Heart

• Circulatory

  Circulatory System
• Heart


  The organ that pumps (propels) blood through the body
• Double circulation


  Blood flows through the heart twice for each complete circuit of the body.
• SystemicCirculation

  When the left atrium carries the oxygenated blood to all parts of the body, hence the deoxygenated blood returns to the right atrium.
• Deoxygenated blood


  Blood that has low oxygen content
• Oxygenated blood


  Blood that has high oxygen content
• Purpose of the circulatory system

  1. Deliver O2 and nutrients to cells

  2. Remove CO2 and metabolic waste products like urea from cells

  3. Distribute heat

  4. Transport hormones

  5. Defend the body
• Systole

  Contraction of the heart
• Diastole

  Relaxation of the heart
• The cardiac cycle

  1. Both atria relax to receive blood (atrial diastole)

  2. Right atrium receives deoxygenated blood from the body

  3. Left atrium receives oxygenated blood from the lungs

  4. A/V valves are closed

  5. As blood fills the atria, pressure increases

  6. When atrial pressure exceeds ventricular pressure, A/V valves open and blood flows into ventricles

  7. Atria contract to push blood into ventricles (atrial systole)

  8. Ventricles contract, A/V valves close causing first heart sound (ventricular systole)

  9. Blood pumped from left ventricle to body, blood pumped from right ventricle to lungs

  10. Ventricles relax, blood in aorta and pulmonary artery tends to backflow causing second heart sound
• Electro cardiogram (ECG)

  Monitoring of Heart activity
• Pulse Rate

  Listening to sounds of valves closing (lub, dubl)
• Effect of physical activity on Heart Rate

  1. During a physical activity, the heart rate increases until it reaches a plateau

  2. The heart rate stays constant at this plateau provided that the physical activity is being done at its highest intensity
• Maximum heart rate

  Depends on the person's fitness level
• After the activity

  The heart rate takes some time but it eventually returns to resting level
• The increase in heart rate was due to the higher demand in oxygen and glucose by the muscles
• The heart takes some time to get back to normal after exercise to transport lactic acid from muscles to the liver to be metabolised (broken down)
• Importance of double circulation

  1. Deoxygenated blood never mixes with oxygenated blood .
  2. Pressure maintain in the arteries.
• Blood flows into right ventricle -> pulmonary valve -> pulmonary artery -> capillaries in lung tissue -> veins -> left auricle -> bicuspid valve -> left ventricle -> aortic valve -> aorta -> systemic circuit
• Circulatory System

  The circulatory system consists of a network of blood vessels, blood (transporting tissue) and a pump (the heart) that ensures the continuous flow of blood throughout the body.