CVS, Resp, Ex/Temp

• Circulatory system

  Made up of the heart, blood vessels, and blood
• Cardiovascular system

  • Impacted by endocrine, nervous, and kidney functions
• Blood

  Made of formed elements and plasma
• Bulk flow


  The rapid flow of blood throughout the body produced by the pumping of the heart
• Bulk flow

  Regulates pH, osmolarity, body water, temperature, and metabolism
• Cardiac output

  1. Right side of the heart pumps through pulmonary circulation

  2. Left side of the heart pumps through systemic circulation
• Cardiac output


  Amount of blood pumped by each side of the heart each minute (at rest 5L/minute)
• Stroke volume


  Amount of blood pumped out of each side of the heart during each beat (at rest 60-80mL)
• Heart rate


  Number times the heart beats per minutes (at rest 50-80 beats)
• Blood flow

  1. Flows through the pulmonary and systemic circuits in series

  2. Systemic circuit flows through branches in parallel
• Distribution of blood to organs

  Based on metabolic demand
• Blood flow

  Flows from a region of high pressure (arteries) to low pressure (veins)
• Resistance to blood flow

  Caused by friction
• Resistance

  • Governed by length of tube, viscosity of liquid, and radius of tube
• Blood flow path

  Aorta → arteries → arterioles → capillaries → venules → veins → vena cava
• Veins

  Contain 40% of blood volume
• Total cross sectional area

  Increases moving away from the heart
• Velocity of blood flow

  Starts fast and slows as it gets to the capillaries for sufficient exchange of nutrients, and will then increase to half of initial velocity once in the veins
• Blood pressure

  Highest when leaving the heart
• Arterioles


  Buffer blood pressure
• Aorta and large arteries

  High pressure conduits which drive blood through the systemic circuit
• Smaller arteries and arterioles

  Resistance vessels determine the flow through circulation
• Capillaries


  Exchange vessels
• Venules and veins

  Return conduits, and are the primary reservoir/capacitance of the vasculature
• Pericardium


  Sac which surrounds and insulates the heart and prevents electrical currents travelling anywhere else in the body
• Epicardium


  Outer muscle layer of the heart
• Myocardium


  Bulk of heart muscle
• Tricuspid valve


  Separates right atrium from right ventricle
• Bicuspid valve


  Separates left atrium from left ventricle
• Interventricular septum


  Separates ventricles
• Aorta


  Largest artery
• Pulmonary trunk


  Pumps deoxygenated blood to the lungs
• Aortic semilunar valve


  Separates left ventricle from aorta
• Pulmonary semilunar valve


  Separates right ventricle from pulmonary trunk
• Chordae tendinae


  Connect the AV valves and papillary muscles and slow the closure of the AV valves
• Contractile myocardial cells

  • Arranged in layers and joined by intercalated discs
  • Have actin and myosin filaments which gives a striated appearance
• Gap junctions


  Found in intercalated discs and allow the passage of ions and small molecules
• Nodal tissue


  Makes up 1% of cardiac cells and are specialised for the generation and conduction of action potentials in the atria
• Action potentials

  1. Spontaneously generated in the SA node and travel from cell to cell by gap junctions arranged in preferential pathways, then into the AV node

  2. Conducted rapidly through the bundle of His, bundle branches, and Purkinje system at 5 ms-1 to the ventricular myocardium where it spreads at 0.5 ms-1 to allow synchronous depolarisation and contraction of the entire ventricles
• Resting membrane potential of heart cells

  Depends on a high resting permeability to K+