NOTES Chapter 7: Control and Coordination Class 10 Science – CBSE NCERT

 Chapter 7: Control and Coordination

Class 10 Science – CBSE NCERT

This chapter focuses on control and coordination in living organisms, which is essential for responding to environmental stimuli and maintaining homeostasis. The chapter explains how both nervous and hormonal systems help coordinate and control various activities in animals, including humans. It also explores how plants respond to stimuli and regulate their growth.

1. Control and Coordination in Humans

In humans and other animals, control and coordination are achieved through the nervous system and the endocrine system.

The Nervous System:

The nervous system helps organisms respond to external and internal stimuli quickly. It consists of the brain, spinal cord, and nerves. The main parts of the nervous system are:

  • Central Nervous System (CNS): Consists of the brain and spinal cord. The brain processes information, and the spinal cord acts as a pathway for signals between the brain and the rest of the body.
  • Peripheral Nervous System (PNS): Consists of nerves branching from the brain and spinal cord that transmit signals to and from different parts of the body.
Structure and Function of Neurons:

Neurons are the functional units of the nervous system that transmit electrical signals. They consist of three main parts:

  • Cell body: Contains the nucleus and cytoplasm.
  • Dendrites: Branch-like extensions that receive signals from other neurons.
  • Axon: Long fiber that transmits impulses away from the cell body.

Neurons communicate through electrical impulses. These impulses travel along the axon, and at the synapse (the junction between two neurons), they are transmitted chemically using neurotransmitters.

Reflex Action:

A reflex action is an involuntary and immediate response to a stimulus. For example, when you touch something hot, the nervous system quickly sends a signal to withdraw your hand before you consciously feel pain. This happens through a reflex arc which involves the sensory neuron, interneuron, and motor neuron.

The Endocrine System:

The endocrine system uses hormones (chemical messengers) to regulate slower, long-term processes such as growth, metabolism, and reproduction. Glands in the body secrete hormones into the bloodstream, which then affect target organs.

  • Endocrine Glands: Some major endocrine glands include the pituitary gland, thyroid gland, adrenal glands, and pancreas.
  • Hormones: Some important hormones include:
    • Insulin (from the pancreas) regulates blood sugar levels.
    • Adrenaline (from the adrenal glands) helps the body respond to stress.
    • Thyroxine (from the thyroid gland) regulates metabolism and growth.

The pituitary gland is often called the "master gland" because it controls the release of hormones from other endocrine glands.

2. Control and Coordination in Plants

Plants also need to respond to environmental stimuli, but they do so without a nervous system. Instead, they rely on chemical signals that regulate growth, development, and responses to stimuli such as light, gravity, and touch.

Plant Hormones (Phytohormones):

Plants produce hormones that help in growth and development. The main plant hormones include:

  • Auxins: Promote cell elongation and are involved in phototropism (growth toward light) and gravitropism (growth in response to gravity). For example, auxins cause plant stems to bend towards light.
  • Gibberellins: Stimulate cell division and elongation, promoting growth, especially in stems and fruits.
  • Cytokinins: Promote cell division and help in shoot and root development.
  • Abscisic Acid (ABA): Inhibits growth and promotes dormancy; it also helps plants respond to stress.
  • Ethylene: A gas that regulates fruit ripening and plant responses to stress.

Tropisms:

Tropisms are directional responses of plants to external stimuli:

  • Phototropism: The growth of a plant in response to light. For example, plants tend to grow towards light, a phenomenon controlled by auxins.
  • Gravitropism: The growth of a plant in response to gravity. Roots grow downwards (positive gravitropism), and stems grow upwards (negative gravitropism).
  • Thigmotropism: A plant's response to touch, as seen in climbing plants like peas, which use tendrils to wrap around supports.

3. The Human Nervous System

The human nervous system is divided into two main parts:

  1. Central Nervous System (CNS): This consists of the brain and spinal cord.
    • Brain: The brain is the control center for thought, memory, and emotions. It also coordinates actions, regulates bodily functions, and processes sensory information.
    • Spinal Cord: The spinal cord acts as the main pathway for communication between the brain and the rest of the body.
  2. Peripheral Nervous System (PNS): This consists of all the nerves that connect the CNS to the rest of the body. The PNS is divided into two parts:
    • Somatic Nervous System: Controls voluntary movements (e.g., moving your hand).
    • Autonomic Nervous System: Controls involuntary movements (e.g., heart rate, digestion).

Reflex Arc:

A reflex arc is a simple nerve pathway that allows for a quick response to stimuli, bypassing the brain. The components of the reflex arc include:

  • Receptor: Detects the stimulus (e.g., pain from touching something hot).
  • Sensory Neuron: Carries the impulse from the receptor to the spinal cord.
  • Interneuron: Located in the spinal cord, it processes the information and sends a signal to the motor neuron.
  • Motor Neuron: Carries the impulse to the effector (e.g., muscles) to produce a response (e.g., withdrawing your hand).
  • Effector: The muscle or gland that carries out the response.

4. Human Endocrine System

The endocrine system in humans consists of various glands that release hormones to regulate body functions:

  • Pituitary Gland: Known as the master gland, it controls other endocrine glands and secretes hormones that regulate growth, metabolism, and reproductive processes.
  • Thyroid Gland: Produces thyroxine, which regulates metabolism, growth, and development.
  • Pancreas: Produces insulin and glucagon to regulate blood sugar levels.
  • Adrenal Glands: Produce adrenaline and noradrenaline, which help the body respond to stress.
  • Gonads: The ovaries (in females) and testes (in males) produce sex hormones like estrogen, progesterone, and testosterone, which control reproduction and secondary sexual characteristics.

5. Coordination in Plants

In plants, growth responses are controlled by hormones called phytohormones. Plants use hormones to coordinate their responses to light, gravity, and touch.

  • Auxins: Promote growth towards light (phototropism) and help in elongation of cells in the shoot.
  • Cytokinins: Promote cell division and help in the development of shoots and leaves.
  • Gibberellins: Promote growth in stems and fruits and are involved in processes like seed germination.
  • Abscisic Acid: Inhibits growth and promotes dormancy.
  • Ethylene: Regulates fruit ripening and abscission (shedding of leaves and fruits).

Conclusion

Chapter 7 on Control and Coordination explains how organisms, including humans and plants, regulate and respond to stimuli. In humans and other animals, the nervous system and endocrine system work together to control rapid and long-term processes, respectively. In plants, phytohormones are responsible for regulating growth and responses to environmental changes. Understanding how these systems work is crucial for comprehending how organisms maintain homeostasis and adapt to their surroundings.

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