Control and Coordination Class 10 || Science|| Chapter 6 Notes

Control and Coordination Class 10 ||Science|| Chapter 6 Notes

1. Introduction to Control and Coordination

Control and coordination in organisms involve the regulation of their body functions to respond to changes in the environment, known as stimuli.

  • In animals, control and coordination are carried out by the nervous system and the endocrine system.
  • In plants, control and coordination occur through the action of plant hormones and response to stimuli.

2. Nervous System in Animals

The nervous system is responsible for controlling and coordinating voluntary and involuntary actions in animals. It consists of three key components:

  • Receptors: These are specialized cells or organs that detect stimuli from the environment (e.g., eyes, ears, skin).
  • Effectors: These are organs or tissues (like muscles and glands) that respond to nervous impulses.
  • Neurons: These are nerve cells that transmit signals throughout the body. A typical neuron has three parts:
    • Cell body: Contains the nucleus and cytoplasm.
    • Dendrites: Receive signals from other neurons.
    • Axon: Transmits signals to other neurons or effectors.

Nerve Impulse Transmission

The nervous system works by transmitting electrical signals called nerve impulses. The transmission of nerve impulses involves:

  1. Stimulus reception by receptors.
  2. Generation of an electrical impulse that travels through the neuron.
  3. Transmission of the impulse across a gap called a synapse to the next neuron or muscle fiber.

3. Human Nervous System

The human nervous system is divided into two parts:

1. Central Nervous System (CNS)

The CNS consists of the brain and spinal cord.

  • Brain: The brain is the control center of the body. It has three main regions:

    • Forebrain: Controls voluntary actions, emotions, reasoning, and memory.
    • Midbrain: Connects the forebrain with the hindbrain, and controls certain reflex actions.
    • Hindbrain: Controls balance, movement, and involuntary actions (like breathing and heart rate).

  • Spinal Cord: It acts as a relay between the brain and the rest of the body, and also controls reflex actions.

2. Peripheral Nervous System (PNS)

The PNS connects the CNS to different parts of the body. It consists of:

  • Sensory nerves: Carry signals from receptors to the CNS.
  • Motor nerves: Carry signals from the CNS to effectors (muscles or glands).

4. Reflex Action and Reflex Arc

A reflex action is a quick, automatic response to a stimulus that does not involve conscious thought. It is controlled by the spinal cord, allowing for a faster response.

  • Example: Pulling your hand away from a hot object is a reflex action.

The pathway taken by nerve impulses in a reflex action is called a reflex arc. It involves:

  1. A receptor that senses the stimulus.
  2. A sensory neuron that transmits the impulse to the spinal cord.
  3. A relay neuron that processes the information and sends a response.
  4. A motor neuron that carries the impulse to an effector (like a muscle), causing a response.

5. Endocrine System

The endocrine system controls and coordinates body functions through hormones, which are chemical messengers. Hormones are secreted by endocrine glands directly into the bloodstream and act on target organs to regulate processes like growth, metabolism, and reproduction.

Major Endocrine Glands in Humans

  1. Pituitary Gland: Often called the “master gland,” it controls the functioning of other endocrine glands and secretes growth hormone.
  2. Thyroid Gland: Produces thyroxine, which regulates metabolism.
  3. Adrenal Glands: Secrete adrenaline, which helps the body respond to stress (the “fight or flight” response).
  4. Pancreas: Produces insulin, which regulates blood sugar levels.
  5. Testes (in males) and Ovaries (in females): Produce sex hormones (testosterone in males, estrogen, and progesterone in females) that control sexual development and reproduction.

6. Coordination in Plants

Unlike animals, plants do not have a nervous system. However, they do show control and coordination through hormones and responses to external stimuli like light, gravity, and touch.

Plant Hormones (Phytohormones)

  1. Auxins: Promote cell elongation and growth, and are responsible for phototropism (growth of plant parts towards light) and geotropism (growth in response to gravity).
  2. Gibberellins: Promote stem elongation, seed germination, and flowering.
  3. Cytokinins: Promote cell division and the growth of shoots and roots.
  4. Abscisic Acid: Inhibits growth and promotes dormancy in seeds. It helps plants to respond to stress conditions like drought by closing stomata.
  5. Ethylene: A gaseous hormone that promotes fruit ripening.

Tropic Movements in Plants

Tropism is the directional growth of a plant in response to stimuli. It can be either:

  • Positive tropism: When growth is towards the stimulus.
  • Negative tropism: When growth is away from the stimulus.

Examples of tropisms:

  • Phototropism: Growth of plants towards light.
  • Geotropism: Growth of roots towards gravity (positive geotropism) and stems away from gravity (negative geotropism).
  • Hydrotropism: Growth towards water.
  • Thigmotropism: Response to touch, seen in plants like vines and tendrils.

7. Movement in Plants

Plants also show nastic movements which are non-directional responses to stimuli. These movements do not depend on the direction of the stimulus.

  • Example: The folding of leaves in Mimosa pudica (the touch-me-not plant) in response to touch.

Summary:

  • Nervous System: Responsible for detecting stimuli, transmitting signals, and controlling responses in animals. It consists of the brain, spinal cord, and nerves.
  • Reflex Action: An automatic, quick response to stimuli that does not involve conscious thought, controlled by the spinal cord.
  • Endocrine System: Consists of glands that secrete hormones into the bloodstream, regulating various body functions like growth, metabolism, and reproduction.
  • Plant Coordination: Plants coordinate growth and responses to stimuli through hormones like auxins and gibberellins. Tropic movements in plants help them respond to light, gravity, water, and touch.

Control and coordination are vital for both plants and animals to maintain homeostasis, respond to environmental changes, and ensure proper functioning of all biological processes.