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www.GOALias.blogspot.comto the lungs and back to the heart fromwhere it is pumped to the rest of thebody.HeartbeatThe walls of the chambers of the heartare made up of muscles. These musclescontract and relax rhythmically. Thisrhythmic contraction followed by itsrelaxation constitute a heartbeat.Remember that heartbeats continueevery moment of our life. If you placeyour hand on the left side of your chest,you can feel your heartbeat. The doctorfeels your heartbeats with the help ofan instrument called a stethoscope.A doctor uses the stethoscope as adevice to amplify the sound of the heart.It consists of a chest piece that carries asensitive diaphragm, two ear pieces anda tube joining the parts. Doctors canget clues about the condition of yourheart by listening through astethoscope.Let us construct a model of astethoscope with the materials that areavailable around us.Activity 11.2Take a small funnel of 6–7 cm indiameter. Fix a rubber tube (50 cm long)tightly on the stem of the funnel. Stretcha rubber sheet (or a balloon) on themouth of the funnel and fix it tightlywith a rubber band. Put the open endof the tube on one of your ears. Place(a) Stethoscope(b) Model ofstethoscopeFig. 11.5 Instrument to hear heartbeatTable 11.2 Heartbeat and pulse rateName of studentWhile resting After running (4 – 5 minutes)HeartbeatPulse rateHeartbeatPulse rate125TRANSPORTATIONIN ANIMALSAND PLANTS125