The Cardio Vascular System

• Anticipatory rise


  An increase in heart rate prior to exercise, due to the release of adrenalin
• Arterio-venous oxygen difference (A-VO2 diff)


  The difference in the oxygen content of the blood between the arterial blood and the venous blood
• Blood pressure


  A measure of the force that your blood exerts against blood vessel walls
• Types of blood pressure


  • Systolic blood pressure: Blood pressure while the heart is contracting
  • Diastolic blood pressure: Blood pressure while the heart is relaxing
• Bohr shift

  When an oxyhaemoglobin dissociation curve moves to the right during exercise
• Bohr shift

  • It occurs as a result of increased CO2 in the blood; increased blood acidity; decreased blood pH; and increased temperature
  • As a result, haemoglobin has a lower affinity for oxygen at working muscles, giving up oxygen more easily
• Bradycardia (athlete's heart)


  A reduction in resting heart rate below 60 beats per minute
• Cardiac conduction system


  A group of specialised cardiac muscle cells in the walls of the heart that send signals to the heart muscle, causing it to contract
• Components of the cardiac conduction system

  • Sino-atrial node (SAN), the heart's pacemaker, which sends an impulse through the atria causing them to contract
  • Atrio-ventricular node (AVN) which delays the impulse to allow ventricular filling
  • Bundle of His which conducts the impulse down the septum
  • Purkinje fibres spread the impulse through the ventricles causing them to contract
• Cardiac hypertrophy

  Increase in thickness of the muscular heart wall, especially around the left ventricle
• Cardiac hypertrophy


  • It increases the maximal strength of contraction
  • It may also make the size of the ventricular cavity bigger
• Cardiac output


  The amount of blood which leaves the left ventricle per minute
• Cardiovascular drift


  A reduction in stroke volume when exercising in warm conditions for longer than 10 minutes
• Cardiovascular drift


  • Results in an increase in heart rate to maintain cardiac output
  • Occurs due to sweating which reduces blood volume and increases viscosity, decreasing venous return which, in line with Starling's law, decreases stroke volume
• Cholesterol


  A type of fat which is transported in the blood
• Types of cholesterol

  • High-density lipoproteins: 'Good' cholesterol which transports excess cholesterol to the liver to be broken down
  • Low-density lipoproteins: 'Bad' cholesterol as too much can result in fatty deposits developing in the arteries
• Haemoglobin

  Found in red blood cells, haemoglobin combines with oxygen to form oxyhaemoglobin, transporting it around the body
• Heart disease


  Also known as coronary heart disease, this occurs when coronary blood vessels become blocked by fatty deposits, called atheroma, limiting the supply of oxygenated blood to the heart
• Myoglobin


  Found in muscle cells, myoglobin stores and transports oxygen. It has a higher affinity for oxygen than haemoglobin, so it aids transport into muscle cells
• Types of receptors

  • Baroreceptors: Located in blood vessels, these detect changes in blood pressure
  • Chemoreceptors: Monitors and detects increases in blood acidity during exercise due to increased carbon dioxide in the blood
  • Proprioceptors: Detect increases in muscle movement during exercise
• Redistribution of blood

  The vascular shunt mechanism directs blood flow around the body
• Mechanisms of redistribution of blood

  • Vasodilation: Precapillary sphincters will relax, widening the internal diameter of blood vessels
  • Vasoconstriction: Precapillary sphincters will contract, decreasing the internal diameter of blood vessels
• Starling's law of the heart

  Increased venous return will result in a higher stroke volume
• Stroke


  A serious life-threatening medical condition that happens when the blood supply to part of the brain is cut off
• Types of stroke

  • Ischaemic strokes occur when a blood clot stops the supply of blood reaching the brain
  • Haemorrhagic strokes are the result of a weakened blood vessel to the brain bursting
• Sympathetic and parasympathetic nervous systems

  The autonomic nervous system subconsciously controls heart rate, breathing rate and redistribution of blood, among other things
• Functions of the sympathetic and parasympathetic nervous systems


  • Sympathetic nervous system is the body's 'fight or flight' system, speeding up heart rate and breathing rate
  • Parasympathetic system is concerned with 'rest and digest', decreasing heart rate and breathing rate
• Venous return mechanisms

  • Valves: Found in veins that prevent the backflow of blood
  • Skeletal muscle pump: Working muscles contract and compress veins to push blood back towards the heart
  • Respiratory pump: Increased respiration/changes in pressure in the thorax compress veins to push blood back towards the heart
  • Smooth muscle: Found in veins, smooth muscle contracts to push blood back towards the heart
  • Suction pump of the heart: As the heart relaxes it creates a vacuum which pulls blood back toward the heart