Transport in animals

• Why do multicellular organisms require transport systems?

  To manage high metabolic rates and oxygen demand
• What is a consequence of large size in multicellular organisms?

  Small surface area to volume ratio
• What is the role of a specialized system in multicellular organisms?

  To ensure a strong oxygen supply to tissues
• How are arteries structured to fulfill their function?

  Thick muscular walls handle high pressure
• What allows arteries to prevent pressure surges?

  Elastic tissue allows recoil
• What is the lumen size of arteries compared to veins?

  Narrow lumen maintains pressure
• What are the types of circulatory systems?

  • Open: Blood can diffuse out (e.g., insects)
  • Closed: Blood confined to vessels (e.g., fish, mammals)
  • Single: Blood passes through pump once
  • Double: Blood passes through heart twice
• Why do veins have thin walls?

  Due to lower pressure in veins
• What is the function of valves in veins?

  To prevent backflow of blood
• Why do veins have less muscular and elastic tissue?

  They don't need to control blood flow
• How are capillaries structured for their function?

  Walls are one cell thick for diffusion
• Why are capillaries very narrow?

  To permeate tissues effectively
• What is the advantage of capillaries being numerous and branched?

  Provides a large surface area for exchange
• What is the function of arterioles and venules?

  To feed blood into capillaries
• Why are arterioles and venules smaller than arteries and veins?

  To allow gradual pressure change
• What is tissue fluid?

  A watery substance supplying nutrients to cells
• How is tissue fluid formed?

  Hydrostatic pressure exceeds oncotic pressure
• What types of pressure influence tissue fluid formation?

  Hydrostatic and oncotic pressure
• How does hydrostatic pressure change in capillaries?

  Higher at arterial end than venous end
• What is oncotic pressure influenced by?

  Proteins in the plasma changing water potential
• How does tissue fluid differ from blood?

  Tissue fluid lacks red blood cells and platelets
• What happens to tissue fluid after it bathes cells?

  It becomes lymph with more waste products
• What occurs during cardiac diastole?

  Heart relaxes, blood enters atria
• What happens during atrial systole?

  Atria contract, pushing blood into ventricles
• What occurs during ventricular systole?

  Ventricles contract, blood flows into arteries
• How is cardiac output calculated?

  Cardiac output = heart rate x stroke volume
• What are the stages of the cardiac cycle?

  1. Cardiac diastole: Heart relaxes, blood enters atria
  2. Atrial systole: Atria contract, blood into ventricles
  3. Ventricular systole: Ventricles contract, blood into arteries
• What does myogenic mean in relation to the heart?

  Contraction initiated from within the muscle
• How does the heart contract?

  SAN initiates impulse, AVN relays it
• What is an electrocardiogram (ECG)?

  A graph of electrical activity in the heart
• What is tachycardia?

  Fast heartbeat over 100 bpm
• What is bradycardia?

  Slow heartbeat under 60 bpm
• What is fibrillation?

  Irregular, fast heartbeat
• What is ectopic heartbeat?

  Early or extra heartbeats
• How does partial pressure of oxygen affect haemoglobin binding?

  Higher pressure increases haemoglobin's affinity
• What do oxyhaemoglobin dissociation curves show?

  Saturation of haemoglobin with oxygen vs. pressure
• What is the role of haemoglobin?

  To carry oxygen in red blood cells
• What is the Bohr effect?

  Increased CO2 lowers haemoglobin's oxygen affinity
• What role do bicarbonate ions play in gas exchange?

  Carry CO2, converted back in lungs
• What is the role of carbonic anhydrase in the Bohr effect?

  Converts CO2 to carbonic acid in RBCs