Lecture 31. Breathing and Ventilation Flashcards
What are the three phases of rhythmic breathing?
Inspiration - Active: Initiated by activation of the nerves to the inspiratory muscles
Post-Inspiration - Active: Recruitment of post-inspiratory muscles
Expiration - Passive: Inspiratory muscles relax and lungs recoil
– Active: activation of expiratory muscles
What do inspiratory muscles do?
Contract to draw air into the lungs and create normal breathing
What is the most important inspiratory muscle?
Diaphragm
Asymmetrically innervated
70% of your Tidal volume
What do post-inspiratory muscles do?
Slow diaphragm recoil and coordinate orofacial movement
When do expiratory muscles become active?
In times of high demand to increase tidal volume
What does contraction of the tongue support?
Supports the airway and reduces resistance during inspiration and expiration
What three types of plural membrane make up the thorax?
Costal parietal pleura
Mediastinal parietal pleura
Diaphragmatic parietal pleura
What is the visceral pleura?
A thin layer of epithelium covering each lung
What is the parietal pleura?
Lines inner surface of the walls of the thorax
What is the pleural cavity?
Maintains a partial vacuum which helps keep the lungs
expanded
What is the intrapleural fluid?
Allows pleurae to slide over one another
What generates pressure within the pleura?
Differential set points of muscles and lungs
What is the transpulmonary pressure (Pₜₚ)?
Difference in pressure between the inside and outside of the lungs within the thorax
What is the intrapleural pressure (Pᵢₚ)?
The pressure outside the lungs in the thorax
What is the alveoli pressure (Palv)?
The pressure inside the lungs is the air pressure inside the alveoli pressure
What keeps the lungs inflated?
Palv > Pip
What causes pneumothorax (collapsed lung)?
Air in the plural cavity
What is Boyle’s law?
Predicts that if the volume inside the lungs is
changed, pressure inside the lungs will also change
What generates air movement in the lung?
Alveolar pressure
What alters trans-pulmonary pressure to draw air into the lungs?
Inspiratory muscle contractions
What alters trans-pulmonary pressure to push air out of the lungs?
Expiratory muscle contractions
What is the exchange of gases in alveoli and tissues dependent on?
Partial pressures O₂ and CO₂
What is Dalton’s Law?
In a mixture of gases, the pressure exerted by each gas (the partial pressure) is the pressure that the gas would exert if it were the only gas in the volume occupied by the mixture
What determines atmospheric pressure?
Patm = PN₂ + PO₂ + PCO₂ + PH₂O = 760 mm Hg
What is anatomical dead space?
Volume of gas within the conducting airways
Increases PCO₂ in the alveoli
What is physiological dead space?
Volume of gas not involved in gas exchange
The two are almost equal in healthy lungs
When does net diffusion of a gas occur?
From a region where its partial pressure is high to a region where it is low
How is oxygen in the blood primarily transported?
On haemoglobin
What is the Bohr effect?
Carbon dioxide (CO₂) shifts the haemoglobin saturation curve to the right causing O₂ to dissociate from haemoglobin
How is CO₂ predominantly transported in the blood?
As bicarbonate ion
When does carbon monoxide poisoning occur?
Haemoglobin has an affinity for CO that is 210 times greater than its affinity for O₂, preventing the unloading of O₂ onto tissues
