2.2.2 The heart and blood vessels

• What is the function of the human heart?

  Pump blood around the body in a double circulatory system
• What is a double circulatory system? Blood passes through heart 2 x for every circuit around body:

  1. Right ventricle pumps blood to lungs

  2. Left ventricle pumps blood to rest of the body
• Describe the journey of blood through the heart

  1. Deoxygenated blood enters right atrium via vena cava (vein)

  2. Blood flows into right ventricle which pumps blood to lungs via pulmonary artery

  3. Oxygenated blood returns to heart, entering left atrium via pulmonary vein

  4. Blood flows into left ventricle which pumps blood to rest of body via aorta
• Describe the functions of blood vessels entering and leaving the heart

  ● Vena cava - returns deoxygenated blood to heart from body

  ● Pulmonary artery - transports deoxygenated blood away from heart to lungs
• Describe the functions of blood vessels entering and leaving the heart

  ● Pulmonary vein - returns oxygenated blood to heart from lungs

  ● Aorta - transports oxygenated blood away from heart to body
• How is natural resting heart rate controlled and how are irregularities in heart rate treated?

  ● A group of cells located in the right atrium

  ● That act as a pacemaker (by sending regular electrical impulses)
• Artificial pacemakers - electrical devices (send out regular electrical impulses)
• Explain how the structure of arteries relates to their function

  Carry blood away from heart at high pressure

  ● Thick muscle tissue → withstand high pressure

  ● Thick elastic tissue → can stretch & recoil, to maintain / withstand high pressure

  ● Narrow lumen → maintain high pressure
• Explain how the structure of veins relates to their function

  Carry blood back to heart at low pressure

  ● Valves → prevent backflow of blood

  ● Large lumen → less resistance to blood flow
• Explain how the structure of capillaries relates to their function Enable diffusion of substances eg. O2 / glucose between blood and cells

  ● One cell thick / thin walls → short diffusion distance

  ● Narrow lumen → blood moves slowly, more time for diffusion
• why is this statement wrong?

  “Arteries have thick cell walls and lots of muscle in cells.”

  Arteries have thick walls, but the cells don’t have cell walls. There are many muscle cells - the muscle isn’t ‘in cells’.
• why is this statement wrong?

  “Blood from the left side of the heart goes to the left side of the body; blood from the right side.”

  The left side pumps blood to the body, while the right side pumps blood to the lungs.
• A ‘hole in the heart’ is a small hole between the right ventricle and the left ventricle. Some blood flows from the right ventricle to the left ventricle. Explain why a ‘hole in the heart’ causes a person to feel tired. (4)

  ● Some blood will go directly to the body without going to the lungs

  ● So blood going to body cells will have less oxygen OR oxygenated and deoxygenated blood will mix

  ● So lower / reduced rate of respiration

  ● So less energy transferred / released
• Axolotls have a double circulatory system but only one ventricle. Explain why this makes the circulatory system less efficient than having 2 ventricles. (2)

  ● Oxygenated and deoxygenated blood mixes

  ● So less oxygen reaches the body / tissues / cells
• A heart attack is caused when the heart muscle cells do not get enough oxygen, causing the cells to die. Many people who survive a heart attack get out of breath easily when they exercise gently. Explain why heart attack survivors get out of breath easily. (4)

  ● Heart (muscle) cannot contract / pump as effectively / powerfully

  ● So less blood pumped out of heart / to body

  ● So less oxygen (reaches cells / body) for (aerobic) respiration

  ● So breathing rate increases to supply more oxygen
• The wall of the left ventricle is much thicker than the wall of the right ventricle. Suggest why. (1)

  ● Has to pump blood further / with a greater force / at a higher pressure (than right ventricle)