Class 10 Science Control and Coordination Notes by PW

Living organisms keep sensing their surroundings and adjusting to them, whether it is you pulling your hand away from a hot pan or a plant bending towards sunlight. Humans use nerves for quick messages and hormones for slower regulation, while plants rely on hormones and growth movements. Questions often ask you to label a neuron, name the function of a brain region or gland, and explain the difference between nastic and tropic movements. 

Physics Wallah offers Control and Coordination Class 10 notes that cover the nervous system, the endocrine glands and plant responses in one place, with the neuron diagram, the reflex arc and the key hormones explained in simple language. Revising them together makes it easier to answer both the definition-based and the reasoning questions that appear in your Class 10 Science board exams.

Basics of Control and Coordination

In humans, control and coordination work through two major systems:

• Nervous system: the brain, spinal cord and nerves.

• Endocrine system: the glands that release hormones.

The nervous system has two main parts. The central nervous system (CNS) is made of the brain and spinal cord. The peripheral nervous system (PNS) is made of nerves spread through the body. Cranial nerves arise from the brain, and spinal nerves arise from the spinal cord.

The endocrine system releases hormones that coordinate growth, development, metabolism and responses to stress.

Basic Terms in Coordination

• Stimulus: any change that affects the activity of an organism, such as touching hot tea, seeing a flower or hearing footsteps.

• Receptor: a cell, tissue or organ that detects a stimulus, such as those in the eyes, nose, tongue and skin.

• Effector: a muscle or gland that produces a response.

• Response: the action produced by the effector, such as pulling your hand away from something hot.

The sequence is: Stimulus → Receptor → Nervous System → Effector → Response

Common Sensory Receptors

• Photoreceptors in the eyes detect light.

• Olfactory receptors in the nose detect smell.

• Gustatory receptors in the tongue detect taste.

• Phonoreceptors in the ears detect sound.

• Thermoreceptors in the skin detect heat and cold.

• Nociceptors in the skin detect pain.

Neuron: Structure and Function

A neuron is a nerve cell that carries information through the nervous system. Its parts are:

• Dendrites: receive information from a receptor or another neuron.

• Cell body: contains the nucleus and cytoplasm, and processes incoming information.

• Axon: a long fibre that carries information away from the cell body towards the nerve ending.

• Myelin sheath: the covering around the axon.

• Nerve ending: the branched end of the axon.

• Synapse: the tiny gap between two neurons.

This is how information travels through neurons:

1. A stimulus causes chemical information to be produced at the receptor.

2. The dendrites receive it and it turns into an electrical signal.

3. The signal travels through the cell body and along the axon.

4. At the nerve ending, it turns back into chemical information.

5. The chemicals cross the synapse.

6. The next neuron receives them and converts them into an electrical signal again.

Types of Neurons

• Sensory neurons carry impulses from receptors to the central nervous system.

• Relay neurons connect sensory neurons with motor neurons.

• Motor neurons carry impulses from the central nervous system to effectors such as muscles and glands.

Memory Tip: Think of a relay race. Relay neurons pass the message from sensory neurons to motor neurons, just like a runner passes the baton.

Types of Actions

• Voluntary actions are performed through conscious choice, such as writing or signing.

• Involuntary actions happen automatically, without conscious control, such as heartbeat, digestion and breathing.

• Reflex actions are rapid, automatic responses to a sudden stimulus, such as pulling your hand away from a hot object.

Reflex Action and Reflex Arc

A reflex action is a quick and automatic response to a stimulus. It protects the body from harm, gives an immediate response and reduces the immediate workload on the brain. In a reflex action, the information reaches the spinal cord and returns quickly to the effector without waiting for the brain to process it. The brain may receive the information a little later.

The pathway followed by the impulse is called the reflex arc:

Receptor → Sensory Neuron → Spinal Cord → Motor Neuron → Effector

Human Brain: Major Regions and Functions

The human brain has three major regions:

• Forebrain: the largest region. The cerebrum controls thinking and voluntary actions. The hypothalamus controls hunger, thirst and sleep, and sends instructions to the pituitary gland.

• Midbrain: passes signals between the forebrain and hindbrain, and controls some reflex movements as well as eye and pupil movements.

• Hindbrain: connected to the spinal cord. The cerebellum controls posture and balance, the pons regulates breathing rate and sleep, and the medulla oblongata controls blood pressure, salivation and vomiting.

Protection of the Brain and Spinal Cord

The brain is protected by the cranium, which is part of the skull. It is also covered by three membranes called meninges: dura mater, arachnoid and pia mater. The spaces between them contain cerebrospinal fluid (CSF), which acts as a shock absorber.

The spinal cord is protected by the meninges, the fluid and the vertebral column, which is made of 33 bones called vertebrae.

Memory Tip: Remember the three membranes as D-A-P: Dura mater, Arachnoid and Pia mater.

Human Endocrine System

The endocrine system is made of glands that release hormones. Hormones regulate growth, metabolism, development and stress responses. The main glands and hormones are:

• Hypothalamus: releases hormones that stimulate the pituitary gland.

• Pituitary gland: releases growth hormone and hormones that control other glands. It is called the master gland.

• Thyroid gland: releases thyroxine, which regulates metabolism.

• Testes: release testosterone, which helps develop male sex organs.

• Ovaries: release oestrogen, which helps develop female sex organs and regulates the menstrual cycle. Revise the reproductive system to see how these hormones fit in.

• Adrenal glands: release adrenaline, which increases heart rate during danger or stress.

• Pancreas: releases insulin, which controls blood sugar levels.

Coordination in Plants

Plants do not have nerves or a brain, but they still respond to their surroundings. Their movements are mainly of two types: nastic and tropic.

Nastic Movement

Nastic movement does not depend on the direction of the stimulus. It is usually quick, temporary and reversible. The leaves of the touch-me-not plant fold up when touched, which is a common example.

Tropic Movement

Tropic movement is directional growth in response to a stimulus. The plant grows towards or away from the stimulus. It is generally slow and may be permanent.

So, in a nastic movement, the stimulus direction does not matter, while in a tropic movement, the stimulus direction decides the direction of growth. A shoot bending towards light is a tropic movement.

Types of Tropism

• Phototropism: growth in response to light. Shoots generally grow towards light.

• Geotropism (gravitropism): growth in response to gravity. Roots grow towards gravity and shoots grow away from it.

• Hydrotropism: growth towards or away from water.

• Chemotropism: growth towards or away from chemicals. Pollen tube growth towards the ovule is an example.

• Thigmotropism: growth in response to touch. Tendrils coil around a support when they touch it.

Plant Hormones

Plant hormones include growth promoters and growth inhibitors.

• Auxin: promotes cell elongation and helps shoots bend towards light.

• Gibberellin: promotes stem growth.

• Cytokinin: promotes cell division.

• Abscisic acid: inhibits growth, especially during stress or water shortage.

• Ethylene: helps fruits ripen.

Abscisic acid helps the plant save energy during a water shortage by slowing growth. Ethylene shifts the plant’s resources towards fruit ripening.

Memory Tip: Auxin elongates, gibberellin lengthens stems, cytokinin divides cells, abscisic acid inhibits and ethylene ripens.

Control and coordination in humans depend on the nervous system and the endocrine system. The nervous system carries information through neurons and responds quickly, and the reflex arc allows the body to react without waiting for the brain. Hormones released by endocrine glands regulate slower processes such as growth, metabolism and blood sugar. Revise the neuron diagram, the reflex arc and the functions of each hormone, and practise questions from the NCERT solutions for Control and Coordination to strengthen your preparation for Class 10 Science.