Chapter – 6

Control and Coordination

In this post we have given the detailed notes of class 10 Science Chapter 6 (Control and Coordination) in English. These notes are useful for the students who are going to appear in class 10 board exams.

Chapter 6: Control and Coordination

Introduction 🧠

All living organisms respond to changes happening around them. Every change in the environment produces an appropriate movement in response. Any movement depends on the event that triggers it. For example, if we touch a hot object, our hand begins to burn, and we respond to it immediately.

Control and Coordination in Animals

• In animals, control and coordination are carried out by nervous and muscular tissue.

Receptors

The specific tips of nerve cells that detect all information from the environment are called receptors.

Types of receptors: Receptors are of the following types:

• Photoreceptors — for vision (eyes)
• Auditory receptors — for hearing (ears)
• Gustatory receptors — for taste (tongue)
• Olfactory receptors — for smell (nose)
• Thermoreceptors/tactile receptors — for sensing heat and touch (skin)

All these receptors are located in our sense organs.

Nervous Tissue

• Nervous tissue is made up of an organised network of nerve cells, or neurons, and is specialised to conduct information through electrical impulses from one part of the body to another.

Parts of a Nerve Cell

• Dendrite: Where information is received.
• Dendrite to cell body: Through which information travels as an electrical impulse.
• Axon: Where this impulse is converted into a chemical signal so it can be transmitted further.

Transmission of information by nerves: All the information that reaches our brain is acquired by the dendritic tip of a nerve cell and generates an electrical impulse through a chemical reaction. This impulse travels from the dendrite to the cell body, then through the axon to reach its end. At the end of the axon, the electrical impulse is converted into a chemical signal so that it can travel further. These chemical signals cross a gap called the synapse and start a similar electrical impulse in the dendrite of the next neuron. In this way, information travels from one place to another.

Synapse: The gap found between two nerve cells is called the synapse (synaptic cleft).

Reflex Action

A sudden response to a stimulus, without the involvement of the brain, is called a reflex action. These are automatic actions that occur without the will of the organism.

Examples:

• Immediately withdrawing the hand upon touching a hot object.
• Salivation upon seeing food.
• Withdrawing the hand after being pricked by a needle, etc.

Control of Reflex Actions

All reflex actions are controlled by the spinal cord.

• Voluntary actions: All the actions that are under our control are called voluntary actions. Example — speaking, walking, writing, etc.
• Control of voluntary actions: Voluntary actions happen through our will and thinking, so they are controlled by the forebrain, our thinking part.
• Involuntary actions: All the actions that happen automatically, and over which we have no control, are called involuntary actions. Example: the beating of the heart, breathing, digestion of food, etc.
• Control of involuntary actions: Involuntary actions are controlled by the midbrain and hindbrain.

Reflex arc: To detect an incoming signal and carry out the outgoing response of a reflex action, sensory neurons and motor neurons, together with the spinal cord, form a pathway called the reflex arc.

Usefulness of the reflex arc in animals: The reflex arc has evolved in most animals because their brain’s thinking process is not very fast. In fact, in most animals, the complex neuron network needed for thinking is either minimal or absent. Therefore, in the absence of an actual thinking process, the reflex arc has evolved as an efficient working mechanism. Even after the existence of a complex neuron network, the reflex arc still works as a more efficient system for immediate response.

In other words, since the thinking power of most animals is very limited, they cannot save themselves by responding immediately through thought alone. To make up for this limitation, the reflex arc functions as an efficient system in most animals.

Human Brain

The human brain is a large part of the nervous system, made of nerve cells, which together with the spinal cord forms the central nervous system.

Spinal Cord

• The spinal cord is a cylindrical bundle of nerve fibres whose tissue passes through the vertebral column from the brain down to the coccyx. It connects all parts of the body through nerves and, together with the brain, forms the central nervous system.

Functions:

• It receives information from all parts of the body and integrates it.
• It sends messages to the muscles.
• The brain allows us to think and perform actions based on thinking.

• All reflex actions are controlled by the spinal cord.
• All voluntary and involuntary actions are controlled by the brain.

Cranium: The part of the human skull that protects the brain, inside which the brain is located.

Meninges: The meninges are a covering made of three thin membranes that protect the human brain from internal shocks. Inside this covering is a fluid called cerebrospinal fluid, which extends from the brain to the spinal cord.

Cerebrospinal fluid: This is a fluid found between two layers of the meninges that protects the brain from internal shocks and from meningitis.

Parts of the Brain and Their Functions

• Forebrain: This is the main thinking part of the brain. It has areas that receive sensory impulses from various receptors. It has specific areas for hearing, sight and smell. It controls the movement of voluntary muscles. It also has a centre related to hunger.
• Midbrain: This controls all involuntary actions of the body.
• Hindbrain: This also controls involuntary actions. All involuntary actions such as blood pressure, salivation and vomiting are controlled by the medulla located in the hindbrain.

The hindbrain consists of three centres:

• Cerebellum: This is responsible for precision of voluntary actions and maintaining the posture and balance of the body — for example, walking in a straight line, riding a bicycle, picking up a pencil, etc.
• Pons: This takes part in regulating and controlling respiration.
• Medulla oblongata: All involuntary actions such as blood pressure, salivation and vomiting are controlled by the medulla located in the hindbrain.

Nervous System

Parts of the nervous system: The nervous system consists of the central nervous system (brain and spinal cord) and the peripheral nervous system (cranial and spinal nerves), which together coordinate all activities of the body.

Control and Coordination in Plants

In plants, control and coordination are carried out by plant hormones, also called phytohormones. Various plant hormones help coordinate growth, development and response to the environment.

Plants show two different types of movement:

• Growth-independent movements: These movements do not depend on growth. Example — the folding up of the leaves of the touch-me-not (Mimosa/chhui-mui) plant on touching.
• Growth-dependent movements: Movements in plants that reflect movement in the growing parts of the plant. Example — the movement of tendrils, the movement of a plant towards light, and the movement of roots towards water.
• Growth-independent movement: Movement in the touch-me-not plant — when we touch the touch-me-not plant, its leaves move in response. This movement is not related to growth.

Immediate response to stimuli in plants: Plants also use electrochemical means to transmit information about touch from one cell to another, but unlike animals, plants do not have specialised tissue for conducting information. Plant cells do not have specialised proteins like those in animal muscle cells; instead, they change shape by changing the amount of water in them, causing them to swell or shrink.

Growth-dependent movements:

• Movement of tendrils
• Tropism
• Phototropism
• Geotropism (gravitropism)
• Chemotropism
• Hydrotropism

Hormones

Control of the Time and Amount of Hormone Secreted

• The timing and amount of hormone secretion is controlled by a feedback mechanism. For example, if the blood sugar level rises, this is detected by cells of the pancreas, which respond by secreting more insulin. When the blood sugar level falls, the secretion of insulin decreases.

Hormones

• Chemical substances that carry out the function of control and coordination in animals or plants are called hormones.

Formation of Hormones in Animals

In animals, hormones are made in endocrine glands. In humans and animals, glands are of two types:

• Endocrine glands
• Exocrine glands

(i) Endocrine glands: Ductless glands are called endocrine glands. Example — pineal gland, pituitary gland, thyroid gland, parathyroid gland, thymus gland, adrenal gland, ovary (in females) and testis (in males), etc.

(ii) Exocrine glands: Glands that release their secretions through ducts are called exocrine glands. Example — liver, pancreas and lacrimal gland, etc.

Phytohormones (Plant Hormones)

• Chemical substances that carry out control and coordination in plants are called phytohormones or plant hormones.

There are five types:

1. Auxin

• Promotes cell elongation and cell differentiation in plants.
• Auxin promotes the growth of fruits.
• Increases the length of cells.

2. Gibberellin

• In the presence of auxin, gibberellin promotes cell elongation and cell differentiation in plants.
• Promotes the growth of fruits and stems.

3. Cytokinin

• Promotes cell division in plants.
• Helps in the opening of flowers.

4. Abscisic Acid

• Inhibits/controls growth in plants.
• Controls water loss in plants.
• Promotes the synthesis of proteins in plants — this is generally regarded as a growth-inhibiting/stress hormone.

5. Ethylene

• Promotes the ripening of fruits.
• Increases the number of female flowers.
• Helps stems to swell/thicken.

Key Points to Remember

• Control and coordination in animals is carried out by nervous and muscular tissue, while in plants it is carried out by hormones (phytohormones). 🧠
• Receptors detect stimuli from the environment — photoreceptors (eyes), auditory receptors (ears), gustatory receptors (tongue), olfactory receptors (nose) and tactile/thermoreceptors (skin).
• A neuron has three main parts — dendrite, cell body and axon — and information is transmitted as an electrical impulse that becomes a chemical signal at the synapse.
• A reflex action is a rapid, involuntary response to a stimulus controlled by the spinal cord through a reflex arc, without direct involvement of the brain.
• The human brain has three parts — forebrain (thinking, voluntary actions), midbrain and hindbrain (involuntary actions), with the hindbrain further divided into cerebellum, pons and medulla oblongata.
• Plants show growth-independent movements (e.g. touch-me-not) and growth-dependent movements (tropisms like phototropism, geotropism, hydrotropism and chemotropism).
• The five major phytohormones are auxin, gibberellin, cytokinin, abscisic acid and ethylene, each with distinct roles in growth and development.
• Hormone secretion is regulated by feedback mechanisms, as seen with insulin and blood sugar levels.

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