Animals

• Mammals are relatively large organisms and cannot take up enough nutrients through their surface to supply their high metabolic rate.
• Blood in the circulatory system carries nutrients from exchange surfaces to the organs of the body for respiration, and carries toxic waste products away from the organs to exchange surfaces so that they can be removed from the body.
• Mammalian blood is mainly composed of a liquid based on water. Water is a good solvent because it is polar, so can be used in mass transport.
• The heart is a muscular organ that lies in the thoracic cavity behind the sternum. It is made up of four interconnected chambers that have muscular walls.
• The contraction of the muscular walls exerts pressure on the blood inside the chambers, which causes the heart to pump blood to the organs of the body through blood vessels.
• The walls of the atria have much less muscle tissue than the ventricles as they have to contract less.
• The walls of the left ventricle are thicker than the walls of the right ventricle because blood needs to go all the way around the body.
• The coronary arteries provide blood flow to the cardiac muscle.
• Diastole pt 2

  Wall status:

  • atrium - relaxed
  • ventricle - relaxed

  Refilling:

  • atrium from veins
  • ventricle from atrium

  Valves:

  • atrium/ventricular - open
  • semi-lunar - closed
• Atrial Contraction (systole)

  Wall status:

  • atrium - contracted
  • ventricular - relaxed

  Pushes blood through atrium/ventricular valves into ventricles

  Valves:

  • atrium/ventricular - open - atrial pressure > ventricular pressure
  • semi-lunar - closed - ventricular pressure < arterial pressure
• Ventricular contraction pt 1 (Isovolumetric contraction)

  Wall status:

  • atrium - relaxed
  • ventricle - contracted

  No blood flow.

  Valves:

  • atrium/ventricular - closed
  • semi-lunar - closed
  • atrial pressure < ventricular pressure < arterial pressure
• Ventricular contraction pt 2 (Rapid Ejection)

  Wall status:

  • atrium - relaxed
  • ventricle - contracted

  Blood flow through arteries.

  Valves:

  • atrium/ventricular - closed - atrial pressure < ventricular pressure
  • semi-lunar - open - ventricular pressure > arterial pressure
• Diastole pt 1 (Isovolumetric)

  Wall status:

  • atrium- relaxed
  • ventricular - relaxed

  Atria refilling - volume stays the same, pressure increases.

  Valves:

  • atrium/ventricular - closed
  • semi-lunar - closed
  • atrial pressure < ventricular pressure < arterial pressure