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6. Control and Coordination

Long Answered Questions

Answers to Questions for Practice

Q1: Name the two substances which are responsible for the control and coordination in plants.

Ans: The two substances responsible for control and coordination in plants are plant hormones (phytohormones) and chemical messengers.

Q2: What are Phytohormones? Name any two.

Ans: Phytohormones are natural chemical substances produced in plants that regulate growth and development. Two examples are Auxin and Gibberellin.

Q3: What is the difference between photoperiodism and phototropism?

Ans: Photoperiodism is the response of plants to the duration of day and night, whereas phototropism is the directional growth of plants in response to light.

Q4: What are nastic movements? Give one example.

Ans: Nastic movements are non-directional movements of plant parts in response to stimuli. Example: Folding of leaves of the touch-me-not (Mimosa pudica) plant.

Q5: What are the different hormones found in plants and their functions?

Ans:

• Auxin – Promotes cell elongation and growth.
• Gibberellin – Stimulates stem elongation and seed germination.
• Cytokinin – Promotes cell division.
• Abscisic Acid (ABA) – Inhibits growth and causes wilting of leaves.
• Ethylene – Promotes fruit ripening.

Q6: What are receptors? What type of receptors detect smell and taste?

Ans: Receptors are specialized cells that receive stimuli and send information to the nervous system. Chemoreceptors detect smell and taste.

Q7: How is the information sent to the brain in animals?

Ans: Information is carried from receptors to the brain through sensory neurons in the form of electrical impulses.

Q8: What is cranium?

Ans: The cranium is the hard bony box of the skull that protects the brain from injury.

Q9: How are tissues protected in the brain?

Ans: Brain tissues are protected by the cranium, three protective membranes called meninges, and cerebrospinal fluid (CSF).

Q10: What is the role of the brain in reflex action?

Ans: The brain is generally not involved in immediate reflex actions. The spinal cord controls reflex actions, while the brain becomes aware of the response afterward.

Q11: What happens at the synapse between two neurons?

Ans: At the synapse, electrical impulses trigger the release of neurotransmitters, which carry the nerve impulse from one neuron to the next.

Q12: What is stimulus?

Ans: A stimulus is any change in the internal or external environment that causes an organism to respond.

Q13: What are the different types of nervous systems found in the human body? Mention the functions of each.

Ans:

• Central Nervous System (CNS) – Controls and coordinates all body activities.
• Peripheral Nervous System (PNS) – Carries messages between the CNS and body organs.
• Autonomic Nervous System (ANS) – Controls involuntary activities such as heartbeat and digestion.

Q14: Draw the schematic diagram of reflex arc. Define reflex action with a suitable example.

Ans: Reflex action is a quick, automatic response to a stimulus without conscious thought.

Example: Pulling the hand away immediately after touching a hot object.

Reflex Arc:

Stimulus
   ↓
Receptor
   ↓
Sensory Neuron
   ↓
Spinal Cord
   ↓
Motor Neuron
   ↓
Effector
   ↓
Response

Q15: Draw the labeled structure of the human brain.

Ans: Students should draw a neat labeled diagram showing:

• Cerebrum
• Cerebellum
• Midbrain
• Pons
• Medulla Oblongata
• Hypothalamus
• Pituitary Gland

Q16: What are the four main parts of the forebrain? Give the function of each part.

Ans:

• Cerebrum – Intelligence, thinking, memory, and voluntary actions.
• Thalamus – Relays sensory information to the cerebrum.
• Hypothalamus – Maintains body temperature, hunger, thirst, and hormonal control.
• Olfactory Lobes – Responsible for the sense of smell.

Q17: What are the three parts of the midbrain and their functions?

Ans: The midbrain mainly contains:

• Corpora Quadrigemina – Controls visual and auditory reflexes.
• Cerebral Peduncles – Carry nerve impulses between the brain and spinal cord.
• Cerebral Aqueduct – Connects brain cavities and allows cerebrospinal fluid to flow.

Q18: Which part of the human brain is responsible for: Intelligence and Memory, Adjustment of Movement and Posture, Smell?

Ans:

• Intelligence and Memory – Cerebrum
• Adjustment of Movement and Posture – Cerebellum
• Smell – Olfactory Lobes

Q19: Give the role of Frontal lobe, Temporal lobe and Medulla Oblongata.

Ans:

• Frontal Lobe – Controls thinking, reasoning, speech, personality, and voluntary movements.
• Temporal Lobe – Controls hearing, memory, and understanding language.
• Medulla Oblongata – Regulates involuntary activities such as breathing, heartbeat, swallowing, and blood pressure.

Answers to Questions for Practice (Q20–Q37)

Q20: Name the different lobes found in the forebrain and give their functions.

Ans:

• Frontal Lobe – Controls thinking, reasoning, speech, emotions, and voluntary movements.
• Parietal Lobe – Receives and interprets sensations such as touch, pain, temperature, and pressure.
• Temporal Lobe – Responsible for hearing, memory, and understanding language.
• Occipital Lobe – Controls vision and interprets visual information.

Q21: What is geotropism?

Ans: Geotropism is the directional growth movement of a plant in response to gravity. Roots show positive geotropism, while shoots show negative geotropism.

Q22: What are plant hormones?

Ans: Plant hormones are chemical substances produced in plants that regulate growth, development, flowering, fruit ripening, and responses to environmental stimuli.

Q23: What are controlled movements? How does this process happen?

Ans: Controlled movements are body movements that occur in response to internal or external stimuli. Receptors receive the stimulus, sensory neurons carry the message to the brain or spinal cord, and motor neurons send instructions to muscles or glands to produce the appropriate response.

Q24: What are electrical impulses? What are their limitations?

Ans: Electrical impulses are electrical signals that travel through neurons to transmit information rapidly.

Limitations:

• They reach only the cells connected by nerve fibers.
• Their effect lasts for a very short time.
• They cannot coordinate activities throughout the entire body.

Q25: How do the stimulated cells overcome the limitations of electrical impulses?

Ans: Stimulated cells release chemical messengers called hormones into the bloodstream. These hormones reach target organs and produce long-lasting and widespread effects, overcoming the limitations of electrical impulses.

Q26: How do auxins promote the growth of a tendril around a support?

Ans: When a tendril touches a support, auxin moves to the side away from the point of contact. The cells on that side grow faster, causing the tendril to bend and coil around the support.

Q27: Which hormone is responsible for the wilting of leaves in plants?

Ans: Abscisic Acid (ABA) is the hormone responsible for the wilting of leaves and the closing of stomata during water shortage.

Q28: What are hormones? Who coined the term hormone?

Ans: Hormones are chemical messengers secreted by endocrine glands that regulate various activities of the body. The term "hormone" was coined by Ernest Starling in 1905.

Q29: What is the function of adrenaline? Explain briefly.

Ans: Adrenaline is the emergency hormone secreted by the adrenal glands. It prepares the body for stressful situations by increasing the heart rate, breathing rate, blood pressure, and blood glucose level. This response is known as the fight-or-flight response.

Q30: Why does diabetes occur? What is insulin?

Ans: Diabetes occurs when the pancreas does not produce enough insulin or when the body cannot use insulin effectively. Insulin is a hormone secreted by the pancreas that helps regulate the level of glucose in the blood.

Q31: Draw the diagram showing endocrine glands in a male body/female body and label: Pituitary, Thyroid, Adrenal, Testis/Ovaries, Thalamus, and Hypothalamus.

Ans: Students should draw a neat labeled diagram showing the following endocrine glands:

• Pituitary Gland
• Hypothalamus
• Thalamus
• Thyroid Gland
• Adrenal Glands
• Testes (Male) / Ovaries (Female)

Q32: Name the hormone associated with:

(a) Reduction of blood glucose in the body
Ans: Insulin

(b) Overall metabolism of the body
Ans: Thyroxine

Q33: Write the functions of testes and ovaries.

Ans:

• Testes – Produce sperm and secrete the hormone testosterone.
• Ovaries – Produce ova (eggs) and secrete the hormones estrogen and progesterone.

Q34: What is the function of the pituitary gland?

Ans: The pituitary gland is known as the master gland because it controls the activities of other endocrine glands. It secretes hormones that regulate growth, reproduction, and the secretion of hormones by other glands.

Q35: What is the need for control and coordination in the body?

Ans: Control and coordination help different organs work together, maintain internal balance, respond to environmental changes, and ensure the proper functioning of the body.

Q36: Which is the structural and functional unit of the nervous system? Describe it with the help of a diagram.

Ans: The neuron (nerve cell) is the structural and functional unit of the nervous system.

Main Parts:

• Dendrites – Receive nerve impulses.
• Cell Body (Cyton) – Contains the nucleus and controls cell activities.
• Axon – Carries nerve impulses away from the cell body.
• Axon Terminals – Transmit impulses to the next neuron.

Simple Diagram:

Dendrites → Cell Body → Axon → Axon Terminals

Q37: "The nervous system and the hormonal system together perform the function of control and coordination in humans." Justify.

Ans: The nervous system controls body activities through rapid electrical impulses, providing quick and short-term responses. The hormonal system controls body functions through hormones carried by the blood, producing slower but longer-lasting effects. Together, these two systems coordinate all body activities, maintain homeostasis, regulate growth and development, and help the body respond effectively to internal and external changes.