Cardiovascular System

The Heart

  • Size of an adult fist
  • 2 halves seperated by septum
  • 4 chambers
  • Left and right atrium at top
  • Left and right ventricle at bottom
  • 4 valves to stop blood flowing backwards
  • Bicusped valve - between left atrium and left ventricle
  • Tricusped valve - between right atrium and right ventricle
  • Aortic valve - leads from left ventricle to aorta
  • Pulmanory valve - leads from right ventricle to pulmonary artery
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Heart Measurements

Heart Rate

  • Average 60-80 beats per minute in a healthy adult
  • Mointored by feeling pulse

Stroke Volume

  • Amount of blood pumped by the heart in one contraction
  • Measured by the volume of blood in the ventricles before they contract

Blood Pressure

  • Force of blood on vessel walls
  • Systolic - Pressure in the atria when the left ventricle contracts and pushes blood into the aorta
  • Diastolic - Pressure in the arteries when the heart is resting

Cardiac Output

  • Calculated by heart rate x stroke volume
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Cardiac Cycle

1. Atria and ventricles relax (diastole) and fill with blood from the vena cava and pulmonary vein.

2. Atria contracts (systole), squeezing more blood into the ventricles.

3. Ventricles contract, squeezing blood into the pulmonary artery and aorta.

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  • Transmitted to the heart through nervous impulses which cause contraction of cardiac muscle
  • Sympathetic nervous system - speeds up heart rate (e.g. during excersise)
  • Parasympathetic nervous system - slows down heart rate (e.g. during sleep)
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Types of Circulation

Pulmonary Circulation

  • The right side of the heart pumps blood to the lungs.
  • Gas exchange takes place - oxygen diffuses into the blood and carbon dioxide diffuses out of the blood and into the air sacs for exhalation.

Systematic Circulation

  • The left side of the heart pumps blood to the body.
  • Cells take oxygen and nutrients.
  • Tissue wastes are passed to the blood for excretion.
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Blood Vessels: From the Heart


  • Walls are thick, muscular and elastic.
  • High blood pressure.


  • Branch off arteries.
  • Deliver blood to capillaries.
  • Walls are thick and elastic.
  • Medium blood pressure.


  • Supply cells and tissues with nutrients from the blood.
  • Walls 1 cell thick to allow oxygen and nutrients to pass through
  • Low blood pressure
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Blood Vessels: To the Heart


  • Returns deoxygenated blood.
  • Have valves to stop the backflow of blood.
  • Low blood pressure.
  • Walls are not elastic, thinner and less muscular.


  • Feed into veins
  • Walls thinner and less muscular.
  • Low blood pressure.
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Blood Structure

Red Blood Cells

  • No nucleus
  • Contain haemoglobin
  • Flat shape gives high surface area to volume ratio 
  • Carry oxygen

White Blood Cells

Fight infection by:

  • Engulfing pathogens
  • Releasing destructive enzymes
  • Producing antibodies


  • Cell fragments which help to clot the blood.
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Blood Function

1. Transport

  • Blood cells, gasses, nutrients, salts, waste products from cells, enzymes, antibodies, hormones and plasma proteins.

2. Regulation (Homeostasis)

3. Defense

4. Clotting

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Disorder 1: Stroke

  • A life-threatening condition.
  • Caused when the blood supply to the brain is interrupted.
  • Haemorrhagic stroke - when a blood vessel in the brain bursts.
  • Ischaemic stroke - when a blood clot blocks the blood supply to the brain.  This is the most common form of stroke.
  • A Transient Ischaemic Attack (TIA) can be caused when there is a temporary interuption of blood supply to the brain.  This can risk future strokes.
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Disorder 2: Coronary Heart Disease (CHD)

  • A life threatening condition.
  • Caused when arteries are narrowed by a gradual build up of fatty matter in vessel walls.  This forms a deposit called plaque.
  • Arteries become so narrow blood can't pass through.  This causes angia (severe chest pain).
  • Small pieces of plaque can break off and cause a complete blockage.
  • If this happens in the coronary arteries it can cause a heart attack.
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Disorder 3: Hypertension

  • Also known as high blood pressure.
  • When blood pressure is higher than 140/90 mm Hg for a long period of time causing the blood vessels to narrow.
  • This can increase the risk of stroke, heart attack, heart failure, kidney disease and coronary thrombosis.
  • There are often no other symptoms.
  • Blood pressure can be controlled through medication and lifestyle changes.
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Disorder 4: Anaemia

  • Caused by a lack of iron in the body.
  • Lack of iron could be due to a diet lacking in iron, or the digestive tract not absorbing enough iron.
  • This results in fewer red blood cells, affecting the amount of oxygen supplied to the tissues and organs.
  • People with anaemia may be tired, pale and short of breath.
  • If anaemia is left untreated, people may bcome more suseptible to illness and infection.
  • Extreme anaemia can result in heart and lung problems.
  • Medication is the most common form of treatment.  A diet rich in iron can also help.
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