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Respiratory Bohr Effect Alterations in hemoglobin’s structure Alterations in hemoglobin’s structure Shift to the right in the oxyhemoglobin dissociation.

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Presentation on theme: "Respiratory Bohr Effect Alterations in hemoglobin’s structure Alterations in hemoglobin’s structure Shift to the right in the oxyhemoglobin dissociation."— Presentation transcript:

1 respiratory Bohr Effect Alterations in hemoglobin’s structure Alterations in hemoglobin’s structure Shift to the right in the oxyhemoglobin dissociation curve Shift to the right in the oxyhemoglobin dissociation curve Loading of O 2 is not affected Loading of O 2 is not affected –the flat upper portion is not altered Unloading of O 2 is enhanced Unloading of O 2 is enhanced –along steep lower portion, more O 2 is unloaded at a given PO 2 with the shift

2 respiratory

3 Myoglobin and Muscle Oxygen Storage Skeletal & cardiac muscle contain compound myoglobin. Skeletal & cardiac muscle contain compound myoglobin. Each myoglobin contains only one heme in contrast to 4 in hemoglobin (Hb). Each myoglobin contains only one heme in contrast to 4 in hemoglobin (Hb). Myoglobin binds and retains O 2 at low pressures. Myoglobin binds and retains O 2 at low pressures. Facilitates oxygen transfer to mitochondria at start of exercise and intense exercise when cellular PO 2 ↓ greatly. Facilitates oxygen transfer to mitochondria at start of exercise and intense exercise when cellular PO 2 ↓ greatly.

4 respiratory Carbon Dioxide Transport in the Blood Dissolved in plasma Dissolved in plasma –CO 2 is 20 times more soluble than O 2 –7% to 10% of CO 2 is dissolved Combined with amino compounds Combined with amino compounds –hemoglobin is most common –Haldane effect: Hb’s de-oxygenation enables bind CO 2 –about 20% of CO 2 is carried as carbamino compounds Bicarbonate Bicarbonate –about 70% carried as bicarbonate

5 respiratory Carbon Dioxide Transport in the Blood

6 respiratory Formation of Bicarbonate at Tissue Level CO 2 diffuses into RBC CO 2 diffuses into RBC Enzyme, carbonic anhydrase, absent in plasma but present in RBC drives reaction of CO 2 + H 2 O => H 2 CO 3 Enzyme, carbonic anhydrase, absent in plasma but present in RBC drives reaction of CO 2 + H 2 O => H 2 CO 3 H 2 CO 3 dissociates a proton => HCO H + H 2 CO 3 dissociates a proton => HCO H + CO 2 + H 2 O => H 2 CO 3 => HCO H + CO 2 + H 2 O => H 2 CO 3 => HCO H + HCO 3 - moves into plasma via HCO 3 - / Cl - anion exchanger to prevent electrical imbalance HCO 3 - moves into plasma via HCO 3 - / Cl - anion exchanger to prevent electrical imbalance Hb acts as buffer and accepts the H + Hb acts as buffer and accepts the H +

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8 respiratory Bicarbonate in the Lungs In lungs, carbon dioxide diffuses from plasma into alveoli; lowers plasma P CO 2. In lungs, carbon dioxide diffuses from plasma into alveoli; lowers plasma P CO 2. HCO H + recombine to form carbonic acid. HCO H + recombine to form carbonic acid. H 2 CO 3 dissociates to H 2 O and CO 2, allowing carbon dioxide to exit through the lungs. H 2 CO 3 dissociates to H 2 O and CO 2, allowing carbon dioxide to exit through the lungs. CO 2 + H 2 O <= H 2 CO 3 <= HCO H + CO 2 + H 2 O <= H 2 CO 3 <= HCO H +

9 respiratory Ventilatory Regulation Two factors regulate pulmonary ventilation: Neural input from higher brain centers provides primary drive to ventilate Neural input from higher brain centers provides primary drive to ventilate Gaseous and chemical state of blood: humoral factors Gaseous and chemical state of blood: humoral factors

10 respiratory Pulmonary Ventilation Control Clusters neurons in medulla oblongata referred to as respiratory center. Clusters neurons in medulla oblongata referred to as respiratory center. Inspiratory center activates diaphragm & intercostals. Inspiratory center activates diaphragm & intercostals. Expiratory center inhibits inspiratory neurons. Expiratory center inhibits inspiratory neurons. Stretch receptors assist regulation of breathing Stretch receptors assist regulation of breathing Pneumotaxic & apneustic centers contribute (depth). Pneumotaxic & apneustic centers contribute (depth).

11 respiratory Humoral Factors Chemoreceptors are specialized neurons. Chemoreceptors are specialized neurons. Chemoreceptors monitor blood conditions, provide feedback Chemoreceptors monitor blood conditions, provide feedback –Peripheral located in aortic arch and bifurcation of common carotid respond to CO 2, “temperature”-no, H + –Central located in medulla affected by PCO 2 & H + Specialized receptors in lungs sensitive to stretch and irritants act to provide feedback Specialized receptors in lungs sensitive to stretch and irritants act to provide feedback Interaction among factors controls ventilation Interaction among factors controls ventilation –CO 2 production is closely associated with ventilation rate

12 respiratory Receptor Location and Function Central chemoreceptors located within the medulla Central chemoreceptors located within the medulla – respond to changes in PCO 2 & H + in cerebral spinal fluid –ventilation increases with elevations of PCO 2 or H +

13 respiratory Receptor Location and Function Peripheral chemoreceptors located in aortic arch and common carotid arteries Peripheral chemoreceptors located in aortic arch and common carotid arteries –respond to changes in PO 2, PCO 2 and H + –at sea level changes in PO 2 have little effect on V E

14 respiratory Ventilatory Control at Rest Carbon dioxide pressure in arterial plasma (P a CO 2 ) provides the most important respiratory stimulus at rest. Urge to breathe after 40 s breath-holding results mainly from increased arterial PCO 2. Hyperventilation decreases Alveolar PCO 2 to 15 mm Hg, which decreases P a CO 2 below normal, allows longer breath holding.

15 respiratory Ventilatory Control in Exercise Very rapid increase at start of exercise Very rapid increase at start of exercise Chemical stimuli cannot explain initial hyperpnea during exercise. Chemical stimuli cannot explain initial hyperpnea during exercise. Nonchemical factors mediate the rapid response Nonchemical factors mediate the rapid response –Cortical: motor cortex –Peripheral: mechanoreceptors in joints, tendons and muscles

16 respiratory Integrated Response Control of breathing is not result of a single factor but of combined result of several chemical and neural factors. Composite of ventilatory response to exercise.

17 respiratory References Axen and Axen Illustrated Principles of Exercise Physiology. Prentice Hall. Axen and Axen Illustrated Principles of Exercise Physiology. Prentice Hall. Kapit, Macey, Meisami Physiology Coloring Book. Harper & Row. Kapit, Macey, Meisami Physiology Coloring Book. Harper & Row. McArdle, Katch, Katch Image Collection Essentials of Exercise Physiology, 3 rd ed. Lippincott William & Wilkens. McArdle, Katch, Katch Image Collection Essentials of Exercise Physiology, 3 rd ed. Lippincott William & Wilkens.


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