exam style questions

What happens to thoracic volume and intrapulmonary pressure when the diaphragm contracts?

Thoracic volume increases and intrapulmonary pressure decreases, allowing air to flow into the lungs.

Why doesn’t air flow into the lungs when pressures are equal?

Because air moves only from areas of higher pressure to lower pressure; equal pressures mean no gradient for airflow.

According to Boyle’s Law, how are pressure and volume related?

They are inversely proportional — as lung volume increases, pressure inside decreases.

According to Dalton’s Law, what determines how gases diffuse?

Each gas moves independently down its own partial pressure gradient.

According to Henry’s Law, what determines how much gas dissolves in a liquid?

The solubility of the gas and its partial pressure.

What is lung compliance?

The ease with which lungs expand; affected by elasticity and surface tension.

What factors decrease lung compliance?

Loss of elastic fibers, high surface tension, or diseases like fibrosis.

What role does surfactant play in breathing?

It reduces surface tension in alveoli, preventing collapse during exhalation.

Why would premature infants struggle with breathing?

They may lack surfactant, causing alveolar collapse (respiratory distress syndrome).

What happens to intrapleural pressure during inspiration?

It becomes more negative, helping the lungs expand.

What keeps lungs inflated despite their elastic tendency to recoil?

Negative intrapleural pressure and the surface tension between pleurae.

What is the respiratory membrane and why must it be thin?

It’s the barrier between alveolar air and blood; it must be thin (0.5–1 μm) for rapid gas exchange.

How is oxygen primarily transported in the blood?

Bound to hemoglobin as oxyhemoglobin.

How is carbon dioxide primarily transported in the blood?

Mostly as bicarbonate ions (HCO₃⁻) in plasma.

What is the chloride shift?

The exchange of chloride ions for bicarbonate ions across the RBC membrane to maintain electrical neutrality.

What is the Bohr effect?

A decrease in pH or an increase in CO₂ causes hemoglobin to release oxygen more readily.

What happens to the oxygen-hemoglobin saturation curve when temperature increases?

It shifts right, meaning hemoglobin releases oxygen more easily.

Which parts of the brain control breathing rhythm?

The medulla oblongata (DRG and VRG) and the pons (pontine centers).

What does the dorsal respiratory group (DRG) do?

It controls normal, quiet inspiration by stimulating the diaphragm and external intercostals.

What does the ventral respiratory group (VRG) do?

It controls forced breathing by activating accessory respiratory muscles.

How do central chemoreceptors affect breathing?

They detect CO₂ and pH changes in cerebrospinal fluid and adjust ventilation rate.

What happens when arterial CO₂ levels rise?

CO₂ forms carbonic acid, lowering CSF pH, which triggers increased breathing rate to expel CO₂.

Why doesn’t arterial O₂ normally control breathing?

Hemoglobin stays saturated until PO₂ drops very low, so O₂ changes have little effect until extreme hypoxia.

What’s the difference between hyperventilation and hypoventilation?

Hyperventilation lowers CO₂ levels (hypocapnia); hypoventilation raises CO₂ (hypercapnia).

How does pulmonary ventilation differ from external respiration?

Pulmonary ventilation is air movement in/out of lungs; external respiration is gas exchange between alveoli and blood.

What structure performs both respiratory and digestive functions?

The oropharynx.