Ce diaporama a bien été signalé.
Le téléchargement de votre SlideShare est en cours. ×

The senses

Chargement dans…3

Consultez-les par la suite

1 sur 31 Publicité

Plus De Contenu Connexe


Plus récents (20)


The senses

  1. 1. THE SENSES Biology 14
  2. 2. Sensory Reception  Sensory receptors - specialized neurons or other cells that are tuned to the conditions of the external world or internal organs. - It sweeps its wide head back and forth, like a beachcomber scanning the shore with a metal detector. - Electroreception, the ability to sense electric field. Hammerhead shark (Sphyrna mokarran)
  3. 3. Sensory receptors convert stimulus energy to action potentials  In stimulus detection, the receptor cell converts one type of signal (the stimulus) to another type, an electrical signal.  This conversion, called sensory transduction, produces a change in the cell’s membrane potential (the potential energy stored by the plasma membrane of the receptor cell.
  4. 4. • Changes in the flow of ions create a graded change in membrane potential called a receptor potential.
  5. 5. Sensory adaptation, the tendency of some sensory receptors to become less sensitive when they are stimulated repeatedly.
  6. 6. Five Categories of Stimuli 1. Pain Receptors respond to excess heat or pressure or to chemicals released from damaged or inflamed tissues. 2. Thermoreceptors detect either heat or cold.
  7. 7. 3. Mechanoreceptors are stimulated by various forms of mechanical energy, such as touch and pressure, stretching, motion, and sound. Five Categories of Stimuli • light touch- transduce very slight inputs of mechanical energy into action potentials. • pressure sensor- lying deeper in the skin, is stimulated by strong pressure. • touch receptor around the base of the hair, detects hair TYPES Another type of mechanoreceptor (not shown) is found in our skeletal muscles. Sensitive to changes in muscle length, stretch receptors monitor the position of body parts.
  8. 8. 4. Chemoreceptors include the sensory receptors in our nose and taste buds, which are attuned to chemicals in the external environment, as well as some receptors that detect chemicals in the body’s internal environment.  Internal chemoreceptors include sensors in some of our arteries that can detect Five Categories of Stimuli
  9. 9. 5. Electromagnetic Receptors detected as Energy occurring as electricity, magnetism, or various wavelengths of light.  Photoreceptors, including eyes, are probably the most common type of electromagnetic receptor. Photoreceptors detect the electromagnetic energy of light, Five Categories of Stimuli
  10. 10. For each of the following senses in humans, identify the type of receptor: seeing, tasting, hearing, smelling.  Photoreceptors  Chemoreceptors  Mechanoreceptors  Chemoreceptors
  11. 11. Hearing and Balance Basic principle: the stimulation of long projections on hair cells (mechanoreceptors) in fluid-filled canals. Three regions: 1. Outer ear 2. Middle ear 3. Inner ear
  12. 12. 1. outer ear consists of the flap-like pinna— the fleshy structure we commonly refer to as our “ear”—and the auditory canal. 2. The pinna and the auditory canal collect sound waves and channel them to the eardrum, a sheet of tissue that separates the outer ear from the middle ear.
  13. 13. When sound pressure waves strike the eardrum, the eardrum vibrates and passes the vibrations to three small bones:  the hammer (more formally, the malleus), anvil (incus), stirrup (stapes) The middle ear also opens into a passage called the Eustachian tube, which connects with the pharynx (back of the throat), allowing air pressure to stay equal on either
  14. 14.  The inner ear consists of fluid-filled channels in the bones of the skull. Sound vibrations or movements of the head set the fluid in motion. One of the channels, the cochlea (Latin for “snail”), is a long, coiled tube.• Our actual hearing organ, the organ of Corti, is located within the middle canal. • The organ of Corti consists of an array of hair cells embedded in a basilar membrane, the floor of the middle
  15. 15. Hearing Sound waves, which move as pressure waves in the air, are collected by the pinna and auditory canal of the outer ear.
  16. 16. Volume and Pitch  The brain senses a sound as an increase in the frequency of action potentials from the auditory nerve. How is the quality of the sound determined? “The higher the volume (loudness) of sound, the higher the amplitude (height) of the pressure wave it generates.”  The pitch of a sound depends on the frequency of the sound waves.
  17. 17. Deafness  Deafness can be caused by the inability of the ear to conduct sounds, resulting from middle-ear infections, a ruptured eardrum, or stiffening of the middle-ear bones (a common age-related problem).  Can also result from damage to sensory receptors or neurons.  In recent years, however, many deaf people have received cochlear implants, electronic devices that convert sounds to electrical impulses that stimulate the auditory nerve
  18. 18.  These fluid-filled structures lie next to the cochlea (Figure 29.5) and include three semicircular canals and two chambers, the utricle and the saccule.  The ear contains three semicircular canals that detect changes in the head’s rate of The inner ear houses our organs of balanc
  19. 19.  What causes motion sickness? Motion sickness is believed to be caused when the brain receives signals from equilibrium receptors in the inner ear that conflict with visual signals from the eyes. Symptoms maybe relieved by closing the eyes, limiting head movements, or focusing on a stable horizon.
  20. 20. Vision 2 types of image-forming eyes: 1. compound eye consists of up to several thousand light- etectors called ommatidia. 2. Single-lens eye evolved independently in vertebrates.
  21. 21.  The human eye has a small opening at the center of the eye, the pupil, through which light enters.  An adjustable doughnut shaped iris changes the diameter of the pupil to let in more or less light.  After going through the pupil, light passes through a single disklike lens.  The lens focuses light onto the retina, which consists of many photoreceptor cells. Photoreceptor cells are highly concentrated at the retina’s center of focus, called the fovea.
  22. 22.  The outer surface of the human eyeball is a tough, whitish layer of connective tissue called the sclera.  At the front of the eye, the sclera becomes the transparent cornea, which lets light into the eye and also helps focus light. The sclera surrounds a pigmented layer called the choroid. The anterior choroid forms the iris, which gives the eye its color.
  23. 23.  The lens and ciliary body divide the eye into two fluid-filled chambers.  The large chamber behind the lens is filled with jellylike vitreous humor.  The much smaller chamber in front of the lens contains the thinner aqueous humor. • A thin mucous membrane helps keep the outside of the eye moist. This membrane, called the conjunctiva
  24. 24. Arrange the following eye parts into the correct sequence encountered by photons of light traveling into the eye: pupil, retina, cornea, lens, vitreous humor, aqueous humor. Cornea aqueous humor pupil vitreous humor lens
  25. 25. Artificial lenses or surgery can correct focusing problems  Reading from an eye chart measures your visual acuity, the ability of your eyes to distinguish fine detail.  People with nearsightedness cannot focus well on distant objects, although they can see well at short distances (the condition is named for the type of vision that is unimpaired).
  26. 26.  Farsightedness (also known as hyperopia) is the opposite of nearsightedness. It occurs when the eyeball is shorter than normal, causing the lens to focus images behind the retina.
  27. 27. 2 types of photoreceptors: 1. Cones- are stimulated by bright light and can distinguish color, but they contribute little to night vision. • Cones contain visual pigments called photopsins, which absorb bright, colored
  28. 28. 2. Rods are extremely sensitive to light and enable us to see in dim light, though only in shades of gray.  Rods contain a visual pigment called rhodopsin, which can absorb dim light.
  29. 29. Taste and Smell Taste and odor receptors detect chemicals present in solution or air  Olfactory (smell) receptors are sensory neurons that line the upper portion of the nasal cavity and send impulses along their axons directly to the olfactory bulb of the brain
  30. 30.  Many animals rely heavily on their sense of smell for survival. Most other mammals have a much more discriminating sense of smell than humans.  Odors often provide more information than visual images about food, the presence of mates, or danger.four familiar taste perceptions: sweet, sour, salty, and bitter and fifth, UMAMI (Japanese for “delicious”)

Notes de l'éditeur

  • Sensory cells detect stimuli: chemical flavorings in your food; light emitted by your TV screen; tension in a muscle as you grasp a computer mouse; sound waves produced by your MP3 player; touch sensations as you hold someone’s hand; or other sensations such as electricity, cold, or heat.
  • Figure 29.2A on the facing page shows sensory transduction occurring when sensory receptor cells in a taste bud detect sugar molecules, as when you lick an ice cream cone.
  • In Figure 29.2B, the taste bud on the left has sensory receptors that respond to sugar, and the taste bud on the right responds to salt.
    The graphs in Figure 29.2B also indicate how action potentials communicate information about the intensity of stimuli. In each case, the left part of the graph represents the rate at which the sensory neurons in the taste bud transmit action potentials when the taste receptors are not stimulated. The right side of each graph shows that the rate of transmission depends on the intensity of the stimulus. The stronger the stimulus, the more neurotransmitter released by the receptor cell and the more frequently the sensory neuron transmits action potentials to the brain.
  • Specialized sensory receptors detect five categories of stimuli.
  • One of the most sensitive chemoreceptors in the animal kingdom is on the antennae of the male silkworm moth Bombyx mori (Figure 29.3C). The antennae are covered with thousands of sensory hairs (visible in the micrograph). The hairs have chemoreceptors that detect a sex pheromone released by the female.
  • The ear converts air pressure waves to action potentials that are perceived as sound. The human ear is really two separate organs, one for hearing and the other for maintaining balance.

  • (Figure 29.4B). Both the outer ear and middle ear are common sites of childhood infections
    (called swimmer’s ear and otitis media, respectively).
  • These pressure waves make your eardrum vibrate with the same frequency as the sound (Figure 29.4E). The frequency, measured in hertz (Hz), is the number of vibrations per second.
  • High-pitched sounds, such as high notes sung by a soprano, generate high-frequency waves. Low-pitched sounds, like the low notes made by a bass, generate low-frequency waves.
  • Several organs in the inner ear detect body position and movement.
  • Boating, flying, or even riding in a car can make us dizzy and nauseated, a condition called motion sickness.
    Because motion sickness can be a severe problem for astronauts, the National Aeronautics and Space Administration (NASA) conducts research on the problem. NASA has discovered that some people can learn to consciously control body functions, including the vomiting reflex. Astronauts receive intensive training in how to exert “mind over body” when zero gravity starts to induce motion sickness.
  • Most invertebrates have some kind of light-detecting organ.
    an important advantage for flying insects and other small animals often threatened by predators. also provide excellent color vision. Some species, such as honeybees, can see ultraviolet light (invisible to humans), which helps them locate certain nectar-bearing flowers.
    single-lens eye (squids)- (The single-lens eye found in squids and other invertebrates differs in some of the details.)
  • Humans have single-lens eyes that focus by changing position or shape
  • A gland above the eye secretes tears, a dilute salt solution that is spread across the eyeball by blinking and that drains into ducts that lead into the nasal cavities. This fluid cleanses and moistens the eye surface. Excess secretion in response to eye irritation or strong emotions causes tears to spill over the eyelid and fill the nasal cavities, producing sniffles. Some scientists speculate that emotional tears play a role in reducing stress.
  • If you can do this accurately, you have normal (20/20) acuity in each eye. This means that from a distance of 20 feet, each of your eyes can read the chart’s line of letters designated for 20 feet.
    Nearsighted– Nearsightedness A nearsighted eyeball is longer than normal (also known as myopia) is corrected by glasses or contact lenses that are thinner in the middle than at the outside edge. The lenses make the light rays from distant objects diverge as they enter the eye.
  • Farsighted people see distant objects normally but cannot focus on close objects.
  • The human retina contains two types of photoreceptors named for their shapes.
    The relative numbers of rods and cones an animal has correlates with whether an animal is most active during the day or night. Each human eye contains about 125 million rod cells and 6 million cone cells.
    (Rhodopsin is derived from vitamin A, which is why vitamin A deficiency can cause “night blindness.”)
  • Your senses of smell and taste depend on receptor cells that detect chemicals in the environment. Chemoreceptors in your taste buds detect molecules in solution; chemoreceptors in your nose detect airborne molecules.
  • Umami describes the savory flavor common in meats, cheeses, and other protein-rich foods, as well as the flavor-enhancing chemical monosodium glutamate (MSG).