Lecture 1

• Cardiovascular and Circulatory system

  Blood, Anatomy, Physiology: Blood and plasma content, volume and function, Heart and Blood vessels
• What's in blood


  • Red blood cells
  • White blood cells
  • Platelets
  • Plasma
  • Carbon dioxide
  • Digested food
  • Waste (urea)
  • Hormones
  • Oxygen
• Plasma


  A straw-coloured liquid that carries the cells and the platelets which help blood clot
• Red Blood Cells


  • Contain haemoglobin, a molecule specially designed to hold oxygen and carry it to cells that need it
  • Can change shape to an amazing extent, without breaking, as it squeezes single file through the capillaries
  • A biconcave disc that is round and flat without a nucleus
• White Blood Cells


  • There are many different types and all contain a big nucleus
  • The two main ones are the lymphocytes and the macrophages
  • Some lymphocytes fight disease by making antibodies to destroy invaders by dissolving them
  • Other lymphocytes make antitoxins to break down poisons
  • Macrophages 'eat' and digest micro-organisms
• Platelets


  • Platelets are bits of cell broken off larger cells
  • Platelets produce tiny fibrinogen fibres to form a net
  • This net traps other blood cells to form a blood clot
  • A normal platelet count ranges from 150,000 to 450,000 platelets per microliter of blood
  • Having more than 450,000 platelets is a condition called thrombocytosis
  • Having less than 150,000 is known as thrombocytopenia
  • You get your platelet number from a routine blood test called a complete blood count (CBC)
• Arteries


  • Carry blood away from the heart
  • Have thick muscle and elastic fibres
  • The elastic fibres allow the artery to stretch under pressure
  • The thick muscle can contract to push the blood along
• Veins


  • Carry blood towards from the heart
  • Have thin muscle and elastic fibres
  • Veins have valves which act to stop the blood from going in the wrong direction
  • Body muscles surround the veins so that when they contract to move the body, they also squeeze the veins and push the blood along the vessel
• Capillaries


  • Link Arteries with Veins
  • The wall of a capillary is only one cell thick
  • They exchange materials between the blood and other body cells
  • The exchange of materials between the blood and the body can only occur through capillaries
• Circulatory system


  • Carries blood and dissolved substances to and from different places in the body
  • The Heart has the job of pumping these things around the body
  • The Heart pumps blood and substances around the body in tubes called blood vessels
  • The Heart and blood vessels together make up the Circulatory System
• 3 Kinds of Circulation

  • Pulmonary circulation - lungs
  • Coronary circulation - Heart
  • Systemic circulation - body
• Sinoatrial (S-A) node


  Known as the heart's natural pacemaker, the S-A node has special cells that create the electricity that makes your heart beat
• Atrioventricular (A-V) node


  • The A-V node is the bridge between the atria and ventricles
  • Electrical signals pass from the atria down to the ventricles through the A-V node
• Parts of the body

  • Lungs
  • Head & arms
  • Liver
  • Digestive system
  • Kidneys
  • Legs
• Blood vessels


  • Pulmonary artery
  • Aorta
  • Pulmonary vein
  • Main vein
• Heart chambers


  • Left
  • Right
• How the circulatory system works

  1. The right side of the system deals with deoxygenated blood

  2. The left side of the system deals with oxygenated blood
• How the heart works

  1. Blood from the body flows into the atria

  2. The atria contract and the valves open to allow blood into the ventricles

  3. The valves close to stop blood flowing backwards

  4. The ventricles contract forcing the blood to leave the heart

  5. At the same time, the atria are relaxing and once again filling with blood

  6. The cycle then repeats itself
• Blood pressure


  • A measure of the force exerted by the blood on the wall of the arteries
  • An example is 120/80 (systolic pressure/diastolic pressure)
  • Systolic pressure is the result of the contraction of the ventricles (normal 110-140)
  • Diastolic pressure is during the ventricle relaxation (normal 70-90)
• Heart sounds are made by the valves as they open and close
• Cardiac control centre


  • Found in the medulla oblongata of the brain
  • Controlled by the autonomic nervous system
  • Consists of sensory and motor nerves from either the sympathetic or parasympathetic nervous system
  • Sympathetic nerves increase heart rate and parasympathetic nerves decrease heart rate
  • Initiates either sympathetic or parasympathetic nerves to stimulate the sino-atrial node to increase or decrease heart rate
• Factors affecting cardiac control centre activity


  • Neural control
  • Hormonal control
  • Intrinsic control
• Neural control


  1. During exercise sensory receptors stimulate the cardiac control centre

  2. These receptors include proprioceptors, chemoreceptors, and baroreceptors

  3. The cardiac control centre responds by stimulating the sino-atrial node via the sympathetic cardiac accelerator nerve to increase heart rate
• Hormonal control


  1. Before and during exercise adrenalin is released in the blood

  2. This stimulates the sino-atrial node to increase heart rate
• Intrinsic control


  1. During exercise temperature increases which increases the speed of nerve impulses which in turn increases heart rate

  2. Venous return increases heart rate