exam questions

• Which term describes the ability of heart muscle to contract without external stimulation?

  • myogenic
• Explain why it is necessary for the cardiac output of marathon runners to increase during a race(2)

  • increase supply of oxygenated blood to muscles
  • to allow aerobic respiration
  • to provide more energy to meet the increased demands
• Adrenaline acts on the heart to cause changes in heart rate.Deduce how adrenaline can cause a change in heart rate(4)

  • adrenaline carried in the blood
  • acts on the sinoatrial node
  • increasing the frequency of impulses produced by the SAN
  • increasing the rate at which the heart contracts
• Explain how starting to exercise causes an increase in breathing rate(3)

  • exercise initiates impulses from the motor cortex/stretch receptors in muscles
  • impulses sent to or from the ventillation centre in the medulla oblongata
  • leading to increased impulses to intercoastal muscles/diaphragm
• explain the effect of exercise on the changes in oxygen consumption(4)

  • excercise will increase oxygen consumption
  • because there is increased aerobic respiration
  • because more energy/ATP is needed by muscles
  • oxygen required to convert lactic acid into glucose/pyruvate
  • oxygen consumption begins to decrease after exercise
• describe how the SAN is involved in bringing about a change in heart rate as the level of activity increases(2)

  • more stimulation/depolarisation of the SAN(more impulses to the SAN)
  • causing more frequent waves of depolarisation from the SAN to the atria
  • leading to morw frequent contraction of atria/stimulation of AVN
• which area of the brain houses the ventillation centre that controls breathing rate(1)

  • medulla oblongata
• decribe the role played by stretch receptors in the lungs in controlling the ventilation rate(2)

  • stretch receptors are stimulated when the lungs fill with air
  • they sent impulses to the inspiritary centre in the medulla oblongata to inhibit inspiration
  • leads to stimulation of expiratory system to initiate exhalation
• compare and contrast the sympathetic and parasympathetic nervous systems in the control of heart rate during periods of exercise and rest(4)

  • BOTH neurones connect to the SAN
  • BOTH parts of the autonomic nervous system-happens without conscious thought
  • sympathetic neurones speed up heart WHEREAS parasympathetic slows it down
  • sympathetic prepares the body for action WHEREAS parasympathetic prepares for rest/recovery
  • release DIFFERENT neurotransmitters
• explain what causes an increase in heart rate while she walks(6)

  • The rate of respiration increases in their muscle cells
  • So the carbon dioxide concentration increases / pH falls
  • Which is detected by chemoreceptors in aortic/carotid bodies
  • (Chemoreceptors) send impulses to the medulla/cardiovascular control centre at an increased frequency; [1 mark]
  • cardiovascular control centre sends impulses along the sympathetic pathway to the SAN
  • SAN stimulated by noradrenaline
  • Waves of electrical activity spread across atria and ventricles at an increased frequency
• outline benefits of prostheses for park runners(2)

  • Encourage participation in (low-impact) sport/activity
  • To reduce weight gain / obesity
  • Reducing the risk of a sedentary/inactive lifestyle leading to heart disease / dementia
  • To provide freedom to walk / go outdoors
  • To reduce pain/discomfort
• outline the way in which a damaged cruciate ligament can be fixed surgically(2)

  • keyhole surgery
  • using small camera to remove damaged ligament tissue
  • replace with a graft from a tendon