Chapter 17: Breathing and Exchange of Gases – Part 3

- April 28, 2025

✅ Chapter 17: Breathing and Exchange of Gases – Part 3

🔍 Regulation of Respiration and Disorders of the Respiratory System

🧠 How is Breathing Regulated?

Breathing is an automatic, rhythmic process — but how does the body control it without conscious effort?
The answer lies in the Respiratory Centers located in the brain.

🧬 Respiratory Centers in the Brain:

Located primarily in the medulla oblongata and pons.

Center	Location	Function
Medullary Respiratory Center	Medulla	Controls rhythm of breathing
Pneumotaxic Center	Pons	Regulates rate and pattern of breathing
Chemosensitive Area	Medulla	Detects chemical changes in blood

🔵 Medullary Respiratory Center:

Has two regions:
1. Inspiratory center: Initiates inspiration
2. Expiratory center: Active during forceful expiration

✅ Normal breathing (eupnea) is controlled by rhythmic impulses from the inspiratory center.

🔵 Pneumotaxic Center:

Located in the upper part of the pons.
Sends inhibitory signals to the inspiratory center.
Function: Limits the duration of inspiration → thus increases the rate of breathing.

✅ Key point:

Strong pneumotaxic signals = Shorter inspiration = Faster breathing.

🔵 Chemosensitive Area:

Adjacent to the respiratory center.
Sensitive to:
- High CO₂ concentration
- High H⁺ ions concentration

When CO₂ or H⁺ levels rise → this center stimulates the respiratory center → breathing rate increases to expel CO₂.

✅ Note:

The body is more sensitive to CO₂ levels than oxygen!

🧪 Role of Chemoreceptors:

Besides the brain, peripheral chemoreceptors also help regulate breathing.

Located in:

Carotid bodies (at the fork of carotid arteries)
Aortic bodies (on the aortic arch)

✅ Function:

Detect low O₂ levels and stimulate respiratory center.

⚡ Important Stimuli for Breathing:

Stimulus	Effect on Breathing
↑ CO₂	Strong stimulation to breathe
↑ H⁺ ions	Strong stimulation
↓ O₂	Moderate stimulation (important in chronic hypoxia)

✅ In normal conditions, CO₂ is the primary regulator of breathing.

🚑 Disorders of the Respiratory System:

The respiratory system is prone to several disorders. Let's discuss major ones.

1. Asthma:

Definition: Chronic inflammatory disease of the airways.
Cause: Allergic reaction to foreign substances like dust, pollen.
Symptoms:
- Wheezing
- Difficulty in breathing
- Coughing

✅ Pathophysiology:

Bronchioles constrict → airflow is restricted → breathing becomes difficult.

2. Emphysema:

Definition: A condition where the alveolar walls are damaged, reducing surface area for gas exchange.
Major cause: Smoking
Symptoms:
- Breathlessness
- Reduced oxygen supply

✅ Key Point:

Elasticity of lungs decreases drastically.

3. Chronic Obstructive Pulmonary Disease (COPD):

Definition: Progressive disease that makes breathing difficult.
Includes: Both chronic bronchitis and emphysema.
Main causes: Smoking, long-term exposure to pollutants.

✅ Important:

COPD is irreversible and worsens over time.

4. Occupational Lung Diseases:

Due to prolonged exposure to dust in certain industries.

Examples:

Silicosis: Inhalation of silica dust.
Asbestosis: Inhalation of asbestos fibers.

✅ Prevention:

Wearing masks, improving ventilation.

5. Pneumonia:

Definition: Infection of the alveoli (lungs).
Cause: Bacteria (e.g., Streptococcus pneumoniae), viruses, fungi.
Symptoms:
- Cough
- Chest pain
- Fever
- Difficulty in breathing

✅ Key Fact:

Alveoli get filled with fluid, hampering gas exchange.

6. Tuberculosis (TB):

Definition: Infectious disease affecting the lungs.
Cause: Mycobacterium tuberculosis
Symptoms:
- Chronic cough (with blood sometimes)
- Weight loss
- Night sweats
- Fever

✅ Important Note:

TB is preventable and curable with proper antibiotics.

🔍 Summary Table:

Disorder	Key Features
Asthma	Bronchial constriction, allergies
Emphysema	Alveolar damage, reduced elasticity
COPD	Progressive breathing difficulty
Silicosis	Dust-induced lung damage
Pneumonia	Infection, fluid in alveoli
Tuberculosis	Bacterial infection, chronic cough

Search This Blog

BIOLOGYATEASE