RRB ALP Science Respiratory System By PW Arti Mam

RRB ALP Science Respiratory System: The respiratory system is vital for life, enabling the exchange of gases essential for metabolic processes. It involves both the mechanical act of breathing and the complex biochemical reactions of cellular respiration. Understanding this system is crucial for grasping how the body generates energy and maintains homeostasis.

Difference between Respiration and Breathing

Breathing is a physical process involving simply inhaling and exhaling air. In contrast, Respiration refers to the biochemical reactions that occur inside the body when air is inhaled, primarily for energy production.

Air Composition during Respiration

We inhale air and exhale air, not just specific gases. The composition of inhaled and exhaled air differs significantly:

Location of Respiration

General respiration, involving air intake and expulsion, occurs in the lungs. Cellular respiration (कोशिकीय श्वसन), the process of energy generation, primarily occurs in the mitochondria.

Process of Cellular Respiration and ATP Production

Food, such as a six-carbon molecule like glucose, is initially broken down in the cytoplasm into a three-carbon molecule (pyruvic acid). This pyruvic acid then enters the mitochondria. In the presence of oxygen, pyruvic acid further breaks down into carbon dioxide, water, and ATP.

ATP (Adenosine Triphosphate) is the energy currency of the cell (कोशिका की ऊर्जा मुद्रा). It is primarily formed during the Krebs cycle within the mitochondria through electron transport, releasing a large amount of energy. The sustenance of life fundamentally depends on ATP production.

Mammalian Respiration

Mammals respire through lungs. However, other organisms use different respiratory organs:

• Gills: Fish

• Skin: Many organisms

• Trachea: Many organisms (e.g., cockroaches)

Location of Aerobic Respiration

Aerobic respiration which requires oxygen, primarily occurs in the mitochondria. The cytoplasm can host both aerobic and anaerobic respiration. The initial breakdown of glucose into pyruvic acid takes place in the cytoplasm, serving as a common step for both types of respiration.

Lobes of the Lungs

The right lung is divided into three lobes, while the left lung is divided into two lobes. The left lung has fewer lobes due to the presence of the cardiac notch (हृदय गुहा), which accommodates the heart.

Lung Capacity

The maximum capacity of the lungs to hold gas, known as Total Lung Capacity, is approximately 5 to 6 liters (or around 5800 mL). During respiration, the exhaled air contains 16% oxygen, as 4-5% of the inhaled 21% oxygen is consumed by the body.

Control of Respiration

Involuntary functions, including respiration, heart rate, and blood circulation, are controlled by the Medulla Oblongata. The Pons Varolii (or just Pons) primarily regulates the rhythm of respiration (number of breaths per minute) and assists the Medulla.

Function of Hemoglobin

Hemoglobin is responsible for the transport of oxygen. Within the blood, RBCs (Red Blood Cells) carry oxygen, and Hemoglobin within RBCs transports it. Oxygen attaches to the iron component of hemoglobin.

Anaerobic Respiration in Microbes

When bacteria and fungi respire without oxygen, this process is called fermentation.

Divisions of the Trachea leading to Alveoli

The trachea (windpipe) undergoes several divisions:

1. Bronchi (ब्रोंकाय): The first division, leading into each lung.

2. Bronchioles (ब्रोनकली): Further divisions resembling tree branches stemming from the bronchi.

3. Alveoli (अल्वलीज़ / कुपिकाएं): Grape-like clusters at the ends of bronchioles, numbering in the millions. These are the final divisions of the tracheal branches and the functional units for gas exchange.

Function of Epiglottis

The epiglottis (घाटी का ढक्कन) is a flap that covers the windpipe during swallowing. This prevents food from entering the windpipe and directs it into the food pipe. To avoid food entering the windpipe, it's generally advised not to talk or laugh loudly while eating.

Occupational Lung Disease: Silicosis

Workers in environments with high dust exposure, such as mines or factories, are highly susceptible to Silicosis. This disease is caused by inhaling excessive silica particles (e.g., from stone cutting, construction), which damage the lungs. Other lung diseases include Pneumonia (bacterial), Bronchitis (bronchiole damage), and Emphysema (often linked to smoking).

Protective Membrane of Lungs

The lungs are covered by the pleura membrane. Between its layers, pleural fluid is present, which helps the lungs tolerate pressure changes during breathing.

Energy Production in Aerobic Respiration

Aerobic respiration is highly efficient, producing 38 ATP molecules from one glucose molecule.

Most Exhaled Gas

During respiration, carbon dioxide is exhaled in the largest amount (approximately 4%), produced by the body from absorbed oxygen.

Oxygen & CO₂ Exchange Dependence

The amount of oxygen uptake and carbon dioxide release in the body largely depends on hemoglobin. Hemoglobin's role in RBCs is crucial for oxygen transport. While RBCs/hemoglobin transport approximately 97% of oxygen, 3% of oxygen can also be transported by plasma.

Common Step in Aerobic and Anaerobic Respiration

Glycolysis is the common step for both aerobic and anaerobic respiration. In glycolysis, a six-carbon glucose molecule is broken down into two three-carbon pyruvic acid molecules in the cytoplasm.

• If aerobic, pyruvic acid proceeds to the mitochondria.

• If anaerobic, it results in products like lactic acid or alcohol.

Final Product of Anaerobic Respiration

The final product of anaerobic respiration in human muscle cells is lactic acid. For example, intense exercise can lead to lactic acid accumulation, causing muscle pain. In the absence of oxygen, carbohydrates are broken down into either lactic acid or ethyl alcohol.

Weight of Lungs

The average weight of a pair of human lungs is approximately 1 to 1.5 kg. The right lung is slightly heavier than the left lung because the left lung has a cardiac notch (a depression) where the heart is situated.

Location of Krebs Cycle

The Krebs cycle occurs in the mitochondria. This cycle involves electron transport, releasing a large amount of energy in the form of ATP. Key intermediate products synthesized during the Krebs cycle include fumaric acid and succinic acid.

Breathing Rate in Adults and Related Terminology

A healthy adult takes 12 to 15 breaths per minute.

• Eupnea: Normal breathing rate. (Memory Tip: Remember 'Eupnea' for normal breathing rate, as it has appeared in reasoning questions.)

• Hypopnea: Breathing rate less than 10 breaths per minute.

• Hyperpnea: Breathing rate more than 20 breaths per minute.

Whistling Sound During Exhalation: A Symptom of Asthma

A whistling sound during inhalation or exhalation is a symptom of Asthma. It is often caused by the fungus Aspergillus fumigatus, which accumulates and narrows the airway in the trachea. This narrowing makes breathing difficult, forcing air through a constricted passage and causing the characteristic whistling sound. Asthma currently has no permanent cure, requiring ongoing management.

Diaphragm Movement During Inhalation

During inhalation (inhaling air), the diaphragm (तनुपट), which is normally C-shaped or dome-shaped, flattens (चपटा). This downward movement expands the chest cavity, allowing the lungs to fill with air.

Gas Exchange in Lungs

Gas exchange in the lungs occurs via the alveoli (कुपिकाएं), the functional units of the lungs. An alveolus receives oxygen-rich air and is connected to a pulmonary artery carrying deoxygenated blood (rich in CO₂). At the alveoli, gas exchange takes place: Carbon dioxide diffuses from the blood into the alveolus, and oxygen from the inhaled air diffuses into the blood. This process effectively purifies the blood, which is then carried by the pulmonary vein to the heart.

Air Component Unchanged During Respiration

The amount of nitrogen in the air remains unchanged during respiration. 78% is inhaled and 78% is exhaled because the body does not consume nitrogen.