Respiratory Physiology: Gas Exchange, Oxygen Transport, and Ventilation Control

What law explains the relationship between pressure and volume of gases?

Boyle's Law

What is the total pressure exerted by a mixture of gases equal to?

The sum of pressures exerted by each gas (Dalton's Law of Partial Pressures)

What does partial pressure refer to?

The pressure exerted by each gas in a mixture, proportional to its percentage in the mixture.

What is Henry's Law in relation to gas mixtures?

Each gas will dissolve in a liquid in proportion to its partial pressure.

Why do alveoli contain more CO2 and water vapor than atmospheric air?

Due to gas exchanges in the lungs where O2 diffuses out and CO2 diffuses in.

What is the thickness range of respiratory membranes?

0.5 to 1 µm thick.

What is the main takeaway regarding blood contact with inspired air?

Blood is in contact with inspired air for about 0.75 seconds, needing 0.25 seconds to gain maximum O2.

What is surfactant and its function in the alveoli?

A detergent-like lipid and protein complex that reduces surface tension and prevents alveolar collapse.

What condition can arise from insufficient surfactant in premature infants?

Infant Respiratory Distress Syndrome (IRDS).

How is oxygen transported in the blood?

1.5% dissolved in plasma and 98.5% bound to hemoglobin (Hb) in red blood cells.

What is oxyhemoglobin?

The combination of hemoglobin and oxygen (HbO2).

What is the role of carbonic anhydrase in CO2 transport?

It catalyzes the conversion of CO2 and H2O into carbonic acid (H2CO3).

What is the significance of the oxygen-hemoglobin saturation curve?

It shows how hemoglobin's properties affect oxygen binding in the lungs and release in tissues.

How does PO2 influence hemoglobin saturation?

Higher PO2 levels lead to increased saturation, while lower PO2 levels cause larger changes in saturation.

What is the effect of temperature on the oxygen-hemoglobin dissociation curve?

Increased temperature decreases hemoglobin's affinity for oxygen, facilitating oxygen release.

What is the chloride shift?

The exchange of bicarbonate (HCO3-) and chloride (Cl-) ions across the red blood cell membrane.

What happens to oxygen and carbon dioxide at the tissues?

Oxygen is released from hemoglobin, and carbon dioxide is picked up.

What is the role of hemoglobin in carbon dioxide transport?

It can bind to CO2 to form carbaminohemoglobin (HbCO2).

What is the importance of the respiratory membrane's surface area?

A larger surface area facilitates greater gas exchange efficiency.

What is the physiological impact of high alveolar surface tension?

It can cause alveoli to collapse, making breathing difficult.

What is the primary function of type II alveolar cells?

To produce surfactant, reducing surface tension in the alveoli.

What is the primary consequence of mechanical ventilation in premature infants?

Survivors may develop bronchopulmonary dysplasia, a chronic lung disease.

How does the body ensure optimal oxygen delivery to tissues?

By adjusting hemoglobin saturation based on local PO2 levels.

What is the relationship between oxygen binding and hemoglobin structure?

Each hemoglobin molecule can transport four oxygen molecules due to its four heme groups.

What happens during internal respiration?

Oxygen is released from hemoglobin to tissues, and carbon dioxide is absorbed.

What is the significance of the S-shaped curve of the oxygen-hemoglobin dissociation curve?

It provides a safety margin for oxygen saturation even with fluctuations in PO2.

What process occurs when carbon dioxide diffuses into red blood cells (RBCs)?

It combines with water to form carbonic acid (H2CO3), which dissociates into hydrogen ions and bicarbonate ions.

What enzyme catalyzes the conversion of carbon dioxide and water to carbonic acid in RBCs?

Carbonic anhydrase.

How is carbon dioxide transported in the blood?

In three forms: dissolved in plasma (7-10%), chemically bound to hemoglobin (20% as carbaminohemoglobin), and as bicarbonate ions (70%).

What happens to bicarbonate ions at the tissues?

Bicarbonate quickly diffuses from RBCs into the plasma.

What occurs at the lungs regarding bicarbonate ions?

Bicarbonate ions move into RBCs, bind with hydrogen ions to form carbonic acid, which is then split to release carbon dioxide and water.

What is the partial pressure of oxygen (PO2) in arterial blood?

100 mm Hg, containing 20 ml of oxygen per 100 ml blood.

What is the saturation percentage of hemoglobin (Hb) in arterial blood?

98% saturated.

What is the venous reserve?

The oxygen remaining in venous blood that can still be used.

What factors influence hemoglobin saturation?

PO2, temperature, blood pH, PCO2, and concentration of BPG.

What is the Bohr effect?

At tissues, as more CO2 enters blood, more oxygen dissociates from hemoglobin.

How does BPG affect hemoglobin's affinity for oxygen?

Increases in BPG levels decrease Hb's affinity for O2, enhancing O2 unloading.

What is the role of the carbonic acid-bicarbonate buffer system?

It helps blood resist changes in pH by balancing H+ concentration.

What happens to blood pH during slow, shallow breathing?

CO2 increases in blood, resulting in a drop in pH.

What is hypoxia?

Inadequate O2 delivery to tissues, which can result in cyanosis.

What are the four types of hypoxia?

Anemic, ischemic, histotoxic, and hypoxemic hypoxia.

What is the effect of carbon monoxide on hemoglobin?

Hb has a 200 times greater affinity for carbon monoxide than for oxygen.

What happens to cardiac output during exercise?

It increases by increasing heart rate (HR) and stroke volume (SV), potentially up to 6 times.

What is the formula for cardiac output (CO)?

CO = HR x SV.

What are the respiratory centers located in the brain stem?

The pons and medulla.

What is the function of the dorsal respiratory group (DRG)?

It integrates peripheral sensory input and modifies the rhythms generated by the ventral respiratory group (VRG).

What nerve innervates the diaphragm?

The phrenic nerve (from C3, C4, C5).

What are intercostal nerves responsible for?

They innervate the external intercostal muscles and diaphragm, aiding in respiration.

What is the role of the ventral respiratory group (VRG)?

It is a rhythm-generating and integrative center for respiration located in the brainstem.

What is eupnea?

Normal respiratory rate and rhythm, typically 12-15 breaths per minute.

What does the dorsal respiratory group (DRG) do?

Integrates input from peripheral stretch and chemoreceptors, sending information to VRG neurons.

What is the function of pontine respiratory centers?

They influence and modify the activity of the VRG, smoothing transitions between inspiration and expiration.

What happens if there are lesions in the pontine respiratory centers?

They can lead to apneustic breathing, characterized by prolonged inspirations.

How do peripheral chemoreceptors influence respiration?

They sense changes in O2, CO2, and H+ levels, affecting the respiratory rate.

What is the most important chemical factor influencing breathing rate?

Changing levels of PCO2, PO2, and pH.

What occurs when arterial PCO2 levels rise?

It leads to increased depth and rate of breathing to lower blood PCO2.

What is hyperventilation?

Increased depth and rate of breathing that exceeds the body's need to remove CO2, often leading to dizziness and fainting.

What is the primary cause of chronic obstructive pulmonary disease (COPD)?

Emphysema and chronic bronchitis, leading to irreversible decrease in lung function.

What is emphysema characterized by?

Permanent enlargement of alveoli and destruction of alveolar walls, reducing lung elasticity.

What are the symptoms of chronic bronchitis?

Inflammation of bronchial tubes, excessive mucus production, and frequent pulmonary infections.

What is asthma?

A condition characterized by acute episodes of airway inflammation, coughing, and wheezing.

What is cystic fibrosis?

A genetic disease causing abnormal mucus production, leading to respiratory infections.

What treatments are available for cystic fibrosis?

Mucus-dissolving drugs, antibiotics, and inhalation of hypertonic saline.

What happens at high altitudes regarding oxygen levels?

Lower atmospheric pressure and PO2 levels can trigger acute mountain sickness (AMS).

What is acclimatization in relation to high altitude?

Physiological adjustments made to increase ventilation and red blood cell production in response to low oxygen levels.

What is the role of erythropoietin (EPO) in high altitude conditions?

It promotes the formation of red blood cells in response to decreased blood oxygen levels.

How does increased arterial PCO2 affect pH?

It decreases pH in brain extracellular fluid, stimulating central chemoreceptors to increase breathing rate.

What is apnea?

Breathing cessation that may occur when PCO2 levels drop abnormally low.

What is the effect of decreased arterial pH on respiration?

It can stimulate increased respiratory rate to raise pH back to normal.

What is the relationship between blood PO2 and ventilation?

Declining PO2 has a slight effect on ventilation until it falls below 60 mm Hg, then it becomes a major stimulus.

What are irritant receptors and their role?

They respond to irritants and can influence respiratory patterns.

What is the consequence of waterlogged lungs?

It increases the effective thickness of the respiratory membrane, impairing gas exchange.

What is the primary physiological response to rising CO2 levels?

Increased depth and rate of breathing to lower blood CO2 levels.

What is the impact of chronic bronchitis on lung function?

It leads to obstructed airways, impairing ventilation and gas exchange.

What is the primary cause of hypercapnia?

Accumulation of CO2 in the blood due to inadequate ventilation.