Respiratory System Part 3

Vocabulary flashcards covering key terms and concepts from the Respiratory System Part 3 lecture notes, including lung volumes, gas laws, hemoglobin physiology, gas transport, and neural control of breathing.

Respiratory Rate (RR)

Number of breaths taken per minute.

Tidal Volume (TV)

Volume of air inhaled or exhaled in one quiet breathing cycle (≈ 500 mL in an average adult male).

Respiratory Minute Volume (Pulmonary Ventilation)

Total amount of air moved into or out of the respiratory tract each minute; calculated as RR × TV.

Anatomic Dead Space

Air remaining in the conducting passages that does not reach alveoli and cannot participate in gas exchange.

Alveolar Ventilation

Volume of air reaching alveoli per minute; (TV – Anatomic Dead Space) × RR.

Inspiratory Reserve Volume (IRV)

Extra air that can be inhaled with maximal effort after a normal inspiration (≈ 3,000 mL).

Expiratory Reserve Volume (ERV)

Extra air that can be exhaled with maximal effort after a normal expiration (≈ 1,200 mL).

Residual Volume (RV)

Air remaining in lungs after maximal expiration (≈ 1,300 mL); cannot be voluntarily exhaled.

Vital Capacity (VC)

Maximum amount of air that can be exhaled after a maximal inhalation (VC = IRV + TV + ERV ≈ 4,700 mL).

Inspiratory Capacity (IC)

Maximum amount of air that can be inhaled after a normal expiration (IC = TV + IRV ≈ 3,500 mL).

Functional Residual Capacity (FRC)

Air remaining in lungs after a normal tidal expiration (FRC = RV + ERV ≈ 2,500 mL).

Total Lung Capacity (TLC)

Maximum amount of air the lungs can hold (TLC = RV + VC ≈ 6,000 mL).

Forced Expiratory Volume in 1 Second (FEV1)

Percentage of vital capacity exhaled in the first second of a forced expiration; normal = 75–85 %.

Obstructive Lung Disease

Condition characterized by difficulty exhaling (air trapping), ↓FEV1, ↓FEV1/FVC ratio < 70 %; e.g., COPD, asthma, emphysema.

Restrictive Lung Disease

Condition characterized by difficulty inhaling (reduced lung expansion), ↓FEV1 and ↓FVC with normal or ↑FEV1/FVC ratio; e.g., pulmonary fibrosis, severe obesity.

Chronic Bronchitis

Type of COPD marked by productive cough ≥ 3 months/year for ≥ 2 years; “blue bloater.”

Emphysema

Type of COPD involving permanent enlargement & destruction of distal airspaces; “pink puffer.”

Chronic Obstructive Pulmonary Disease (COPD)

Progressive obstructive disorder, usually caused by smoking, combining chronic bronchitis and/or emphysema.

Boyle’s Law

Gas pressure is inversely proportional to volume (P ∝ 1/V) at constant temperature.

Dalton’s Law

Total pressure of a gas mixture equals the sum of the partial pressures of each component gas.

Henry’s Law

Amount of gas dissolved in a liquid is proportional to its partial pressure and solubility at a given temperature.

Partial Pressure (Pgas)

Pressure exerted by a single gas in a mixture; determines its diffusion direction.

Composition of Dry Air

≈ 78 % N₂, 20.9 % O₂, 0.04 % CO₂, 0.5 % H₂O vapor at sea level.

Decompression Sickness (The Bends)

Condition from rapid ascent in diving; dissolved N₂ forms bubbles in tissues, causing pain & neurologic signs.

Solubility of CO₂

High; CO₂ dissolves readily in body fluids, enabling transport mostly as bicarbonate.

Oxyhemoglobin Dissociation Curve

Graph showing percentage saturation of hemoglobin versus PO₂; sigmoidal due to cooperative binding.

Hemoglobin Saturation

Percentage of heme sites bound to O₂ at a given PO₂.

Positive Cooperativity

Binding of one O₂ to hemoglobin increases affinity of remaining sites for O₂.

Bohr Effect

Decrease in blood pH or increase in CO₂ shifts Hb–O₂ curve right, promoting O₂ unloading to tissues.

2,3-Biphosphoglycerate (2,3-BPG)

RBC metabolite that binds deoxyhemoglobin, stabilizing T-state and decreasing O₂ affinity (right shift).

T-State Hemoglobin

Low-affinity, deoxygenated conformation of hemoglobin.

R-State Hemoglobin

High-affinity, fully oxygenated conformation of hemoglobin.

Fetal Hemoglobin (HbF)

Hemoglobin with γ-chains that bind 2,3-BPG poorly, giving higher O₂ affinity than adult HbA.

Carbaminohemoglobin

Complex formed when CO₂ binds to globin’s amino groups (not the heme iron) of hemoglobin.

Chloride Shift

Exchange of HCO₃⁻ out of RBCs for Cl⁻ into RBCs, maintaining electric neutrality during CO₂ transport.

Haldane Effect

High O₂ levels decrease Hb’s affinity for CO₂ (and H⁺), promoting CO₂ release in lungs; low O₂ does opposite.

Hypercapnia

Elevated arterial PCO₂, often from hypoventilation; leads to respiratory acidosis and stimulates ventilation.

Hypocapnia

Low arterial PCO₂, usually from hyperventilation; causes respiratory alkalosis and decreases ventilation drive.

Pre-Bötzinger Complex

Cluster of neurons in medulla that acts as the pacemaker setting basic respiratory rhythm.

Dorsal Respiratory Group (DRG)

Medullary center with inspiratory neurons active during quiet breathing; integrates sensory input.

Ventral Respiratory Group (VRG)

Medullary center with inspiratory & expiratory neurons; drives forced breathing during high demand.

Pontine Respiratory Group (PRG)

Group in pons that fine-tunes breathing by modifying VRG/DRG output; includes pneumotaxic & apneustic centers.

Apneustic Center

Pontine area that prolongs inspiration by preventing inspiratory neurons from switching off.

Pneumotaxic Center

Pontine area that sends ‘off’ signals to end inspiration, limiting tidal volume; overrides apneustic center.

Hering-Breuer Reflex

Inflation reflex mediated by lung stretch receptors that terminates inspiration to prevent overinflation.

Peripheral Chemoreceptors

Receptors in carotid & aortic bodies sensing blood pH, PO₂, and (to lesser extent) PCO₂; signal via CN IX & X.

Central Chemoreceptors

Receptors on ventrolateral medulla that monitor CSF pH reflecting arterial PCO₂.

Irritant Receptors

Airway receptors that respond to chemicals or particulates, triggering cough or bronchoconstriction via vagus.

Stretch Receptors

Pulmonary mechanoreceptors that detect lung inflation and initiate the Hering-Breuer reflex.

Respiratory Alkalosis

Blood pH > 7.45 due to CO₂ loss from hyperventilation.

Respiratory Acidosis

Blood pH < 7.35 due to CO₂ retention from hypoventilation.

Hyperbaric Oxygen Therapy

Treatment delivering O₂ at high pressure; used for decompression sickness and CO poisoning.