1. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology: Concepts and Connections, Fifth Edition – Campbell, Reece, Taylor, and Simon Lectures by Chris Romero Chapter 29 The Senses

2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings An Animal's Senses Guide Its Movement Animals use sensory information gathered by sensory receptors and processed in the brain to guide behavior – Salmon use their sense of smell to return to a particular stream to reproduce – Bears use their acute sense of smell to find streams where salmon run

5. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 29.1 Sensory inputs become sensations and perceptions in the brain Sensory receptor cells are tuned to internal and external conditions – Detect stimuli – Trigger action potentials that go to central nervous system Sensation: action potential received by brain Perception: brain's interpretation of the action potential integrated with other information

7. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings SENSORY RECEPTION 29.2 Sensory receptors convert stimulus energy to action potentials Sensory receptors are specialized cells or neurons that detect stimuli All stimuli represent forms of energy Sensory transduction converts stimulus energy into receptor potentials Receptor potentials trigger action potentials that enter CNS for processing

8. LE 29-2a-3 Tongue Taste pore Taste bud Sugar molecule Sensory receptor cells Sensory neuron Sugar molecule (stimulus) Membrane of sensory receptor cell Signal transduction pathway Ion channels Sensory receptor cell Ion Receptor potential Neuro- transmitter Sensory neuron Action potential No sugar Sugar present mV Action potentials

9. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Different sensory receptors respond to different stimuli – Synapse with interneurons in brain Brain distinguishes types of stimuli by patterns of interneuron stimulation Action potential frequency reflects stimulus intensity Repeated stimulus may lead to sensory adaptation, a decrease in sensitivity

10. LE 29-2b Sugar receptor Taste bud Brain “Sugar” interneuron “Salt” interneuron Sensory neurons Salt receptor No saltNo sugar Taste bud Increasing sweetnessIncreasing saltiness

11. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 29.3 Specialized sensory receptors detect five categories of stimuli Pain receptors detect dangerous stimuli Thermoreceptors detect heat or cold and monitor blood temperature deep in the body Various mechanoreceptors respond to mechanical energy such as touch, pressure, and sound – Stretch receptors monitor the position of body parts – Hair cells are cilia that detect movement in water; important in hearing and balance

12. LE 29-3a Heat Epidermis Dermis Light touch PainColdHair Light touch Nerve Hair movement Connective tissue Strong pressure

13. LE 29-3b “Hairs” of receptor cell Neurotransmitter at synapse Sensory neuron Action potentials More neurotransmitter Less neurotransmitter Action potentials Receptor cell at restFluid moving in one directionFluid moving in other direction

14. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chemoreceptors respond to chemicals in the external or internal environment Electromagnetic receptors detect energy occurring as electricity, magnetism, or light – Photoreceptors, including eyes, detect varying visible or ultraviolet light

15. LE 29-3d Eye Infrared receptor

16. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings VISION 29.4 Several types of eyes have evolved among invertebrates Eye cups – Sense light intensity and direction but do not form images Compound eyes – Brain forms a mosaic image of data from many tiny light-detecting omatidia Single-lens eye – Works on the principle of a camera

17. LE 29-4a Eye cups

20. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 29.5 Vertebrates have single-lens eyes The vertebrate eye evolved independently of the invertebrate single-lens eye and differs in many details Structure of the human eye – Sclera: tough, whitish outer surface – Cornea: transparent thinning of sclera – Choroid: pigmented layer that forms the iris

21. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Pupil: opening in center of the iris that lets light into interior of eye – Lens: focuses images on the retina – Retina: photoreceptor cells Transduce light energy Send action potentials to the brain through the optic nerve Concentrated in the fovea Blind spot cannot detect light

22. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Vitreous and aqueous humors make up bulk of the eye – Maintain shape – Fluid secreted by ciliary body supplies nutrients and oxygen and removes wastes Mucous membrane keeps outside of eye moist

23. LE 29-5 Choroid Retina Fovea (center of visual field) Optic nerve Artery and vein Blind spot Sclera Ciliary body Ligament Cornea Iris Pupil Aqueous humor Lens Vitreous humor

24. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 29.6 To focus, a lens changes position or shape The lens focuses light onto the retina by bending light rays Focusing can occur in two ways – Muscles move rigid lens back and forth – Lens changes shape Contraction of ciliary muscle produces accommodation (near vision) Relaxation of ciliary muscle produces distance vision

25. LE 29-6 Ciliary muscle contracted Ligaments slacken Light from a near object (diverging rays) Lens Choroid Retina Near vision (accommodation) Ciliary muscle relaxed Ligaments pull on lens Light from a distant object (parallel rays) Distance vision

26. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Animation: Near and Distance Vision Animation: Near and Distance Vision

27. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings CONNECTION 29.7 Artificial lenses or surgery can correct focusing problems Visual acuity: ability to distinguish fine detail Nearsightedness (myopia): inability to focus on far objects – Eyeballs are elongated; focal point is in front of retina Farsightedness (hyperopia): inability to focus on near objects – Eyeballs are too short; focal point is behind retina

28. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Astigmatism: blurred vision caused by misshapen lenses or corneas Compensating for deficient visual acuity – Corrective lenses bend light rays to compensate – Surgery can reshape the cornea, reducing bending of light rays

29. LE 29-7a Shape of normal eyeball Diverging corrective lens Focal point Lens Retina Focal point

30. LE 29-7b Shape of normal eyeball Focal point Converging corrective lens Focal point

31. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 29.8 Our photoreceptors are rods and cones Rods – Sensitive to dim light – Distinguish shades of gray, not color – Use light-absorbing pigment rhodopsin Cones – Stimulated by bright light – Distinguish color Blue, red, and green cones use three types of the pigment photopsin

32. LE 29-8a Cell body Synaptic knobs Membranous disks containing visual pigments Rod Cone

33. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Vision pathway – Light absorbed by pigment in rods and cones – Chemical changes trigger signal transduction pathway, resulting in receptor potential – Signals integrated in a layer of neurons on the surface – Signals combine and leave eye via the optic nerve

34. LE 29-8b Optic nerve fibers Retina Optic nerve Retina Neurons Photoreceptors Cone Rod

35. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings HEARING AND BALANCE 29.9 The ear converts air pressure waves to action potentials that are perceived as sound The human ear is composed of three regions – Outer ear Pinna and auditory canal collect and channel sounds Eardrum separating outer and middle ear vibrates when sound waves strike – Middle ear Hammer, anvil, and stirrup bones receive vibrations

36. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Vibrations pass through oval window in skull to inner ear Opens into Eustachian tube, which connects to pharynx and equalizes pressure – Inner ear Contains three fluid-filled canals, including cochlea Hair cells in organ of Corti are the ear's sensory receptors Hair cells are embedded in basilar membrane, contact tectorial membrane

37. LE 29-9a Inner ear Outer Ear Eardrum Middle ear Eustachian tube Auditory canal Pinna

38. LE 29-9b StirrupSkull bones Semicircular canals (function in balance) Auditory nerve, to brain Anvil Hammer Cochlea Eardrum Oval window (behind stirrup) Eustachian tube

39. LE 29-9c Middle canal Bone Auditory nerve Upper canal Lower canal Organ of Corti Cross section through cochlea Basilar membrane Hair cells To auditory nerve Tectorial membrane Sensory neurons

40. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Function of the ear in hearing – Vibrations are amplified as sound (pressure) waves are transferred through middle ear – Pressure waves produced by oval window vibration pass into cochlear canals – Vibrations of basilar membrane bend hair cells, developing a receptor potential – Action potentials travel from hair cells to brain via auditory nerve

41. LE 29-9d Outer EarMiddle EarInner Ear Pinna Auditory canal Ear- drum Hammer, anvil, stirrup Oval window Cochlear canals Upper and middle Lower Time Organ of Corti stimulated Amplification in middle ear Amplitude One vibration Pressure

42. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Volume and pitch – Volume depends on the amplitude of pressure waves Louder sounds generate higher amplitude waves and thus more action potentials – Pitch depends on the frequency of sound waves High-pitched sounds generate high- frequency waves Different pitches stimulate different regions of the organ of Corti

43. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 29.10 The inner ear houses our organs of balance Several organs in the inner ear detect body position and movement – Semicircular canals detect changes in head's rate of rotation or angular movement – Utricle and saccule detect position of head with respect to gravity – All operate by bending of hairs on hair cells

44. LE 29-10 Semicircular canals Utricle Saccule Nerve Cochlea Flow of fluid Cupula Hairs Hair cell Nerve fibers Cupula Flow of fluid Direction of body movement

45. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings CONNECTION 29.11 What causes motion sickness? Motion sickness may be caused by conflicting signals from the equilibrium receptors in the inner ear and from the eyes

46. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings TASTE AND SMELL 29.12 Taste and odor receptors detect chemicals present in solution or air Taste receptors located in taste buds on the tongue produce perceptions of sweet, sour, salty, bitter, and umami Olfactory (smell) sensory neurons line the nasal cavity – Odorous substances bind to receptor proteins on cilia – Receptor potentials send impulses directly to olfactory bulb of brain

47. LE 29-12 Brain Nasal cavity Action potentials Olfactory bulb Bone Epithelial cell Sensory neuron (chemo- receptor) Cilia Mucus

48. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings CONNECTION 29.13 Our sense of taste may change as we age Taste sensitivity declines with age Reduced sense of smell contributes to diminishing flavor perception

49. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 29.14 Review: The central nervous system couples stimulus with response Sensory receptors provide an animal's nervous system with vital data that enable the animal to survive