Respiratory Physiology: Gas Exchange, Transport, and Regulation

What is Boyle's Law?

Pressure and volume are inversely related.

What does Dalton's Law of Partial Pressures state?

The total pressure exerted by a mixture of gases equals the sum of the pressures exerted by each gas.

What is partial pressure?

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

What does Henry's Law describe?

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

What is the significance of the respiratory membrane's thickness?

The respiratory membrane is very thin (0.5 to 1 µm), facilitating gas exchange.

What is the main function of surfactant in the alveoli?

Surfactant reduces surface tension of alveolar fluid, preventing alveolar collapse.

What condition is caused by insufficient surfactant in premature infants?

Infant Respiratory Distress Syndrome (IRDS).

How is oxygen primarily transported in the blood?

1.5% is dissolved in plasma; 98.5% is bound to hemoglobin.

What is oxyhemoglobin?

The combination of hemoglobin and oxygen.

What happens to hemoglobin when it releases oxygen?

It becomes reduced hemoglobin (deoxyhemoglobin).

What is the role of carbonic anhydrase in CO2 transport?

It catalyzes the conversion of CO2 and water into bicarbonate and protons.

What is the chloride shift?

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

How does temperature affect the oxygen-hemoglobin dissociation curve?

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

What is the effect of increased PCO2 on hemoglobin saturation?

Increased PCO2 decreases hemoglobin's affinity for oxygen, facilitating oxygen delivery to tissues.

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

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

What occurs during external respiration?

Gas exchange between the alveoli and blood in the lungs.

What occurs during internal respiration?

Gas exchange between blood and tissues.

What is the primary gas exchanged in the lungs?

Oxygen (O2) is taken in, and carbon dioxide (CO2) is released.

What is the role of hemoglobin in oxygen transport?

Hemoglobin binds oxygen in the lungs and releases it in tissues where it is needed.

What is the typical time blood is in contact with inspired air for gas exchange?

Approximately 0.75 seconds.

What happens to alveoli without sufficient surfactant?

They collapse after each breath, requiring significant energy to reinflate.

What is carbaminohemoglobin?

Hemoglobin that has bound carbon dioxide.

What is the relationship between PO2 and hemoglobin saturation?

Higher PO2 leads to increased hemoglobin saturation; lower PO2 leads to decreased saturation.

What is the primary factor influencing the oxygen-hemoglobin binding?

The partial pressure of oxygen (PO2) available locally.

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

It ensures that hemoglobin remains saturated even with substantial decreases in PO2.

What is the effect of low PO2 on hemoglobin saturation?

Large changes in PO2 cause significant changes in Hb saturation, ensuring oxygen delivery to tissues.

What happens 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: 7-10% dissolved in plasma, 20% chemically bound to hemoglobin as carbaminohemoglobin, and 70% as bicarbonate ions (HCO3-).

What occurs at the lungs regarding bicarbonate ions?

Bicarbonate ions move into RBCs and 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 (20 volume %).

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

98% saturated.

What is the venous reserve of oxygen?

The oxygen remaining in venous blood that can still be used, with a PO2 of 40 mm Hg and 15 volume % oxygen.

What effect do increases in temperature, H+, PCO2, and BPG have on hemoglobin?

They decrease Hb's affinity for O2, enhancing O2 unloading in systemic capillaries.

What is the Bohr effect?

At tissues, as more CO2 enters blood, more oxygen dissociates from hemoglobin, facilitating O2 unloading.

What is the role of BPG in oxygen transport?

BPG is produced during glycolysis and rises when oxygen levels are low, decreasing Hb affinity for O2.

How does the carbonic acid-bicarbonate buffer system help maintain blood pH?

It resists changes in pH by removing excess H+ or releasing H+ when concentrations drop.

What is hypoxia?

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

What are the classifications of hypoxia?

Anemic, ischemic, histotoxic, hypoxemic, and carbon monoxide poisoning.

What is the primary function of the respiratory centers in the brain stem?

To regulate the rhythm and pattern of respiration.

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

It contains rhythm generators that drive respiration.

What does the dorsal respiratory group (DRG) do?

It integrates peripheral sensory input and modifies the rhythms generated by the VRG.

What is the function of the phrenic nerve?

It innervates the diaphragm to facilitate breathing.

How does breathing affect blood pH?

Slow, shallow breathing increases CO2 and lowers pH, while rapid, deep breathing decreases CO2 and raises pH.

What is the maximum increase in cardiac output during exercise?

Up to 6 times the resting value.

What is the formula for cardiac output (CO)?

CO = Heart Rate (HR) x Stroke Volume (SV).

What happens to blood flow during exercise?

Blood flow is redistributed, with vasoconstriction in the GI tract and increased flow to muscles.

What is the effect of carbon monoxide on hemoglobin?

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

What are the symptoms of low exposure to carbon monoxide?

Headaches and flushed skin.

What happens at high exposure to carbon monoxide?

Victims have zero ability to carry oxygen.

What is eupnea?

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

What do inspiratory neurons in the VRG do?

They excite inspiratory muscles via phrenic and intercostal nerves.

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

It integrates input from peripheral stretch and chemoreceptors and sends information to VRG neurons.

What is the role of pontine respiratory centers?

They influence and modify the activity of the VRG to smooth transitions between inspiration and expiration.

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

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

What are central chemoreceptors sensitive to?

They respond to changes in CO2 and H+ levels in the brain's extracellular fluid.

How do peripheral chemoreceptors influence respiration?

They sense arterial O2 levels and respond primarily when PO2 drops below 60 mm Hg.

What is hypercapnia?

An increase in blood CO2 levels that can stimulate respiratory centers to increase breathing rate.

What is the physiological response to rising CO2 levels?

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

What is hyperventilation?

Increased depth and rate of breathing that exceeds the body's need to remove CO2.

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

Emphysema and chronic bronchitis.

What are the consequences of emphysema?

Permanent enlargement of alveoli, decreased lung elasticity, and increased energy expenditure for breathing.

What characterizes chronic bronchitis?

Inflammation of bronchial tubes leading to excessive mucus production and obstructed airways.

What is asthma characterized by?

Coughing, dyspnea, wheezing, and chest tightness due to airway inflammation and bronchospasms.

What is cystic fibrosis?

A genetic disease causing abnormal, viscous mucus that clogs passageways and leads to infections.

What is the effect of high altitude on respiration?

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

What is acclimatization in response to high altitude?

Adjustments in respiratory and hematopoietic functions to stabilize oxygen levels.

What stimulates the production of erythropoietin (EPO) at high altitudes?

A decline in blood O2 levels.

What is the oxygen-hemoglobin saturation curve?

A graph that shows how hemoglobin saturation with oxygen changes with varying PO2 levels.

What is the role of irritant receptors in the respiratory system?

They respond to harmful substances and can trigger reflexes such as coughing.

What is apnea?

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

What is the impact of decreased pH on respiration?

It can stimulate an increase in respiratory rate and depth to raise pH.

How does the body respond to hypercapnia?

By increasing the depth and rate of breathing to expel excess CO2.

What are the symptoms of acute mountain sickness (AMS)?

Headaches, shortness of breath, nausea, and dizziness.

What is the primary function of stretch receptors in the lungs?

To monitor lung expansion and prevent over-inflation.

What are the main risk factors for chronic bronchitis?

Smoking and environmental pollutants.

What is the effect of high CO2 levels on blood pH?

It causes a drop in pH, leading to increased acidity.

What is the role of the hypothalamus in respiration?

It integrates emotional stimuli that can influence breathing patterns.