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Think about… 3.1 Importance of regulating gas content in blood 3.2 Control of breathing

Think about… 3.1 Importance of regulating gas content in blood 3.2 Control of breathing 3.3 Control of heartbeat 3.4 Effects of exercise on breathing and cardiac output Recall ‘Think about…’ Summary concept map. CPR - a skill for life. c ardio p ulmonary r esuscitation ( 心肺復蘇法 ).

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Think about… 3.1 Importance of regulating gas content in blood 3.2 Control of breathing

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  1. Think about… 3.1 Importance of regulating gas content in blood 3.2 Control of breathing 3.3 Control of heartbeat 3.4 Effects of exercise on breathing and cardiac output Recall ‘Think about…’ Summary concept map

  2. CPR - a skill for life cardiopulmonary resuscitation (心肺復蘇法)

  3. CPR - a skill for life The survival chance is higher if patients are treated by CPR within 6 minutes after breathing and heartbeat have stopped.

  4. CPR - a skill for life CPR involves blowing exhaled air forcefully into the lungs and compressing the chest.

  5. CPR - a skill for life They are done alternately in rhythm until breathing and pulse resume.

  6. 1 Why does blowing exhaled air into the lungs of the patient help sustain life

  7. 2 What is the purpose of compressing the chest

  8. 3.1 Importance of regulating gas content in blood Which gas content in blood must be kept stable?

  9. 3.1 Importance of regulating gas content in blood oxygen content carbon dioxide content for respiration

  10. 3.1 Importance of regulating gas content in blood oxygen content carbon dioxide content • affects blood pH • affects functioning of enzymes

  11. 3.1 Importance of regulating gas content in blood oxygen content carbon dioxide content depend on • how fast the gases are exchanged in the air sacs • how fast blood is transported from the heart to the lungs and body cells

  12. 3.1 Importance of regulating gas content in blood oxygen content carbon dioxide content regulated by controlling breathing and heartbeat

  13. 3.1 Importance of regulating gas content in blood 1 Importance of regulating the gas content in blood: a To ensure there is a sufficient supply of oxygen to body cells for . respiration

  14. 3.1 Importance of regulating gas content in blood 1 Importance of regulating the gas content in blood: b To maintain a stable blood pH for in cells to function properly. enzymes

  15. 3.1 Importance of regulating gas content in blood 2 By controlling and breathing , the body can regulate heartbeat The gas content in blood.

  16. 3.2 Control of breathing • under the involuntary control by the medulla oblongata front back

  17. 3.2 Control of breathing Which part of the medulla oblongata controls breathing? respiratory centre contains chemoreceptors detect changes in carbon dioxide content and oxygen content in blood

  18. 3.2 Control of breathing chemoreceptors in: • carotid bodies • aortic bodies respiratory centre nerve impulses stretch receptors in lungs

  19. 3.2 Control of breathing chemoreceptors in: • carotid bodies • aortic bodies respiratory centre nerve impulses to respiratory muscles to trigger inhalation stretch receptors in lungs

  20. 3.2 Control of breathing respiratory centre stimulated when the lungs inflate Inhibitory nerve impulses stretch receptors in lungs

  21. 3.2 Control of breathing chemoreceptors in: • carotid bodies • aortic bodies respiratory centre when there is no impulse, exhalation occurs stretch receptors in lungs

  22. 3.2 Control of breathing chemoreceptors in: • carotid bodies • aortic bodies respiratory centre nerve impulses stretch receptors in lungs

  23. 3.2 Control of breathing How does the respiratory centre control breathing? • the basic rhythm is brought about by feedback mechanisms between the respiratory centre and stretch receptors

  24. 3.2 Control of breathing neurones inhibited stretch receptors stimulated respiratory centre inhalation exhalation stretch receptors no longer stimulated neurones stimulated

  25. 3.2 Control of breathing • one breath = inhalation + exhalation • rate of breathing (呼吸速率) = number of breaths per minute  measures how fast we breathe • depth of breathing (呼吸深度) = volume of air that we breathe in after an exhalation  measures how deeply we breathe

  26. 3.2 Control of breathing Effects of CO2 content in blood on breathing • respiratory centre responds to changes in blood pH • in blood: in body cells (high CO2 conc) HCO3- CO2 H2O H+ in air sacs (low CO2 conc) lowers blood pH

  27. 3.2 Control of breathing respiratory centre (contains chemoreceptors) faster and stronger contraction of intercostal muscles and diaphragm muscles chemoreceptors in aortic and carotid bodies rate and depth of breathing increase CO2 content in blood rises (blood pH falls) CO2 content falls normal CO2 content in blood

  28. 3.2 Control of breathing normal CO2 content in blood CO2 content rises CO2 content in blood falls (blood pH rises) rate and depth of breathing decrease slower and weaker contraction of intercostal muscles and diaphragm muscles chemoreceptors in aortic and carotid bodies respiratory centre (contains chemoreceptors)

  29. 3.2 Control of breathing 1 The feedback mechanisms between the and the respiratory centre in the lungs stretch receptors bring about the basic rhythm of breathing.

  30. 3.2 Control of breathing 2 When carbon dioxide content in blood rises, blood pH . This is detected by the in the respiratory centre, the aortic and carotid bodies. falls chemoreceptors

  31. 3.2 Control of breathing 2 The receptors send to the respiratory centre. The centre causes the muscles and nerve impulses intercostal muscles to contract diaphragm faster and more strongly. This increases the rate and depth of breathing. The opposite occurs when carbon dioxide content in blood falls.

  32. Animation 3.3 Control of heartbeat Which part of our body initiates heartbeat? • sinoatrial (SA) node (竇房結) a group of special cardiac muscles

  33. 3.3 Control of heartbeat Which part of our body initiates heartbeat? • sinoatrial (SA) node (竇房結) generates electrical impulses

  34. 3.3 Control of heartbeat Which part of our body initiates heartbeat? • sinoatrial (SA) node (竇房結) also called the pacemaker

  35. 3.3 Control of heartbeat aorta pulmonary artery anterior vena cava pulmonary veins left artrium right atrium left ventricle right ventricle posterior vena cava

  36. 3.3 Control of heartbeat • both atria contract at the same time pacemaker

  37. 3.3 Control of heartbeat • the ventricles contract after contraction of the atria atrio-ventricular (AV) node

  38. 3.3 Control of heartbeat Animation What happens in a cardiac cycle? the sequence of events that take place in one heartbeat

  39. 3.3 Control of heartbeat 0.1s 0.4s 0 0.8s 1Atria contract (atrial systole) • electrical impulses spread from the pacemaker to the atria • the atria contract relaxation / diastole atria contraction / systole ventricles

  40. 3.3 Control of heartbeat 0.1s 0.4s 0 0.8s 1Atria contract (atrial systole) • the ventricles are in a relaxed state • the semilunar valves are closed relaxation / diastole atria contraction / systole ventricles

  41. 3.3 Control of heartbeat 0.1s 0.4s 0 0.8s 2Ventricles contract (ventricular systole) • the atria relax • electrical impulses reach the ventricles and cause them to contract • this occurs about 0.1 s after the atria started contracting relaxation / diastole atria contraction / systole ventricles

  42. 3.3 Control of heartbeat 0.1s 0.4s 0 0.8s 2Ventricles contract (ventricular systole) • time is allowed for the ventricles to fill completely with blood before they contract • the pressure inside the ventricles increases as they contract, the semilunar valves are forced to open relaxation / diastole atria contraction / systole ventricles

  43. 3.3 Control of heartbeat 0.1s 0.4s 0 0.8s 2Ventricles contract (ventricular systole) • the tricuspid and bicuspid valves are forced to close  the first heart sound ‘lub’ relaxation / diastole atria contraction / systole ventricles

  44. 3.3 Control of heartbeat 0.1s 0.4s 0 0.8s 3Atria and ventricles relax (diastole) • both the atria and the ventricles are in a relaxed state • the semilunar valves are closed  the second heart sound ‘dub’ relaxation / diastole atria contraction / systole ventricles

  45. 3.3 Control of heartbeat 0.1s 0.4s 0 0.8s 3Atria and ventricles relax (diastole) • blood from the venae cavae and the pulmonary veins flows into the atria and the cycle repeats relaxation / diastole atria contraction / systole ventricles

  46. 3.3 Control of heartbeat What is cardiac output? • heart rate (心搏率) = number of heartbeats per minute When a person is at rest, the heart rate is about 60 to 80 beats/min.

  47. 3.3 Control of heartbeat What is cardiac output? • stroke volume (心搏量) = volume of blood pumped by each ventricle in one heartbeat When a person is at rest, the stroke volume is about 70 mL.

  48. 3.3 Control of heartbeat What is cardiac output? • cardiac output (心輸出量) = volume of blood pumped by each ventricle per minute cardiac output (mL/min) stroke volume (mL/beat) heart rate (beats/min) x =  measures the performance of the heart as a pump

  49. 3.3 Control of heartbeat How does the body control cardiac output? Nervous control Hormonal control

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