Human Physiology RESPIRATORY SYSTEM

Does the respiratory system participate in all steps of respiration?

No, the respiratory system does not participate in all steps of respiration.

What is cellular respiration?

intracellular metabolic processes carried out within the mitochondria.

What is external respiration?

sequence of events involved in the exchange of O2 and CO2 between the atmosphere and the body.

What are some nonrespiratory functions of the respiratory system?

leaving a route for water loss and heat elimination, and enhancing venous return.

What is systemic ventilation?

1) Ventilation or gas exchange between the atmosphere and air sacs (alveoli) in the lungs. 2) Exchange of O2 and CO2 between air in the alveoli and the blood in the pulmonary capillaries. 3) Transport of O2 and CO2 by the blood between the lungs and the tissues. 4) Exchange of O2 and CO2 between the blood in the systemic capillaries and the tissue cells.

What do the respiratory airways do?

conduct air between the atmosphere and the alveoli.

What are the tubes that carry air called?

The tubes that carry air between the atmosphere and the air sacs are known as air-conducting tubes.

Where does gas exchange occur?

The alveoli are the only site where gases can be exchanged between air and blood.

What are the gas-exchanging alveoli?

The gas-exchanging alveoli are thin-walled air sacs encircled by pulmonary capillaries.

What types of cells are found in the alveoli?

The alveoli contain Type I and II alveolar cells.

How are the lungs divided?

Each lung is divided into several lobes and is supplied by one of the bronchi.

What separates each lung from the thoracic wall?

pleural sac

What is the pleural cavity?

The pleural cavity is the interior of the pleural sac.

Why are pressures inside and outside the lungs important?

The interrelationships among pressures inside and outside the lungs are important in ventilation.

What is atmospheric pressure also known as?

barometric pressure

What is intra-alveolar pressure?

pressure within the alveoli

What is intrapleural pressure?

Intrapleural pressure is the pressure within the pleural cavity surrounding the lungs.

What is bronchoconstriction?

Bronchoconstriction is the narrowing of the airways, which increases resistance to airflow.

How does bronchoconstriction affect resistance to airflow?

Bronchoconstriction increases resistance to airflow due to a decrease in the radius of the airways.

What are the physiological control factors for bronchoconstriction?

Physiological control factors include neural control (parasympathetic stimulation) and local chemical control (increased CO2 concentration).

What are some pathological factors causing bronchoconstriction?

Pathological factors include allergy-induced spasm of the airways (leukotrienes and histamine) and physical blockage (excess mucus, edema, airway collapse).

What is bronchodilation?

Bronchodilation is the widening of the airways, which decreases resistance to airflow.

How does bronchodilation affect resistance to airflow?

Bronchodilation decreases resistance to airflow due to an increase in the radius of the airways.

What are the physiological control factors for bronchodilation?

Physiological control factors include neural control (sympathetic stimulation, minimal effect), hormonal control (epinephrine), and local chemical control (decreased CO2 concentration).

What causes abnormally increased airway resistance?

Abnormally increased airway resistance is associated with conditions like Chronic Obstructive Pulmonary Disease (COPD), chronic bronchitis, asthma, and emphysema, leading to difficulty in expiring air from the lungs.

What contributes to the lungs' elastic behavior?

The lungs' elastic behavior results from elastin fibers and alveolar surface tension.

What is compliance in the context of lung function?

Compliance refers to how much effort is required to stretch or distend the lungs.

What is elastic recoil in lung function?

What is elastic recoil in lung function?

What is elastic recoil in lung function?

What is elastic recoil in lung function?

How does surface tension affect the lungs?

How does surface tension affect the lungs?

What is the function of pulmonary surfactant?

Pulmonary surfactant decreases surface tension and contributes to lung stability.

What is pulmonary surfactant made of?

It is a complex mixture of lipids and proteins secreted by Type II alveolar cells.

What is newborn respiratory distress syndrome?

It is a condition characterized by symptoms produced due to an insufficient amount of pulmonary surfactant, leading to high alveolar surface tension.

What happens when there is insufficient pulmonary surfactant?

Insufficient surfactant results in increased alveolar surface tension, making it difficult for the lungs to expand and contract effectively.

What are the forces that keep the alveoli open?

transmural pressure gradient, elasticity of stretched elastin fibers in lung connective tissue, and pulmonary surfactant.

What is the transmural pressure gradient?

It is the difference in pressure inside the alveoli compared to the pressure outside, which helps keep the alveoli open.

How do elastin fibers contribute to alveolar stability?

The elasticity of stretched elastin fibers in lung connective tissue helps maintain the shape and openness of the alveoli.

How does pulmonary surfactant affect alveoli?

Pulmonary surfactant opposes alveolar surface tension, helping to prevent collapse and maintain lung stability.

What forces promote alveolar collapse?

The primary force promoting collapse is alveolar surface tension, which can overcome the forces keeping the alveoli open.

How much of the total energy expenditure is normally required for breathing?

The work of breathing normally requires only about 3% of total energy expenditure.

What factors can increase the work of breathing?

Increased work occurs when pulmonary compliance is decreased, airway resistance is increased, elastic recoil is decreased, or when there is a need for increased ventilation.

How do the lungs normally operate in terms of volume?

The lungs normally operate about "half full."

What are lung volumes and capacities?

the various measurements of air that the lungs can hold during different phases of breathing.

What is respiratory dysfunction?

Respiratory dysfunction refers to any condition that impairs breathing efficiency and can affect lung volumes and the work of breathing.

What is pulmonary ventilation and how is it calculated?

Pulmonary ventilation remains constant at 6000 mL/min and is calculated as tidal volume × respiratory rate.

What is alveolar ventilation?

What is alveolar ventilation?

the volume of air reaching the alveoli for gas exchange.

When is alveolar ventilation highest?

Alveolar ventilation is highest during deep, slow breathing at 5250 mL/min.

What is the alveolar ventilation during quiet breathing?

Alveolar ventilation during quiet breathing is moderate at 4200 mL/min.

What happens to alveolar ventilation during shallow, rapid breathing?

Alveolar ventilation is zero during shallow, rapid breathing because all air remains in the dead space without reaching the alveoli.

What do local controls act on to match airflow to blood flow?

Local controls act on bronchiolar and arteriolar smooth muscle.

What happens to bronchiolar smooth muscle when CO2 levels increase?

bronchodilation, relaxing the bronchiolar smooth muscle and widening the airways.

How does low oxygen affect pulmonary arteriolar smooth muscle?

Low oxygen levels cause pulmonary arterioles to constrict, directing blood flow away from poorly ventilated areas.

Why are local controls important in the lungs?

They help match airflow to blood flow, optimizing gas exchange efficiency.

What do gases move down?

Gases move down partial pressure gradients.

What is partial pressure?

Partial pressure is the individual pressure exerted independently by a particular gas within a mixture of gases.

What are partial pressure gradients?

the difference in partial pressure between the capillary blood and the surrounding structures.

What happens to O2 and CO2 in the lungs?

O2 enters and CO2 leaves the blood in the lungs down partial pressure gradients.

How does alveolar PO2 compare to atmospheric PO2?

Alveolar PO2 is lower than atmospheric PO2.

What happens when atmospheric air enters the respiratory passages?

It is exposed to moist airways, which saturates it with H2O.

What occurs as blood passes through the lungs?

Blood picks up O2 and gives up CO2 by diffusion down partial pressure gradients between blood and alveoli.

What are the key steps in gas exchange between the lungs and tissues?

1. Alveolar PO2 remains high and PCO2 remains low due to fresh air exchange with each breath. 2. Systemic venous blood entering the lungs is low in O2 and high in CO2. 3. Partial pressure gradients cause passive diffusion of O2 into the blood and CO2 out until pressures equalize. 4. Blood leaving the lungs is high in O2 and low in CO2. 5. Tissues have low O2 and high CO2, favoring O2 movement into cells and CO2 into the blood. 6. Blood leaving tissues is low in O2 and high in CO2, returning to the lungs to replenish O2 and release CO2.

How does gas exchange occur across systemic capillaries?

Gas exchange occurs down partial pressure gradients, where oxygen (O2) moves from areas of higher partial pressure to areas of lower partial pressure, and carbon dioxide (CO2) moves in the opposite direction.

What are the PO2 and PCO2 gradients across systemic capillaries?

In systemic capillaries, PO2 is higher in the blood than in the tissues, promoting O2 diffusion into tissues. Conversely, PCO2 is higher in tissues than in the blood, facilitating CO2 diffusion into the blood.

What is the net diffusion of O2 and CO2 between the alveoli and tissues?

occurs from the alveoli into the blood in the lungs, while CO2 diffuses from the blood into the alveoli to be exhaled. In tissues, O2 diffuses from blood to cells, and CO2 diffuses from cells to blood.

How is most O2 transported in the blood?

bound to hemoglobin

How much O2 is physically dissolved in plasma?

Little O2 is physically dissolved in plasma water because O2 is poorly soluble in body fluids.

What is hemoglobin's role in oxygen transport?

Hemoglobin, an iron-bearing protein in red blood cells, forms a loose, easily reversible combination with O2, facilitating oxygen transport.

What is hemoglobin's role at the alveolar level?

Hemoglobin acts as a "storage depot" for O2, removing O2 from solution as soon as it enters the blood from the alveoli.

How does hemoglobin function at the tissue level?

At the tissue level, O2 immediately diffuses from the blood into the tissues, lowering blood PO2.

How does CO2 affect hemoglobin saturation?

Increased levels of CO2 in the blood can lead to a decrease in %Hb saturation, promoting the release of O2 from hemoglobin.

What is the effect of acid on hemoglobin saturation?

An increase in acidity (lower pH) reduces %Hb saturation, facilitating the release of O2 to tissues.

What is the Bohr effect?

The Bohr effect describes how increased CO2 and acidity lower hemoglobin's affinity for O2, enhancing O2 delivery to tissues.

How does temperature influence hemoglobin saturation?

Higher temperatures decrease %Hb saturation, promoting O2 release from hemoglobin to meet increased metabolic demands.

What is the role of respiratory centers in the brain stem?

establish a rhythmic breathing pattern.

What are the components of neural control of respiration?

includes inspiratory and expiratory neurons in the medullary center.

How is the respiratory rhythm generated?

primarily controlled by neurons in the medulla oblongata.

What influences do the pneumotaxic and apneustic centers have?

The pneumotaxic center helps regulate the rate and pattern of breathing, while the apneustic center promotes prolonged inhalation.

What factors can influence ventilation unrelated to gas exchange?

Ventilation can be influenced by protective reflexes, swallowing, pain, breathing patterns, and hiccups.

What happens during apnea and dyspnea?

During apnea, a person "forgets to breathe," while during dyspnea, a person feels "short of breath."

What is Sudden Infant Death Syndrome?

(SIDS) is the unexplained death of an infant, often during sleep, and is associated with irregularities in breathing.

What is dyspnea?

the sensation of shortness of breath or difficulty in breathing, often caused by respiratory or cardiac conditions.