Heart and Blood

• ventricular systole


  ventricular pressure rises above atrial pressure - contraction
• atrial systole

  • small increase in pressure by this contraction (muscle walls are thin)
  • helps push blood into ventricles, stretching their walls and ensuring they are full of blood - atria contract
• diastole


  muscular walls of all four chambers relax
• myogenic


  cardiac muscle initiates its own contractions. Heart can continue contracting and relaxing even when not connected to body
• single circulation

  • fish and some other organisms
  • blood pressure drops as blood passes through gills
  • rate of delivery is slower
• double circulation

  • mammals and other organisms
  • blood pressure must not be too high
  • heart can increase pressure of blood after passing lungs to allow quicker flow
• open circulatory system

  • common in insects
  • blood not always in blood vessels -> directly bathes cells and tissue
• closed circulatory system

  • blood travels in vessels
  • separate fluid called tissue fluid bathes cells and tissues
  • higher BP and faster flow
  • faster delivery of nutrients
  • faster removal of waste
• arterioles


  small blood vessels that ditribute blood from an artery to capillaries
• venules


  from capillaries blood flows into venules which collect blood from the capillaries to veins
• tunica


  membranous sheath lining an organ
• Lymph

  • excess tissue fluid drained into lymphatic system, where it forms lymph
  • lymph is colourless/ pale yellow fluid similar to tissue fluid containing lipids
  • lymphatic system drains into circulatory system near vena cava via thorocic duct
• oncotic pressure

  • both blood in blood vessels and tissue fluid exert pressure -hydrostatic pressure
  • presence of dissolved solutes in fluids creates oncotic pressure - has negative figure
  • forces oppose eachother - force thats greater leads to fluid leaving or entering blood vessels
  • when all forces interact they result in fluid being forced out capillaries at arteriole end and into capillary at venule end
• oncotic: pulls water back into blood

  hydrostatic: pushes fluid out into tissue
• sinus thythm


  normal heart rate
• bradycardia


  slow heart rate

  • caused by ageing,sleep apnoea,medications
• tachycardia


  fast heart rate

  • excersize, stress, alcohol
• atrial fibrillation


  atria beat more frequently than ventricles

  • lung cancer, high bp, lung disease
• ectopic heartbeat


  third beat is an early ventricular beat

  • patient feels heartbeat has been missed
  • alcohol, drugs, caffeine, pregnancy
• P wave: depolarisation of atria

  QRS complex: depolarisation of ventricles

  T wave: repolarisation of ventricles
• after depolarisation of atria, impulse help at AVN before moving down bundle of His to depolarise ventricles
• 'lub' : AV valves closing

  'dub' : semi-lunar valves closing
• oncotic pressure: tendency for water to move into blood by osmosis
• 1. heartbeat begins at sino-atrial node (SAN). generate wave of electrical stimulation (depolarisation)
  2. depolarisation spreads through atria where they contract
  3. atrioventricular nodes (AVN) stimulated by electrical wave. Depolarisation passed into conducting fibres known as bundle of His.
  4. ventricules contract. Bundle of His splits into 2 branches known as purkinje fibres which carry wave upwards to ventricles - enable ventricles to fill with blood before contracting
• transport in animals reasons

  • meet high metabolic demand
  • maintain steep concentration gradient
  • overcome low surface area: volume ratio
  • allow diffusion across large distances
• • arterioles: artery - capillaries under low pressure
  • venule: capillary - veins under low pressure
• artery

  • elastic layer - stretches and recoils to maintain high blood pressure
  • muscle layer - contracts and relaxes to control blood flow
  • thick wall prevents bursting from high pressure
• arteriole

  • thick muscle layer - contracts to reduce blood flow into capillaries
• veins

  • thin walls - low blood pressure
  • valves to prevent backflow
• blood vessel layers

  1. lumen
  2. endothelium
  3. elastic layer
  4. muscle layer
  5. outer layer
• tissue fluids

  • tissue fluids surround cells and consist of water, glucose, ions which control exchange of substances between blood and cells
  • formed by blood plasma
  • blood moving into capillaries has high hydrostatic pressure - pressure exerted by a fluid and is greater than oncotic pressure#
• hydrostatic > oncotic


  forces water out of capillaries forming tissue fluid
• oncotic > hydrostatic


  forces fluid out of tissue fluid and back into venus end of capillary
• coronary artery - supplies heart with blood
• diastole - atrial systole - ventricular systole
• diastole

  • atria relaxed
  • ventricles relaxed and blood enters atria
  • pressure in atria > pressure in ventricles - atria ventricular valves open
• atrial systole

  • atria contract
  • ventricles relaxed
  • atria contract - volume decreases and pressure increases
  • remaining blood enters ventricles
• ventricular systole

  • ventricles contract - volume decreases + pressure increases
  • atria relaxed
  • pressure in ventricles > pressure in atria - atrioventricular valves close preventing backflow of blood into atria
  • semi-lunar valves open and blood pushed into vessels
  • when pressure in blood vessels > ventricular pressure, semi-lunar valves shut preventing backflow
• cardiac output

  • volume of blood pumped by a ventricle in 1 minute
  • stroke volume x heart rate
• controlling resting heart rate - depolarisation of atrial muscle

  • SAN - sends out wave of depolarisation and causes atria to contract - reaches AVN
  • AVN - delayed for 0.1 seconds - when wave released its conducted bundle of his - collection of specialised muscle fibres between and below ventricles called purkyne fibres
  • wave of depolarisation causes ventricles to contract