Heart Beat And Pulse Rate

Transportation in animals and plants of Class 7

  • Heart beat is due to the rhythmic contraction and relaxation of heart muscles.
  • The average pumping rate of heart in an adult person under  rest is about 70 times a minute. This rate goes upto 150 times a minute when a person is doing muscular work, during exercise  or even during excitement.
  • The sequence of events, which take place during the completion of one heartbeat, is known as cardiac cycle. It involves repeated contraction and relaxation of the heart muscle. A contraction is termed systole and diastole.
  • One contraction (systole) and one relaxation  (diastole) of heart constitute one heart beat. It lasts for about 0.8 seconds.
  • First measured by British physiologist Stephan Hales (1733) in carotid artery of man.
  • The abnormal rise in B.P. (hypertension) occurs due to defect of any of the above three components with increasing age the rigidity of  arterial wall causes high B.P.
  • Hypotension (low B.P.) may be due to chronic vasodilation, anemia, blood loss and improper heart action.

 

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