Question 3
Describe the human central nervous system along with its parts and functions.
The central nervous system consists of the brain and the spinal cord. It is the control centre for all body functions. It is the site for all information processing in the body. It is responsible for processing every sensation and thought a human being experiences. It has two parts — Brain and Spinal Cord.
- Brain — The Brain is the main control centre of the nervous system situated in the cranium of the skull. It controls our thinking, feelings, movement and senses. It has three parts — Cerebrum, Cerebellum and Medulla oblongata.
- Cerebrum — The cerebrum is the uppermost, largest and the most prominent part of the brain. It is responsible for the sensation of pain, temperature, touch, sight, sound, taste and smell. It also controls mental activities such as memory, intelligence, thinking and reasoning.
- Cerebellum — The cerebellum is a small, egg-shaped lobe located at the base under the cerebrum. It helps in the muscle coordination and balance of the body.
- Medulla oblongata — The Medulla oblongata is the lowermost part of the brain located at the base of the skull. It controls breathing, heartbeat, coughing, sneezing and other involuntary functions.
- Spinal cord — The spinal cord is the continuation of the medulla oblongata of the brain. It is like a cord that emerges from a hole at the base of the skull and runs through the vertebral column. The spinal cord conducts reflexes below the neck. It conducts sensory impulses from the skin and muscles to the brain. It conducts motor responses from the brain to the muscles of the trunk and limbs.
Nervous System – Interactive Study Guide
The nervous system controls and coordinates all body activities through electrical impulses. It consists of the CNS (brain + spinal cord) and PNS (nerves connecting CNS to body).
Neuron – Quick Structure
- Cell body: Nucleus, metabolic centre
- Dendrites: Receive impulses (towards cell body)
- Axon: Carries impulses away (from cell body)
- Myelin sheath: Insulation, speeds up impulse
- Synaptic knob: Transmits to next neuron
Brain Parts – Quick Reference
| Part | Function | Memory Aid |
|---|---|---|
| Cerebrum | Thinking, memory, senses, voluntary actions | BRainpower |
| Cerebellum | Balance, coordination | BaLLance |
| Medulla | Involuntary actions (breathing, heartbeat) | Must Do |
Reflex Action – Step by Step
Stimulus → Receptor (skin) → Sensory neuron → Spinal cord (relay neuron) → Motor neuron → Effector (muscle) → Response (hand pulls away)
Controlled by spinal cord (NOT brain) for faster response.
Voluntary vs Involuntary vs Reflex
| Voluntary | Involuntary | Reflex | |
|---|---|---|---|
| Control | Conscious | Unconscious | Unconscious |
| Centre | Cerebrum | Medulla | Spinal cord |
| Speed | Slow | Moderate | Very fast |
| Example | Writing | Breathing | Knee-jerk |
Self-Test Questions
- Draw and label a neuron.
- Why are reflex actions controlled by the spinal cord and not the brain?
- Name the three parts of the brain and state one function of each.
- What is the difference between sensory and motor neurons?
- Draw a reflex arc and label all parts.