Class 10 Science – Control and Coordination

Class 10 Science Chapter 6: Concepts

Chapter 6: Control and Coordination

Introduction

In order to survive and function efficiently, all living organisms need to control and coordinate various activities. Control refers to the regulation of body functions, while coordination ensures that different parts of the body work together harmoniously.

  • In animals, this is achieved by the nervous system and the endocrine system (hormonal control).
  • In plants, coordination is carried out by plant hormones and responses to stimuli like light, gravity, and touch.

These systems help organisms detect changes in the environment (stimuli) and respond appropriately, ensuring survival.

Nervous System in Humans

The nervous system is responsible for sending, receiving, and interpreting information. It consists of:

A. Components of the Nervous System

  1. Receptors – Special cells that detect stimuli (Example: Eyes detect light, skin detects touch).
  2. Effectors – Organs (muscles or glands) that respond to nerve impulses.
  3. Neurons – Nerve cells that transmit signals.

B. Structure of a Neuron

A neuron (nerve cell) is the basic unit of the nervous system. It consists of:

  • Dendrites: Receive signals from other neurons or receptors.
  • Cell Body: Processes information and generates a response.
  • Axon: Transmits impulses to other neurons or muscles.
Example: If you touch a hot object, receptors in the skin detect the heat and send a signal to the brain through neurons. The brain then processes this information and sends a signal to your hand to pull away.

Diagram of Neuron:

 

Neuron

Reflex Action and Reflex Arc

A reflex action is a quick, automatic response to a stimulus that does not involve the brain. It is controlled by the spinal cord to save time and prevent injury.

Example of Reflex Action:

  • Pulling your hand away from a hot surface.
  • Blinking when something approaches your eye.
  • Knee-jerk reaction when the doctor taps below your knee.

The reflex arc is the pathway followed by the nerve impulse in a reflex action. It consists of:

  1. Receptor – Detects stimulus (Example: Skin detects heat).
  2. Sensory Neuron – Carries the signal to the spinal cord.
  3. Interneuron (Relay Neuron) – Processes the signal in the spinal cord.
  4. Motor Neuron – Sends the response signal to muscles.
  5. Effector (Muscle or Gland) – Performs the action (Example: Hand pulls away).
Diagram of Reflex Arc:

 

Human Brain

The brain is the control center of the body. It is protected by:

  • Skull (Cranium): Hard outer covering.
  • Meninges: Protective membranes.
  • Cerebrospinal Fluid: Provides cushioning.

Major Parts of the Brain and Their Functions:

  1. Cerebrum (Largest Part): Controls thinking, memory, speech, and voluntary movements.
  2. Cerebellum: Maintains posture, balance, and muscle coordination.
  3. Medulla Oblongata: Controls involuntary actions like heartbeat, breathing, and digestion.
Example:
  • If you decide to raise your hand in class, your cerebrum controls this voluntary action.
  • If you trip while walking, your cerebellum helps you regain balance.
  • Your medulla oblongata ensures your heart keeps beating even when you sleep.
Diagram of Human Brain:

Coordination in Plants

Unlike animals, plants lack a nervous system but still respond to stimuli. These responses are controlled by plant hormones and environmental factors.

A. Types of Plant Movements

  1. Tropic Movements (Directional Responses) – Growth in response to external stimuli:

    • Phototropism: Movement towards light (Example: Sunflower bends toward sunlight).
    • Geotropism: Movement in response to gravity (Example: Roots grow downward, shoots grow upward).
    • Hydrotropism: Growth towards water (Example: Roots grow toward a water source).
    • Thigmotropism: Growth in response to touch (Example: Climbing plants like Pea tendrils wrap around a support).

  2. Nastic Movements (Non-Directional Responses) – Movements that do not depend on the direction of the stimulus:

    • Example: The leaves of Mimosa pudica (Touch-Me-Not plant) close when touched.
Diagram of Tropic Movements in Plants:

Hormonal Coordination in Animals

The endocrine system controls body functions using hormones, which are chemical messengers secreted by endocrine glands into the bloodstream.

Important Endocrine Glands and Their Functions:

  1. Pituitary Gland (Master Gland): Controls growth and other glands.
    • Example: Growth hormone regulates height.
  2. Thyroid Gland: Produces thyroxine, which controls metabolism.
    • Example: Iodine deficiency causes goiter.
  3. Adrenal Glands: Secrete adrenaline, which helps in emergency “fight or flight” response.
    • Example: When scared, your heart beats faster due to adrenaline.
  4. Pancreas: Produces insulin, which controls blood sugar levels.
    • Example: Insulin deficiency leads to diabetes.
  5. Testes (Males): Produce testosterone, responsible for male features like deep voice and facial hair.
  6. Ovaries (Females): Produce estrogen and progesterone, which regulate the menstrual cycle and pregnancy.
Diagram of Endocrine System:

Hormonal Coordination in Plants

Plants regulate their growth and responses using phytohormones (plant hormones).

Important Plant Hormones:

  1. Auxins: Promote cell elongation and help in phototropism.
    • Example: Auxins make plant stems bend toward light.
  2. Gibberellins: Promote stem growth and seed germination.
    • Example: Farmers use gibberellins to increase fruit size.
  3. Cytokinins: Promote cell division and delay aging in leaves.
  4. Abscisic Acid: Inhibits growth and helps plants survive drought.
    • Example: Causes leaves to fall in autumn to prevent water loss.
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