Ch 22: Respiratory Part 2 Flashcards
What is internal respiration?
Capillary gas exchange in body tissues
Describe the molecular O2 in the blood
1.5% dissolved in plasma
98.5% loosely bound to each Fe of hemoglobin
What is the term for hemoglobin-O2 combination?
Oxyhemoglobin
What is the term when hemoglobin releases O2?
Deoxyhemoglobin
What make a fully saturated Hb?
4 heme groups that carry O2
What makes a Hb partially saturated?
1-3 hemes with O2
What happens when the Hb affinity for O2 increases?
O2 binds
What happens when the Hb affinity for O2 decreases?
O2 released
What factors effect the rate of loading and unloading of O2 regulation for delivery to cells?
- Po2
- Temperature
- Blood pH
- Pco2
- Concentration of BPG
Describe the influence of Po2 on hemoglobin saturation
According to the O2-hemoglobin dissociation curve, hemoglobin saturation plotted against Po2 creating an S curve
Binding and release of O2 influenced by Po2
What is the Hb saturation in arterial blood?
98%
What is the Hb saturation in venous blood?
75%
What is a venous reserve?
Oxygen remaining in venous blood
What happens in the factors influencing hemoglobin saturation increases?
- Modify structure of hemoglobin; decrease its affinity for O2
- Shift O2-hemoglobin dissociation curve to right
What happens in the factors influencing hemoglobin saturation decrease?
- Shifts curve to the left
2, Decreases O2 unloading from blood
What occurs when the cells metabolize glucose and use O2?
- Pco2 and H+ increase in capillary blood
- Declining blood pH and increasing Pco2
- Heat production increases -> directly and indirectly decreases Hb affinity for O2 -> increased O2 unloading to active tissues
What is the Bohr effect?
Hb-O2 bond weakens and oxygen unloading where needed most
What are the 3 forms CO2 is transported in the blood?
- 7 to 10% dissolved in plasma
- 20% bound to globin of hemoglobin (carbaminohemoglobin)
- 70% transported as bicarbonate ions (HCO3–) in plasma
What enzyme catalyzes CO2 + H2O -> carbonic acid?
Carbonic anhydrase
What occurs in systemic capillaries?
HCO3– quickly diffuses from RBCs into plasma
When would a chloride shift occur in systemic capillaries?
Outrush of HCO3– from RBCs balanced as Cl– moves into RBCs from plasma
What occurs in the pulmonary capillaries?
- HCO3– moves into RBCs (while Cl- move out); binds with H+ to form H2CO3
- H2CO3 split by carbonic anhydrase into CO2 and water
- CO2 diffuses into alveoli
What is the Haldane effect?
Amount of CO2 transported affected by Po2:
1. Reduced hemoglobin (less oxygen saturation) forms carbaminohemoglobin and buffers H+ more easily ->
2. Lower Po2 and hemoglobin saturation with O2; more CO2 carried in blood
How is carboaminohemoglobin created?
As HbO2 releases O2, it more readily forms bonds with CO2
What occurs during the carbonic acid-bicarbonate buffer system?
- If H+ concentration in blood rises, excess H+ is removed by combining with HCO3 -> H2CO3
- If H+ concentration begins to drop, H2CO3 dissociates, releasing H+
What is the alkaline reserve of the carbonic acid-bicarbonate buffer system?
HCO3-
How is pH and CO2 affected by shallow breathing?
Increased CO2 in blood causing a drop in pH
How is pH and CO2 affected by rapid breathing?
Decreased CO2 in blood causing a rise in pH
What controls respiration?
- Higher brain centers
- Chemoreceptors
- Neural controls in medulla and pons
What is eupnea?
Normal respiratory rate and rhythm
What are the components ventral respiratory group?
- Inspiratory neurons excite inspiratory muscles via phrenic (diaphragm) and intercostal nerves (external intercostals)
- Expiratory neurons inhibit inspiratory neurons
What are the components dorsal respiratory group?
Integrates input from peripheral stretch and chemoreceptors sending information to VRG
What is the importance of pontine respiratory centers?
- Influence and modify activity of VRG
- Smooth out transition between inspiration and expiration
- Transmit impulses to VRG -> modify and fine tune breathing rhythms during vocalization, sleep, exercise
What is one hypothesis that can explain the generation of the respiratory rhythm?
Pacemaker neurons with intrinsic rhythmicity
How is breathing rate determined?
Determined by how long inspiratory center active
How is the breathing depth determined?
Determined by how actively respiratory center stimulates respiratory muscles
Why are breathing rate and depth modified?
- Changing levels of CO2, O2, and H+
- Sensed by central and peripheral chemoreceptors
What occurs during hypercapnia?
- CO2 accumulates in brain
- CO2 in brain hydrated -> carbonic acid -> dissociates, releasing H+ -> pH drops
- H+ stimulates central chemoreceptors of brain stem
- Chemoreceptors synapse with respiratory regulatory centers -> increased depth and rate of breathing -> lower blood Pco2 -> pH rises
What is hyperventilation?
increased depth and rate of breathing that exceeds body’s need to remove CO2
What is the decrease in blood CO2 levels called?
Hypocapnia
What is apnea?
Breathing cessation; may be due to abnormally low Pco2
How does declining Po2 affect vasodilation?
- Huge O2 reservoir bound to Hb
- Requires substantial drop in arterial Po2 to stimulate increased ventilation
What is the purpose of Peripheral chemoreceptors in aortic and carotid bodies?
When excited, cause respiratory centers to increase ventilation
What mediated arterial pH?
peripheral chemoreceptors
How does the respiratory system controls raise pH?
Increasing respiratory rate and depth
What are the influences of higher brain centers for breathing?
- Hypothalamic controls
- Rise in body temperature
- Cortical controls
How does the hypothalamic controls affect breathing?
Modify rate and depth of respiration
How does the cortical controls affect breathing?
Direct signals from cerebral motor cortex that bypass medullary controls
How does the rise in temperature affect breathing?
Increases respiratory rate
What are irratants?
- Promote reflexive constriction of air passages
- Same irritant -> cough in trachea or bronchi; sneeze in nasal cavity
What is the Hering-Breuer Reflex?
Stretch receptors in pleurae and airways stimulated by lung inflation
