Heart Rate & Exercise (Edexcel IGCSE Biology)
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Heart Rate & Exercise
Control of the heart rate
A heart rate is measured by counting the number of times a heart beats in a minute (bpm)
Factors such as exercise or levels of adrenaline, will affect the rate of
The natural resting heart rate is controlled by a group of cells located in the right atrium called the pacemaker
The role of the pacemaker is to coordinate the contraction of the heart muscle and regulate the heart rate
Pacemaker cells send out electrical impulses which initiate a contraction in the cardiac muscle
Exercise and heart rate
The heart pumps blood to respiring cells to supply oxygen and glucose and remove respiratory waste
During exercise, muscle cells respire faster to increase energy supply
Respiration is aerobic during moderate exercise and anaerobic during intense exercise
Increased respiration raises the need for oxygen, glucose, and waste removal
The nervous system responds by:
Increasing heart rate to deliver oxygen and glucose more frequently
Increasing the volume of blood pumped to supply larger amounts of oxygen and glucose
At the end of a period of exercise, the heart rate may remain high for a period of time as oxygen is required in the muscles to break down the lactic acid from anaerobic respiration
Production of the hormone adrenaline also increases heart rate as part of a 'fight or flight' response
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