1. End Show Slide 1 of 49 Copyright Pearson Prentice Hall Biology

2. End Show Slide 2 of 49 Copyright Pearson Prentice Hall 35–4 The Senses

3. End Show 35–4 The Senses Slide 3 of 49 Copyright Pearson Prentice Hall Sensory Receptors Neurons that react directly to stimuli from the environment are called sensory receptors. Sensory receptors react to stimuli by sending impulses to other neurons and to the central nervous system. Sensory receptors are located throughout the body but are concentrated in the sense organs.

4. End Show 35–4 The Senses Slide 4 of 49 Copyright Pearson Prentice Hall Sensory Receptors These sense organs include the: eyes ears nose mouth skin

5. End Show 35–4 The Senses Slide 5 of 49 Copyright Pearson Prentice Hall Sensory Receptors What are the five types of sensory receptors?

6. End Show 35–4 The Senses Slide 6 of 49 Copyright Pearson Prentice Hall Sensory Receptors There are five general categories of sensory receptors: pain receptors thermoreceptors mechanoreceptors chemoreceptors photoreceptors

7. End Show 35–4 The Senses Slide 7 of 49 Copyright Pearson Prentice Hall Sensory Receptors Pain receptors are located throughout the body except in the brain. They respond to chemicals released by damaged cells. Pain usually indicates danger, injury, or disease.

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9. End Show 35–4 The Senses Slide 9 of 49 Copyright Pearson Prentice Hall Thermoreceptors are located in the skin, body core, and hypothalamus. They detect variations in temperature. Sensory Receptors

10. End Show 35–4 The Senses Slide 10 of 49 Copyright Pearson Prentice Hall Sensory Receptors Mechanoreceptors are found in the skin, skeletal muscles, and inner ears. They are sensitive to touch, pressure, stretching of muscles, sound, and motion.

11. End Show 35–4 The Senses Slide 11 of 49 Copyright Pearson Prentice Hall Sensory Receptors Chemoreceptors, located in the nose and taste buds, are sensitive to chemicals in the external environment. Photoreceptors, found in the eyes, are sensitive to light.

12. End Show 35–4 The Senses Slide 12 of 49 Copyright Pearson Prentice Hall Vision The sense organ that animals use to sense light is the eye. The eye has three layers: the retina the choroid the sclera

13. End Show 35–4 The Senses Slide 13 of 49 Copyright Pearson Prentice Hall Vision The retina is the inner layer of eye that contains photoreceptors. Retina

14. End Show 35–4 The Senses Slide 14 of 49 Copyright Pearson Prentice Hall Vision The choroid is the middle layer of eye that is rich in blood vessels. Choroid

15. End Show 35–4 The Senses Slide 15 of 49 Copyright Pearson Prentice Hall Vision The sclera is the outer layer of eye that maintains its shape. The sclera serves as point of attachment for muscles that move the eye. Sclera

16. End Show 35–4 The Senses Slide 16 of 49 Copyright Pearson Prentice Hall Vision

17. End Show 35–4 The Senses Slide 17 of 49 Copyright Pearson Prentice Hall Vision Light enters the eye through the cornea, a tough transparent layer of cells. Cornea

18. End Show 35–4 The Senses Slide 18 of 49 Copyright Pearson Prentice Hall Vision The cornea helps focus light, which then passes through a chamber filled with a fluid called aqueous humor. Cornea Aqueous humor

19. End Show 35–4 The Senses Slide 19 of 49 Copyright Pearson Prentice Hall Vision At the back of the chamber is a disklike structure called the iris, which is the colored part of the eye. Iris

20. End Show 35–4 The Senses Slide 20 of 49 Copyright Pearson Prentice Hall Vision In the middle of the iris is a small opening called the pupil. Muscles in the iris adjust pupil size to regulate the amount of light that enters the eye. Pupil

21. End Show 35–4 The Senses Slide 21 of 49 Copyright Pearson Prentice Hall Vision In dim light, the pupil becomes larger. In bright light, the pupil becomes smaller.

22. End Show 35–4 The Senses Slide 22 of 49 Copyright Pearson Prentice Hall Vision Just behind the iris is the lens. Muscles attached to the lens change its shape to adjust focus to see near or distant objects. Lens

23. End Show 35–4 The Senses Slide 23 of 49 Copyright Pearson Prentice Hall Vision Behind the lens is a large chamber filled with a transparent, jellylike fluid called vitreous humor. Vitreous humor

24. End Show 35–4 The Senses Slide 24 of 49 Copyright Pearson Prentice Hall Vision The lens focuses light onto the retina. Photoreceptors are arranged in a layer in the retina. Retina

25. End Show 35–4 The Senses Slide 25 of 49 Copyright Pearson Prentice Hall Vision The photoreceptors convert light energy into nerve impulses that are carried to the central nervous system. There are two types of photoreceptors: rods and cones.

26. End Show 35–4 The Senses Slide 26 of 49 Copyright Pearson Prentice Hall Vision Rods are sensitive to light, but not color. Cones respond to light of different colors, producing color vision.

27. End Show 35–4 The Senses Slide 27 of 49 Copyright Pearson Prentice Hall Vision Cones are concentrated in the fovea, which is the site of sharpest vision. Fovea

28. End Show 35–4 The Senses Slide 28 of 49 Copyright Pearson Prentice Hall Vision There are no photoreceptors where the optic nerve passes through the back of the eye, which is called the blind spot.

29. End Show 35–4 The Senses Slide 29 of 49 Copyright Pearson Prentice Hall Optic nerve Vision The impulses leave each eye by way of the optic nerve. Optic nerves carry impulses to the brain. The brain interprets them as visual images and provides information about the external world.

30. End Show 35–4 The Senses Slide 30 of 49 Copyright Pearson Prentice Hall The Ear The human ear has two sensory functions: hearing balance

31. End Show 35–4 The Senses Slide 31 of 49 Copyright Pearson Prentice Hall The Ear Hearing Ears can distinguish both the pitch and loudness of those vibrations.

32. End Show 35–4 The Senses Slide 32 of 49 Copyright Pearson Prentice Hall The Ear The Human Ear

33. End Show 35–4 The Senses Slide 33 of 49 Copyright Pearson Prentice Hall The Ear Vibrations enter the ear through the auditory canal. Auditory canal

34. End Show 35–4 The Senses Slide 34 of 49 Copyright Pearson Prentice Hall The Ear The vibrations cause the tympanum, or eardrum, to vibrate. Tympanum

35. End Show 35–4 The Senses Slide 35 of 49 Copyright Pearson Prentice Hall The Ear The vibrations are picked up by the hammer, anvil, and stirrup. Hammer Anvil Stirrup

36. End Show 35–4 The Senses Slide 36 of 49 Copyright Pearson Prentice Hall The Ear The stirrup transmits the vibrations to the oval window. Oval window Stirrup

37. End Show 35–4 The Senses Slide 37 of 49 Copyright Pearson Prentice Hall The Ear Vibrations of the oval window create pressure waves in the fluid-filled cochlea of the inner ear. Cochlea

38. End Show 35–4 The Senses Slide 38 of 49 Copyright Pearson Prentice Hall The Ear The cochlea is lined with tiny hair cells that are pushed back and forth by these pressure waves. In response to the waves, the hair cells produce nerve impulses that are sent to the brain through the cochlear nerve.

39. End Show 35–4 The Senses Slide 39 of 49 Copyright Pearson Prentice Hall The Ear Balance Your ears help you to maintain your balance, or equilibrium.

40. End Show 35–4 The Senses Slide 40 of 49 Copyright Pearson Prentice Hall The Ear Within the inner ear, just above the cochlea are three semicircular canals. Semicircular canals

41. End Show 35–4 The Senses Slide 41 of 49 Copyright Pearson Prentice Hall The Ear The canals are filled with fluid and lined with hair cells. As the head changes position, fluid in the canals changes position, causing the hair on the hair cells to bend. This sends impulses to the brain that enable it to determine body motion and position.

42. End Show 35–4 The Senses Slide 42 of 49 Copyright Pearson Prentice Hall Smell The sense of smell is actually an ability to detect chemicals. Chemoreceptors in the nasal passageway respond to chemicals and send impulses to the brain through sensory nerves.

43. End Show 35–4 The Senses Slide 43 of 49 Copyright Pearson Prentice Hall Taste The sense of taste is also a chemical sense. The sense organs that detect taste are the taste buds. Most taste buds are on the tongue. Tastes detected by the taste buds are classified as salty, bitter, sweet, and sour. Sensitivity to these tastes varies on different parts of the tongue.

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45. End Show 35–4 The Senses Slide 45 of 49 Copyright Pearson Prentice Hall Touch and Related Senses The skin’s sensory receptors respond to temperature, touch, and pain. Not all parts of the body are equally sensitive to touch, because not all parts have the same number of receptors. The greatest density of sensory receptors is found on your fingers, toes, and face.

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47. End Show - or - Continue to: Click to Launch: Slide 47 of 49 Copyright Pearson Prentice Hall 35–4

48. End Show Slide 48 of 49 Copyright Pearson Prentice Hall 35–4 The sensory receptor that detects variations in body temperature is a a.chemoreceptor. b.mechanoreceptor. c.thermoreceptor. d.photoreceptor.

49. End Show Slide 49 of 49 Copyright Pearson Prentice Hall 35–4 The part of the eye containing tiny muscles that adjust the size of the pupil is the a.cornea. b.iris. c.lens. d.retina.

50. End Show Slide 50 of 49 Copyright Pearson Prentice Hall 35–4 The part of the ear that produces the nerve impulses sent to the brain is the a.tympanum. b.Eustachian tube. c.cochlea. d.oval window.

51. End Show Slide 51 of 49 Copyright Pearson Prentice Hall 35–4 The structures in your ears that help maintain your sense of balance a.is the auditory canal. b.is the hammer. c.is the tympanum. d.are the semicircular canals.

52. End Show Slide 52 of 49 Copyright Pearson Prentice Hall 35–4 Photoreceptors in the eye that are sensitive to color are a.rods. b.cones. c.rods and cones. d.the optic nerve.

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