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Chemical Coordination and Integration - Human endocrine system (Pituitary, Pineal, Thyroid, Parathyroid, Adrenal, Pancreas, Gonads)

Grade 11CBSEBiology

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Hormones are non-nutrient chemicals which act as intercellular messengers and are produced in trace amounts.

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The Hypothalamus contains several groups of neurosecretory cells called nuclei which produce hormones like GnRHGnRH (Gonadotropin Releasing Hormone) and Somatostatin.

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The Pituitary gland is divided into adenohypophysis and neurohypophysis. Adenohypophysis secretes GHGH, PRLPRL, TSHTSH, ACTHACTH, LHLH, and FSHFSH. Neurohypophysis stores and releases Oxytocin and Vasopressin (ADHADH).

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The Pineal gland secretes Melatonin, which plays a central role in the regulation of a 2424-hour (diurnal) rhythm of our body.

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Thyroid gland produces Thyroxine (T4T_4) and Triiodothyronine (T3T_3). Iodine is essential for the normal rate of hormone synthesis. It also secretes a protein hormone called Thyrocalcitonin (TCTTCT) which regulates blood calcium levels.

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Parathyroid glands secrete Parathyroid hormone (PTHPTH), a peptide hormone that increases the Ca2+Ca^{2+} levels in the blood (hypercalcemic hormone).

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Adrenal Medulla secretes Adrenaline (epinephrine) and Noradrenaline (norepinephrine), known as catecholamines or '3F' hormones (Fight, Flight, Fright).

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Adrenal Cortex secretes Glucocorticoids (e.g., Cortisol) for carbohydrate metabolism and Mineralocorticoids (e.g., Aldosterone) for Na+Na^+ and H2OH_2O reabsorption and K+K^+ excretion.

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Pancreas is a composite gland; Islets of Langerhans contain α\alpha-cells (secreting Glucagon) and β\beta-cells (secreting Insulin).

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Testes secrete Androgens (Testosterone) while Ovaries produce Estrogen and Progesterone.

📐Formulae

Blood Ca2+ Level∝[PTH]−[TCT]\text{Blood } Ca^{2+} \text{ Level} \propto [PTH] - [TCT]

Blood Glucose Level∝[Glucagon][Insulin]\text{Blood Glucose Level} \propto \frac{[Glucagon]}{[Insulin]}

Basal Metabolic Rate (BMR)∝[T3]+[T4]\text{Basal Metabolic Rate (BMR)} \propto [T_3] + [T_4]

💡Examples

Problem 1:

A patient presents with persistent hyperglycemia, glycosuria, and the presence of ketone bodies in the urine. Which endocrine disorder and hormone deficiency is likely involved?

Solution:

The disorder is Diabetes Mellitus, caused by a deficiency of the hormone Insulin.

Explanation:

Insulin is a hypoglycemic hormone that enhances cellular glucose uptake. In its absence, glucose levels in blood increase (Hyperglycemia>140 mg/dL\text{Hyperglycemia} > 140 \text{ mg/dL}), leading to glucose excretion in urine (GlycosuriaGlycosuria) and the breakdown of fats resulting in KetoneKetone bodies.

Problem 2:

Explain the antagonistic relationship between PTHPTH and TCTTCT regarding bone mineralization.

Solution:

PTHPTH stimulates bone resorption (demineralization) while TCTTCT inhibits it.

Explanation:

Parathyroid Hormone (PTHPTH) increases blood Ca2+Ca^{2+} by stimulating osteoclasts to dissolve bone matrix. Conversely, Thyrocalcitonin (TCTTCT) lowers blood Ca2+Ca^{2+} levels by promoting Ca2+Ca^{2+} deposition in bones, thus these two hormones maintain Ca2+Ca^{2+} homeostasis.

Problem 3:

What is the physiological effect of Aldosterone on the renal tubules?

Solution:

Aldosterone acts mainly at the renal tubules and stimulates the reabsorption of Na+Na^+ and H2OH_2O and excretion of K+K^+ and phosphate ions.

Explanation:

This maintains electrolytes, body fluid volume, osmotic pressure, and blood pressure. The reaction can be summarized as: ↑[Aldosterone]  ⟹  ↑Renal Reabsorption of Na++H2O\uparrow [Aldosterone] \implies \uparrow \text{Renal Reabsorption of } Na^+ + H_2O.