Senses and sensory organs

Transcription

1 Senses and sensory organs

2 An Animal's Senses Guide Its Movements The brown bear is able to capture a fast and agile salmon Sensory structures of both the bear and salmon gather the information that guides the behaviors involved in this encounter

3 Nostrils on each side of the head of the salmon allow water to flow into one and out the other Sensory cells in the nostrils detect specific chemicals in the water These cells aid the salmon in its homing ability

4 Salmon have a lateral line system, seen here as a blue line along the sides of the fish This enables the salmon to sense the direction and velocity of water currents and thus distinguish which direction is upstream Unfortunately for the salmon, it cannot perceive a bear's paw descending from above

5 29.1 Sensory inputs become sensations Sensation Awareness of sensory stimuli (action potentials reaching the brain) Perception Brain s full integration of sensory data and perceptions in the brain Figure 29.1

6 29.2 Sensory receptor cells convert stimuli into electrical energy Sensory transduction A sensory cell converts a stimulus into an electrical signal called a receptor potential Occurs as a change in the membrane potential of a receptor cell

7 Tongue Taste pore Sugar molecule Sugar molecule Ion channels Ion Taste bud Sensory receptor cells Receptor cell membrane 2 Sugar binding 3 Receptor potential 1 Taste bud anatomy Sensory neuron Sensory receptor cell Neurotransmitter molecules Sensory neuron Action potential 4 Synapse mv No sugar Sugar present 5 Action potentials Figure 29.2A

8 Action potentials representing the stimuli are transmitted to the CNS via sensory neurons The brain distinguishes different types of stimuli These synapse with different interneurons in the brain

9 The strength of a stimulus alters the rate of action potential transmission This communicates information about the intensity of a sensation In sensory adaptation, sensory neurons become less sensitive when stimulated repeatedly

10 Sugar receptor Interneurons Salt receptor BRAIN Sensory neurons TASTE BUD No sugar No salt Increasing sweetness Increasing saltiness Figure 29.2B

11 29.3 Specialized sensory receptors detect five categories of stimuli Pain receptors Sense dangerous stimuli Thermoreceptors Detect heat or cold Mechanoreceptors Respond to mechanical energy (touch, pressure, and sound)

12 Heat Light touch Pain Cold (Hair) Light touch Epidermis Dermis Nerve Touch Strong pressure Figure 29.3A

13 Stretch receptors and hair cells are two types of mechanoreceptors Hairs of receptor cell Neurotransmitter at synapse More neurotransmitter Less neurotransmitter Sensory neuron Action potentials (1) Receptor cell at rest (2) Fluid moving in one direction (3) Fluid moving in other direction Figure 29.3B

14 Chemoreceptors Respond to chemicals in the body fluids or external environment A male silkworm moth has chemoreceptors on his antennae that can detect the sex attractant produced by the female silkworm moth Figure 29.3C

15 Electromagnetic receptors Respond to electricity, magnetism, and light Photoreceptors sense light They are the most common electromagnetic receptors Eye Infrared receptor Figure 29.3D

16 29.4 Three different types of eyes have evolved among Eye cup Simplest type of photoreceptor Senses intensity and direction of light Found in flatworms invertebrates Light Light Figure 29.4A

17 Compound eye Contains thousands of ommatidia working together to produce a visual image Acute motion detector Provides excellent color vision Found in crabs, crayfish, and nearly all insects Figure 29.4B

18 Single-lens eye Works on a principle similar to that of a camera Found in vertebrates and some invertebrates, such as squids Figure 29.4C

19 29.5 Vertebrates have single-lens eyes Sclera Muscle Ligament Cornea Iris Pupil Aqueous humor Choroid Retina Fovea (center of visual field) Optic nerve Lens Vitreous humor Artery and vein Blind spot Figure 29.5

20 Eye parts Sclera outer surface Cornea- transparent sclera (focusing) Choroid pigmented layer Iris eye color, muscular Pupil opening in iris Lens disk /ligaments Fovea center of focus on retina Blind spot spot where optic nerve passes Vitreous humor- large jelly filled chamber Aqueous humor smaller fluid filled chamber

21 Human eye Cornea and lens focus light on photoreceptor cells in the retina Photoreceptors are most concentrated in the fovea Having two eyes with overlapping fields of view compensates for the blind spot The blind spot is where the optic nerve passes through the retina

22 29.6 To focus, a lens changes position or shape Focusing can occur in two ways Moving the lens closer to or farther away from an object is one focusing method It is similar to focusing with a magnifying glass This occurs in squid and some fishes

23 Accommodation, or changing the shape of the lens, occurs in the mammalian eye Thick and round for near vision Thin and flat for distance vision Muscle contracted Ligaments Choroid Retina Muscle relaxed Light from a near object NEAR VISION (ACCOMMODATION) Lens Light from a distant object DISTANCE VISION Figure 29.6

24 29.7 Connection: Artificial lenses or surgery can correct focusing problems Corrective lenses bend light rays to compensate for focusing problems There are three common vision problems Astigmatism is a condition involving a distortion of the lens or cornea

25 In nearsightedness (myopia), the focal point is located in front of the retina Shape of normal eyeball Corrective lens Lens Focal point Focal point Retina Figure 29.7A

26 In farsightedness (hyperopia), the focal point is located behind the retina Shape of normal eyeball Corrective lens Focal point Focal point Figure 29.7B

27 29.8 Our photoreceptor cells are rods and cones Human photoreceptor cells are named for their shapes Rods Cones Cell body ROD CONE Synaptic knobs Membranous discs containing visual pigments Figure 29.8A

28 Rods Function in dim light Contain a visual pigment called rhodopsin There are 125 million in the human retina

29 Cones Stimulated by bright light Enable color vision Do not function in night vision There are 6 million in the human retina Cones contain visual pigments called photopsins There are three types of cones blue, green, and red named for the color absorbed by their photopsin

30 Retina Photoreceptors Neurons Cone Rod Optic nerve fibers Retina Fovea Optic nerve Figure 29.8B

31 29.9 The ear converts air pressure waves into action potentials that The basic function of the ear is hearing The outer ear channels sound waves to the eardrum are perceived as sound Pinna OUTER EAR Auditory canal MIDDLE EAR Eustachian tube INNER EAR Figure 29.9A

32 The eardrum passes vibrations to the chain of bones in the middle ear Stirrup Anvil Hammer Skull bones Semicircular canals (function in balance) Auditory nerve, to brain Cochlea Eardrum Oval window (behind stirrup) Eustachian tube Figure 29.9B

33 The bones transmit vibrations to fluid in the cochlea, which houses the organ of Corti Vibrations in cochlear fluid move hair cells (mechanoreceptors) against the overlying membrane Bending hair cells trigger nerve signals to the brain via the auditory nerve

34 Middle canal Upper canal Bone Auditory nerve Hair cells Overlying membrane Lower canal Sensory neurons Cross section through cochlea ORGAN OF CORTI Basilar membrane To auditory nerve Figure 29.9C

35 Louder sounds generate higher amplitude pressure waves These waves result in the vigorous vibration of cochlear fluids There is then a more pronounced bending of hair cells Thus more action potentials are generated

36 OUTER EAR MIDDLE EAR INNER EAR Pinna Auditory canal Eardrum Hammer, anvil, stirrup Oval window Cochlear canal Upper and middle Lower Pressure Time One vibration Amplitude Amplification in middle ear Organ of Corti stimulated Figure 29.9D

37 Pitch depends on the frequency of sound waves High sounds generate high frequency sound waves Low sounds generate low frequency sound waves Sounds of different pitches stimulate hair cells in different parts of the organ of Corti

38 29.10 The inner ear houses our organs of balance Organs of balance are located in the inner ear Semicircular canals Utricle Saccule Detection of body position and movement are determined by stimulation of hair cells in the semicircular canals, utricle, and saccule

39 Equilibrium structures in the inner ear Semicircular canals Nerve Cochlea Utricle Saccule Flow of fluid Flow of fluid Cupula Hairs Hair cell Figure Cupula Nerve fibers Direction of body movement

40 29.11 Connection: What causes motion sickness? Motion sickness is a result of the brain receiving signals from equilibrium receptors in the inner ear that conflict with visual signals from the eyes

41 29.12 Odor and taste receptors detect categories of chemicals Smell and taste depend on chemoreceptors sending nerve signals to the brain Specific molecules binding to chemoreceptors determine signals

42 Olfactory (smell) receptors are sensory neurons that line the upper part of the nasal cavity BRAIN Action potentials Bone NASAL CAVITY Epithelial cell Chemoreceptor cell MUCUS Cilia Figure 29.12A

43 Taste receptors are sensory neurons located in the back of the throat and on the tongue (taste buds) There are several types of taste receptors Sweet, sour, salty, bitter, umami

44 Insects have taste receptors located in sensory hairs on their They feet can taste food by simply stepping on it Chemoreceptor cells To brain Sensory hair Pore at tip Figure 29.12B

45 Receptor potential is generated when specific chemical molecules bind with olfactory or taste receptors Receptor potential alters the rate of action potentials passing into the brain The various odors and tastes we perceive result from the integration of input from a combination of receptors

46 29.13 Review: The central nervous system couples stimulus with response Coupling of stimuli to response by the nervous system Receptor cells receive stimulus Sensory neurons send information to the CNS The CNS integrates information from receptor cells The CNS sends commands to effector cells via motor neurons Response is carried out

47 Sensory neurons CNS Stimuli Receptors Integration Motor neuron Response Effector Figure 29.13