Respiratory Physiology Overview

Permanent stoppage of breathing, requiring immediate medical intervention.

Difficult or labored breathing, a symptom that can be either pathological or not.

The act of breathing air into the lungs due to the muscles that expand the thoracic cavity.

Breathing air out of the lungs, usually through relaxation of muscles.

Muscles important for breathing, that expands the thoracic cavity.

The pressure inside the alveoli, which changes during inspiration and expiration to drive air movement.

The pressure within the pleural cavity, the space surrounding the lungs. It's always slightly lower than atmospheric pressure, helping the lungs expand during inspiration.

When intrapleural pressure decreases, the alveoli expand and alveolar pressure decreases. This creates a pressure gradient that pulls air into the lungs.

As intrapleural pressure increases, the alveoli compress, alveolar pressure rises, and air is pushed out of the lungs.

The vocal cords, controlled by the somatic nervous system, are involved in both phonation (voice production) and breathing. You can voluntarily control both your voice and your breathing.

A condition where the vocal cords partially close during exercise, causing a high-pitched, whistling sound (stridor) during inhalation.

A type of exercise that aims to improve the coordination of muscles and nerves, which can help resolve conditions like exercise-induced laryngeal obstruction.

Breathing requires energy to move air, which is why it uses a small percentage of our total energy. This percentage increases during exercise.

The use of muscles to force air out of the lungs, unlike passive expiration which relies on relaxation.

When breathing muscles work too hard for a long time, it can lead to reduced function and make breathing even more difficult.

The bronchioles have the greatest resistance to airflow due to their smooth muscle, which can constrict and their lack of cartilage to keep them open.

During inspiration, airway resistance decreases as the lungs inflate, pulling apart the airway tissue and widening the airways.

During expiration, airway resistance increases as the lungs deflate, compressing the airways and reducing their size.

Inflammation increases airway resistance by causing: 1. Blood filling the airway walls, 2. Edema in the airway walls, 3. Blockages in the airway lumen with mucus, tumors, or foreign objects.

The parasympathetic nervous system, through acetylcholine, causes bronchoconstriction. It's like a brake on the airways.

Medications that widen the airways by activating β-adrenergic receptors, making it easier to breathe.

Medications that reduce inflammation in the airways, helping to prevent bronchoconstriction and improve breathing.

Reduced ability of the lungs to expand easily due to stiffness, caused by inflammation or scar tissue.

The lungs don't recoil as much, requiring active expiration using muscles, which increases energy expenditure.

The pressure exerted by a specific gas within a mixture of gases, such as the air we breathe or the dissolved gases in our blood.

The partial pressure of oxygen in the alveoli, typically around 100-105mmHg at sea level.

The partial pressure of oxygen in arterial blood, usually around 100mmHg at sea level, similar to the alveoli.

The partial pressure of oxygen in venous blood, typically around 40mmHg at rest. This value decreases during exercise.

Gases move across the respiratory membrane from areas of higher partial pressure to lower partial pressure. Oxygen moves from alveoli to blood, and carbon dioxide moves from blood to alveoli.

Reduced concentration gradients (high altitude, pulmonary disease), decreased surface area (fluid in alveoli, blocked airways, emphysema), and thickened membranes can all hinder gas exchange.