Peripheral nervous system consists of different types of nerves which connect the central nervous system to all parts of the body. Cranial nerves, spinal nerves, sympathetic and parasympathetic nerves are all connected to different parts of the body. Which of the following does not belong to cranial nerves ?
- Olfactory nerves
- Auditory nerves
- Optic nerves
- Sympathetic nerves
Sympathetic nerves
Reason — Cranial nerves emerge from the brain. Some of the cranial nerves are — the olfactory (for nose), optic (for eyes) and auditory (for ears). While cranial nerves are a part of Somatic nervous system, Sympathetic nerves are a part of Autonomic nervous system.
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.