Test: Endocrine System - UPSC MCQ

Hypothalamus is the gland that releases neurohormones. It is a vital part of the brain that regulates various physiological processes by producing and releasing these neurohormones. These neurohormones travel to the pituitary gland, which then controls the release of hormones from other glands in the body. The hypothalamus acts as a crucial link between the nervous system and the endocrine system, allowing for the coordination and control of numerous bodily functions.

Histamine is a hormone that is synthesized from the amino acid histidine. It plays a crucial role in various physiological processes, including regulating the immune response, stomach acid secretion, and neurotransmission. Histamine is released by certain cells in the body, such as mast cells, and is involved in allergic reactions and inflammation. It also acts as a neurotransmitter in the brain, contributing to various functions related to sleep, appetite, and cognition.

Thyroid hormones (T3 - triiodothyronine and T4 - thyroxine) are fat-soluble hormones. They are produced by the thyroid gland and play a vital role in regulating metabolism and overall body growth and development. Being fat-soluble means they can easily pass through cell membranes and bind to intracellular receptors, allowing them to have widespread effects on various tissues and organs throughout the body. In contrast, amine and peptide hormones are typically water-soluble, and protein hormones are a subclass of peptide hormones, so they are also water-soluble.

The hypothalamus is NOT an endocrine gland. While it plays a crucial role in the endocrine system by producing and releasing neurohormones that control the pituitary gland's activities, it is a region in the brain and not a gland itself. The pituitary gland (option B), parathyroid glands (option C), and pancreas (option D) are all endocrine glands that secrete hormones directly into the bloodstream to regulate various physiological processes in the body.

Dopamine is not inhibited by the effect of somatostatin. Somatostatin, also known as growth hormone-inhibiting hormone (GHIH), inhibits the secretion of growth hormone (GH) (option A), thyroid-stimulating hormone (TSH) (option B), and glucagon (option C). However, dopamine (option D) is not affected by somatostatin in the same way as the other hormones mentioned. Dopamine is a neurotransmitter and plays a role in various physiological processes in the brain and body, but it is not directly regulated by somatostatin.

Oxytocin is the hormone that is released by the posterior pituitary gland. The posterior pituitary stores and releases two main hormones: oxytocin and vasopressin (also known as antidiuretic hormone, ADH). Oxytocin is responsible for various functions, including uterine contractions during childbirth and milk ejection during breastfeeding. It also plays a role in social bonding and affectionate behaviors. TSH (option B), ICSH (option C), and prolactin (option D) are hormones released by the anterior pituitary gland, which is a separate part of the pituitary gland with different functions.

In the pancreas, the cells that secrete insulin and decrease blood glucose levels are called beta cells. Insulin is a hormone produced and released by these beta cells in response to high blood glucose levels. When you eat food, especially carbohydrates, the blood glucose levels rise, and insulin is released to help transport glucose from the bloodstream into cells, where it can be used for energy or stored for future use. This process helps regulate blood sugar levels and prevents them from becoming too high. Alpha (option B), delta (option A), and gamma (option D) cells have different functions in the pancreas and are not involved in insulin secretion.

Endocrine glands are ductless and release hormones directly into the bloodstream, affecting distant target cells. Exocrine glands, on the other hand, release their secretions through ducts to the body's surface or into body cavities, such as sweat, saliva, or digestive enzymes. This key difference distinguishes the functions of endocrine and exocrine glands in the body.

The secretions from the gonadal glands (testes in males and ovaries in females) differ between males and females. These glands produce hormones such as testosterone in males and estrogen and progesterone in females, which play crucial roles in the development and functioning of the male and female reproductive systems, leading to the development of secondary sexual characteristics and regulating reproductive processes.

Parathyroid hormone (PTH) is not a hormone of the anterior pituitary. It is a hormone produced by the parathyroid glands, which are separate from the pituitary gland. PTH plays a crucial role in regulating calcium and phosphate levels in the blood and bones. The other options, human growth hormone (GH), follicle-stimulating hormone (FSH), and thyroid-stimulating hormone (TSH), are all hormones secreted by the anterior pituitary gland.

Hormones are chemical messengers secreted by ductless glands, called endocrine glands. They are released directly into the bloodstream and travel to target cells or organs to regulate various physiological processes. By binding to specific receptors, hormones induce specific biological responses, playing a crucial role in maintaining homeostasis and coordinating body functions. Unlike exocrine glands, which release their secretions through ducts to the body's surface or cavities, endocrine glands are ductless and rely on the circulatory system to transport their hormones throughout the body.

Insulin is a protein-based hormone produced by the beta cells of the pancreas. It plays a crucial role in regulating glucose metabolism in the body by facilitating the uptake of glucose into cells, thereby lowering blood glucose levels. Oxytocin (A), TSH (C), and Antidiuretic hormone (D) are peptide hormones, which are also protein-based, but the specific hormone requested in the question is insulin.

Cholesterol serves as the precursor for the synthesis of steroid hormones. The body converts cholesterol into various steroid hormones through enzymatic reactions in specific endocrine glands, such as the adrenal glands and gonads (testes and ovaries). These steroid hormones include cortisol, aldosterone, testosterone, estrogen, and progesterone, among others, and they play essential roles in regulating various physiological processes in the body.

Hormones do not directly play a significant role in maintaining body temperature. Instead, temperature regulation is primarily controlled by the hypothalamus in the brain, which monitors the body's temperature and initiates responses such as sweating or shivering to regulate it. Hormones are involved in various other functions, including reproduction and sexual differentiation (A), maintenance of the internal environment (B), and development and growth (D).

Cholesterol is actually a precursor for steroid hormones, which are a type of hormone. However, it is not a precursor for all hormones. Amino acids (A) are the building blocks for peptide hormones, proteins (D) are involved in the synthesis of some peptide hormones, and phospholipids (C) are not directly involved in hormone synthesis but play essential roles in cell membrane structure and signaling.

Somatostatin, also known as Growth Hormone-Inhibiting Hormone (GHIH), is a peptide hormone that inhibits the secretion of growth hormone (GH) from the anterior pituitary gland. It acts as a regulator to prevent excessive GH release and is produced in the hypothalamus and other tissues throughout the body. On the other hand, FSH (A) stands for Follicle-Stimulating Hormone, TRH (B) stands for Thyrotropin-Releasing Hormone, and GHRH (C) stands for Growth Hormone-Releasing Hormone.

The endocrine system is a collection of ductless glands that secrete hormones directly into the bloodstream. These hormones are then transported through the blood to target cells or organs, where they cause changes in metabolic activities and physiological processes. Endocrine effects are often prolonged and can have significant and widespread impacts on the body. Therefore, all the statements A, B, and C are true about the endocrine system.

The pineal gland is responsible for regulating the body's circadian rhythm. It is a small gland located near the center of the brain. The pineal gland secretes the hormone melatonin, which helps control the sleep-wake cycle and plays a crucial role in maintaining the body's internal clock. Melatonin levels increase in the evening, signaling the body that it is time to sleep, and decrease in the morning, signaling wakefulness. The other options, Thymus gland (A), Parathyroid gland (C), and Pituitary gland (D), are not directly responsible for regulating the circadian rhythm.

The hypothalamus produces and releases various releasing and inhibiting hormones, which are transported to the anterior pituitary gland through a specialized system of blood vessels called the hypothalamic-pituitary portal system. These releasing and inhibiting hormones control the secretion of specific hormones from the anterior pituitary gland. The anterior pituitary, in turn, releases its own hormones, which regulate various endocrine glands and their functions throughout the body.

Calcium levels in the blood are regulated by both the thyroid and parathyroid glands. While the parathyroid glands primarily control calcium levels through the secretion of parathyroid hormone (PTH), the thyroid gland also influences calcium levels indirectly through the release of calcitonin. When blood calcium levels are high, the thyroid gland releases calcitonin, which helps lower calcium levels by promoting its deposition in bones and inhibiting its release from bones into the blood. Thus, both the parathyroid and thyroid glands play roles in regulating blood calcium levels.