A partly blocked coronary artery reduces blood flow to the heart muscle. This means less oxygen and glucose are delivered to the heart muscle cells. This leads to a lower rate of aerobic respiration, so less energy (ATP) is released. The heart muscle may have to respire anaerobically, which produces lactic acid and is less efficient. This can cause chest pain (angina). If the artery becomes completely blocked, the heart muscle cells will be deprived of oxygen and die, leading to a heart attack (myocardial infarction).
The coronary arteries are the blood vessels that supply the heart muscle itself with oxygen and glucose.
1. **Reduced Blood Flow:** A blockage (caused by a build-up of fatty material, called an atheroma) narrows the lumen of the artery, restricting blood flow to the cardiac (heart) muscle.
2. **Reduced Supply of Reactants:** This means the heart muscle cells receive less oxygen and glucose.
3. **Impact on Respiration:** Oxygen and glucose are the reactants for aerobic respiration. With a reduced supply, the rate of aerobic respiration in the heart muscle cells decreases.
4. **Energy Deficiency:** Since aerobic respiration is the process that releases energy (in the form of ATP), less energy is available for the heart muscle to contract.
5. **Consequences:** To compensate, the heart muscle may start to respire anaerobically. This is less efficient and produces lactic acid, which can cause chest pain (angina). If the artery becomes completely blocked by a blood clot forming on the atheroma, the cells are completely starved of oxygen and will die. This is a heart attack (myocardial infarction) and can be fatal.
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