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  1. 2. Relationship between rate of respiration and oxygen and carbon dioxide contents <ul><li>During vigorous exercise (eg:running) </li></ul><ul><ul><li>Muscle cells need more oxygen and glucose to release energy </li></ul></ul><ul><ul><li>Rate of respiration increase </li></ul></ul><ul><ul><li>O 2 content decrease </li></ul></ul><ul><ul><li>CO 2 content increase </li></ul></ul><ul><li>To supply more O 2 and discharge more CO 2 ; </li></ul><ul><ul><li>Breathing rate increase </li></ul></ul><ul><ul><li>Heart beat increase </li></ul></ul><ul><ul><li>More O 2 supplied </li></ul></ul><ul><ul><li>More CO 2 removed </li></ul></ul>
  2. 3. Human respiratory response and rate of respiration in different situations <ul><li>Resting point (normal rate): </li></ul><ul><ul><li>Breathing rate range of 16 to 18 breaths per minute </li></ul></ul><ul><ul><li>Heartbeat rate range 60 to 70 per minute. </li></ul></ul><ul><li>Vigorous activities (swimming, running etc): </li></ul><ul><ul><li>Breathing rate increases up to 30 breaths per minute (increase in ventilation rate) </li></ul></ul><ul><ul><li>Heartbeat rate increases to 120 beats per minute </li></ul></ul><ul><li>In fear: </li></ul><ul><ul><li>Breathing and heartbeat rates increase to supply O2 to meet demand of higher respiration rate in cells. </li></ul></ul><ul><ul><li>Hormone adrenaline secreted by adrenal glands to increase heartbeat and breathing rate. </li></ul></ul><ul><ul><li>More glucose and oxygen supplied to the muscles. </li></ul></ul>
  3. 4. Regulatory mechanism of oxygen and carbon dioxide contents in the body <ul><li>Breathing is an involuntary process which is controlled by the respiratory center (located in the medulla oblongata of the brain) </li></ul><ul><li> Vigorous exercise </li></ul><ul><li>During vigorous exercise, partial pressure of CO2 increases </li></ul><ul><li>Higher level of CO2 results in pH value drop in blood and cerebrospinal fluid. </li></ul><ul><li>Drop in pH is detected by central chemoreceptors (in medulla oblongata) </li></ul>
  4. 5. <ul><li>Central chemoreceptors send nerve impulses  respiratory centre  diaphragm and intercostal muscles  respiratory muscles contract and relax faster  increase breathing and ventilation rate. </li></ul><ul><li>Excess CO 2 eliminated from the body </li></ul><ul><li>Concentration of CO 2 and pH value in blood return to normal level. </li></ul>
  5. 8. <ul><li>Very high altitudes (O 2 severely low) </li></ul><ul><li>Peripheral chemoreceptors (aortic bodies and carotid bodies) also sensitive to CO 2 content and pH of blood. </li></ul><ul><li>Peripheral chemoreceptors are stimulated  send nerve impulses  respiratory centre  respiratory muscles stimulated to contract and relax faster  breathing and ventilation rates increase </li></ul><ul><li>More O 2 inhaled </li></ul><ul><li>O 2 concentration returns to normal level </li></ul>