Endocrine Glands and Hormones — NEET Biology
📚 Practice ConceptEndocrine glands lack ducts and are hence, called ductless glands. Their secretions are called hormones. The classical definition of hormone as a chemical produced by endocrine glands and released into the blood and transported to a distantly located target organ has current scientific definition as follows: Hormones are non-nutrient chemicals which act as intercellular messengers and are produced in trace amounts. The new definition covers a number of new molecules in addition to the hormones secreted by the organised endocrine glands. Invertebrates possess very simple endocrine systems with few hormones whereas a large number of chemicals act as hormones and provide coordination in the vertebrates. The human endocrine system is described here.
Which of the above statements are correct? S1: Hormones are non-nutrient chemicals that act as intercellular messengers and are produced in trace amounts. S2: The classical definition of hormones emphasizes their secretion by ductless glands and subsequent transport through blood to distantly located target organs. S3: The neural system, unlike the endocrine system, is primarily responsible for the continuous regulation of cellular functions throughout all cells of the body. S4: Hypothalamic hormones that regulate the anterior pituitary reach it through direct neural regulation, while the posterior pituitary is regulated by a portal circulatory system. S5: The endocrine systems of invertebrates are typically more complex and diverse than those found in vertebrates.
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