The big picture
This chapter has two carriers. One is the nerve. The other is the hormone in the blood.
| Idea | The rule |
|---|---|
| One body, many parts | A body has many parts with different jobs. They must act together, not alone. The nervous system and hormones keep them in step. |
| The message and the messenger | A neuron is a nerve cell. It carries a signal as electricity, one way, dendrite to nerve ending. At a synapse, it crosses as a chemical to the next cell. |
| The shortest path | A reflex is a fast, automatic response. Its arc often closes in the spinal cord. The muscle acts without waiting for the thinking part of the brain. |
| The centre and the cable | The brain and spinal cord are the body's centre. The brain has three parts: forebrain, midbrain and hindbrain. The cerebellum keeps balance. The medulla runs blood pressure, salivation and vomiting. |
| Messages in the blood | A hormone is a chemical messenger. A gland releases it into the blood. The blood carries it round the body. It acts only on its target cells. |
| Sugar and feedback | Feedback keeps blood sugar steady. When blood sugar rises, the pancreas makes more insulin. When the sugar falls, it makes less. |
| Plants bend toward the light | Plants coordinate by chemistry, not nerves. Light makes a growth chemical gather on the shaded side. The shaded side grows more, so the shoot bends toward light. |
| Other plant hormones | Plants make other hormones too. Gibberellins help stems grow longer. Cytokinins help cells divide. Abscisic acid slows growth. |
| Fast and slow, side by side | Nerves are usually fast and reach one place. Hormones are usually slower and reach many places, and some last longer. Each fits jobs the other does badly. |
Two habits help with every row. Follow the signal, not the organ. Ask if it travels fast along a nerve. Or does the blood carry it to many places? Ask how long it lasts. A reflex is over at once. A hormone can keep working for longer.
Chapter 6 of your Class 10 Science book is Control and Coordination. Read it now. Its figures will already make sense.
Next, Chapter 7 asks where new bodies come from. It is called How do Organisms Reproduce?