Changes In Heart Rate


 
 
Concept Explanation
 

Changes In Heart Rate

The rate at which your heart beats changes according to the needs of your body. Stress or fear causes the body to produce a hormone called nonadrenalin. Hormone are chemicals that act as messengers int he body. Noradrenalin affects the heart in two ways, both of which increase blood flow. It increases the  :-

  • Rate at which  the heart beats
  • Strength of the contractions
  • Noradrenalin can stimulate the heart to pump up to five times as much blood per minute as normal.
  • Vigorous exercise increases the heart rate in two ways :-

  • As cellular respiration increases, so does the carbon dioxide (CO_2) level in the blood. This change is detected by receptors. Receptors are specialised cells that detect stimuli changes. In this case, receptors in the carotid artery and aorta detect the increased  CO_2 concentration and send messages to the brain. Nerves then stimulate the heart to beat faster. 
  • As muscular activity increases, more blood is pumped back to the right atrium. The atrium wall stretches to hold the extra blood. Stretch receptors in the wall of the atrium send nerve impulses to the brain, which stimulates the heart to beat faster.
  • When you stop exercising vigorously, receptors in the aorta and the carotid artery send messages to the brain to slow the heart beat.
  • Sample Questions
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    Question : 1

    Stress or fear causes the body to produce a hormone called _____________________

     

     

    Right Option : C
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    Explanation
    Question : 2

    Non adrenaline can stimulate the heart to pump upto _____________ times as much as blood per minute as normal.

    Right Option : B
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    Explanation
    Question : 3

    During vigorous exercise the signals from the receptors are send to which system of the body for action?

    Right Option : A
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    Explanation
     
     


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