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.