Đề thi, bài tập trắc nghiệm online Sinh lý nội tiết – Đề 6

Parathyroid hormone (PTH), secreted by the parathyroid glands, is the major hormone regulating blood calcium levels. It increases blood calcium by stimulating calcium release from bones, increasing calcium absorption in the intestines, and increasing calcium reabsorption in the kidneys.

In a negative feedback loop, the response counteracts the initial stimulus. In the case of calcium regulation, when blood calcium levels decrease, PTH is released. PTH increases blood calcium, and as calcium levels rise back to normal, PTH secretion is inhibited, thus 'negatively feeding back′ to the initial stimulus.

Steroid hormones are lipid-soluble, allowing them to cross the cell membrane and bind to intracellular receptors (cytoplasmic or nuclear). This hormone-receptor complex then acts as a transcription factor, altering gene expression and ultimately protein synthesis, leading to cellular changes.

Aldosterone is a mineralocorticoid hormone secreted by the adrenal cortex. Its primary role is to regulate electrolyte balance, specifically sodium and potassium, in the kidneys. By controlling sodium reabsorption and potassium excretion, aldosterone plays a key role in blood volume and blood pressure regulation.

Glucagon, secreted by the alpha cells of the pancreas, has the opposite effect of insulin. Its primary function is to raise blood glucose levels. It does this by stimulating glycogenolysis (breakdown of glycogen to glucose) in the liver and gluconeogenesis (production of new glucose from non-carbohydrate sources) in the liver.

Melatonin, produced by the pineal gland, is primarily involved in regulating the sleep-wake cycle (circadian rhythm). Its secretion is influenced by light exposure, with levels increasing in darkness, promoting sleepiness.

The hypothalamus acts as the control center for the endocrine system. It secretes releasing and inhibiting hormones that travel to the anterior pituitary gland, regulating the release of anterior pituitary hormones which, in turn, control other endocrine glands and tissues.

Prolactin, secreted by the anterior pituitary gland, is the hormone primarily responsible for stimulating milk production (lactation) in the mammary glands after childbirth. Oxytocin is involved in milk ejection (let-down reflex), but prolactin initiates and maintains milk synthesis.

Diabetes Mellitus is a metabolic disorder characterized by persistently high blood glucose (hyperglycemia). This is primarily due to either the body′s cells becoming resistant to insulin (Type 2 Diabetes) or the pancreas not producing enough insulin (Type 1 Diabetes).

Addison′s disease, also known as primary adrenal insufficiency, occurs when the adrenal glands do not produce enough cortisol and aldosterone. These are hormones produced by the adrenal cortex, and their deficiency leads to various symptoms, including fatigue, muscle weakness, weight loss, and low blood pressure.

Cushing′s syndrome is an endocrine disorder caused by prolonged exposure to high levels of cortisol, a glucocorticoid hormone. This can be due to various factors, including adrenal tumors, pituitary tumors that secrete excess ACTH (which stimulates cortisol production), or long-term use of corticosteroid medications.

The thyroid gland is located in the anterior neck, just inferior to the larynx (voice box). It is characterized by its butterfly shape, consisting of two lobes connected by an isthmus. The thyroid gland is responsible for producing thyroid hormones (T3 and T4) and calcitonin.

Thyroid hormones, primarily T3 and T4, are crucial for regulating the body′s metabolic rate. They influence how quickly the body uses energy, affects protein synthesis, and contributes to the maintenance of body temperature.

Thyroid hormones (T3 and T4) are lipid-soluble, allowing them to cross the cell membrane. They bind to intracellular receptors, primarily in the nucleus, forming hormone-receptor complexes. These complexes act as transcription factors, influencing gene expression and protein synthesis, which ultimately mediate the effects of thyroid hormones on metabolism and development.

Epinephrine (adrenaline), secreted by the adrenal medulla, is the primary hormone mediating the 'fight or flight′ response. It causes physiological changes like increased heart rate, bronchodilation (widening of airways), and increased blood glucose, preparing the body for immediate action in stressful situations.

Calcitonin, produced by the thyroid gland (parafollicular cells or C-cells), acts to lower blood calcium levels. It does this by inhibiting bone resorption (breakdown of bone and release of calcium) and increasing calcium excretion by the kidneys. It acts in opposition to PTH.

Non-steroid hormones (peptide hormones, protein hormones, and most amino acid-derived hormones) are generally water-soluble and cannot easily cross the cell membrane. They exert their effects primarily by binding to receptors located on the cell membrane. This binding activates intracellular signaling pathways, often involving second messengers like cAMP or calcium ions, to elicit cellular responses.

Antidiuretic hormone (ADH), or vasopressin, is produced by the hypothalamus and released by the posterior pituitary. Its main function is to reduce water loss by promoting water reabsorption in the kidneys, thus concentrating urine and helping to maintain body water balance.

Growth Hormone (GH), secreted by the anterior pituitary, has widespread effects throughout the body. Its primary target tissues include the liver and bones. In the liver, GH stimulates the production of Insulin-like Growth Factor-1 (IGF-1), which mediates many of GH′s growth-promoting effects. GH also directly stimulates bone growth.

Insulin, secreted by the beta cells of the pancreas, is the key hormone for lowering blood glucose. It facilitates glucose uptake into cells (especially muscle and adipose tissue) and stimulates glycogenesis (glycogen synthesis) in the liver, thus reducing blood sugar levels.

Oxytocin, released by the posterior pituitary gland, is crucial for stimulating uterine contractions during labor and delivery. It also plays a role in the milk ejection reflex and social bonding.

Type 1 diabetes mellitus is an autoimmune disease where the body′s immune system mistakenly attacks and destroys the beta cells in the pancreas. These beta cells are responsible for producing insulin. The destruction of beta cells leads to a severe deficiency or complete lack of insulin production, resulting in hyperglycemia.

Water-soluble hormones, such as peptide and protein hormones (like insulin), cannot easily cross the cell membrane. They typically bind to receptors on the cell surface and initiate intracellular signaling cascades using second messengers. Steroid and thyroid hormones are lipid-soluble.

The adrenal medulla is responsible for the 'fight-or-flight′ response to stress. Its primary hormone in this response is epinephrine (adrenaline), which increases heart rate, blood pressure, and blood glucose levels to prepare the body for immediate action.

Antidiuretic Hormone (ADH), or vasopressin, is produced in the hypothalamus and stored and released by the posterior pituitary gland, not the anterior pituitary. Growth Hormone (GH), Thyroid-Stimulating Hormone (TSH), and Adrenocorticotropic Hormone (ACTH) are all secreted by the anterior pituitary.

Estrogens, primarily estradiol, are the main female sex hormones produced by the ovaries. They are crucial for the development and maintenance of female secondary sexual characteristics (e.g., breast development, widening of hips), regulating the menstrual cycle, and supporting pregnancy.

In males, luteinizing hormone (LH), secreted by the anterior pituitary, primarily targets Leydig cells in the testes. LH stimulates these cells to produce and secrete testosterone, which is essential for male sexual development and function.

Follicle-Stimulating Hormone (FSH), secreted by the anterior pituitary, plays a crucial role in reproduction in both sexes. In females, FSH stimulates the development of ovarian follicles (which contain eggs). In males, FSH is essential for stimulating spermatogenesis (sperm production) in the testes.

The pituitary gland, although itself controlled by the hypothalamus, is often called the 'master gland′ because it secretes hormones that regulate the activity of many other endocrine glands, such as the thyroid, adrenal glands, and gonads.

Hormone receptors exhibit high specificity, meaning each receptor type is designed to bind with a particular hormone (or a class of structurally similar hormones). This specificity ensures that hormones exert their effects only on appropriate target cells and tissues.