Respiratory System – Exam Review Flashcards

30 question-and-answer flashcards covering ventilation mechanics, gas laws, gas exchange, hemoglobin properties, carbonic acid buffering, and neural control of breathing.

What is ventilation and how is it commonly expressed when measured?

Ventilation is the mechanical movement of air into and out of the lungs, usually expressed as volume per unit time (e.g., liters / minute).

How does airflow relate to pressure differences and resistance?

Airflow is directly proportional to the pressure gradient between two points and inversely proportional to airway resistance (Flow = ΔP / R).

According to Boyle’s law, what happens to gas pressure when the volume of its container increases or decreases?

Pressure decreases when volume increases and increases when volume decreases (P ∝ 1/V).

How do changes in pleural cavity volume create inhalation and exhalation?

Increasing pleural volume lowers intrapulmonary pressure below atmospheric, drawing air in (inhalation); decreasing pleural volume raises pressure above atmospheric, pushing air out (exhalation).

What creates resistance to airflow in the respiratory tract?

Airway diameter (especially in bronchioles) is the main source of resistance; mucus, smooth-muscle tone, and airway obstruction also contribute.

How can the autonomic nervous system alter airway resistance?

Sympathetic stimulation causes bronchodilation (↓ resistance); parasympathetic stimulation causes bronchoconstriction (↑ resistance), adjusting airflow during exercise, rest, or irritant exposure.

Using Dalton’s law, define partial pressure of a gas.

Partial pressure is the pressure a gas would exert if it alone occupied the volume; it equals its fractional concentration multiplied by total pressure.

What are the typical PO₂ and PCO₂ of dry atmospheric air at sea level?

PO₂ ≈ 160 mm Hg; PCO₂ ≈ 0.3 mm Hg.

How does partial pressure drive gas diffusion?

Gases diffuse from regions of higher partial pressure to regions of lower partial pressure until equilibrium is reached.

What are the PO₂ and PCO₂ in alveolar air versus deoxygenated pulmonary blood, and how do they move during external respiration?

Alveolar air: PO₂ ≈ 104 mm Hg, PCO₂ ≈ 40 mm Hg; deoxygenated blood: PO₂ ≈ 40 mm Hg, PCO₂ ≈ 45 mm Hg. O₂ diffuses into blood; CO₂ diffuses into alveoli.

Define external respiration in 1–2 sentences.

External respiration is the exchange of gases between alveolar air and pulmonary capillary blood, driven by partial-pressure gradients.

According to Henry’s law, what three factors determine how much gas dissolves in a liquid?

Partial pressure of the gas, solubility of the gas in the liquid, and temperature of the liquid.

How and why does oxygen bind to hemoglobin for transport?

Each hemoglobin molecule reversibly binds up to four O₂ molecules via its heme iron, greatly increasing blood O₂-carrying capacity because O₂ has low solubility in plasma.

Define internal respiration in 1–2 sentences.

Internal respiration is the exchange of gases between systemic capillary blood and tissue cells driven by local partial-pressure gradients.

Describe O₂ and CO₂ movement during internal respiration.

O₂ diffuses from blood (PO₂ ≈ 95 mm Hg) into cells (PO₂ ≈ 40 mm Hg); CO₂ diffuses from cells (PCO₂ ≈ 46 mm Hg) into blood (PCO₂ ≈ 40 mm Hg).

What is the primary factor governing hemoglobin’s binding or release of oxygen?

The partial pressure of oxygen (PO₂) is the main determinant, illustrated by the O₂-Hb dissociation curve.

Approximately what percentage saturation is hemoglobin near the alveoli and near systemic tissues at rest?

About 98 % saturated in alveolar blood and ~75 % saturated in systemic venous blood after passing through tissues.

Name three factors that shift the O₂-hemoglobin dissociation curve and explain a rightward shift.

Increased CO₂/acidity (↓pH), increased temperature, and increased 2,3-BPG shift the curve right, meaning hemoglobin releases O₂ more readily at a given PO₂.

What does a leftward shift of the dissociation curve indicate?

Hemoglobin has a higher affinity for O₂, leading to less O₂ release to tissues at a given PO₂ (e.g., lower CO₂, lower temperature, lower 2,3-BPG).

How does carbon monoxide affect oxygen-hemoglobin binding and the dissociation curve?

CO binds hemoglobin with ~200× the affinity of O₂, reducing available binding sites and shifting the curve left, impairing O₂ release to tissues.

Define chemical equilibrium in a reversible reaction.

Chemical equilibrium occurs when forward and reverse reaction rates are equal, so reactant and product concentrations remain constant.

Write the carbonic acid equilibrium equation in blood.

CO₂ + H₂O ⇌ H₂CO₃ ⇌ H⁺ + HCO₃⁻.

What is a buffer, and why is carbonic acid/bicarbonate the blood’s main buffer?

A buffer resists pH change by reversibly binding H⁺; the H₂CO₃/HCO₃⁻ system is abundant in blood and can be rapidly adjusted via respiration and renal function.

According to the equilibrium, how does raising CO₂ affect blood pH?

Higher CO₂ drives the reaction right, increasing H⁺ concentration and lowering pH (more acidic).

How does ventilation rate influence blood CO₂ and pH?

Increased ventilation blows off CO₂, lowering H⁺ and raising pH (alkalosis); decreased ventilation retains CO₂, raising H⁺ and lowering pH (acidosis).

What are chemoreceptors and where are CO₂-sensitive ones located?

Chemoreceptors detect chemical changes; central chemoreceptors in the medulla and peripheral chemoreceptors in carotid and aortic bodies sense CO₂/H⁺ levels.

Where is the respiratory control center located?

Primarily in the medulla oblongata (with modulatory centers in the pons).

Outline the negative-feedback loop regulating ventilation.

Stimulus: altered blood CO₂/H⁺; Receptors: central & peripheral chemoreceptors; Control center: medullary respiratory centers; Effectors: diaphragm & respiratory muscles; Response: ventilation adjusts to restore CO₂/pH toward normal.

What ventilatory response occurs to elevated blood CO₂ or increased acidity?

Chemoreceptor stimulation increases ventilation depth and rate, reducing CO₂ and H⁺ levels.

What ventilatory response occurs to reduced blood CO₂ or increased basicity?

Chemoreceptor activity decreases, ventilation slows/shallow, retaining CO₂ and raising H⁺ to correct alkalinity.