What went wrong when the king rode under the arch?

It was too low and knocked off his crown

How does the chain of blame unfold in the poem?

Each accused person blames another, ending with the king's own changes

Define an exocrine gland, an endocrine gland and a hormone.

An exocrine gland secretes through ducts, an endocrine gland is ductless and secretes into blood, and a hormone is a non-nutrient intercellular messenger produced in trace amounts.

Which hormones are secreted by the anterior pituitary?

Growth hormone, prolactin, thyroid stimulating hormone, adrenocorticotrophic hormone, luteinizing hormone and follicle stimulating hormone.

What disorders result from abnormal secretion of growth hormone?

Over-secretion causes gigantism in children and acromegaly in adults, while low secretion causes pituitary dwarfism.

What is the role of melatonin from the pineal gland?

Melatonin regulates the 24-hour diurnal rhythm of the body, including the sleep-wake cycle and body temperature.

Why is iodine important for the thyroid gland and what does its deficiency cause?

Iodine is essential for the synthesis of thyroid hormones; its deficiency causes hypothyroidism and enlargement of the thyroid called goitre.

What are the functions of parathyroid hormone?

PTH is a hypercalcemic hormone that raises blood calcium by bone resorption, reabsorption of calcium by renal tubules and absorption from food.

Name the hormones of the adrenal medulla and their role.

Adrenaline and noradrenaline, the fight-or-flight hormones, which increase alertness, heart rate, respiration and breakdown of glycogen during stress.

How do insulin and glucagon regulate blood glucose?

Insulin lowers blood glucose by promoting cellular uptake and glycogenesis, while glucagon raises it by glycogenolysis and gluconeogenesis; their imbalance causes diabetes mellitus.

Which hormones are secreted by the testis and the ovary?

The testis secretes androgens such as testosterone, and the ovary secretes estrogen and progesterone.

How do hormones act on their target tissues?

They bind to specific membrane-bound receptors, generating second messengers, or to intracellular receptors that regulate gene expression, producing biochemical and physiological effects.

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Chapter 19: Chemical Coordination and Integration — Class 11 Biology

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Chapter 19: Chemical Coordination and Integration

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Endocrine glands are also called ductless glands because they:

Summary

This chapter describes the endocrine system, which provides chemical coordination and integration through hormones. Endocrine glands are ductless and secrete hormones, which are non-nutrient chemicals acting as intercellular messengers in trace amounts. The human endocrine system includes the hypothalamus, pituitary, pineal, thyroid, parathyroid, thymus, adrenal, pancreas and gonads, while organs such as the heart, kidney and gastrointestinal tract also secrete hormones. The hypothalamus produces releasing and inhibiting hormones that control the pituitary. The pituitary has the anterior part (secreting GH, prolactin, TSH, ACTH, LH and FSH) and the posterior part (releasing oxytocin and vasopressin); disorders include gigantism, dwarfism, acromegaly and diabetes insipidus. The pineal gland secretes melatonin, which regulates diurnal rhythms. The thyroid secretes thyroxine, important for basal metabolic rate, and its iodine deficiency causes goitre. The parathyroid raises blood calcium, the thymus produces thymosins for immunity, and the adrenal medulla secretes the fight-or-flight hormones adrenaline and noradrenaline while the cortex secretes glucocorticoids and mineralocorticoids. The pancreatic islets secrete insulin and glucagon to regulate blood glucose, and their imbalance causes diabetes mellitus. Gonads secrete androgens, estrogen and progesterone. Hormones act by binding to membrane-bound or intracellular receptors, generating second messengers or regulating gene expression.

Endocrine glands and hormonesHypothalamus and pituitary glandPineal, thyroid and parathyroid glandsThymus and adrenal glandsPancreas and the gonadsHormones of other organs and mechanism of action

Key terms

Hormone

A non-nutrient chemical that acts as an intercellular messenger, produced in trace amounts by endocrine glands or tissues.

Endocrine gland

A ductless gland that secretes its hormones directly into the blood.

Hypothalamus

The basal forebrain region that produces releasing and inhibiting hormones controlling the pituitary.

Insulin

A peptide hormone from pancreatic beta-cells that lowers blood glucose by promoting its uptake and glycogenesis.

Glucagon

A peptide hormone from pancreatic alpha-cells that raises blood glucose by glycogenolysis and gluconeogenesis.

Hormone receptor

A specific protein, membrane-bound or intracellular, to which a hormone binds to produce its effect.

Important questions

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A non-nutrient chemical that acts as an intercellular messenger, produced in trace amounts by endocrine glands or tissues.

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