Question 2
sensory nerves and mixed nerves.
| Sl. No. | Sensory Nerves | Mixed Nerves |
|---|---|---|
| 1. | Sensory nerves are the nerves that carry messages from the sense organs to either the spinal cord or the brain. | Mixed nerves perform the function of both sensory nerves and motor nerves. They transmit messages from the central nervous system to the muscles of the body. |
| 2. | They contain only sensory fibres. | They contain sensory fibres as well as motor fibres. |
| 3. | For example, the optic nerve that sends messages from the eye to the brain is a sensory nerve. | For example, the nerve that transmits messages to the tongue is a mixed nerve. |
Chapter 8: Human Body: Nervous System — ICSE Class VII Biology Notes
Comprehensive ICSE Class VII Biology notes on the Human Nervous System covering brain parts (cerebrum, cerebellum, medulla), spinal cord, neuron structure, reflex action, reflex arc, and voluntary vs involuntary actions.
Key Concepts and Topics
Topics covered: Brain, Spinal cord, Neurons, Reflex action, Reflex arc
Weightage: Approximately 8 marks in the exam
Important Points to Remember
- CNS = brain + spinal cord; PNS = nerves
- Brain parts: cerebrum (thinking), cerebellum (balance), medulla (involuntary)
- Neuron: cell body + dendrites (receive) + axon (transmit)
- Reflex action: automatic response controlled by spinal cord
- Reflex arc: receptor to sensory nerve to spinal cord to motor nerve to effector
- Brain protected by skull, meninges, and cerebrospinal fluid
- Voluntary actions involve brain; reflex actions bypass brain
Frequently Asked Questions
Q: What is a reflex action?
A: A quick, automatic, involuntary response to a stimulus, controlled by the spinal cord without involving the brain.
Q: What are the three main parts of the brain?
A: Cerebrum (thinking), Cerebellum (balance), and Medulla oblongata (involuntary actions).
Q: What is a reflex arc?
A: The pathway of a reflex: Receptor → Sensory nerve → Spinal cord → Motor nerve → Effector.
Exam Preparation Tips
- Focus on understanding concepts rather than rote memorization
- Practice drawing and labelling diagrams regularly
- Use comparison tables for topics that require differentiation
- Solve previous year questions and practice papers
- Review the chapter notes provided by Bright Tutorials for comprehensive coverage
For complete chapter notes, practice questions, and test papers, contact Bright Tutorials at 9403781999.