Respiratory & Renal Physiology – Exam Review

Key question-and-answer flashcards covering respiratory mechanics, gas transport, acid–base balance, hypoxia types, hormonal regulation of kidneys, and related physiology for exam preparation.

According to Boyle’s law, what happens to pressure when thoracic cavity volume increases during diaphragm contraction?

Pressure inside the lungs (intrapulmonary pressure) falls below atmospheric pressure, allowing air to flow in.

What intrapulmonary pressure (relative to atmosphere) is typically reached when the diaphragm contracts during a quiet inspiration?

Approximately –3 mm Hg (negative to atmosphere).

What is lung “compliance”?

A measure of how easily the alveoli can open and close (inverse of resistance to airflow).

Which substance most directly increases alveolar compliance by reducing surface tension?

Pulmonary surfactant.

Why do many premature infants require mechanical ventilation?

They lack sufficient surfactant, so their alveoli collapse easily and they cannot generate the force to reopen them.

Which autonomic neurotransmitter/hormone is administered via an EpiPen to reverse anaphylactic bronchioconstriction?

Epinephrine (sympathetic agonist).

During an asthma attack, inhalers typically contain a drug that mimics which hormone to dilate bronchioles?

A β₂-adrenergic agonist related to epinephrine (e.g., albuterol).

How does pneumonia impair gas exchange?

It thickens the respiratory membrane with fluid/inflammation, slowing diffusion of gases.

How does long-term smoking reduce gas-exchange efficiency?

It destroys alveoli, decreasing total surface area for diffusion.

What blood gas change results from severely reduced alveolar surface area (e.g., emphysema)?

CO₂ retention (hypercapnia).

Define hypercapnia.

An abnormally elevated partial pressure of carbon dioxide (CO₂) in the blood.

Which acid–base disturbance results from hypercapnia due to poor ventilation?

Respiratory acidosis (low pH, high H⁺).

Write the complete carbonic-anhydrase (CAH) reaction important for CO₂ transport.

CO₂ + H₂O ⇌ H₂CO₃ ⇌ H⁺ + HCO₃⁻

In systemic capillaries, what keeps the CAH reaction moving toward bicarbonate formation?

The chloride shift removes HCO₃⁻ from RBCs and H⁺ binds to hemoglobin, keeping products low so the reaction proceeds to the right.

What is the Bohr effect?

H⁺ binding to hemoglobin decreases its affinity for O₂, promoting O₂ unloading in metabolically active tissues.

At the lungs, what triggers the CAH reaction to run in reverse, releasing CO₂ for exhalation?

O₂ binding to hemoglobin displaces H⁺, and a reverse chloride shift brings HCO₃⁻ back into RBCs, making H⁺ + HCO₃⁻ → CO₂ + H₂O.

Why does exercise assist in weight loss at the molecular level?

Oxidizing glucose in mitochondria produces six CO₂ molecules that are exhaled, removing carbon atoms (calories) from the body.

Which variable is the primary driver of ventilation rate: low O₂ or high CO₂?

High CO₂ (and the associated drop in cerebrospinal-fluid pH).

Where are the central chemoreceptors that monitor CSF pH located?

In the medulla oblongata (brainstem).

Why is CSF pH such a powerful ventilatory stimulus?

CSF lacks significant buffers, so changes in CO₂ rapidly change H⁺ concentration and pH.

Define hyperventilation in terms of blood CO₂ and pH changes.

Excessive ventilation lowers CO₂ (hypocapnia), reduces H⁺, and raises blood pH (respiratory alkalosis).

How does the body compensate for respiratory alkalosis?

Hypoventilation (slower breathing) raises CO₂, generating more H⁺ and lowering pH toward normal.

List the four major types of hypoxia and a key example of each.

1) Hypoxic (high altitude), 2) Ischemic (poor circulation—e.g., diabetes), 3) Anemic (low Hb/iron/B₁₂ deficiency), 4) Histotoxic (CO poisoning).

Why is carbon monoxide (CO) so dangerous?

It binds hemoglobin ~200× tighter than O₂, preventing O₂ transport and causing hypoxic injury even when O₂ is plentiful.

What hormone do kidneys secrete in response to hypoxia, and what is its target?

Erythropoietin (EPO), which stimulates red-bone-marrow production of erythrocytes.

What does ventilation–perfusion coupling ensure?

Airflow (ventilation) is matched to blood flow (perfusion) so that increased breathing is effective only if blood delivery also increases.

Name the three blood filters in the body and the one lymph filter.

Blood filters: liver, spleen, kidneys. Lymph filter: lymph nodes.

Where are the kidneys situated relative to the peritoneum?

Retroperitoneal (posterior to the peritoneal cavity).

Trace the flow of urine from kidney to exterior.

Kidney → Ureter → Urinary bladder → Urethra → Outside the body.

Which hormone causes the renal collecting ducts to insert aquaporins and reabsorb more water?

Antidiuretic hormone (ADH/vasopressin).

Which adrenal-cortex hormone promotes Na⁺ (and thus water) reabsorption in the distal nephron?

Aldosterone.

What happens to water when the kidney reabsorbs Na⁺ under aldosterone’s influence?

Water follows the osmotic gradient, so blood volume increases.

Which kidney-activated form of vitamin D raises blood Ca²⁺ levels?

Calcitriol.

Name three hormones that together regulate blood calcium and give their primary actions.

Calcitonin (lowers Ca²⁺), Parathyroid hormone—PTH (raises Ca²⁺), Calcitriol (raises Ca²⁺ and phosphate absorption).

What is the function of atrial natriuretic peptide (ANP) in renal physiology?

It promotes Na⁺ and water excretion, lowering blood volume and pressure.

How does increased body temperature (fever) affect O₂ unloading from hemoglobin?

Raises BPG production in RBCs, decreasing Hb’s O₂ affinity and enhancing O₂ delivery to tissues.

During metabolic acidosis (e.g., ketoacidosis), what respiratory compensation occurs?

Hyperventilation (Kussmaul breathing) to lower CO₂ and raise pH.

What is the typical physiologic response (heart rate) when respiration increases?

Heart rate rises to increase perfusion of ventilated lungs (respiration drives cardiac response).

Which lung cells produce surfactant?

Great (type II) alveolar cells.

What common allergen-triggered reaction causes life-threatening bronchioconstriction and is treated with epinephrine?

Anaphylactic shock.

Explain the term 'chloride shift' in systemic capillaries.

Exchange of intracellular HCO₃⁻ for plasma Cl⁻ in RBCs, maintaining electrical neutrality and driving CO₂ transport.

State the inverse relationship between pH and H⁺ concentration.

As H⁺ concentration increases, pH decreases; as H⁺ concentration decreases, pH increases (scale 0–14 with 7 neutral).

Why is drowning classified as hypoxic hypoxia?

Water prevents O₂ entry into alveoli, so inspired O₂ partial pressure is effectively zero.

Which reaction direction (left or right) removes H⁺ when CO₂ is blown off during hyperventilation?

Leftward (H⁺ + HCO₃⁻ → H₂CO₃ → CO₂ + H₂O), thereby lowering H⁺ concentration.

What enzyme inside RBCs accelerates the interconversion of CO₂ and carbonic acid?

Carbonic anhydrase (CAH).