Control and Coordination – Class 10 Science Chapter 6 Notes & NCERT PDF

Introduction

When we see a tasty dish, our mouth waters; when we touch something hot, we pull our hand back at once. Living organisms respond to changes in the environment in carefully controlled ways. In animals this control and coordination is done by two systems working together — the nervous system (electrical impulses) and the endocrine system (chemical messengers called hormones). Plants, which have no nervous system, also coordinate their responses using chemical signals.

Key Concepts

1. Nervous system in animals

Information from the environment is detected by receptors in sense organs — e.g., gustatory receptors (taste) in the tongue and olfactory receptors (smell) in the nose. A neuron (nerve cell) is the unit of the nervous system:

2. Reflex actions and the reflex arc

A reflex action is a sudden, automatic response to a stimulus, done without thinking — like pulling the hand away from a flame. Thinking would take too long, so the body uses a shorter pathway called a reflex arc:

Receptor → sensory neuron → relay neuron in the spinal cord → motor neuron → effector (muscle)

Reflex arcs are formed in the spinal cord, where input nerves meet output nerves. Information also reaches the brain, but the response has already happened.

3. Human brain

The brain and spinal cord form the central nervous system (CNS). The peripheral nervous system consists of cranial nerves (from the brain) and spinal nerves (from the spinal cord). The brain has three regions:

The brain is protected inside a bony box (the skull) and cushioned by a fluid-filled balloon; the spinal cord is protected by the vertebral column.

4. How nervous tissue causes action

Muscle cells move when special proteins in them change their shape and arrangement in response to nervous impulses, making the muscle cell shorter.

5. Coordination in plants

Plants use two kinds of movement:

- Phototropism — shoots bend towards light, roots away from it.

- Geotropism — roots grow downwards (towards gravity), shoots upwards.

- Hydrotropism — response to water.

- Chemotropism — response to chemicals, e.g., growth of pollen tubes towards ovules.

- Tendrils — the part touching a support grows less rapidly than the part away from it, so the tendril coils around the support.

Plant hormones:

6. Hormones in animals

Hormones are secreted by endocrine glands directly into the blood and act on target cells. The book's Table 6.1 lists:

Feedback mechanism — the timing and amount of hormones are regulated. If blood sugar rises, pancreatic cells detect it and produce more insulin; as sugar falls, insulin secretion is reduced.

Diagrams to Draw (described in words)

Activities in the Chapter

Board Exam Focus

Key Terms

Common Mistakes