Respiratory Physiology Lecture 2: The Work of Breathing

Podcast Beta

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary function of lung surfactant?

To decrease the resistance in the airways

To increase alveolar surface tension

To prevent alveolar collapse by reducing surface tension (correct)

To increase the elastic properties of the lung

Which of the following is NOT a factor affecting ventilation?

Blood pressure (correct)

Elastic properties of the lung

Resistance to flow in the airways

Surface tension of the alveoli

What is the role of compliance in the respiratory system?

To increase the resistance in the airways

To increase the surface tension of the alveoli

To decrease the elastic properties of the lung

To aid in the expansion of the lung (correct)

What happens to the lungs when the stretching force is removed?

They collapse Signup and view all the answers

What is Laplace's law related to in the context of the respiratory system?

Surface tension of the alveoli Signup and view all the answers

What is the main reason why inspiration is an active process?

Because it requires energy to overcome both airway resistance and stretch the lung Signup and view all the answers

What is the main factor that drives airflow in healthy individuals?

Modest differences in pressure between the atmosphere and alveoli Signup and view all the answers

During which phase of respiration is airway resistance the lowest?

Inspiration Signup and view all the answers

What is the mathematical formula for airway resistance?

R = 8ηL/πr4 Signup and view all the answers

What is the effect of lung expansion on airway resistance?

Decreases airway resistance Signup and view all the answers

What is the result of increased tension within lung tissue during inspiration?

Increased diameter of airways and blood vessels Signup and view all the answers

What is the location of the highest resistance to airflow?

Airways Signup and view all the answers

What is the primary mechanism by which the lungs expand during inhalation?

Radial traction on airways due to stretch of elastic fibers Signup and view all the answers

What is the purpose of hypoxic vasoconstriction in the pulmonary arteries?

To decrease blood flow to poorly ventilated regions of the lung Signup and view all the answers

What percentage of total energy metabolism is accounted for by respiratory work at rest?

1-2% Signup and view all the answers

What is the main component of respiratory work?

Work required to overcome elastic forces of the lungs and thoracic cage Signup and view all the answers

What is the effect of salbutamol on the airways?

Dilation of airways Signup and view all the answers

What is the primary function of pulmonary surfactant?

To reduce alveolar surface tension Signup and view all the answers

Study Notes

Respiratory Physiology Introduction

The work of breathing is an active process that requires energy to expand the lungs and overcome airway resistance.

The Work of Breathing

Factors affecting ventilation include:
- Resistance to flow in the airways
- Elastic properties of the lung
- Surface tension of the alveoli
Inspiration is an active process that requires energy to:
- Stretch the lung (collagen, elastin, and surface tension)
- Overcome the resistance of the airways (RAW)
Lungs must collapse when the stretching force is removed, aided by elasticity.

Resistance to Airflow in Airways

In health, flow resistance in the airways is small, and modest differences in pressure drive a lot of airflow.
In disease, airway resistance can increase, and must be overcome by the action of inspiratory muscles.
Airway resistance is lowest during inspiration and highest during expiration.
The formula for airway resistance is: R = 8ηL / πr4

Elasticity of Lung Tissue

Elasticity of lung tissue affects the work of breathing.
Stretching the lung increases tension within lung tissue.
Tension pulls on airways and blood vessels, increasing their diameter and reducing pulmonary vascular resistance and airway resistance.

Regulation of Airway Resistance

SNS release of adrenaline acts on β2 receptors, causing bronchodilation (during exercise and stress).
Airway dilation reduces airway resistance.

Resistance to Blood Flow (Perfusion)

Regulation of resistance is a key concept in pulmonary blood flow.
Pulmonary Hypoxic Vasoconstriction (HPV) occurs when alveolar PO2 is low, leading to increased pulmonary arterial resistance and diversion of blood away from poorly ventilated regions of the lung.

The Metabolic Cost of Breathing

At rest, respiratory work accounts for 1-2% of total energy metabolism.
During exercise, respiratory work can be up to 10% of total energy metabolism.
The majority of respiratory work (90%) is due to overcoming alveolar surface tension and the elastic forces of the lungs, while frictional work due to airway resistance accounts for 10%.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This lecture covers the fundamentals of respiratory physiology, focusing on the work of breathing, ventilation, perfusion, gas exchange, and central control of ventilation. Learn about the physical properties of the lung and the forcing mechanisms behind breathing.