B2: Cardiovascular System

• Structure of the heart:

  • Superior Vena Cava
  • Right Atrium
  • Tricuspid Valve
  • Right Ventricle
  • Pulmonary Valve
  • Pulmonary Artery
  • Pulmonary Vein
  • Left Atrium
  • Bicuspid Valve
  • Left Ventricle
  • Aortic Valve
  • Aorta
• Functions of the cardiovascular system:


  • Transport of oxygen and carbon dioxide, as well as nutrients, hormones, waste products e.g. urea.
  • Fighting infections.
  • Distribution of heat.
• Journey of red blood cell(RBC)


  1. Deoxygenated RBC enters the heart via superior vena cava into the right atrium.
  2. It passes through the tricuspid valve into the right ventricle.
  3. Then it goes through the pulmonary valve to the pulmonary artery to the lungs for gas exchange.
  4. RBC becomes oxygenated and enters via the pulmonary vein to the left atrium.
  5. Travels through bicuspid valve into left ventricle.
  6. Passes through the aortic valve to the aorta to go through the rest of the body.
  7. Cycle repeats.
• Cardiac muscle


  • Myogenic - self initiating heartbeat
  • The atrial muscle beats at a different pace from the ventricular muscle, so the contractions are organised and co-ordinated by a nerve, supply (Nervous system). This is known as the 'Cardiac Cycle'.
  • Has it's own blood supply from the coronary arteries and veins.
• Cardiac Cycle - one complete heartbeat


  • Controlled by the nerves
  • Atrial and Ventricular diastole - chambers are relaxed and filling with blood.
  • Atrial systole - Atria contracts and remaining blood is pushed into ventricles.
  • Ventricular systole - Ventricles contract and push blood out through aorta & pulmonary artery.
• Systole


  Heart muscle contracts, increases pressure.
• Diastole


  Heart muscle relaxes, decreases pressure.
• Regulation of heart rate

  • Medulla regulates rate of sinoatrial through autonomic nervous system
  • Sympathetic nervous system (fight or flight) - increases heart rate - when CO2 levels increase or blood pressure decreases, the nerve impulse from medulla is triggered. Adrenaline also speeds up HR.
  • Parasympathetic nervous system (rest & digest) - slows heart rate down - when CO2 levels decrease or blood pressure increases, brain receptors are activated, which release acetylcholine which decreases HR.
• Sinoatrial Node (SA Node)

  • Also known as a pacemaker.
  • Sends electrical impulses that cause the muscular walls of atria to contract ( Atrial Systole)
• HR


  1. SA Node
  2. Atrioventricular Node
  3. Bundle of His
  4. Purkinje fibres
• • Sinoatrial node fires impulse on regular basis.
  • Impulse travels through atrial muscles causing atria to contract.
  • Impulse stops at connection between atria and ventricles due to tough fibres.
  • Atrioventricular node picks up impulse and sends impulse down bundle of His.
  • Impulse travels down bundle of His towards bottom (apex) of heart.
  • Impulse travels along Purkinje fibres in ventricle walls causing ventricles to contract from bottom up.
• • Both atria contract - blood forced into ventricles.
  • Atrioventricular valves (tricuspid and bicuspid) shut.
  • Ventricles contract. Semilunar valves (aortic and pulmonary valves) open.
  • Contracting ventricles forces blood on right to enter pulmonary artery and on left to enter aorta.
  • Ventricles relax. Semilunar valves (aortic and pulmonary valves) close.
  • Atria relax. Blood fills atria.
• Cardiac Output


  Total volume of blood pumped by the heart per minute.

  Measured in ml per minute.
• Stroke Volume


  Volume of blood pumped one beat of the heart.

  Measured in ml.
• Heart Rate


  Number of times heart beats in one minute.

  Measured in beats per minuted (bpm).
• Arteries


  • Carry blood away from heart to organs.
  • Carry blood under high pressure.
  • Thick, muscular walls and a round lumen.
  • Contains blood with a high oxygen content and low CO2 and water content.
  • Large elastic arteries close to the heart help the intermittent flow from the ventricles become a continuous flow through circulation.
  • Largest artery is the aorta.
  • Pulmonary artery is the only deoxygenated artery.
• Veins


  • Carry blood to heart from organs.
  • Carry blood under low pressure.
  • Has thin, muscular walls & oval lumen.
  • Contain blood with low oxygen content and high CO2 and water content.
  • Apart from pulmonary veins and umbilical veins - which carry oxygenated.
  • Veins in limbs contain valves at regular intervals and sandwiched between muscle groups to help travel against gravity - prevents backflow.
• Capillaries


  • Connect arteries to veins.
  • Arterioles and capillaries cause the greatest drop in pressure due to overcoming the friction of blood passing through small vessels.
  • Single-cell walls..
  • Deliver protein-free plasma filtrate with a high oxygen content to cells and collect respiratory waster products (CO2 & water) - leaks out of the arterial end - tissue fluid - never far from body cells.
  • Walls are formed from a single layer of epithelium cells.
• Pulmonary Circulation


  • Right atrium - deoxygenated
  • Right ventricle - deoxygenated
  • Pulmonary artery - deoxygenated
  • Lungs - Gas exchange
  • Pulmonary vein - oxygenated
• Systemic Circulation


  • Left atrium - oxygenated
  • Left ventricle - oxygenated
  • Aorta - oxygenated
  • Body systems - gas exchange
  • Vena cava vein - deoxygenated
• Function of pulmonary circulation


  To take deoxygenated blood to the lungs to remove carbon dioxide and pick up oxygen.
• Function of systemic circulation


  To take oxygenated blood to all the tissues and organs of the body (apart from the lungs) to deliver oxygen and nutrients and pick up waste e.g. carbon dioxide.
• Structure and function of the plasma


  • Straw coloured
  • Mainly water in which various substances are carried, such as oxygen, CO2, glucose, amino acids, hormones.
• Structure and function of red blood cells


  • Also known as Erythrocytes
  • Small cells with elastic membrane
  • No nucleus - making it biconcave, providing a larger surface area to be exposed to oxygen.
  • Packed with haemoglobin (special iron-containing protein)
  • Arterial blood - oxygenated - oxyhaemoglobin.
  • Venous blood - deoxygenated - reduced haemoglobin.
• Structure and function of platelets


  • Also known as thrombocytes.
  • Much larger cells that have broken up.
  • Important role in blood clotting.
• Structure and functions of Neutrophils


  • Contains granules in cytoplasm.
  • Lobed nuclei.
  • Can change shape and engulf foreign material. - Phagocytes.
• Structure and function of monocytes


  • Larger than lymphocytes.
  • Large, round nuclei & clear cytoplasm.
  • Efficient at phagocytosis of foreign material.
  • Can leave circulatory blood vessels to travel to infection site.
• Structure and function of T lymphocytes


  Recognise abnormal cells and destroy them.
• Structure and function of B lymphocytes


  • Recognise specific proteins (antigens).
  • Produces specific antibodies against the antigens.
• Coronary Heart Disease (CHD)


  • Causes
  • Blockage of the coronary artery (artery that supplies the heart muscle).
  • Blockage known as atheroma made of fatty deposits.
  • Caused by genetics, diet high in fat, high cholesterol, smoking, lack of exercise.
  • Effects
  • Sometimes there are no symptoms.
  • Partial blockage leads to chest pain when active - known as angina.
  • Can cause heart attacks.
  • Treatment
  • Lifestyle changes such as low fat diet and exercising, stopping smoking.
  • Heart bypass operation.
  • Stents in artery to reduce impact of atheroma.
• Stroke

  • Causes
  • Haemorrhagic stroke -burst blood vessels in the brain leading to bleed into the brain which kills brain cells.
  • Ischaemic stroke - blockage of blood vessels in the brain causing death of brain cells.
  • Caused by high fat diet, smoking, high blood pressure.
  • Effects
  • Symptoms vary depending on area of brain affected. Can lead to:
  • One sided weakness or paralysis.
  • Difficulty with speech.
  • Mood changes.
  • Confusion.
  • Treatments
  • Blood thinning medication.
  • Physiotherapy to regain some lost function.
• Anaemia


  • Causes
  • Iron deficiency anaemia caused by lack of iron in diet leading to inability to make sufficient haemoglobin.
  • Pernicious anaemia caused by lack of vitamin B12 in the diet or inability to absorb it due to intestinal damage.
  • Effects
  • Lack of haemoglobin means lack of oxygen which means less energy is produced - leads to fatigue and loss of energy.
  • Pernicious anaemia can lead to brain damage and dementia-like symptoms.
  • Treatment
  • Iron or vitamin B12 supplements or injections.
• Hypertension


  • Causes
  • High blood pressure - 140/90 mmHg over a long period of time.
  • Caused by high salt in diet, being overweight, lack of exercise, smoking.
  • Effects
  • Usually no symptoms.
  • Causes damage to tissues and organs.
  • Can lead to diabetes.
  • Damages blood vessels leading to atherosclerosis (and therefore coronary heart disease, heart attacks and strokes).
  • Treatment
  • Low fat, low salt diet, exercise.
  • Medication to lower blood pressure.