Cardiovascular L1

• Cardiovascular system


  Composed of: fluid (e.g. blood or haemolymph), a pump (usually called a heart), and vessels to carry the fluid between the pump and body tissues

  
• Functions of cardiovascular systems

  • Nutrient delivery (e.g. amino acids, glucose, electrolytes)
  • Oxygen delivery
  • Waste removal (e.g. CO2)
  • Regulate body temperature
  • Signalling pathway (hormones)
  • Defence system
• General features of cardiovascular systems

  • It is a delivery system (transport)
  • Most important physiological system for maintaining homeostasis
  • Evolved to overcome problems with diffusion
• Diffusion is extremely slow over long distances
• Circulatory systems are much faster and use bulk transport to move things around in the same medium (e.g. blood)
• Open circulatory systems


  • Haemolymph flows through open spaces (haemocoel) and channels
  • Flow of haemolymph is slow
  • High pressure cannot be developed
  • Haemolymph comes directly into contact with tissues

  
• Closed circulatory systems


  • Blood confined to vessels that are separate from the interstitial fluid
  • Blood flows at a faster speed
  • High blood pressure can be maintained
  • Increased efficiency for meeting high metabolic demands
  • Blood does not come in contact with tissues
  • Selective blood flow

  
• Even very primitive animals have circulation, but usually no pump
• Cardiac output


  Cardiac output = heart rate × stroke volume
• Distribution of cardiac output during rest & exercise

  • Bone & other 600 mL/min (rest)
  • Skeletal 1400 mL/min (rest)
  • Cardiac 250 mL/min (rest)
  • Bone & other 1700 mL/min (exercise)
  • Skeletal 21000 mL/min (exercise)
  • Cardiac 1200 mL/min (exercise)
• Mammalian heart structure


  • Right and left sides of the heart operate as two separate pumps
  • Right side (blue): receives and pumps O2-depleted and CO2-rich blood. Pulmonary circulation
  • Left side (red): receives and pumps O2-rich and CO2-low blood. Systemic circulation
  • Pulmonary artery: carries blood from the right ventricle to the lungs to be oxygenated
  • Aorta: large artery carrying blood away from the left ventricle to the rest of the body

  
• Arteries


  Vessels that carry blood away from the heart under high pressure
• Veins


  Vessels that carry blood back to the heart under low pressure
• Capillaries


  Tiny networks of blood vessels connecting arteries and veins

  
• Tracking the journey of a drop of blood through the heart and body

  1. Superior venae cavae

  2. Right atrium

  3. Right ventricle

  4. Pulmonary artery

  5. Lungs

  6. Pulmonary veins

  7. Left atrium

  8. Left ventricle

  9. Aorta

  10. Body tissues

  
• Skeletal muscle


  • Striated
  • Contracts via actin and myosin binding
  • Single, very long cells
  • Voluntary contractions
• Cardiac muscle


  • Striated
  • Contracts via actin and myosin binding
  • Branching chains of cells
  • Involuntary contractions
  • Loaded with mitochondria (25-35% of each cell!)
  • Covered by a matrix of connective tissue (endomysium) full of capillaries
  • Muscle tissue structurally and functionally separate
  • Both physically and electrically connected all the time
• Pacemaker cells


  • Special group of cells that can generate action potentials repeatedly
  • Trigger rhythmic beating without any nervous stimulation
  • Directly control heart rate
• Intrinsic cardiac conduction system

  1. Sinoatrial (SA) node

  2. Atrioventricular (AV) node

  3. Bundle of His

  4. Purkinje fibres
• The spread of cardiac excitement is coordinated to ensure efficient pumping
• Atrial contraction is always completed prior to ventricle contraction
• The pair of atria and pair of ventricles contract simultaneously
• Electrocardiogram (ECG or EKC)


  When working cells depolarize enough current is generated to be measured in the limbs
• Sinus bradycardia


  The SA node produces an electrical charge at a slower rate than normal
• Bradycardia-tachycardia syndrome


  The heart rate alternates between abnormally slow and fast rhythms, usually with a long pause (asystole) between heartbeats
• Humans are not diving mammals with a very poor diving ability compared with true divers
• Humans do show a dive reflex