Chapter 19: Chemical Coordination and Integration Application Questions | biology Class 11 CBSE

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Chapter 19: Chemical Coordination and Integration Application Questions | biology Class 11 CBSE | ByteNotes.in

Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 1

Applied Concept

A doctor suspects a patient has a growth hormone disorder. The patient is 35 years old with enlarged hands, feet, and facial features but is of normal height. What disorder is this, what is its cause, and which gland is implicated?

The patient is likely suffering from acromegaly, which occurs due to excess secretion of growth hormone (GH) in adults, especially in middle age.
At this age, the long bones have already fused, so excess GH does not cause overall height increase but instead causes disfigurement of extremities and facial features.
The implicated gland is the pituitary gland (specifically the pars distalis/anterior pituitary), which over-secretes GH.
The condition can lead to serious complications and premature death if unchecked; it is hard to diagnose in early stages and often goes undetected for years until external features become noticeable.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 2

Applied Concept

A pregnant woman living in a hilly region with poor iodine intake in water and food delivers a baby who shows stunted growth, mental retardation, and hearing impairment. Identify the condition and explain the underlying cause.

The baby is suffering from cretinism, which is caused by hypothyroidism during pregnancy.
The mother's iodine deficiency prevented normal synthesis of thyroid hormones (T3 and T4) during the critical developmental period of the foetus.
Thyroid hormones are essential for normal development and maturation of the central nervous system; their deficiency leads to stunted growth, mental retardation, low IQ, abnormal skin, and deaf-mutism.
Prevention requires adequate iodine intake during pregnancy; in adult women, hypothyroidism may also cause irregular menstrual cycles.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 3

Applied Concept

A student notices that before a sports competition, her heart beats faster, she sweats more, and her pupils dilate even though she has not started exercising. Explain this response in terms of the hormones involved.

This is the 'fight or flight' response mediated by catecholamines—adrenaline (epinephrine) and noradrenaline (norepinephrine)—secreted by the adrenal medulla in response to stress and anticipation.
These emergency hormones rapidly prepare the body: they increase heart rate, strength of heart contraction, rate of respiration, cause pupilary dilation, piloerection, and sweating.
They also stimulate glycogenolysis in the liver, increasing blood glucose to provide energy for imminent physical activity.
The neural system triggers adrenal medulla secretion almost instantaneously, demonstrating neuroendocrine coordination under stress.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 4

Applied Concept

With reference to the role of ADH, explain what happens physiologically when a person is dehydrated and why patients with Diabetes Insipidus cannot retain water.

During dehydration, blood osmolarity rises, stimulating the hypothalamus to signal the neurohypophysis to release more ADH (vasopressin).
ADH acts on the distal tubules of the kidney, stimulating reabsorption of water and electrolytes, thus reducing water loss through urine and restoring body fluid balance.
In Diabetes Insipidus, an impairment in ADH synthesis or release means the kidney cannot respond adequately; the distal tubules fail to reabsorb sufficient water.
This results in large volumes of dilute urine being produced, causing continuous water loss, dehydration, and electrolyte imbalance despite normal fluid intake.

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Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 5

Applied Concept

A 50-year-old patient develops progressive weakness, fatigue, and blood tests show low cortisol and aldosterone. Identify the probable disease, its cause, and explain how these hormonal deficiencies lead to the observed symptoms.

The patient is likely suffering from Addison's disease, caused by underproduction of hormones by the adrenal cortex.
Low cortisol (glucocorticoid) impairs gluconeogenesis and carbohydrate metabolism, leading to low blood glucose, fatigue, and muscle weakness.
Low aldosterone (mineralocorticoid) reduces renal reabsorption of Na+ and water while increasing K+ retention, leading to low blood pressure, electrolyte imbalance, and further fatigue.
Both deficiencies together disrupt metabolic homeostasis and cardiovascular function, explaining the acute weakness and fatigue seen in Addison's disease.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 6

Applied Concept

A doctor prescribes insulin injections to a patient who has been experiencing excessive thirst, frequent urination, and weight loss despite increased appetite. Explain the hormonal basis of these symptoms.

The patient has diabetes mellitus, caused by insulin deficiency (or insulin resistance), leading to prolonged hyperglycaemia.
Without adequate insulin, glucose cannot be taken up by cells (hepatocytes and adipocytes), so cells remain energy-deprived despite high blood glucose, causing increased appetite (polyphagia) and weight loss from fat and protein breakdown.
Excess blood glucose spills into the urine (glycosuria), drawing water by osmosis and causing frequent, copious urination (polyuria), which in turn leads to excessive thirst (polydipsia).
Insulin therapy restores cellular glucose uptake and utilisation, normalising blood glucose and resolving the symptoms.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 7

Applied Concept

With reference to the role of oxytocin, explain two physiological events in a female where this hormone plays a critical role.

Oxytocin is synthesised by the hypothalamus, stored in and released from the neurohypophysis (posterior pituitary), and acts on smooth muscles of the body.
First, during childbirth (parturition), oxytocin stimulates vigorous contractions of the uterine smooth muscles, facilitating delivery of the baby; this forms part of a positive feedback loop that strengthens contractions.
Second, during breastfeeding, oxytocin stimulates milk ejection (let-down) from the mammary glands when the baby suckles, ensuring the infant receives nutrition.
Both roles illustrate neuroendocrine integration: sensory stimuli (uterine stretch, nipple stimulation) are processed by the hypothalamus, which directs the posterior pituitary to release oxytocin.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 8

Applied Concept

An elderly man notices that he recovers slowly from infections and his vaccines seem less effective than when he was younger. Explain this observation in the context of the endocrine system.

With advancing age, the thymus gland undergoes degeneration (atrophy), leading to a significant decrease in the production of thymosin hormones.
Thymosins are essential for the differentiation of T-lymphocytes (which provide cell-mediated immunity); reduced thymosins mean fewer functional T-lymphocytes.
Thymosins also promote antibody production for humoral immunity; declining levels reduce the body's ability to mount robust antibody responses, explaining reduced vaccine effectiveness.
Together, the loss of both cell-mediated and humoral immune capacity with age makes elderly individuals more susceptible to infections and results in slower recovery.

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Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 9

Applied Concept

A pathology report shows elevated PTH levels in a patient with low blood calcium. Trace the sequence of events initiated by PTH to restore calcium levels, mentioning all three target sites.

When blood calcium falls below normal levels, the parathyroid glands detect this change (PTH secretion is regulated by circulating Ca2+ levels) and increase PTH secretion.
PTH acts on bones, stimulating osteoclast activity to cause bone resorption (demineralisation), releasing Ca2+ stored in bone matrix into the bloodstream.
PTH acts on renal tubules to stimulate reabsorption of Ca2+ (reducing its loss in urine), thereby increasing blood Ca2+ levels.
PTH increases Ca2+ absorption from digested food in the gastrointestinal tract; through all three mechanisms, blood calcium is restored to normal (hypercalcaemic effect), and PTH secretion reduces via negative feedback.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 10

Applied Concept

A patient is found to have protruding eyeballs, an enlarged neck, increased heart rate, and rapid weight loss. Identify the condition, the causative hormonal imbalance, and the gland involved.

The patient is suffering from Graves' disease (exophthalmic goitre), a form of hyperthyroidism characterised by enlargement of the thyroid gland and protrusion of the eyeballs (exophthalmos).
The condition is caused by abnormally high secretion of thyroid hormones (T3 and T4), leading to a significantly elevated basal metabolic rate.
Increased BMR causes rapid weight loss and increased heart rate; the enlargement of the thyroid causes the visible neck swelling.
Hyperthyroidism can result from cancer of the thyroid gland or development of thyroid nodules that cause uncontrolled synthesis and secretion of thyroid hormones.

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Chapter 19: Chemical Coordination and Integration | Application Questions

A doctor suspects a patient has a growth hormone disorder. The patient is 35 years old with enlarged hands, feet, and facial features but is of normal height. What disorder is this, what is its cause, and which gland is implicated?

A pregnant woman living in a hilly region with poor iodine intake in water and food delivers a baby who shows stunted growth, mental retardation, and hearing impairment. Identify the condition and explain the underlying cause.

A student notices that before a sports competition, her heart beats faster, she sweats more, and her pupils dilate even though she has not started exercising. Explain this response in terms of the hormones involved.

With reference to the role of ADH, explain what happens physiologically when a person is dehydrated and why patients with Diabetes Insipidus cannot retain water.

A 50-year-old patient develops progressive weakness, fatigue, and blood tests show low cortisol and aldosterone. Identify the probable disease, its cause, and explain how these hormonal deficiencies lead to the observed symptoms.

A doctor prescribes insulin injections to a patient who has been experiencing excessive thirst, frequent urination, and weight loss despite increased appetite. Explain the hormonal basis of these symptoms.

With reference to the role of oxytocin, explain two physiological events in a female where this hormone plays a critical role.

An elderly man notices that he recovers slowly from infections and his vaccines seem less effective than when he was younger. Explain this observation in the context of the endocrine system.

A pathology report shows elevated PTH levels in a patient with low blood calcium. Trace the sequence of events initiated by PTH to restore calcium levels, mentioning all three target sites.

A patient is found to have protruding eyeballs, an enlarged neck, increased heart rate, and rapid weight loss. Identify the condition, the causative hormonal imbalance, and the gland involved.

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