SSC CGL - Detailed Guide 2025
Self-Paced Course
Respiratory and Nervous Systems
Reference: NCERT Class 10-12, Lucent GK
1. Human Respiratory System
The respiratory system facilitates the exchange of oxygen and carbon dioxide between the body and the environment.
A. Organs of Human Respiration (In order)
| Organ | Function |
|---|---|
| Nostrils | Air enters; hairs filter dust |
| Nasal Cavity | Warms, moistens, and filters air |
| Pharynx | Common passage for food and air |
| Larynx (Voice box) | Produces sound; air passage |
| Trachea (Windpipe) | Tube with cartilage rings; filters air with cilia and mucus |
| Bronchi | Two branches from trachea into each lung |
| Bronchioles | Smaller airways inside lungs |
| Alveoli | Thin-walled sacs for gas exchange with capillaries |
B. Mechanism of Breathing
| Phase | Process |
|---|---|
| Inhalation | Diaphragm contracts (moves down); rib cage expands; air enters lungs |
| Exhalation | Diaphragm relaxes (moves up); rib cage contracts; air exits lungs |
Note: Breathing is a physical process; respiration is biochemical.
C. Types of Respiration
| Type | Site | Oxygen Used | End Products |
|---|---|---|---|
| Aerobic | Mitochondria | Yes | CO₂, H₂O, and Energy (ATP) |
| Anaerobic | Cytoplasm | No | Lactic acid / Alcohol + CO₂ + less ATP |
Aerobic Respiration Equation:
C₆H₁₂O₆ + 6O₂ ⟶ 6CO₂ + 6H₂O + Energy (ATP)
In humans, anaerobic respiration occurs temporarily in muscles during heavy exercise → causes fatigue.
2. Nervous System
The nervous system controls and coordinates all voluntary and involuntary activities of the body.
A. Parts of Human Nervous System
| Division | Description |
|---|---|
| Central Nervous System (CNS) | Brain and Spinal Cord -- command and integration center |
| Peripheral Nervous System (PNS) | Nerves (cranial and spinal) -- link CNS to body |
| Autonomic Nervous System (ANS) | Controls involuntary actions (heart rate, digestion) |
B. Brain
Protected by skull and three membranes (meninges); surrounded by cerebrospinal fluid.
| Part | Function |
|---|---|
| Cerebrum | Largest part; controls voluntary actions, intelligence, learning, memory |
| Cerebellum | Coordinates balance and muscular activity |
| Medulla Oblongata | Controls involuntary actions (breathing, heartbeat, vomiting) |
| Hypothalamus | Controls hunger, thirst, temperature, emotions; regulates pituitary gland |
| Pituitary Gland | "Master gland" -- controls endocrine functions |
Brain is divided into Forebrain (Cerebrum, Hypothalamus), Midbrain, and Hindbrain (Cerebellum, Medulla).
C. Spinal Cord
| Feature | Description |
|---|---|
| Location | Extends from medulla down the vertebral column |
| Function | Conducts signals between brain and body; controls reflexes |
Reflex Action: Immediate response to a stimulus without conscious brain involvement (e.g. pulling hand from flame)
D. Nerves
| Type | Function | Origin |
|---|---|---|
| Sensory Nerves | Carry messages from sense organs to brain | Skin, eyes, ears, etc. |
| Motor Nerves | Carry instructions from brain to muscles | Brain/spinal cord to muscles |
| Mixed Nerves | Carry both sensory and motor signals | Most common type |
Key Points:
- • Synapse is a junction between two neurons.
- • Impulse travels as electrical signal within neurons and as chemical signal across synapse.
- • Neurotransmitters like acetylcholine help signal transmission across synapse.
Master Biology Concepts with Us!
Join Courage Library for comprehensive study materials and expert guidance.
Be a Couragian!