Explain coronary artery blockage and muscle supply
Link a narrowed coronary lumen to reduced oxygen delivery to the heart wall.
Section B9.2 · Heart
Exam scope and assessment notes
Mapped to the named 0973 section using teaching from the corresponding single-science course. A 0973-specific review of every Core and Supplement objective is still in progress. Written practice is self-checked; it does not demonstrate supervised laboratory competence or award an official Cambridge grade. This qualification reports two grades on the 9–1 scale; confirm the entry route for your zone and exam series.
Before you begin
- Recall coronary arteries and cellular respiration.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What is a coronary artery lumen?
What you will learn
- Plaque narrows the supply route
- Follow supply, respiration and contraction
Plaque narrows the supply route
Coronary heart disease can involve fatty deposits building up in coronary artery walls, narrowing their lumen and reducing blood flow to heart muscle. A clot can cause a further blockage. The lumen is the space through which blood flows; the deposit is in the artery wall, not a lump of food inside a heart chamber.
Less flow can reduce oxygen and nutrient delivery to the muscle. The cells need oxygen for aerobic respiration, which provides energy for contraction. A severe interruption can damage heart muscle. Do not confuse coronary artery narrowing with a blocked airway or a faulty one-way valve.
Follow supply, respiration and contraction
A linked explanation is artery narrowing → reduced muscle blood supply → reduced oxygen for aerobic respiration → less energy available for contraction. That chain explains why a problem in a supply vessel can affect pumping, even when blood is still present inside the chambers.
The diagram contrasts an open lumen with a narrowed one as a simplified teaching model. It gives no clinical percentage stenosis, flow measurement or diagnosis. You cannot infer a person’s coronary condition from a school pulse count or from the normal pig-heart surface image.
Sources for this lesson
Pause and explain
Which chain explains the effect of narrowing?
Worked example
Explain why reduced coronary blood flow can affect pumping.
Show the worked solution
- Less blood reaches muscle, reducing oxygen delivery.
- Less aerobic respiration can mean less energy for contraction.
Answer Reduced coronary supply can limit oxygen for muscle respiration and energy for contraction.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
State what narrows and what tissue loses supply in coronary heart disease.
Give me a hint
Name the artery lumen and its destination.
Compare my reasoning
- Deposits narrow the coronary artery lumen.
- Heart muscle receives less blood.
Coronary artery lumen narrows; blood supply to heart muscle is reduced.
Look for these in your work
- Correct vessel structure
- Correct tissue destination
Explain why chamber blood does not remove the need for an unobstructed coronary supply.
Give me a hint
Heart muscle cells need delivery through their supply vessels.
Compare my reasoning
- The chambers carry blood for the main circulation.
- Coronary vessels deliver oxygen and nutrients to the muscle itself.
Chamber contents do not replace coronary delivery to muscle cells, which need oxygen and nutrients for respiration and contraction.
Look for these in your work
- Distinguish chamber and tissue supply
- Link supply with muscle respiration
A learner infers coronary blockage from one elevated pulse count after exercise. Why is this not justified?
Give me a hint
A rate response is not an image or measurement of a coronary lumen.
Compare my reasoning
- Activity itself can raise heart rate.
- The observation does not establish narrowing or diagnose disease.
The count shows a rate response, not coronary lumen blockage; the claim needs appropriate clinical evidence beyond this exercise.
Look for these in your work
- Identify the alternative activity explanation
- Respect the evidence limit
Common mistakes
- Calling the coronary blockage a valve.
- Saying oxygen supplies energy without mentioning respiration.
What can you explain now?
Which chain explains the effect of narrowing?
Compare with the explanation
Less flow → less oxygen for muscle respiration → less energy for contraction
It links vessel supply to muscle function.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Explain the complete chain from a narrowed lumen to a possible pumping effect.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.