Exam 3 slides 2 Flashcards

Question

Define saturation in terms of hemoglobin.

Answer 1

o A fully saturated Hgb molecule has all 4 heme groups bound to O2 o A partially saturated Hb molecule has 1-3 heme groups bound to O2 o The rate of loading/unloading O2 is regulated by PO2, temperature, blood pH, and PCO2 o Under normal, resting conditions arterial blood Hgb is 98% saturated o Under normal, resting conditions venous blood Hgb is 75% saturated o Venous Reserve: substantial amounts of O2 still available in venous blood

Answer 2

o O2 is loaded/unloaded by changes in the shape of Hgb o As O2 binds, Hgb’s affinity for O2 increases – efficient loading! o As O2 is released, Hgb’s affinity for O2 decreases – efficient unloading!

Answer 3

o The amount of O2 carried by Hgb depends on the PO2 ( the amount of O2 available locally) o If more O2 is present, more O2 is bound to Hgb o If less O2 is present, less O2 is bound to Hgb o Safety Margin: At a high PO2, Hgb stays almost fully saturated even with a large change in PO2 o Efficiency: At a low PO2, Hgb experiences sharp decreases in saturation with similar changes in PO2 o Curve will shift to the right when PCO2, temperature, or H+ rise o Curve will shift to the left when PCO2, temperature, or H+ fall

Answer 4

o Active body cells produce about 200mL of CO2 /minute o CO2 is transported in blood in 3 forms: o 7-10% dissolved in plasma o 20% bound to globin of hemoglobin (as HbCO2 or carbaminohemoglobin) o 70% as bicarbonate ions (HCO3-) in plasma

Answer 5

o Most CO2 molecules entering plasma quickly enter RBCs o Inside RBCs, CO2 combines with water to form carbonic acid  CO2 + H2O -> H2CO3 o Carbonic acid is unstable and dissociates into hydrogen and bicarbonate ions  H2CO3 -> H+ and HCO3- o Carbonic Anhydrase: enzyme found in RBCs that catalyzes the above reactions

Answer 6

o Once generated, HCO3- moves from RBCs into plasma and is carried to the lungs  Movement of HCO3- out of the RBCs is counterbalanced by movement of Cl- into the RBCs o Inside the lungs, HCO3- moves back into RBCs and Cl- moves out o HCO3- will bind with H+ to form H2CO3 o H2CO3 is split by carbonic anhydrase into CO2 and H2O o CO2 is diffused from the blood into the alveoli and expelled

Answer 7

o Bohr  O2 unloading from Hgb is enhanced by an increased PCO2  Enhances O2 delivery where it is most needed  Ex: an exercising thigh muscle o Haldane  CO2 unloading from Hgb is enhanced by an increased PO2  Enhances CO2 delivery for expiration  Ex: pulmonary circulation

Answer 8

o Bicarbonate Buffer System: important for resisting shifts in blood pH o If H+ concentration increases, H+ is removed by forming H2CO3 o If H+ concentration decreases, H2CO3 dissociates into H+ o Slow, shallow breathing allows CO2 to accumulate – carbonic acid forms, and pH drops – Respiratory Acidosis o Rapid, deep breathing depletes CO2 – carbonic acid is reduced, and pH rises – Respiratory Alkalosis o Ventilation provides a fast-acting system to adjust blood pH when it is disturbed by metabolic factors

Answer 9

o Slow, shallow breathing allows CO2 to accumulate – carbonic acid forms, and pH drops – Respiratory Acidosis o Rapid, deep breathing depletes CO2 – carbonic acid is reduced, and pH rises – Respiratory Alkalosis

Answer 10

o Inadequate delivery of O2 to the body’s tissues o Symptom: cyanosis when Hbg saturation dips below 75% o Types: o Anemic Hypoxia: too few RBCs or abnormal RBCs o Ischemic Hypoxia: impaired/blocked blood circulation o Histotoxic Hypoxia: body cells are unable to use delivered O2 o Hypoxemic Hypoxia: reduced arterial PO2 o CO Poisoning: CO outcompetes O2 for heme binding sites

Answer 11

o Control of respiration primarily involves neurons in the reticular formation of the medulla and the pons o Medullary Respiratory Centers:  1- Ventral Respiratory Group (VRG): rhythm generating * Impulses for inspiration travel along the phrenic and intercostal nerves * Eupneic respiratory rate of ~12-16 breaths/minute  2- Dorsal Respiratory Group (DRG): integration center * Integrates inputs from stretch and chemoreceptors and communicates them to the VRG o Respiration stops when VRG neurons are completely suppressed o Depth of ventilation is determined by the intensity of the stimulation to the inspiratory muscles o Chemoreceptors: receptors responding to chemical fluctuations in the blood – the amounts of H+, CO2, O2 o The level of CO2 is the most potent and closely monitored – a rise in CO2 triggers increases in the rate + depth of respiration

Answer 12

Depth of ventilation is determined by the intensity of the stimulation to the inspiratory muscles

Answer 13

Control of respiration primarily involves neurons in the reticular formation of the medulla and the pons Medullary Respiratory Centers: 1- Ventral Respiratory Group (VRG): rhythm generating Impulses for inspiration travel along the phrenic and intercostal nerves Eupneic respiratory rate of ~12-16 breaths/minute 2- Dorsal Respiratory Group (DRG): integration center Integrates inputs from stretch and chemoreceptors and communicates them to the VRG Respiration stops when VRG neurons are completely suppressed Depth of ventilation is determined by the intensity of the stimulation to the inspiratory muscles Chemoreceptors: receptors responding to chemical fluctuations in the blood – the amounts of H+, CO2, O2 The level of CO2 is the most potent and closely monitored – a rise in CO2 triggers increases in the rate + depth of respiration

Answer 14

Working muscles consume O2 and produce CO2 Ventilation will increase 10-20 fold Hypernea: increased ventilation in response to metabolic needs “the limitation is not the lungs” Hyperventilation: an increase in the rate + depth of breathing – exceeds the body’s need to remove CO2 Often happens involuntarily during times of stress and anxiety Leads to reduced levels of CO2 in the blood and vascular constriction Symptoms: decreased perfusion, tingling/numbness, dizziness, fainting

Answer 15

o Hyperventilation: an increase in the rate + depth of breathing – exceeds the body’s need to remove CO2 o Often happens involuntarily during times of stress and anxiety o Leads to reduced levels of CO2 in the blood and vascular constriction o Symptoms: decreased perfusion, tingling/numbness, dizziness, fainting

Answer 16

o Hypothalamic Controls: strong emotions and pain send signals to the respiratory centers – responses are mediated through the limbic system and the hypothalamus  Ex: gasping in shock, breath holding in anger, hyperventilation in excitement o Cortical Controls: taking conscious control of respiratory rate - direct impulses from the cerebral motor cortex – medullary controls are bypassed  Ex: voluntary breath holding – the VRG with be automatically reinitiated when CO2 concentrations reach critical levels

Answer 17

o Emphysema or Chronic Bronchitis  Irreversible decrease in the ability to force air out of the lungs  Emphysema: permanent enlargement/destruction the alveoli and pulmonary capillaries, use of accessory muscles, hyperinflation of the lungs  Chronic Bronchitis: chronic and excessive mucus production, inflamed lower respiratory tact, obstructed airways, impaired ventilation o Other common features:  80% of people with a COPD have a smoking history  Dyspnea: “air hunger”, labored breathing  Coughing + frequent pulmonary infections  Development of respiratory failure – hypoventilation, respiratory acidosis, hypoxemia o Treatments: bronchodilators, corticosteroids, supplemental O2

Answer 18

o A short-term or reversible COPD o Affects about 1:10 Americans – children > adults o Symptoms: coughing, dyspnea, wheezing, and chest tightness o Active inflammation of airways proceeds bronchospasms o Airways are inflamed by immune response, thickened with inflammatory exudate o Common triggers: dust mites, cats, dogs, fungi o Treatments: bronchodilators, corticosteroids

Answer 19

o Obstructive Sleep Apnea (OSA): collapse of the upper airway, musculature of the pharynx relaxes during sleep o Central Sleep Apnea: reduced drive from the brain’s respiratory centers