cardiovascular system

• cardiovascular system includes - the heart, the arteries, veins and capillaries
• heart -

  • a 4 chamber pump
  • located centrally within the thorax
  • has a slight incline to the left of the chest
  • enriches on the left lung reducing the lung size compared to the right
  • size of an adult fist
• Structure of the heart wall - endocardium, myocardium and pericardium
• The atrioventricular (AV) valves -

  • blood returning to the heart field atria pressing against the AV valves. The increased pressure forces AV valves to open
  • As the ventricles fill, the AV flaps hang limply into ventricles
  • atria contracts. forcing additional blood into ventricles
  • Ventricles contract, forcing blood against AV valve cusps
  • AV valves close
  • papillary muscles contract and chord tendineae tightens which prevents valve flaps from everting into there atria
• The semilunar valves -

  • as ventricles contract and intraventricular pressure rises, blood is pushed up against semilunar valves forcing them to open
  • As ventricles relax and intraventricualr pressure falls, blood flows back from arteries, filling the cusps of semilunar valves and forcing them to close
• Explain the heart's 'lub' and 'dup' sound?

  • the first heart sound, lub occurs when the atrioventricular valves close
  • the second dup sound occurs when the semilunar valves close
• Cardiac conduction -

  1 - an electrical impulse travels from the sinoatrial code to the walls of the ratio, causing them to contract.

  2- the impulse reaches the atrioventricular node, which delays to by 0.1 second.

  3 - Bundle branches carry signals from the atrioventricular node to the heart apex.

  4 - signal spreads though the ventricle wall, causing them to contract.
• Cardiac Cycle - Refers to the sequence of events that occur and repeat with every heart beat. Can be divided into two major phases: systole and diastole each which subdivides into many smaller phases.
• Systole - heart muscles contract and pumps blood out of the chambers into the arteries. This is when the ventricles are contracting and pushing blood out to the rest of the body.
• Atrial Systole - Atria Contract
• Diastole - relaxation phase of the heart cycle
• Diastole - heart muscle relaxes and fills with blood from the veins, when the atria are contracting and filling ventricles with blood.
• Cardiac Cycle - begins with the atria contracting to push blood into the ventricles, followed by the ventricles contracting to pump blood out of the heart. Cycle then repeats with the heart relaxing and filling with blood.
• Cardiac cycle is controlled by electrical signals from the hearts natural pacemaker, the sinoatrial node and is regulated by the ANS to ensure beats at a regular rhythm and pumps blood throughout the body.
• Cardiac Output = heart rate x stroke volume (SV) 


  70mins x V70ml : 4900ml - 4900ml/min
• SV - the amount of blood pumped out with each vetricualr.
• SV = difference between ventricular end diastolic volume and ends systolic volume

  120ml - 50ml =70 ml
• what is an adult's average heart rate?


  60-80bpm
• What is a neonates average heart rate?


  110-140bpm
• what is heart rate controlled by?

  cardiovascular centre in the medulla cons
• Heart rate controls rate and force of contraction and Vasco motor centre which controls blood vessels and blood pressure
• Blood distribution

  9% - pulmonary vessels

  7% - heart

  13% - systematic arteries

  7% - systematic capillaries

  64% - systematic veins and venues
• Three types of blood vessels - arteries, veins and capllaries
• Veins -

  less elastic

  thinner muscular layer

  easily distended

  larger diameter

  capacity vessels

  changed by venomotor tone

  depend on smaller pressure gradients

  endothelial lining modified to form valves

  skeletal muscle and respiratory pump
• Blood -

  • adults have 4-6 litres of circulating blood
  • transports nutrients and oxygen to cells
  • carries carbon dioxide, urea and other waste products away from cells
  • has a role in tempreature regulation by removing heat produced in the body to the skin surface
  • protection against disease ]has 4 main components
• Blood cells - red blood less and thrombocyte
• White blood cells -

  • basophil
  • eosinophil
  • neutrophil
  • monocytes
  • lymphocytes
• The muscular 'pump' + blood 'pools" -

  • changes in posture affect blood flow through the systematic circulation
  • in an individual who stands still in a ventricle position, blood 'pools' in the veins of their ankle and feet
  • A skeletal muscle pump helps to prevent this pooling
• Capillary beds are where exchange between blood and tissue fluid occurs
• Muscular pump - contraction of skeletal muscles increases pressure in veins which forces blood back towards heart
• Arteries carry blood away from the heart
• The respiratory pump -

  • as we inhale, abdominal pressure increases, squeezing the local veins and forcing the blood to the heart.
  • at the same time, the pressure increases, squeezing the local veins and forcing blood to the heart
  • at the same time, the pressure in the chest decreases, allowing the thoracic veins to expand and speeding blood entry into the right atrium
• Blood pressure = peripheral resistance x cardiac output\
• Vasoconstriction -

  • increased contraction of the muscle wall and resistance
  • decreased blood flow through the vessels
• Vasodilation -

  • decreased contraction of the muscle wall and resistance
  • increased blood flow through the vessels
• Systole - period when ventricles contract (pump out)
• Blood pressure - force per unit area exerted on the wall of the blood vessel by its contained blood. an increase in blood flow leads to vasoconstriction
• Blood pressure is calculated by measuring pressure needed to stop the flow of blood through an artery