Physio: Lung and Renal Flashcards
Part of nervous system controlling bronchodilation
Sympathetic
Part of nervous system controlling bronchoconstriction
Parasympathetic
Differences between false vocal folds and true vocal folds
False folds are proximal and have glands under their epithelium. True vocal folds are distal and have skeletal muscle (the vocalis m.) beneath their epithelium.
Sequence of airways from largest to smallest
Trachea => primary bronchi => lobar bronchi (R3, L2) => segmented bronchi => smaller bronchi => bronchioles => terminal bronchioles => respiratory bronchioles => alveoli
What histology all feature marks the bronchi to bronchiole transition?
Bronchioles have no cartilage
What histological feature marks the bronchioles to alveoli transition?
The alveoli have no smooth muscle in their walls
What is a dust cell?
A macrophage in the lung
Structure and function of type I pneumocytes
Cells in alveolar epithelium with flat nuclei. They appear similar to squamous cells and can differentiate into type II pneumocytes
Structure and function of type II pneumocytes
Rounder and larger than type I pneumocytes, these cells secrete surfactant. They are often found at the junctions of alveolar walls
Mechanism of matching perfusion and ventilation
As PO2 in an alveolus drops, arteriolar resistance increases. This prevents blood flow to poorly ventilated areas. As PO2 increases, vascular resistance decreases.
Pressure in the lung
P(lung) = P(alveoli) - P(pleural space)
Compliance: definition and equation
D: the distensibility of a tissue
Compliance = dV/dP
At high volume, the lung has ______ compliance. At low volume, the lunch has ______ compliance.
Low; high
Concept of interdependence
Pressure in a smaller alveolus is higher than pressure in a lower alveolus. Mitigated with surfactant.
Surfactant function
Modulation of alveolar surface tension
How does surfactant balance pressure between large and small alveoli?
In small alveoli, it is more concentrated. Therefore the surface tension is lowered and the volume increases. In large alveoli, the diluted surfactant lowers surface tension less, and the volume decreases.
Functions or pleurae and pleural fluid
Maintain pressure differential
Fluid lubricates
Fluid helps maintain pleural connection
Effect of emphysema on compliance and respiratory function
Increases compliance, so tissue is more distensible.
Harder to expel air from lung.
Effect of fibrosis on compliance and respiratory function
Decreases compliance, so tissue is stiffer. It also increases the elastic recoil.
The lung collapses on filling and it is harder to force air into the lung.
Method by which O2 moves from alveoli to the blood and from blood to peripheral tissue
simple diffusion
Factors that proportionally affect rate of diffusion
- solubility of the gas in fluid (constant)
- difference in partial pressures between compartments
- cross sectional surface area
- temperature
Factors that inversely affect the rate of diffusion
- square root of molecular weight of gas (constant)
2. distance of diffusion
How has the respiratory system been anatomically optimized for rapid diffusion?
- there is a large surface area formed by the capillary sheets
- the membranes across which the gas must diffuse are very thin, and the alveolar lumen and the RBC are in close proximity to one another
structure of hemoglobin
two alpha chains and two beta chains form a larger molecule. Each chain contains a heme group, which binds one molecule of oxygen
What is allosteric binding in hemoglobin?
As one heme group binds/releases O2, the entire molecule undergoes a conformational change that facilitates the binding/release of the other molecules.
compare and contrast the oxygen-hemoglobin dissociation curve with the oxygen-myoglobin dissociation curve
The oxygen-hemoglobin dissociation curve has greater variability over the physiological range than the oxygen-myoglobin curve. Therefore, when partial pressure of O2 is high, hemoglobin is saturated. When it is low, hemoglobin releases oxygen. Myoglobin is saturated across the majority of the physiological range.
Explain the relationship between rest/exercise and partial pressure of oxygen in the interstitial tissue
During rest, arterial pO2 is about 94mmHg, giving a saturation of ~97%. Interstitial pO2 is about 40mmHg, giving saturation of ~72%. Therefore, hemoglobin supplies about 25% of is O2 content. While exercising, the interstitial pO2 decreases. this causes hemoglobin to supply more O2 to working tissue.
What products of exercise cause a shift in the O2-Hemoglobin dissociation curve (“Bohr effect”)?
Increased H+ (decreased pH), increased CO2, increased temperature, increased 2,3-BPG (glycolytic product)
How do increased H+ ions (decreased pH), increased CO2, increased temperature, and increased 2,3-BPG affect the O2-Hemoglobin dissociation curve?
Each of these things cause a shift to the right. This means that hemoglobin is less saturated at a given pO2 than it would normally be.
A decrease in these factors causes a shift to the left.
This is known as the Bohr Effect
How does anemia alter the supply of oxygen to peripheral tissue?
blood O2 carrying capacity is diminished
pO2 in the alveoli and hemoglobin saturation remain the same
may be compensated by cardiac output
How does CO poisoning alter oxygen supply to peripheral tissue?
CO irreversibly binds the heme group, preventing O2 transport. This reduces O2 saturation of hemoglobin. Additionally, carboxyhemoglobin causes the other subunits to increase O2 affinity (shift left)
pO2 in the alveoli remains the same
How is O2 transported in the blood?
97% bound to hemoglobin
3% dissolved in plasma/RBC cytoplasm
How is CO2 transported in the blood?
7% dissolved in cytoplasm/plasma
23% bound to protein (mostly hemoglobin)
70% is dissolved in the form of bicarbonate anions (HCO3-)
Write the chemical formula of the bicarbonate buffer
CO2 + H20 H2CO3 H+ + HCO3-
carbonic
anhydrase
What is the role of chlorine in the bicarbonate transport system?
Chlorine anions are exchanged for bicarbonate anions at the RBC plasma membrane via a bicarbonate-chloride exchanger protein.
It maintains electroneutrality in the RBC.
What is the “chloride shift”?
The change in intracellular chloride content. Venous blood has a higher concentration than arterial blood.
Explain how shifts in the CO2 dissociation curve happen (the Haldane effect)
O2 binding to hemoglobin causes CO2 to be released from the blood more effectively. This occurs because O2 binding to hemoglobin causes bound H+ ions to dissociate. These ions bind to bicarbonate to form carbonic acid, which dissociates into CO2 and water. CO2 is displaced directly by O2 binding.
Calculate pH from pCO2 and bicarbonate
pH = pK + log{ [HCO3-]p / [CO2 + H2CO3] }
= pK + log{ [HCO3-]p / 0.03 * pCO2] }
What part of the bicarbonate buffer system is under respiratory control, and what part is under renal control?
Respiratory system controls pCO2 directly
plasma HCO3- concentration is under renal control
Review the Davenport diagram from CO2 transport lecture
YOU BETTER DO IT TOO, FUCKER
Describe respiratory acidosis
increased arterial pCO2 => increased H+ and HCO3- => lower pH
arterial pCO2 > 44mmHg
blood pH < 7.35
What can cause respiratory acidosis?
decreased alveolar ventilation (drug overdose) decreased lung-diffusing capacity (pulmonary edema) decreased diffusion (acute respiratory distress)
How does the body compensate for respiratory acidosis?
The renal system increases HCO3- to return blood pH to normal levels
Describe respiratory alkalosis
decreased arterial pCO2 => decreased h+ and HCO3- => higher pH
arterial pCO2 < 35mmHg
blood pH > 7.45
What can cause respiratory alkalosis?
hypoxia
anxiety
drug toxicity
fever
How does the body compensate for respiratory alkalosis?
renal system decreases HCO3- to return blood pH to normal levels
What are some causes of metabolic acidosis and alkalosis?
renal failure shock diabetes mellitus vomiting/diarrhea (severe) **the respiratory system can compensate in these instances
Define hyperventilation
breathing is increased more than is required, resulting in lower arterial pCO2 than normal
define hypoventilation
breathing is decrased more than required, resulting in higher arterial pCO2 than normal
Define hyperpnea
increased breathing to match metabolic needs (during exercise)
What do central chemoreceptors detect changes in and where are they located?
They detect H+ ions. They are located in the brainstem, separate from the VRG and DRG.
CENTRAL CHEMORECEPTORS ARE NOT SENSITIVE TO HYPOXIA.
What do peripheral chemoreceptors detect changes in?
They detect changes in O2, CO2, and H+ ions.
Describe the two regulatory groups of cells that reside in the medulla to control breathing.
The dorsal regulatory group (DRG) and ventral regulatory group (VRG) are located in the medulla. The DRG is mainly inspiratory. The VRG is inspiratory and expiratory, including sending signals to the abdominals during exercise. They generate rhythm via a pacemaker effect.
Describe the pontine regulatory group (PRG)
There are two groups: the pneumotaxic center (upper pons) and the apneustic center (lower pons).
The pneumotaxic center turns off inspiration to make the switch to expiration. It is stimulated by medullary inspiratory neurons, which shortens inspiration and increases rate.
The apneustic center’s role is unclear.
How do central chemoreceptors detect changes in blood pH and pCO2?
The blood brain barrier prevents H+ ions and HCO3- from crossing into the brain. However, these ions react in the blood to form CO2, which easily crosses the barrier. Once across, they dissociate again to cause a drop in CSF pH, which stimulates chemoreceptors to send signals to the DRG to increase ventilation.
What is the difference between acute and chronic stimulation of central chemoreceptors?
Stimulation of the respiratory center by increased pCO2 declines over 1-2 days as HCO3- diffuses through the BBB and renal adaptation produces increased blood HCO3-.
The acute effect of pCO2 change is strong, but its chronic effect is weak after only a few days.
