Control and Coordination Class 10 Biology Chapter 6 Notes

Control and Coordination Class 10 Biology Notes: In biology, every living organism needs a proper system to manage and respond to changes happening inside the body and in the environment. This process is called control and coordination. In the chapter Control and Coordination Class 10 Biology Notes, students learn how the body controls different activities and how organs work together to maintain balance and proper functioning.

The control and coordination class 10 Chapter 6 Notes mainly explain the role of the nervous system, brain, spinal cord, neurons, and hormones in regulating body activities. These systems help the body react to stimuli such as light, sound, heat, or touch. For example, when we touch a hot object, the nervous system quickly sends signals to the brain and muscles so that we remove our hand immediately. This is an example of a reflex action.

In addition to the nervous system, the endocrine system also plays an important role in coordination by releasing hormones that control growth, development, and metabolism. Understanding these concepts through control and coordination class 10 notes helps students build a strong base for higher biology studies.

These Control and Coordination Class 10 Biology Notes are prepared in simple language so that students can easily understand the key ideas of the chapter. Many students also search for control and coordination class 10 notes pdf to revise quickly before exams, and these notes can be helpful for quick revision and concept clarity. Sometimes students feel this chapter is little confusing at first, but with proper explanation it becomes much easier.

What is Control and Coordination?

Control and Coordination refers to the systematic working together of an organism's organs to produce appropriate responses to changes in the environment.

• The environment constantly changes temperature, light, seasons and organisms must adapt to survive.
• Stimuli are changes in the internal or external environment that provoke a physiological or behavioural response.
  • Examples of stimuli: light, heat, cold, sound, touch, chemicals.
• The organism's response to a stimulus is characteristic of that species.
• For a proper response, different parts of the body must work in coordination.

Definition: Coordination is the working of various organs of an organism in a systematic manner to produce a proper response to stimuli.

Difference between Plants vs Animals

Coordination in Plants

Plants lack a nervous system, muscles, and sense organs. Yet they respond effectively to stimuli such as light, gravity, water, touch, and chemicals.

• Plants use chemical messengers called phytohormones for coordination.
• Directional movements in response to stimuli are called tropisms.
• A stimulus is defined as any change in the internal or external environment that provokes a physiological and behavioural response.

Phytohormones (Plant Hormones)

Phytohormones are naturally occurring organic chemical substances produced in plants that regulate one or more physiological processes even when present in very low concentrations. They are also called Plant Growth Regulators (PGR).

Classification of Plant Hormones

Plant Hormones

• Growth Promoters
  • Auxins (IAA)
  • Gibberellins
  • Cytokinins
• Growth Inhibitors
  • Abscisic Acid (ABA)

Functions of Major Plant Hormones

Three Stages of Plant Growth

1. Cell Division
2. Cell Enlargement
3. Cell Differentiation

Note: Dormancy is the state of rest in which metabolism is stopped. Seeds remain dormant for a period before germinating.

General Functions of Plant Hormones

• Germination of seeds (breaking dormancy)
• Growth of roots, stems, and leaves
• Flowering and fruiting
• Ripening of fruits
• Movement of stomata
• Phototropism, geotropism, chemotropism, and nastic movements

Effects of Light on Plant Development

The effect of light on plant development is called photomorphogenesis.

• Plants contain a pigment called phytochrome that absorbs red and far-red light.
• Many developmental processes are mediated by low intensities of red light.

Phytochrome-Controlled Phenomena

Etiolated Plant: When a plant grows in the dark, it appears pale yellow, with elongated, thin internodes. This is called an etiolated plant. It allows maximum growth with minimum reserve food.

Photoperiodism and Flowering

The response of plants to the duration of light (day length) is called photoperiodism.

Tropism – Types and Examples

Tropism (or Tropic Movement) is a directional movement or orientation of a specific plant part in response to an external stimulus.

• Positive tropism – growth toward the stimulus
• Negative tropism – growth away from the stimulus

Types of Tropism

Role of Auxin in Tropism

Auxin hormone is synthesised at the tip of the stem. When a plant receives unilateral light:

1. Auxin migrates from the lit side to the shaded (dark) side.
2. The shaded side accumulates more auxin → cells elongate more rapidly.
3. The stem bends toward the light source — this is positive phototropism.

In thigmotropism (e.g., pea tendrils):

• When a tendril touches a support, auxin diffuses to the side away from the support.
• That side grows faster, causing the tendril to coil around the support.

Nastic Movements

Nastic movements (nasties) are non-directional movements of a plant part in response to an external stimulus where the direction of movement is not determined by the direction of the stimulus.

Types

Thigmonasty – Non-directional movement in response to touch.

• Example: Mimosa pudica (Touch-me-not) leaves fold when touched due to sudden loss of water from pad-like swellings called pulvini at the base of leaves, causing loss of turgor pressure.

Photonasty – Non-directional movement in response to light.

• Example: Dandelion flowers open in bright morning light and close in the evening.

Nastic vs Tropic Movements

Coordination in Animals

In animals, coordination operates through two integrated systems:

1. Nervous System – Composed of specialised cells called neurons that send electrical signals (nerve impulses). Control is speedy and localised.
2. Endocrine System – Composed of specialised endocrine glands that release chemical messengers (hormones) into the bloodstream. Control is slower but diffuse.

The Human Nervous System

The human nervous system is the most complex nervous system known. It is divided into:

Nervous System

• Central Nervous System (CNS)
  • Brain
  • Spinal Cord
• Peripheral Nervous System (PNS)
  • Cranial Nerves (12 pairs)
  • Spinal Nerves (31 pairs)
• Autonomic Nervous System (ANS)
  • Sympathetic
  • Parasympathetic

Nervous Systems in Lower Animals

• Cnidarians (Hydra, Jellyfish): Simplest nervous organisation — a net of nerve cells and fibres. No brain.
• Insects: Small centralised brain + ganglia + nerve cord.

Types of Nerves

Structure of a Neuron

The neuron is the structural and functional unit of the nervous system.

Parts of a Neuron

Layers Covering the Axon

1. Axolemma – innermost layer
2. Myelin Sheath (Medullary Sheath) – middle insulating layer; speeds up impulse conduction
3. Neurilemma – outermost protective layer (Schwann cells)

Terms

• Nodes of Ranvier – Gaps between adjacent myelin sheaths; allow saltatory conduction (nerve impulse "jumps" between nodes)
• Myelinated fibres – Conduct impulses at twice the speed of non-myelinated fibres
• Synaptic knobs – Terminal branches of axon; contain neurotransmitters

Types of Neurons by Function

• Sensory neurons – Transmit impulses from sensory cells to CNS
• Motor neurons – Transmit impulses from CNS to effectors (muscles/glands)
• Relay (Interneurons) – Connect sensory and motor neurons within CNS

Receptors

Receptors are specialised cells in sense organs that detect specific stimuli:

• Photoreceptors – sensitive to light
• Phonoreceptors – sensitive to sound
• Tangoreceptors – sensitive to touch
• Olfactoreceptors – sensitive to smell
• Thermoreceptors – sensitive to heat and cold

Synapse and Nerve Impulse Transmission

A synapse is the microscopic gap between the terminal end of one axon and the dendrite of the next neuron. It acts as a one-way valve impulses travel in only one direction.

How Impulse Crosses a Synapse

1. Nerve impulse reaches the terminal end of the axon.
2. Neurotransmitters (e.g., Acetylcholine, Adrenaline) are released from synaptic vesicles.
3. Neurotransmitters cross the synaptic cleft.
4. They bind to receptors on the next neuron's dendrite and trigger a new nerve impulse.

Types of Synapses: Electrical synapse and Chemical synapse.

Reflex Action and Reflex Arc

What is a Reflex Action?

A reflex action is a spontaneous, automatic, and mechanical response to a stimulus, controlled by the spinal cord without the involvement of the brain. It is the fastest type of response.

Examples:

• Withdrawing hand from a hot object
• Blinking when a particle enters the eye
• Sneezing or coughing
• Watering of mouth at the sight of food
• Knee-jerk reflex

Reflex Action Pathway

Stimulus → Receptor cells → Sensory nerve → Spinal Cord (Relay neuron) → Motor nerve → Effector (Muscle/Gland) → Response

Reflex Arc

The reflex arc is the complete pathway followed by a nerve impulse from receptor to effector.

Four Components of a Reflex Arc:

1. Receptor – Sensory organ that detects the stimulus
2. Sensory (Afferent) nerve – Carries impulse from receptor to spinal cord
3. Relay neuron – In spinal cord; relays impulse from sensory to motor neuron
4. Motor (Efferent) nerve – Carries impulse from spinal cord to effector

Types of Reflexes

The Brain – Structure and Functions

The brain (encephalon) is the highest coordinating centre of the body. It is protected by:

• Cranium (skull bones)
• Meninges – three protective membranes
• Cerebrospinal fluid (CSF) – acts as a shock absorber

Three Main Regions of the Brain

1. Forebrain (Prosencephalon)

2. Midbrain (Mesencephalon)

• Connects forebrain to hindbrain
• Controls reflex movements of head, neck, and eye muscles in response to visual/auditory stimuli

3. Hindbrain (Rhombencephalon)

Spinal Cord

• Cylindrical cord arising from medulla oblongata; runs through vertebral column
• Two functions:
  1. Conducts sensory and motor impulses to/from brain
  2. Acts as centre for reflex actions

Cerebrospinal Fluid (CSF)

• Clear, slightly alkaline fluid in ventricles and spinal cord canal
• Supplies nutrients and oxygen to CNS; removes waste; protects from mechanical shocks; reduces weight of brain

Autonomic Nervous System (ANS)

The ANS (visceral nervous system) controls involuntary functions of internal organs.

Chemical Coordination – Endocrine Glands and Hormones

Hormones are chemical messengers secreted by endocrine (ductless) glands directly into the bloodstream, transported to target organs.

Types of Glands

Characteristics of Hormones

• Organic compounds
• Secreted in small amounts
• Poured directly into blood
• Act on specific target organs
• Act away from the site of production
• Used up during action (unlike enzymes)
• Can be slow or fast acting

Major Endocrine Glands

Hypothalamus

• Located in the brain
• Produces releasing hormones and inhibitory hormones to regulate the pituitary gland
• Controls homeostasis: thirst, hunger, body temperature, sleep, osmoregulation

Pituitary Gland (Master Gland / Hypophysis)

Located just below the brain. Has three lobes:

Anterior Lobe (6 hormones):

GH Disorders:

• Dwarfism – GH deficiency from early age
• Gigantism – GH excess during childhood
• Acromegaly – GH excess after adolescence

Intermediate Lobe:

• MSH (Melanocyte-Stimulating Hormone) – Controls skin pigmentation

Posterior Lobe:

• Oxytocin ("birth hormone") – uterine contractions; milk ejection
• Vasopressin (ADH) – reduces water loss in urine; raises blood pressure. Deficiency causes diabetes insipidus

Thyroid Gland (Largest Endocrine Gland)

Located in the neck; secretes:

• Thyroxine (T₄) and Triiodothyronine (T₃): Regulate basal metabolic rate (BMR); promote growth and mental development; metamorphosis in frogs; require iodine for synthesis
• Calcitonin: Regulates calcium-phosphorus balance

Thyroid Disorders:

Parathyroid Glands

• 4 small glands on posterior surface of thyroid
• Secrete Parathormone (PTH) raises blood calcium when levels are low
• PTH and Calcitonin act antagonistically to regulate calcium-phosphorus balance

Adrenal Glands (Glands of Emergency / Suprarenals)

Located on top of each kidney. Two distinct parts:

Adrenal Cortex:

Adrenal Medulla:

• Adrenaline (Epinephrine) and Noradrenaline – "Fight or Flight" hormones
• Released in large amounts during stress/danger
• Effects: ↑ heart rate, ↑ breathing rate, ↑ blood sugar, ↑ blood pressure, redirects blood to muscles

Pancreas

Located below the stomach. Islets of Langerhans (endocrine cells) secrete:

• Insulin (β-cells) – Lowers blood glucose level
• Glucagon (α-cells) – Raises blood glucose level
• Deficiency of insulin → Diabetes Mellitus (sugar in urine, excessive thirst, excessive urination)

Diabetes Mellitus vs Diabetes Insipidus:

Testes (Males only)

• Located in scrotum
• Leydig cells secrete Testosterone (under influence of LH)
• Functions: development of male accessory glands, secondary sexual characters, spermatogenesis

Ovaries (Females only)

• Located in abdomen
• Secrete:
  • Estrogen – oogenesis; female secondary sexual characters; onset of menstrual cycle
  • Progesterone – maintains pregnancy; uterine changes during menstrual cycle
  • Relaxin – helps in easy childbirth (widening of pelvis)

Pineal Gland

• Located between cerebral hemispheres
• Secretes Melatonin regulates working of gonads

Thymus Gland

• Located in upper chest near heart
• Secretes Thymosin – stimulates development of lymphocytes; immunity
• Known as the seat of the immune system

Feedback Mechanism

The body regulates hormone levels through a feedback mechanism to prevent harmful effects of excess or deficiency.

Example – Blood Glucose Homeostasis:

Carbohydrate-rich meal
↓
Blood glucose level RISES
↓
Pancreas β-cells secrete INSULIN
↓
Insulin stimulates cells to take up glucose
↓
Blood glucose level FALLS
↓
Inhibits further insulin synthesis (negative feedback)

This is called negative feedback control it maintains homeostasis (stable internal environment).

Control and Coordination Solved Examples

Q. What are stimuli? Give two examples.

Ans. Stimuli are changes in the external or internal environment that provoke a physiological or behavioural response in an organism. Examples: light (causes phototropism), touch (causes Mimosa leaves to fold).

Q. Define phytohormones.

Ans. Phytohormones are naturally occurring chemical substances produced in plants that regulate physiological processes such as growth, differentiation, and development, even when present in very low concentrations.

Q. Why is auxin important in phototropism?

Ans. Auxin synthesised at the stem tip migrates to the shaded side when light comes from one direction. More auxin causes the shaded side cells to elongate faster, bending the stem toward the light positive phototropism.

Q. Name the gaseous plant hormone and its function.

Ans. Ethylene (Ethene) is the only gaseous plant hormone. It promotes growth and ripening of fruits.

Q. What is the difference between nastic and tropic movements?

Ans. Tropic movements are directional (toward or away from stimulus) and growth-dependent and slow. Nastic movements are non-directional, growth-independent, rapid, and caused by changes in turgor pressure (e.g., Mimosa folding).

Q. What is a synapse?

Ans. A synapse is the microscopic gap between the terminal end of one neuron's axon and the dendrite of the next neuron. It acts as a one-way valve; impulses are transmitted across it by chemical neurotransmitters such as acetylcholine.

Q. What is a reflex arc? Name its components.

Ans. A reflex arc is the pathway followed by a nerve impulse from receptor to effector during a reflex action. Components: (i) Receptor, (ii) Sensory/Afferent nerve, (iii) Relay neuron in spinal cord, (iv) Motor/Efferent nerve.

Q. State the functions of the cerebellum.

Ans. The cerebellum maintains posture and balance, and coordinates smooth voluntary movements such as walking in a straight line, riding a bicycle, and picking up objects.

Q. Why is adrenaline called the "emergency hormone"?

Ans. During stress or danger, adrenaline is released in large amounts. It increases heart rate, breathing rate, blood sugar level, and blood pressure, and redirects blood to muscles preparing the body for "fight or flight."

Q. What is diabetes mellitus? How does it differ from diabetes insipidus?

Ans. Diabetes mellitus results from insulin deficiency, causing high blood sugar and glucose excretion in urine. Diabetes insipidus results from ADH (vasopressin) deficiency, causing excessive water loss in urine with normal blood sugar levels.

Q. What is the role of iodine in thyroid function?

Ans. Iodine is essential for the synthesis of thyroid hormones thyroxine (T₄) and triiodothyronine (T₃). Iodine deficiency leads to enlargement of the thyroid gland called iodine deficiency goitre, prevented by iodised salt.

Q. What is the function of ADH (vasopressin)?

Ans. ADH (antidiuretic hormone), secreted by the posterior pituitary, reduces water loss by increasing water reabsorption in kidney tubules. It also constricts arterioles, raising blood pressure. Its deficiency causes diabetes insipidus.

Q. Why is the pituitary gland called the master endocrine gland?

Ans. The pituitary gland secretes hormones (TSH, ACTH, FSH, LH) that regulate other endocrine glands. However, the pituitary itself is regulated by the hypothalamus, making the hypothalamus-pituitary system the true master regulatory axis.

Q. Explain the role of insulin and glucagon in blood sugar regulation.

Ans. Insulin (from β-cells) lowers blood glucose by stimulating cells to absorb glucose. Glucagon (from α-cells) raises blood glucose by stimulating glycogen breakdown in the liver. They work antagonistically to maintain blood glucose homeostasis.

Q. What is geotropism? Explain with an experiment.

Ans. Geotropism is the directional growth of plant parts in response to gravity. When a potted plant is placed on its side, the stem bends upward (negative geotropism) and the root bends downward (positive geotropism) within a few days demonstrating geotropic responses mediated by auxin.

Q. What are the functions of the hypothalamus?

Ans. The hypothalamus controls: thirst, hunger, body temperature (thermoregulation), sleep patterns, fear, osmoregulation, and regulates pituitary hormone secretion via releasing and inhibitory hormones.

Q. Distinguish between sensory and motor neurons.

Ans. Sensory (afferent) neurons carry impulses from receptors to the CNS. Motor (efferent) neurons carry impulses from the CNS to effectors (muscles and glands).

Q. What is hydrotropism? Design an experiment to demonstrate it.

Ans. Hydrotropism is the directional growth of roots toward water. Experiment: Plant seedlings in two troughs (A and B). Water trough A uniformly throughout the soil. In trough B, place a clay pot with water buried in the soil and water only that pot. After a few days, the root in trough B bends toward the clay pot — demonstrating positive hydrotropism.

Q. What are Islets of Langerhans?

Ans. Islets of Langerhans are specialised clusters of endocrine cells in the pancreas. They contain α-cells (secrete glucagon) and β-cells (secrete insulin) to regulate blood glucose levels.

Q. What happens at the neuromuscular junction?

Ans. The neuromuscular junction is the synapse between a motor neuron's axon terminal and a muscle cell's membrane (sarcolemma). When a nerve impulse arrives, a neurotransmitter is released, creating an electrical disturbance in the muscle cell that causes it to contract, producing movement.

Control and Coordination Notes Quick Revision Summary