Reading Essentials for Biology Glencoe (794133), страница 102
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Read the terms and their definitions in the Mini Glossary on page 448. Use the space belowto write a brief paragraph explaining the functions of the cerebrum and the cerebellum.________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________2. Use the chart below to fill in the missing divisions of the nervous system.Nervous SystemPeripheral NervousSystem (PNS)Copyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Somatic NervousSystem (voluntary)Sympathetic Nervous SystemVisit the Glencoe Science Web site at science.glencoe.com to findyour biology book and learn more about the nervous system.READING ESSENTIALSChapter 36449NameDateClassSection36.2 The SensesSC.F.1.4.7 The student knows that organisms respond to internal and external stimuli.◗ Before You ReadBefore you sit down for a meal, you probably can guess what you are having by sniffing the air coming from the kitchen.
During the meal, you may have positive or negative reactions to the way certain foods taste. You might also touch your food or beverage to see if it is too hot or too cold. In thissection, you will learn about how the senses work. On the lines below, list the senses you know ofand the body parts most closely associated with each sense.____________________________________________________________________________________________________________________________________________________________________________________________________________________________________◗ Read to LearnIdentify MainIdeas As you read the section, highlight the main pointin each paragraph. Stateeach main point in your ownwords.1.
What is the name for thesensory receptors thatallow you to taste?________________________________________________________________________450Chapter 36How are you able to smell and taste an orange? As you sniffand eat the fruit, chemical molecules of the orange touch receptors in your nose and mouth. The receptors for smell are hairlikenerve endings located in the upper portion of your nose.Chemicals acting on these nerve endings initiate impulses in theolfactory nerve, which is connected to your brain.
The brain theninterprets this signal as a particular odor.The senses of taste and smell are closely linked. Think aboutwhat your sense of taste is like when your nose is all stuffed upand you are not able to smell much at all. Your sense of taste isaffected because much of what you taste depends on your senseof smell.You taste something when chemicals dissolved in saliva contactsensory receptors on your tongue called taste buds. Tastes canbe divided into four basic categories: sour, salty, bitter, and sweet.As seen with the sequence of electrochemical changes a neuronundergoes as it is depolarized, each of the different tastes produces a similar change in the cells of taste buds. As these cells aredepolarized, signals from your taste buds are sent to the cerebrum.
There the signal is interpreted and you become aware of aparticular taste.A young adult has approximately 10 000 taste buds. As a personages, the sense of smell becomes less sharp and the taste buds maydecrease in number or become less sensitive. A reduced sense oftaste can result.READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Sensing ChemicalsNameDateClassSection36.2The Senses, continuedSensing LightHow are you able to see? Your sense ofsight depends on receptors in your eyesthat respond to light energy. The retinaRetinais a thin layer of tissue made up of lightreceptors and sensory neurons.
It is foundat the back of the eye. Light enters theeye through the pupil and is focused bythe lens onto the back of the eye, where itstrikes the retina.The retina contains two types of lightreceptor cells—rods and cones. Rodsare receptor cells adapted for vision indim light. They help you detect shapeOptic nerveand movement. Cones are receptor cellsadapted for sharp vision in bright light.They also help you detect color.At the back of the eye, retinal tissue comes together to formthe optic nerve.
The optic nerve leads to the brain, where imagesare interpreted.LensLightPupil2. What forms the opticnerve?________________________Copyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Sensing Mechanical Stimulation________________________When you walk in a park, how are you able to hear the leavesrustle or feel the things you reach out to touch? Both of thesesenses, hearing and touch, depend on receptors that respond tomechanical stimulation.________________________How does your sense of hearing work?Every sound causes the airaround it to vibrate. Thesevibrations travel outward fromthe sources in sound waves.Sound waves enter your outerear and travel down to the endof the ear canal.
In the earcanal, they strike a membranecalled the eardrum and cause itto vibrate. The vibrations thenpass to three small bones inthe middle ear—the malleus,the incus, and the stapes. Asthe stapes vibrates, it causesREADING ESSENTIALSMalleusIncusStapesSemicircular canalsAuditorynerveEarcanalOvalwindowCochleaEardrumOuter earMiddle earInner earChapter 36451NameDateClassSection36.2The Senses, continued3.
Analyze Why woulddamage to the cochleaor auditory nerve resultin hearing loss?________________________________________________________________________the membrane of the oval window, a structure between the middleand inner ear, to move back and forth.From here, the vibrations continue to travel deeper into the ear.The movement from the oval window causes fluid in the cochlea,a snail-shaped structure in the inner ear, to move.
Inside the circular walls of the cochlea are structures that are lined with haircells. The fluid in the cochlea moves like a wave against thehair cells causing them to bend.The movement of the hairs produces electrical impulses, whichtravel along the auditory nerve to the sides of the cerebrum. Oncethey reach the cerebrum, they are interpreted as sound.
Hearingloss can occur if the auditory nerve or the hair cells in the cochleaare damaged.4. Where are receptorslocated that respondto pain, pressure, andtemperature?________________________________________________________________________HeatFree nerveendingLighttouchThe inner ear also converts information about the position ofyour head into nerve impulses, which travel to your brain, informing it about your body’s balance.Maintaining balance is the function of your semicircularcanals.
Like the cochlea, the semicircular canals are filled with athick fluid and lined with hair cells. When you tilt your head, thefluid moves, causing the hairs to bend. This movement stimulatesthe hair cells to produce impulses. Then neurons from the semicircular canals carry the impulses to the brain.
The brain sends animpulse to stimulate your neck muscles and readjust the positionof your head.HairshaftOpening ofsweat glandHeavypressureCold452Chapter 36How does your sense of touchwork?Like the ear, your skin also respondsto mechanical stimulation with receptorsthat convert the stimulus into a nerveimpulse. Receptors in the dermis of theskin respond to changes in temperature,pressure, and pain.
With the help of thesereceptors, your body can respond to itsexternal environment.Although receptors are found all overyour body, those responsible for respondingto particular stimuli are usually concentrated within certain areas of your body. Forexample, many receptors that respond tolight pressure are found in the dermis ofREADING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.How does your sense of balance work?NameDateClassSection36.2The Senses, continuedyour fingertips, eyelids, lips, the tip of your tongue, and the palmsof your hands. When these receptors are stimulated, you will feela light touch.Receptors that respond to heavier pressure are found insideyour joints, in muscle tissue, and in certain organs.
They alsoare abundant on the skin of your palms and fingers and on thesoles of your feet. When these receptors are stimulated, you feelheavy pressure.Free nerve endings extend into the lower layers of the epidermis. Free nerve endings act as receptors for itch, tickle, hot andcold, and pain sensations. Heat receptors are found deep in thedermis, while cold receptors are found closer to the surface ofyour skin. Pain receptors can be found in all tissues of the bodyexcept those in the brain.◗ After You ReadMini GlossaryCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.cochlea: snail-shaped structure in the innerear containing fluid and hairs; produceselectrical impulses that the brain interpretsas soundcones: receptor cells in the retina adaptedfor sharp vision in bright light and colordetectionretina: thin layer of tissue found at the back ofthe eye made up of light receptors and sensory neuronsrods: receptor cells in the retina that areadapted for vision in dim light; also helpdetect shape and movementsemicircular canals: structures in the inner earcontaining fluid and hairs that help thebody maintain balancetaste bud: sensory receptors located on thetongue that result in taste perception1.
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