1. Sense Organs

2. 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
Jacobsen’s organ - snakes

3. 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

4. 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

5. 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

6. Human Eye

7. 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

8. Eye Lens Aqueous humor Vitreous humor
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

9. Disorders of eye Presbyopia – old-sightedness Nearsighted (myopia)
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

10. 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

11. 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!!

12. Sense of Balance Semicircular canals – mechanoreceptors
Rotational equilibrium – head rotation
Gravitational equilibrium – straight line movement

13. 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