Respiratory Physiology – Mechanics & Control of Breathing

These flashcards cover the mechanics of breathing, neural and chemical regulation, acid–base balance, and clinical correlations discussed in the lecture.

In which direction does air naturally flow in relation to pressure?

From regions of higher pressure to regions of lower pressure.

Which primary muscle creates pressure differences for breathing?

The diaphragm.

What happens to thoracic cavity volume when the diaphragm contracts?

Volume increases.

How does intrapulmonary pressure change when diaphragm contraction increases thoracic volume?

Intrapulmonary pressure decreases.

During inspiration, why does air enter the lungs after diaphragm contraction?

Atmospheric pressure becomes higher than intrapulmonary pressure, so air flows in.

What changes occur when the diaphragm relaxes?

Thoracic volume decreases, intrapulmonary pressure rises, and air is expelled.

At rest, why is there no airflow between atmosphere and alveoli?

Atmospheric and intrapulmonary pressures are equal.

Numerically, what does a −3 mm Hg intrapulmonary pressure indicate?

Alveolar pressure is 3 mm Hg lower than atmospheric, driving air into the lungs.

Which brain‐stem regions house the respiratory centers for unconscious breathing?

The medulla oblongata and pons.

What is Odin’s curse (congenital central hypoventilation syndrome)?

A disorder in which a person must consciously think about breathing because automatic control is lost.

Give the chemical equation linking CO₂, water, carbonic acid, and bicarbonate.

CO₂ + H₂O ⇌ H₂CO₃ ⇌ HCO₃⁻ + H⁺

What blood pH change results from increasing H⁺ concentration?

pH decreases (becomes more acidic).

Define hypercapnia.

An abnormally elevated level of CO₂ in the blood.

How can hypercapnia lead to respiratory acidosis?

Excess CO₂ drives the reaction toward more H⁺, lowering pH.

Which pulmonary disease often produces hypercapnia and respiratory acidosis?

Emphysema.

Differentiate respiratory vs. metabolic acidosis by typical clinical clues.

Respiratory acidosis: lung dysfunction/O₂ tank; Metabolic acidosis: uncontrolled diabetes (ketoacidosis).

What type of receptors monitor blood pH, CO₂, and O₂ levels?

Chemoreceptors.

Where are the most powerful central chemoreceptors located, and what do they monitor?

In the medulla, monitoring pH of cerebrospinal fluid (CSF).

Why is CSF pH a sensitive indicator for central chemoreceptors?

CSF lacks significant buffers, so pH changes rapidly with H⁺ concentration.

What ventilatory response occurs when CSF pH falls (acidity rises)?

Respiratory centers increase rate and depth of breathing to blow off CO₂.

Name two major peripheral chemoreceptor locations.

Carotid bodies (in carotid arteries) and aortic bodies (in aortic arch).

What is atelectasis and its usual mechanical cause?

Collapse of lung tissue due to separation of visceral and parietal pleura (loss of intrapleural negative pressure).

Define pulmonary compliance.

The ease with which the lungs expand; inverse of resistance to airflow.

Which immune mediator causes bronchoconstriction during allergic reactions?

Histamine.

What emergency drug counteracts severe histamine‐induced bronchoconstriction?

Epinephrine (administered via an EpiPen).

Why do yoga breathing exercises focus on prolonged exhalation?

To expel more CO₂, lower blood CO₂ levels, slow respiration rate, and promote relaxation.

How does elevated CO₂ affect heart rate via respiratory control?

High CO₂ (and low pH) stimulates increased respiration, which can raise heart rate; lowering CO₂ helps relax and slow heart rate.

Which direction does the CO₂/H₂CO₃/HCO₃⁻ reaction move when CO₂ accumulates?

Toward the right (producing more H⁺ and decreasing pH).

What is the inverse relationship between pH and H⁺ concentration?

As H⁺ concentration increases, pH decreases, and vice versa.

List two physiological buffers present in blood but largely absent from CSF.

Hemoglobin and plasma proteins.