the heart (1.1-1.4)

• explain why larger organisms need a mass transport system but smaller organisms do not

  -larger organisms have smaller SA:V ratio

  -some cells are far from the surface

  -so diffusion alone cannot supply oxygen/glucose/nutrients to the cell
• why do some organisms rely on a mass transport system to move substances around their bodies?

  because they are too large for diffusion to move substances around their bodies quickly enough

  they rely on a mass transport system to move substances efficiently over a long distance by mass flow
• why do some organisms not need a mass transport system to move substances around their bodies?

  because diffusion is usually fast enough to meet the organism's requirements and they have a large SA:V ratio
• What is the cardiac cycle?

  Series of events in one heartbeat
• What is the contraction of the heart called?

  Systole
• What is the relaxation of the heart called?

  Diastole
• How does one cardiac cycle relate to another?

  One cycle follows another continuously
• What happens to blood flow between cardiac cycles?

  Blood flow does not stop between cycles
• What happens to volume and pressure during heart contraction?

  Volume decreases, pressure increases
• What happens to volume and pressure during heart relaxation?

  Volume increases, pressure decreases
• How do heart valves operate during the cardiac cycle?

  They open and close due to pressure changes
• When do valves open in the heart?

  When pressure behind them is greater
• When do valves close in the heart?

  When pressure in front is greater
• What is the function of heart valves?

  To prevent blood from flowing backwards
• What occurs during atrial systole?

  • Atria contract
  • Atrial volume decreases
  • Atrial pressure increases
  • AV valves open, forcing blood into ventricles
• What happens to ventricular pressure during atrial systole?

  It increases slightly as blood fills
• What occurs during ventricular systole?

  • Ventricles contract
  • Ventricular volume decreases
  • Ventricular pressure increases
  • AV valves close, SL valves open
• What happens to pressure in the ventricles during ventricular systole?

  It exceeds pressure in the atria
• What forces blood into the aorta during ventricular systole?

  Pressure in the left ventricle
• What occurs during diastole?

  • Both ventricles and atria relax
  • Pressure in ventricles drops
  • SL valves close
  • Atria fill with blood
• What happens to the pressure in the ventricles during diastole?

  It drops below pressure in the aorta
• How does blood return to the heart during diastole?

  Via the vena cava and pulmonary vein
• What happens to the AV valves during diastole?

  They open when atrial pressure exceeds ventricular pressure
• What happens during late diastole?

  • Left ventricle expands
  • Internal volume increases
  • Ventricular pressure decreases
  • Blood flows into left ventricle
• What causes a brief decrease in pressure in the left atrium during late diastole?

  Blood flows into the left ventricle
• How do the events of the cardiac cycle facilitate blood pumping?

  They allow blood to flow to lungs and body
• What happens to pressure in the left atrium during late diastole?

  It increases as it fills with blood
• What is the relationship between atrial and ventricular pressure during atrial systole?

  Atrial pressure is higher than ventricular pressure
• What occurs to the left ventricle during the beginning of diastole?

  It has been emptied of blood
• What happens to the aortic valve during the beginning of diastole?

  It closes when ventricular pressure falls
• What is the significance of the cardiac cycle?

  It enables the heart to pump blood effectively
• What do circulatory systems transport?

  Fluids containing materials and waste
• How are circulatory systems classified?

  As open or closed systems
• What characterizes a closed circulatory system?

  Blood is contained within blood vessels
• How does an open circulatory system function?

  Blood bathes the organs in the body cavity
• What are the two types of circulatory systems based on loops?

  Single and double circulatory systems
• What is a double circulatory system?

  It has two loops: one to lungs, one to body
• What is a single circulatory system?

  It has one loop that includes lungs and body
• What type of circulatory system do humans have?

  Closed, double circulatory system
• How many times does blood pass through the heart in one complete circuit?

  Twice