The Sensory Organs

1. The Sensory Organs Chapter 23B

2. Sense Organs • All sense organs have receptors. • A receptor usually is sensitive to only one type of stimulus.

3. Senses of the Skin • Cutaneous sensations • feeling due to receptors in the skin • Examples • temperature, touch, pain, pressure

4. Sense of Taste • 10,000 taste buds in average adult • Most on papillae of the tongue • NOT neurons • Constantly replaced, but slows with age

5. Sense of Smell • Olfactory receptors • line the upper regions of the nasal cavities • don’t regenerate • easily fatigued • accommodation • Helps with taste

6. The Ear: Hearing and Balance

7. Outer Ear auricle auditory canal (ceruminous glands) tympanic membrane

8. Middle Ear • Ossicles • malleus (hammer) • incus (anvil) • stapes (stirrup) • Eustachian tube • equalizes air pressure

9. Inner Ear • Bony labyrinth enclosing a membranous labyrinth • oval window • cochlea • organ of Corti

10. Sense of Balance • Semicircular canals • Static equilibrium • sense of body position when still • achieved by sensory hair cells in the fluid-filled saccule and utricle

11. Sense of Balance • Semicircular canals • Dynamic equilibrium • response to changes while in motion • sensory hair cells embedded in a jelly-like substance in the semicircular canals

12. The Eye and Sight

13. Outer Layer • Sclera • white of the eye • maintains shape • Cornea • transparent, anterior portion of the sclera • allows light to enter

14. Middle Layer • Choroid • contains many blood vessels • iris • pupil

15. Innermost Layer • Retina • photoreceptors

16. Photoreceptors • Rods • night vision • scattered over the retina • Cones • detect color • concentrated at the fovea

17. Innermost Layer • Retina • photoreceptors • optic nerve • blind spot

18. The Lens • Biconvex, semisolid • Visual accommodation

19. Fluids of The Eye • Aqueous humor • Vitreous humor • Lacrimal gland • produces tears that contain lysozyme

20. Eye Disorders • Myopia • Hyperopia • Astigmatism