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Heart rate, heart disease and circulation
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The heart pumps blood around a double circulation. Its rate changes with exercise and adrenaline, and some factors raise the risk of heart disease.
Changing heart rate
Adrenaline, released by the adrenal glands when frightened or stressed, also increases heart rate, preparing the body for action.
Coronary heart disease
Fatty deposits containing cholesterol can build up in their walls, narrowing them. Less oxygen reaches the heart muscle, which can cause a heart attack.
Risk factors: smoking, a diet high in saturated fat, lack of exercise, obesity, high blood pressure, stress, inherited factors and age.
The circulation system
Explain why heart rate increases during exercise.
- Muscles respire faster, so they need more oxygen and glucose.
- They also produce more carbon dioxide.
- A faster heart rate delivers more blood to supply oxygen and glucose and remove carbon dioxide.
Answer: To supply more oxygen and glucose to respiring muscles and remove the extra carbon dioxide.
Exercise and adrenaline raise heart rate to deliver more oxygen and glucose and remove carbon dioxide. Fatty deposits narrowing the coronary arteries cause coronary heart disease; risk factors include smoking, saturated fat, inactivity, obesity and high blood pressure. Renal vessels serve the kidneys; hepatic vessels serve the liver.
The interactive lesson includes the diagrams for this topic.
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