CIE IGCSE Biology

Revision Notes

9.3 Heart Disease & Exercise

Exercise & Heart Rate

  • Heart activity can be monitored by using an ECG, measuring pulse rate or listening to the sounds of valves closing using a stethoscope
  • Heart rate (and pulse rate) is measured in beats per minute (bpm)
  • To investigate the effects of exercise on heart rate, record the pulse rate at rest for a minute
  • Immediately after they do some exercise, record the pulse rate every minute until it returns to the resting rate
  • This experiment will show that during exercise the heart rate increases and may take several minutes to return to normal
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Why does Heart Rate Increase during Exercise?

  • So that sufficient blood is taken to the working muscles to provide them with enough nutrients and oxygen for increased respiration
  • An increase in heart rate also allows for waste products to be removed at a faster rate
  • Following exercise, the heart continues to beat faster for a while to ensure that all excess waste products are removed from muscle cells
  • It is also likely that muscle cells have been respiring anaerobically during exercise and so have built up an oxygen debt
  • This needs to be ‘repaid’ following exercise and so the heart continues to beat faster to ensure that extra oxygen is still being delivered to muscle cells
  • The extra oxygen is used to break down the lactic acid that has been built up in cells as a result of anaerobic respiration

Coronary Heart Disease

The coronary arteries, IGCSE & GCSE Biology revision notesThe coronary arteries

 

  • The heart is made of muscle cells that need their own supply of blood to deliver oxygen, glucose and other nutrients and remove carbon dioxide and other waste products
  • The blood is supplied by the coronary arteries
  • If a coronary artery becomes partially or completely blocked by fatty deposits called ‘plaques’ (mainly formed from cholesterol), the arteries are not as elastic as they should be and therefore cannot stretch to accommodate the blood which is being forced through them – leading to coronary heart disease
  • Partial blockage of the coronary arteries creates a restricted blood flow to the cardiac muscle cells and results in severe chest pains called angina
  • Complete blockage means cells in that area of the heart will not be able to respire and can no longer contract, leading to a heart attack

 

Buildup of plaque in the coronary arteries, IGCSE & GCSE Biology revision notesBuildup of plaque in the coronary arteries

 

Effect of narrowing of arteries, IGCSE & GCSE Biology revision notesEffect of narrowing of arteries

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Risk Factors for Coronary Heart Disease

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Prevention & Treatment

Reducing the risks of developing coronary heart disease

  • Quit smoking
  • Reduce animal fats in diet and eat more fruits and vegetables – this will reduce cholesterol levels in the blood and help with weight loss if overweight
  • Exercise regularly – again, this will help with weight loss, decrease blood pressure and cholesterol levels and help reduce stress

Treatment of coronary heart disease

  • Aspirin can be taken daily to reduce the risk of blood clots forming in arteries
  • Surgical treatments include:
  1. Angioplasty
    • A narrow catheter (tube) is threaded through the groin up to the blocked vessel
    • A tiny balloon inserted into the catheter is pushed up to the blocked vessel and then inflated
    • This flattens the plaque against the wall of the artery, clearing the blockage
    • To keep the artery clear, a stent (piece of metal / plastic mesh) is also inserted which pushes against the wall of the artery
    • Sometimes the stent is coated with a drug that slowly releases medication to prevent further build-up of plaque

Inserting a stent into a blocked artery, IGCSE & GCSE Biology revision notesInserting a stent into a blocked artery

2) Coronary bypass surgery

    • A piece of blood vessel is taken from the patient’s leg, arm, or chest and used to create a new passage for the flow of blood to the cardiac muscle, bypassing the blocked area
    • The number of bypass grafts gives rise to the name of the surgery, so a ‘triple heart bypass’ would mean three new bypass grafts being attached

Coronary bypass graft, IGCSE & GCSE Biology revision notesCoronary bypass graft

Author: Jenna

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.
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