Control and Coordination
Welcome to HSLC Guru. This article gives you complete English-medium notes and question answers for Class 10 Science Chapter 7 — Control and Coordination, prepared strictly according to the ASSEB syllabus. You will find an organised summary, all textbook intext and exercise questions, additional MCQs, fill in the blanks, true or false statements and a glossary table to make your revision faster and easier.
Summary
All living organisms respond to changes in their environment. These changes are called stimuli and the responses are controlled by special systems in the body. In animals, control and coordination is carried out by the nervous system and the endocrine system. The structural and functional unit of the nervous system is the neuron. A neuron has three main parts — cell body (cyton), dendrites that receive impulses, and a long axon that carries the impulse away. Neurons are of three types — sensory neurons, motor neurons and association/relay neurons. Information travels along a neuron as an electrical impulse and across the synapse as a chemical signal called a neurotransmitter.
A reflex action is a sudden, automatic and involuntary response to a stimulus, like withdrawing the hand on touching a hot object. The pathway through which the reflex impulse travels — receptor, sensory neuron, spinal cord, motor neuron and effector — is called the reflex arc. Reflexes are mostly controlled by the spinal cord. The human nervous system is divided into the Central Nervous System (CNS) consisting of the brain and spinal cord, and the Peripheral Nervous System (PNS) made of cranial and spinal nerves. The brain has three main regions — the cerebrum (thinking, memory, voluntary actions), the cerebellum (balance and coordination of movement), and the medulla oblongata (involuntary actions like heartbeat, breathing, blood pressure, vomiting, salivation).
The endocrine system uses chemical messengers called hormones secreted by ductless glands directly into the blood. Important glands include the pituitary (master gland — secretes growth hormone), thyroid (secretes thyroxine which regulates carbohydrate, protein and fat metabolism; needs iodine), adrenal (secretes adrenaline — fight or flight hormone), pancreas (secretes insulin which controls blood sugar), testes (testosterone) and ovaries (oestrogen and progesterone). Deficiency of iodine causes goitre and lack of insulin causes diabetes. Hormone secretion is controlled by a feedback mechanism so that the right amount is released at the right time.
Plants do not have a nervous system, but they show coordination through plant hormones (phytohormones) and movements called tropisms. Tropisms are directional growth movements in response to stimuli — phototropism (light), geotropism (gravity), hydrotropism (water) and chemotropism (chemicals, e.g., growth of pollen tube). The four major plant hormones are auxin (promotes cell elongation and phototropic bending), gibberellin (stem elongation, seed germination), cytokinin (cell division, delays ageing of leaves) and abscisic acid (inhibitory hormone causing wilting, leaf fall and closure of stomata). Together, nervous control, hormonal control in animals and tropic and hormonal responses in plants ensure proper coordination of all life activities.
Textbook Question Answers
1 Mark Questions
Q1. What is the structural and functional unit of the nervous system?
Answer: The neuron (nerve cell) is the structural and functional unit of the nervous system.
Q2. What is a stimulus?
Answer: Any change in the environment that causes a response in a living organism is called a stimulus, e.g., light, heat, sound, touch.
Q3. Name the master gland of the human body.
Answer: The pituitary gland is called the master gland.
Q4. Which hormone is secreted by the pancreas?
Answer: The pancreas secretes insulin and glucagon. Insulin lowers blood sugar level.
Q5. Define reflex action.
Answer: A sudden, quick and involuntary response to a stimulus, controlled mainly by the spinal cord, is called a reflex action.
Q6. What is a synapse?
Answer: The microscopic gap between the axon ending of one neuron and the dendrite of the next neuron, across which impulses are transmitted by neurotransmitters, is called a synapse.
Q7. Name the hormone responsible for the “fight or flight” response.
Answer: Adrenaline, secreted by the adrenal gland.
Q8. Which plant hormone promotes cell elongation?
Answer: Auxin promotes cell elongation, especially behind the tip of the shoot.
Q9. What is geotropism?
Answer: The directional growth movement of a plant part in response to gravity is called geotropism. Roots show positive geotropism and shoots show negative geotropism.
Q10. Which hormone is essential for normal growth and metabolism, and which mineral is needed for its production?
Answer: Thyroxine, secreted by the thyroid gland; iodine is needed for its synthesis.
2 to 3 Marks Questions
Q1. Draw a labelled diagram of a neuron and write the function of its parts.
Answer: A neuron has three main parts:
- Dendrites — short branched processes that receive impulses from other neurons or receptors.
- Cell body (Cyton) — contains the nucleus and cytoplasm; processes information.
- Axon — a long fibre that conducts impulses away from the cell body to the next neuron or effector. The axon ends in axon terminals which release neurotransmitters at the synapse.
Q2. Differentiate between the central nervous system (CNS) and peripheral nervous system (PNS).
| CNS | PNS |
|---|---|
| Made up of brain and spinal cord. | Made up of cranial and spinal nerves. |
| Controls and coordinates all activities. | Carries impulses to and from the CNS. |
| Protected by skull and vertebral column. | Spread throughout the body. |
Q3. What is a reflex arc? Draw it and explain.
Answer: The pathway taken by a nerve impulse during a reflex action is called a reflex arc. It includes — Receptor (skin) → Sensory neuron → Spinal cord (relay neuron) → Motor neuron → Effector (muscle). The impulse does not need to travel up to the brain, so the response is very fast. Example: pulling away the hand on touching a hot object.
Q4. Name three parts of the human brain and write one function of each.
- Cerebrum — Centre of intelligence, memory, thinking and voluntary actions.
- Cerebellum — Maintains posture and coordinates muscular movements (balance).
- Medulla oblongata — Controls involuntary actions like heartbeat, breathing, blood pressure, vomiting and salivation.
Q5. Differentiate between tropic and nastic movements in plants.
| Tropic Movement | Nastic Movement |
|---|---|
| Direction depends on the direction of stimulus. | Direction is independent of stimulus direction. |
| Caused by unequal growth. | Caused by changes in turgor pressure. |
| Slow and permanent. | Fast and temporary. e.g., touch-me-not plant. |
Q6. Explain how plant hormones help in growth. Name the four major plant hormones.
Answer: Plant hormones are chemical substances produced in small amounts that regulate growth and development. The four major hormones are — Auxin (cell elongation, phototropism), Gibberellin (stem elongation, seed germination), Cytokinin (cell division, delays ageing), and Abscisic acid (inhibits growth, causes wilting and leaf fall).
5 to 6 Marks Questions
Q1. Describe the structure and functions of the human nervous system.
Answer: The human nervous system is divided into:
- Central Nervous System (CNS): Brain and spinal cord. The brain has three parts — cerebrum (thinking, memory, voluntary movement), cerebellum (posture, balance) and medulla oblongata (involuntary actions). The spinal cord controls reflex actions and connects the brain with the body.
- Peripheral Nervous System (PNS): Made up of 12 pairs of cranial nerves arising from the brain and 31 pairs of spinal nerves arising from the spinal cord, carrying impulses to and from the CNS.
- Autonomic Nervous System: A part of PNS that controls involuntary activities (heartbeat, digestion, etc.) through sympathetic and parasympathetic systems.
Functions: receives stimuli through receptors, processes information, and sends responses to effectors (muscles/glands), thus coordinating all body activities.
Q2. Explain the endocrine system in humans by writing the name of any five glands, the hormone they secrete and one function of each.
| Gland | Hormone | Function |
|---|---|---|
| Pituitary | Growth hormone | Controls growth of bones and body. |
| Thyroid | Thyroxine | Regulates metabolism of carbohydrate, protein and fat. |
| Adrenal | Adrenaline | Prepares body for emergency (fight or flight). |
| Pancreas | Insulin | Lowers blood glucose level. |
| Testes/Ovaries | Testosterone / Oestrogen | Develops male / female secondary sexual characters. |
Q3. What are tropisms? Explain four types of tropic movements with one example each.
Answer: Tropisms are directional growth movements in plants in response to external stimuli.
- Phototropism: Growth in response to light. Shoots bend towards light (positive); roots away (negative). Example — a plant kept near a window bends towards the window.
- Geotropism: Growth in response to gravity. Roots grow downwards (positive); shoots grow upwards (negative).
- Hydrotropism: Growth in response to water. Roots grow towards water (positive).
- Chemotropism: Growth in response to chemicals. Example — pollen tube grows towards the ovule due to chemicals secreted by it.
Q4. How does chemical coordination occur in plants? Discuss the role of any three plant hormones.
Answer: Plants do not have a nervous system. They coordinate their activities through chemical messengers called phytohormones produced in small amounts.
- Auxin: Produced at the shoot tip; promotes cell elongation. When light falls on one side, auxin moves to the shaded side, cells there elongate more, and the shoot bends towards light (phototropism).
- Gibberellin: Promotes stem elongation, seed germination and breaking of dormancy.
- Cytokinin: Promotes cell division and delays ageing of leaves; abundant in fruits and seeds.
- Abscisic acid: A growth inhibitor; causes wilting of leaves, closure of stomata and falling of leaves.
Q5. Compare the nervous control and hormonal control in animals.
| Nervous Control | Hormonal Control |
|---|---|
| Information travels as electrical impulses through neurons. | Information travels as chemicals (hormones) through blood. |
| Action is very fast. | Action is slower. |
| Effect is short-lived. | Effect is long-lasting. |
| Specific in action — affects only target organs through nerves. | Hormones travel everywhere but act only on specific target organs. |
| Example: withdrawing hand from hot object. | Example: insulin lowering blood sugar. |
Additional MCQs
Q1. The structural and functional unit of the nervous system is —
(a) Nephron (b) Neuron (c) Axon (d) Synapse
Answer: (b) Neuron
Q2. Which part of the brain controls balance and posture?
(a) Cerebrum (b) Cerebellum (c) Medulla (d) Pons
Answer: (b) Cerebellum
Q3. Reflex actions are mainly controlled by —
(a) Cerebrum (b) Cerebellum (c) Spinal cord (d) Medulla
Answer: (c) Spinal cord
Q4. The master gland of the human body is —
(a) Thyroid (b) Pituitary (c) Adrenal (d) Pancreas
Answer: (b) Pituitary
Q5. Iodine is required for the synthesis of —
(a) Insulin (b) Adrenaline (c) Thyroxine (d) Auxin
Answer: (c) Thyroxine
Q6. Which hormone controls blood sugar level?
(a) Adrenaline (b) Insulin (c) Thyroxine (d) Testosterone
Answer: (b) Insulin
Q7. The bending of shoot towards light is called —
(a) Geotropism (b) Hydrotropism (c) Phototropism (d) Chemotropism
Answer: (c) Phototropism
Q8. Which plant hormone promotes cell elongation?
(a) Cytokinin (b) Auxin (c) Abscisic acid (d) Ethylene
Answer: (b) Auxin
Q9. Adrenaline is secreted by —
(a) Pituitary (b) Thyroid (c) Adrenal gland (d) Pancreas
Answer: (c) Adrenal gland
Q10. Which of the following is an inhibitory plant hormone?
(a) Auxin (b) Gibberellin (c) Cytokinin (d) Abscisic acid
Answer: (d) Abscisic acid
Fill in the Blanks
Q1. The gap between two neurons is called __________.
Answer: synapse
Q2. __________ is known as the master gland.
Answer: Pituitary
Q3. Roots show __________ geotropism.
Answer: positive
Q4. Deficiency of __________ hormone causes diabetes.
Answer: insulin
Q5. __________ is the fight or flight hormone.
Answer: Adrenaline
True or False
Q1. The cerebellum controls thinking and memory.
Answer: False (Cerebrum controls thinking and memory.)
Q2. The pituitary gland is located at the base of the brain.
Answer: True
Q3. Auxin causes leaves to fall.
Answer: False (Abscisic acid causes leaf fall.)
Q4. The CNS includes the brain and spinal cord.
Answer: True
Q5. Hydrotropism is the growth of roots towards water.
Answer: True
Glossary
| Term | Meaning |
|---|---|
| Stimulus | A change in the environment that causes a response. |
| Neuron | Structural and functional unit of the nervous system. |
| Synapse | Microscopic gap between two neurons. |
| Reflex action | Sudden involuntary response to a stimulus. |
| Reflex arc | Pathway of a reflex action through receptor, sensory neuron, spinal cord, motor neuron and effector. |
| CNS | Central Nervous System — brain and spinal cord. |
| PNS | Peripheral Nervous System — cranial and spinal nerves. |
| Cerebrum | Largest part of the brain; centre of intelligence and memory. |
| Cerebellum | Brain part controlling balance and coordination. |
| Medulla oblongata | Brain part controlling involuntary actions. |
| Hormone | Chemical messenger secreted by endocrine glands. |
| Pituitary | Master endocrine gland. |
| Thyroxine | Hormone of thyroid gland; regulates metabolism. |
| Insulin | Pancreatic hormone that lowers blood sugar. |
| Adrenaline | Emergency hormone of adrenal gland. |
| Tropism | Directional growth movement of a plant due to a stimulus. |
| Phototropism | Growth in response to light. |
| Geotropism | Growth in response to gravity. |
| Hydrotropism | Growth in response to water. |
| Chemotropism | Growth in response to chemicals. |
| Auxin | Plant hormone causing cell elongation. |
| Gibberellin | Plant hormone promoting stem elongation and germination. |
| Cytokinin | Plant hormone promoting cell division. |
| Abscisic acid | Inhibitory plant hormone causing wilting and leaf fall. |