exam questions

• Explain why mammals born with a hole between their 2 ventricles experience a lack of energy (3)

  -       A hole between both ventricles means deoxygenated and oxygenated blood mixes 

  -       Therefore, when aorta pumps blood around the body, blood has lower concentration of oxygen (less oxygen circulating the body)

  -       Therefore, muscle cells receiving less oxygen for aerobic respiration for less energy is produced in respiration
• Explain how pressure differences in the heart ensure efficient pumping of blood into the arteries (3)

  -       Pressure increases in the ventricles 

  -       Greater pressure in the ventricles than the atria 

  -       Causing atrioventricular valves to close and the semi lunar valves to open, forcing blood at high pressure into the arteries
• Explain what happens in ventricular systole (1)

  -       Ventricle’s contract, the atrioventricular valves close and the semi lunar valves open

   
• Explain the changes in blood pressure in the ventricles during the cardiac cycle (4)

  -       Ventricles fill with blood during atrial systole, this increases the ventricular pressure 

  -       After atrial systole finishes, there is a fall in ventricular pressure

  -       There is an increase in pressure due to ventricular systole

  Then ventricular pressure decreases due to ventricular diastole
• Explain why multi-cellular organisms require a circulatory system and single celled organisms e.g., bacteria do not (2)

  • Multi-cellular organisms have a smaller surface area to volume ratios and made up of many layers of cells
  • Diffusion pathways/ distances too long and thus inefficient
• Explain how the structure of the aorta/arteries relates to its function (5) 

  -       Thick muscular wall (lots of collagen)- withstand blood pressure

  -       Elastic/muscular walls- elastic recoil to maintain blood pressure

  -       Smooth endothelium wall to reduce friction/resistance

  -       Semi-lunar valve present to prevent backflow
• Explain 2 differences between the structure of a capillary and structure of a vein

  -       The capillary wall is one cell thick however veins have thicker walls 

  -       Capillaries have a small lumen whereas veins have a large lumen

  -       No valves in capillaries however there are in veins
• Give 2 differences between the structure of an artery and a capillary (2) 

  -       Capillary has a one cell thick wall, no muscular wall however artery has a thick muscular wall 

  -       Artery has a narrow lumen however capillaries narrower

  -       Artery has elastic tissue and collagen fibres in walls however capillaries do not