area of cerebral cortex sound!!

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Sense of Balance

• Semicircular canals mechanoreceptors
• Rotational equilibrium head rotation
• Gravitational equilibrium straight line
  movement

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Sensory receptors in animals

• Lateral line fish
• Detects water currents and pressure waves
• Collection of hair cells with cilia
• Statocysts gravitational equilibrium
• Cnidarians, molluscs, crustaceans
• Give information only about the head