Respiratory Physiology, Mechanics, and Pulmonary Terms

A complete set of vocabulary flashcards derived from the lecture notes covering respiratory regulation, airflow mechanics, lung volumes and capacities, and clinical respiratory terms.

Peripheral chemoreceptors

Sensory receptors located in the carotid and aortic bodies that detect low blood levels of oxygen and send impulses to the medulla to increase the rate and depth of respirations.

Central chemoreceptors

Sensory receptors located in the brainstem that monitor the pH of cerebrospinal fluid (CSF)—which mirrors blood carbon dioxide levels—and signal respiratory centers to increase breathing rate and depth when pH falls.

Hering-Breuer reflex

A mechanism where receptors in the lungs and chest wall detect stretching as the lungs inflate during inspiration and signal the respiratory centers to exhale and inhibit inspiration, preventing lung damage from overinflation.

Carbon dioxide

The primary regulator of respiration that easily crosses the blood-brain barrier; rising levels stimulate an increase in the rate and depth of respirations.

Atmospheric pressure

The weight of the air around us that drives respiration by creating pressure gradients between the outside air and the lungs.

Inspiration

An active process requiring muscle use (intercostals and diaphragm) where pressure within the lungs drops lower than atmospheric pressure, causing air to flow down the pressure gradient into the lungs.

Expiration

A passive process resulting from the recoil of healthy elastic lung tissue where pressure within the lungs rises above atmospheric pressure, pushing air out of the lungs.

Intrapleural pressure

The negative pressure maintained in the potential space between the parietal pleura and visceral pleura, which is slightly less than atmospheric pressure and creates a suction-like effect holding the lungs to the chest wall.

Intrapulmonic pressure

The pressure within the bronchi and alveoli that drops below atmospheric pressure as the lungs expand, driving air inflow.

Boyle's Law

A law of physics stating that at a constant temperature, the pressure of a given quantity of gas is inversely proportional to its volume.

Bronchodilation

An increase in the diameter of a bronchiole triggered by epinephrine and sympathetic nerves, which decreases resistance and increases airflow.

Bronchoconstriction

A reduction in the diameter of a bronchiole stimulated by parasympathetic nerves, histamine, cold air, and chemical irritants, which restricts airflow.

Pulmonary compliance

The elasticity of lung tissue, referring to the ability of the lungs and thorax to stretch and recoil during ventilation.

Surfactant

A lipoprotein secreted by alveolar cells that disrupts the electrical attraction between water molecules on the inner alveolar surface, lowering surface tension and preventing alveolar collapse.

Respiratory distress syndrome

A condition commonly developed by neonates born before $28\text{ weeks'}$ gestation due to a lack of surfactant, requiring administration of artificial surfactant.

Emphysema

A form of chronic obstructive pulmonary disease (COPD) in which alveolar walls are progressively destroyed, leading to loss of elastic recoil, trapped air, barrel chest, and airways collapse.

Barrel chest

A chest shape created over time when trapped air continuously enlarges the diameter of the chest, commonly seen in patients with emphysema.

Spirometer

A device through which a person breathes to measure lung capacities and volumes to provide information about lung health.

Tidal volume

The amount of air inhaled and exhaled during quiet breathing, typically about $500 reader\,ml$ in a healthy young adult.

Inspiratory reserve volume

The amount of air inhaled using maximum effort after a normal inspiration, typically about $3000\,ml$.

Expiratory reserve volume

The amount of air that can be exhaled using maximum effort after a normal expiration, typically about $1200\,ml$.

Residual volume

The amount of air (approximately $1300\,ml$) remaining in the lungs after a forced expiration that ensures gas exchange continues between breaths.

Vital capacity

The maximum amount of air that can be inhaled and exhaled with the deepest possible breath (tidal volume combined with inspiratory and expiratory reserve volumes, typically $4700\,ml$).

Total lung capacity

The maximum amount of air that the lungs can contain, calculated as vital capacity plus residual volume (typically $6000\,ml$).

Anatomical dead space

The conducting airways where approximately $150\,ml$ of inhaled air remains without reaching the alveoli, preventing it from participating in gas exchange.

Physiological dead space

All air in conducting airways (anatomical dead space) plus air in any alveoli that are poorly perfused and less efficient in gas exchange.

Apnea

Temporary cessation of breathing.

Biot's respirations

An abrupt, irregular breathing pattern in which periods of apnea alternate with periods of breathing that are consistent in rate and depth, often resulting from increased intracranial pressure.

Bradypnea

Abnormally slow breathing.

Cheyne-Stokes respirations

A cyclical breathing pattern beginning with an increase in rate and depth (crescendo effect) followed by a gradual decrease in rate and depth (decrescendo effect), culminating in a short period of apnea before repeating.

Dyspnea

Labored or difficult breathing.

Eupnea

Relaxed, quiet breathing.

Hyperpnea

An increased rate of breathing that may be physiological (such as during exercise) or pathological (such as from severe infection).

Hyperventilation

An increased rate of respirations resulting in lowered blood levels of carbon dioxide, often resulting from anxiety.

Hypoventilation

A reduced rate and depth of respirations, resulting in increased blood levels of carbon dioxide.

Kussmaul respiration

Very deep, gasping respirations associated with diabetic ketoacidosis.

Orthopnea

Labored breathing that occurs when a person is lying flat but improves when standing or sitting up, serving as a classic symptom of left ventricular heart failure.

Tachypnea

Rapid breathing.