How does your hand instantly pull back when touching a hot pan? How do sunflowers track the sun across the sky? How does your body maintain blood sugar levels after a meal? All these intricate responses are regulated by Control and Coordination, which forms Chapter 7 of the CBSE Class 10 Biology curriculum.
In this guide, we examine the structural organization of the human nervous system, neuron anatomy and synaptic transmission, reflex arc pathways, human brain regions, plant tropisms and phytohormones, the endocrine gland system, and hormonal feedback control mechanisms.
- 1. The Nervous System & Structure of a Neuron
- 2. Transmission of Impulses & The Synapse
- 3. Reflex Action & Reflex Arc Pathway
- 4. Human Brain Anatomy & Protection of CNS
- 5. Coordination in Plants — Nastic vs Tropic Movements
- 6. Plant Hormones (Phytohormones)
- 7. Animal Endocrine Glands & Hormonal Feedback
- 8. Solved Board Exam Questions
- 9. Frequently Asked Questions (FAQ)
1. The Nervous System & Structure of a Neuron
The nervous system receives information from the environment through specialized sense organs called Receptors:
- Photoreceptors: Eyes (detect light)
- Phonoreceptors: Inner Ear (detect sound & balance)
- Gustatory Receptors: Tongue (detect taste)
- Olfactory Receptors: Nose (detect smell)
- Thigmoreceptors: Skin (detect touch, pain, pressure, temperature)
Key Components of a Neuron:
1. Dendrites: Fine, branched projections that acquire information/stimuli from receptors or preceding neurons.
2. Cyton (Cell Body / Soma): Contains nucleus and cytoplasm; converts stimulus into an electrical impulse.
3. Axon: Longest single cylindrical nerve fiber that conducts electrical impulse away from cell body towards terminal branches. Covered by insulating Myelin Sheath.
4. Axon Terminals: End branches that release chemical neurotransmitters across the synaptic gap.
2. Transmission of Impulses & The Synapse
How does an electrical nerve impulse travel across neurons? Electrical impulses travel along the length of an axon. However, when the impulse reaches the nerve ending (axon terminal), it triggers the release of chemical substances called Neurotransmitters (e.g., Acetylcholine).
3. Reflex Action & Reflex Arc Pathway
A Reflex Action is a rapid, automatic, involuntary, and instantaneous response of the body to a stimulus without conscious thinking by the brain (e.g., withdrawing hand from a hot object, knee-jerk, watering of mouth at good food smell).
Thinking is a complex process involving millions of brain neurons, which takes time. Reflex actions are emergency survival mechanisms. By processing the pathway directly in the Spinal Cord, response time is minimized, preventing tissue damage. Information is simultaneously sent to the brain for record-keeping.
4. Human Brain Anatomy & Protection of CNS
The Central Nervous System (CNS) consists of the Brain and Spinal Cord. The human brain is divided into three major regions:
| Brain Region | Sub-Parts | Major Functions & Controls |
|---|---|---|
| 1. Forebrain (Main Thinking Part) |
Cerebrum | Seat of intelligence, thinking, memory, reasoning, willpower, emotions, and voluntary actions. Receives sensory inputs (vision, hearing, smell, taste, touch) and interprets them. |
| Hypothalamus | Controls body temperature, hunger, thirst, sleep cycle, and regulates pituitary gland secretions. | |
| 2. Midbrain | Tectum & Tegmentum | Connects forebrain to hindbrain. Controls involuntary visual and auditory reflexes (head & eye tracking movements). |
| 3. Hindbrain | Cerebellum | Coordinates precision of voluntary movements (walking in a straight line, riding a bicycle, picking up a pencil) and maintains body posture & equilibrium. |
| Medulla Oblongata | Controls involuntary activities crucial for survival: blood pressure, heartbeat, salivation, vomiting, coughing, swallowing, and sneezing. | |
| Pons | Relays signals between cerebrum and cerebellum; regulates respiratory rate. |
Protection of the Central Nervous System (CNS):
- Brain: Enclosed inside a bony box called the Cranium (Skull). Protected internally by three protective membrane layers called Meninges and cushioned by Cerebrospinal Fluid (CSF) which acts as a shock absorber.
- Spinal Cord: Enclosed within a hard bony structure called the Vertebral Column (Spine/Backbone).
5. Coordination in Plants — Nastic vs Tropic Movements
Plants lack a nervous system and muscle tissue. They coordinate movements using electrical-chemical means by changing cellular water content (turgor pressure) or via growth.
• Thigmonasty: Folding of leaves in Mimosa pudica (Touch-me-not plant) upon touch. Happens due to rapid loss of water (turgor pressure) from pulvinus cell bases.
• Photonasty: Opening of dandelion flowers in morning and closing at night.
• Phototropism: Growth in response to light (Shoot +ve, Root −ve).
• Geotropism: Growth in response to gravity (Root +ve, Shoot −ve).
• Hydrotropism: Growth towards water (Roots +ve).
• Chemotropism: Growth towards chemicals (Growth of pollen tube towards ovule).
• Thigmotropism: Twining of tendrils around a support.
6. Plant Hormones (Phytohormones)
| Phytohormone | Primary Role & Mechanism of Action |
|---|---|
| Auxin | Synthesized at shoot tips. Promotes cell elongation. When light falls on one side of plant, auxin diffuses to the shaded side, stimulating cells there to grow longer → causes shoot to bend towards light (Phototropism). |
| Gibberellin | Promotes stem elongation, seed germination, and flowering in plants. Works synergistically with auxins. |
| Cytokinin | Promotes rapid cell division. Present in high concentrations in areas of rapid cell division like fruits, seeds, and root tips. Delay leaf senescence. |
| Abscisic Acid (ABA) | Growth Inhibitor. Inhibits plant growth, causes wilting and falling of leaves, promotes seed dormancy, and closes stomata during drought stress. |
| Ethylene | Gaseous plant hormone that promotes fruit ripening and leaf abscission. |
7. Animal Endocrine Glands & Hormonal Feedback
The Endocrine System consists of ductless glands that secrete chemical messengers called Hormones directly into the bloodstream.
| Endocrine Gland | Hormone Secreted | Function & Associated Deficiency/Excess Disorder |
|---|---|---|
| Pituitary Gland ("Master Gland") | Growth Hormone (GH) | Regulates growth and development of bones & tissues. Deficiency in childhood = Dwarfism; Excess = Gigantism. |
| Thyroid Gland (Neck) | Thyroxin | Regulates carbohydrate, protein, and fat metabolism. Requires Iodine for synthesis. Deficiency = Goitre (swollen neck). |
| Pancreas (Abdomen) | Insulin & Glucagon | Insulin lowers blood glucose levels by aiding cell absorption. Deficiency causes Diabetes Mellitus (treated by insulin injections). |
| Adrenal Glands (Above Kidneys) | Adrenaline ("Fight or Flight") | Secreted during stress/emergency. Increases heart rate, blood pressure, breathing rate, and diverts blood to skeletal muscles. |
| Testes (Male) | Testosterone | Controls development of male secondary sexual characteristics and sperm production. |
| Ovaries (Female) | Estrogen & Progesterone | Controls development of female secondary sexual characteristics, menstrual cycle, and pregnancy. |
High Blood Glucose Level → Detected by Pancreas Beta Cells → Secretion of Insulin Increased → Liver & Muscle cells absorb glucose → Blood Glucose Level Falls to Normal → Detected by Pancreas → Insulin Secretion Reduced.
8. Solved Board Exam Questions
Transmission across Synapse: When an electrical impulse reaches the end of an axon (axon terminal), it triggers the release of microscopic chemical signals called neurotransmitters into the synaptic gap. These chemicals diffuse across the gap and bind to specific receptor sites on the dendrites of the next neuron, setting off a new electrical impulse. Because neurotransmitters are present only at axon tips, signal transmission is strictly unidirectional.
Why Spinal Cord: Thinking in the brain involves complex neuronal processing which takes precious seconds. Processing the reflex arc directly in the spinal cord cuts down response time to milliseconds, minimizing severe burn damage to skin tissue.
Mechanism: Auxin is synthesized at the shoot tip. When sunlight falls on one side of the plant stem, auxin diffuses away from light towards the shaded side of the shoot. The higher concentration of auxin on the shaded side stimulates cells there to elongate faster than cells on the illuminated side. This differential growth causes the stem to bend towards the light source.
(2) Cerebellum: Located in the Hindbrain (below cerebrum). Controls coordination of voluntary muscle movements (e.g., walking in a straight line) and maintains body balance and posture.
If iodine is deficient in our diet, thyroxin synthesis drops, leading to the enlargement of the thyroid gland in the neck — a condition called Goitre. Using iodised salt ensures adequate daily iodine intake.
Explore Related CBSE Class 9 & 10 Science Guides
9. Frequently Asked Questions (FAQ)
Nervous Control: Fast transmission via electrical impulses through neurons, short-lived effects, localized target cells, limited to connected cells.
Hormonal Control: Slower transmission via chemical messengers (hormones) through bloodstream, long-lasting effects, widespread target tissues throughout the body.
(1) Auxin: Shoot cell elongation and phototropism.
(2) Gibberellin: Stem growth and seed germination.
(3) Cytokinin: Rapid cell division in fruits and seeds.
(4) Abscisic Acid (ABA): Growth inhibitor, leaf wilting, and stomata closure.
(5) Ethylene: Fruit ripening.
Diabetes Mellitus is a disease characterized by high blood glucose levels. It is caused by the deficiency or inadequate secretion of the hormone Insulin produced by the Pancreas.
Medulla Oblongata: Controls essential involuntary actions like blood pressure, heartbeat, salivation, and vomiting.
Cerebellum: Controls posture, body balance, and precision of voluntary muscle movements (e.g., walking, riding a bike).
A Reflex Arc is the neural pathway that controls a reflex action.
Order of components: (1) Receptor → (2) Sensory Neuron → (3) Spinal Cord (Relay Neuron) → (4) Motor Neuron → (5) Effector Muscle/Gland.
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