📝 Chapter Notes & Revision
Control and Coordination
📐 Formula & Cheat Sheet (English)
Quick Revision Notes & Formula Sheet
Class: 10th Science
Chapter: Control and Coordination
Board: MP Board (NCERT)
1. Introduction to Control and Coordination
- Control and Coordination: The working together of various organs of an organism in a systematic manner to produce a proper response to the stimulus is called control and coordination.
- Stimulus: Any change in the environment (external or internal) that brings about a reaction in an organism (e.g., heat, light, touch, pain).
- Response: The reaction of our body to a stimulus.
2. Control and Coordination in Animals
Control and coordination in animals are brought about by two main systems:
- Nervous System (Electrical impulses)
- Endocrine System (Chemical messengers/Hormones)
A. The Human Nervous System
The nervous system consists of the Brain, Spinal Cord, and a network of Nerves. The structural and functional unit of the nervous system is the Neuron.
Structure of a Neuron (Nerve Cell)
- Dendrite: Acquires information/impulses from the environment or other neurons.
- Cell Body (Cyton): Information travels as an electrical impulse from the dendrite to the cell body.
- Axon: Conducts the impulse away from the cell body to its distal end.
- Synapse: The microscopic gap between the nerve ending of one neuron and the dendrite of the next neuron. Here, electrical signals are converted into chemical signals (neurotransmitters) to cross the gap.
Reflex Action and Reflex Arc
- Reflex Action: A sudden, involuntary, and automatic response to a stimulus to protect the body from harm.
- Reflex Arc: The pathway taken by nerve impulses in a reflex action. $$\text{Stimulus} \rightarrow \text{Receptor} \rightarrow \text{Sensory Neuron} \rightarrow \text{Spinal Cord (CNS)} \rightarrow \text{Motor Neuron} \rightarrow \text{Effector (Muscle/Gland)} \rightarrow \text{Response}$$
B. Human Brain
The brain is the main thinking part of the body and part of the Central Nervous System (CNS). It is protected by a bony box called the cranium and filled with cerebrospinal fluid for shock absorption.
The brain is divided into three main regions:
- Forebrain:
- The main thinking part of the brain.
- Has regions for hearing, smell, sight, memory, etc.
- Controls voluntary actions.
- Midbrain: Controls involuntary actions like reflex movements of head, neck, and trunk.
- Hindbrain:
- Cerebellum: Controls posture, balance, and precision of voluntary actions (e.g., riding a bicycle, walking in a straight line).
- Medulla: Controls involuntary actions like blood pressure, salivation, vomiting, heart rate, and respiration.
- Pons: Regulates respiration.
C. Coordination in Plants
Plants do not have a nervous system or muscles. They show two types of movements:
1. Nastic Movements (Non-directional movements)
- Independent of growth.
- Immediate response to stimulus.
- Example: Drooping of leaves of the Mimosa pudica (touch-me-not) plant when touched.
2. Tropic Movements (Directional growth movements)
- Dependent on growth.
- Direction of response is determined by the direction of the stimulus.
- Types of Tropism:
- Phototropism: Movement towards or away from light (e.g., Shoot bends towards light).
- Geotropism: Movement towards or away from gravity (e.g., Roots grow downward).
- Hydrotropism: Movement towards water (e.g., Roots grow towards water).
- Chemotropism: Movement in response to chemicals (e.g., Growth of pollen tube towards ovule).
D. Plant Hormones (Phytohormones)
Chemical compounds that help to coordinate growth, development, and responses to the environment in plants.
| Plant Hormone | Major Function |
|---|---|
| Auxin | Promotes cell elongation, shoot growth, and bends towards light (phototropism). |
| Gibberellins | Promotes stem elongation, germination, and fruit growth. |
| Cytokinins | Promotes cell division; found in high concentration in fruits and seeds. |
| Abscisic Acid (ABA) | Inhibits growth; causes wilting and falling of leaves (stress hormone). |
E. Animal Hormones (Endocrine System)
Hormones are chemical messengers secreted directly into the blood by endocrine glands. They act on specific target organs.
Major Endocrine Glands and Their Functions in Humans:
| Gland | Hormone Produced | Key Functions |
|---|---|---|
| Hypothalamus | Releasing Hormones | Regulates secretions of pituitary gland. |
| Pituitary Gland (Master Gland) | Growth Hormone (GH) | Regulates overall body growth and development. |
| Thyroid Gland | Thyroxine | Regulates metabolism of carbohydrates, fats, and proteins. (Requires Iodine for synthesis) |
| Pancreas | Insulin | Lowers blood sugar (glucose) levels. (Deficiency causes Diabetes) |
| Adrenal Gland | Adrenaline | Prepares the body for emergency situations (Fight or Flight response). Increases heart rate and breathing. |
| Testes (in males) | Testosterone | Controls secondary sexual characters and sperm production in males. |
| Ovaries (in females) | Estrogen & Progesterone | Control secondary sexual characters, menstrual cycle, and pregnancy. |
3. Important Board Exam Terms to Remember
- Feedback Mechanism: The regulatory mechanism in which the level of hormones in the blood is maintained by self-adjustment (e.g., if blood sugar rises, insulin is released; when normal, insulin release stops).
- Goitre: A disease caused by the deficiency of iodine in diet, leading to the swelling of the thyroid gland.
- Diabetes: A disease caused by insufficient secretion of insulin by the pancreas, leading to high blood glucose levels.