Cardiovascular system

• What is the effect of physical activity on heart disease?

  It keeps the heart healthy and more efficient.
• How does physical activity affect cholesterol levels?

  It lowers 'bad' LDL cholesterol levels and increases 'good' HDL cholesterol levels.
• What is the potential reduction in stroke risk associated with maintaining a healthy weight through physical activity?

  It can reduce your risk of stroke by 27%.
• What is stroke volume (SV)?

  • Volume of blood pumped out by the heart ventricles in each contraction
  • Average resting stroke volume is approximately 70 ml
• How does stroke volume change with exercise intensity?

  SV increases with exercise intensity up to 40-60% of maximum effort, then plateaus.
• What does Starling's law explain regarding stroke volume during exercise?

  It explains that stroke volume increases with greater diastolic filling due to increased venous return.
• What is heart rate (HR)?

  It is the number of times the heart beats per minute.
• How can maximum heart rate be calculated?

  Maximum heart rate can be calculated as 220 minus age.
• What physiological change occurs in a trained performer regarding heart rate?

  A trained performer has a lower resting heart rate and a greater heart rate range.
• What happens to heart rate during exercise and recovery?

  • Heart rate increases with exercise intensity
  • Rapid decline in heart rate occurs after exercise stops
  • Slower recovery as body systems return to resting levels
• What is cardiac output (Q)?

  It is the amount of blood pumped out by each ventricle per minute.
• How is cardiac output calculated?

  Cardiac output is calculated using the formula $Q =$$SV \times HR$.
• How does cardiac output change during exercise for trained versus untrained performers?

  During exercise, maximum cardiac output increases for both, but trained performers benefit more due to higher SV and HR.
• What is the cardiac conduction system?

  • Heart muscle is myogenic; the beat originates in the heart muscle
  • Electrical signal starts in the SAN, spreads through atria, then to AVN
  • Impulse travels through the bundle of His and Purkinje fibres to ventricles
• What role do chemoreceptors, baroreceptors, and proprioceptors play in heart rate regulation?

  They detect changes in blood chemistry, pressure, and muscle movement to regulate heart rate through the cardiac control centre.
• What is the function of adrenaline in heart rate regulation during exercise?

  Adrenaline stimulates the SAN, increasing both the speed and force of contraction.
• What is cardiovascular drift?

  • Increase in heart rate accompanied by a decrease in stroke volume
  • Occurs after 10 minutes in warm conditions
  • Caused by reduction of fluid in blood plasma due to sweating
• How does cardiovascular drift affect cardiac output during prolonged exercise?

  HR increases to maintain cardiac output despite a decrease in SV due to increased blood viscosity.
• What are the characteristics of blood vessels?

  Veins - thin muscle because of low blood pressure, wider lumen

  Arteries - thick muscle, high blood pressure, narrow lumen

  capillaries - one cell thick, easy for gaseous exchange
• What are the active mechanisms for venous return?

  skeletal muscle pump - contract and relax squeezing the blood

  respiratory pump - contract and relax during inspiration and expiration to change pressure of veins to compress them

  Valves - prevent back flow of blood

  Thin smooth muscle - helps squeeze blood

  Gravity
• Explain the process of Starlings law?

  Increased Venous return, increased diastolic filling of the heart, cardiac muscle stretched, increased force of contraction, increased ejection fraction, increased stroke volume
• What is the role of the vasomotor centre in blood pressure and flow control?

  It controls both blood pressure and blood flow.
• Where is the vasomotor centre located?

  In the medulla oblongata of the brain.
• What triggers the vasomotor centre during exercise?

  Chemical changes such as increases in carbon dioxide and lactic acid.
• How do chemoreceptors contribute to blood flow redistribution during exercise?

  They detect chemical changes and send impulses to the vasomotor centre.
• What happens to sympathetic stimulation during exercise?

  An increase in sympathetic stimulation causes vasoconstriction.
• What is the effect of decreased sympathetic stimulation on blood vessels?

  It causes vasodilation.
• Why does vasodilation occur in arterioles supplying working muscles during exercise?

  To increase blood flow and supply more oxygen.
• What happens to arterioles supplying non-essential organs during exercise?

  Vasoconstriction occurs in these arterioles.
• What are pre-capillary sphincters?

  Tiny rings of muscle located at the openings of capillaries.
• How do pre-capillary sphincters aid in blood redistribution during exercise?

  They relax around the muscles to increase blood flow.
• What are the key reasons for blood redistribution during exercise?

  • Increase oxygen supply to working muscles
  • Remove waste products like carbon dioxide and lactic acid
  • Regulate body temperature by directing blood to the skin
  • Supply more blood to the heart for extra oxygen
• What does the arterio-venous oxygen difference (A-VO₂ diff) represent?

  The difference between the oxygen content of arterial blood arriving at the muscles and venous blood leaving the muscles.
• What happens to the A-VO₂ diff during exercise?

  It is high, indicating more oxygen is taken in and more carbon dioxide is removed.
• How does training affect the A-VO₂ diff?

  Trained performers can extract a greater amount of oxygen from the blood.