Week 19 / Endocrine system 2 Flashcards
What is the function of Thyroid-stimulating hormone (TSH)?
[3]
TSH promotes vascularization and growth of the thyroid gland and stimulates the secretion of thyroid hormones.
Q: What stimulates the secretion of TSH?
A: TSH secretion is stimulated by Thyrotropin-releasing hormone (TRH) from the hypothalamus.
Q: What is the function of Adrenocorticotropic hormone (ACTH)?
A: ACTH controls the growth of the adrenal cortex and stimulates the secretion of cortisol by the adrenal cortex.
Q: What stimulates the secretion of ACTH?
A: ACTH secretion is stimulated by Corticotropin-releasing hormone (CRH) from the hypothalamus.
Q: What is the function of Follicle-stimulating hormone (FSH) in females?
A: FSH stimulates the growth and development of ovarian follicles and promotes ovarian secretion of estrogen.
Q: What is the function of Follicle-stimulating hormone (FSH) in males?
A: FSH is required for sperm production.
Q: What stimulates the secretion of FSH?
A: FSH secretion is stimulated by Gonadotropin-releasing hormone (GnRH) from the hypothalamus.
Q: What is the function of Luteinizing hormone (LH) in females?
A: LH is responsible for ovulation, development of the corpus luteum, and regulation of ovarian secretion of sex hormones.
Q: What is the function of Luteinizing hormone (LH) in males?
A: LH stimulates the testes to secrete testosterone.
Q: What stimulates the secretion of LH?
A: LH secretion is stimulated by Gonadotropin-releasing hormone (GnRH) from the hypothalamus.
Q: What is the function of Prolactin (PRL) in females?
A: Prolactin enhances breast development and milk production.
Q: What inhibits the secretion of Prolactin (PRL)?
A: Prolactin secretion is inhibited by Dopamine (DA) from the hypothalamus.
Q: Where are Antidiuretic hormone (ADH) and oxytocin produced?
A: ADH and oxytocin are produced in the Paraventricular nucleus and Supraoptic nucleus of the hypothalamus.
Q: What is the role of the optic chiasma in the hypothalamus?
A: The optic chiasma is a structure where the optic nerves partially cross, located near the hypothalamus.
Q: What connects the hypothalamus to the pituitary gland?
A: The infundibulum connects the hypothalamus to the pituitary gland.
Q: How are ADH and oxytocin transported to the posterior pituitary?
A: ADH and oxytocin are transported via the Hypothalamo-hypophyseal tract.
Q: Where are ADH and oxytocin released?
A: ADH and oxytocin are released from the posterior pituitary.
Q: What is the shape and location of the pineal gland?
A: The pineal gland is a tiny, pinecone-shaped gland located in the diencephalon.
Q: What hormone does the pineal gland secrete, and when is it primarily produced?
A: The pineal gland secretes melatonin, known as the “hormone of darkness,” primarily produced during the night.
Q: What stimulates melatonin production in the pineal gland?
A: Melatonin production is stimulated by the suprachiasmatic nucleus (SCN), the body’s master “biological clock.”
Q: What are the main functions of melatonin?
A: Melatonin synchronizes the body’s circadian rhythms with the 24-hour light-dark cycle, promotes sleep, and influences reproductive activity, including the onset of puberty.
Q: Where is the thyroid gland located?
A: The thyroid gland is located in the neck, just below the larynx.
Q: What are the two main structural components of the thyroid gland?
A: The thyroid gland consists of two lobes of endocrine tissue joined by a narrow strip of gland called the isthmus.
Q: What hormones do follicular cells secrete?
A: Follicular cells secrete two iodine-containing hormones: Tetra-iodothyronine (T4 or thyroxine) and Tri-iodothyronine (T3).
Q: What are the two distinct secretory cell types in the thyroid gland?
A: The thyroid gland contains follicular cells and parafollicular (C) cells.
Q: What hormone do parafollicular (C) cells secrete, and what type of hormone is it?
A: Parafollicular (C) cells secrete calcitonin, which is a peptide hormone.
Q: What are thyroid hormones synthesized from? [2]
A: Thyroid hormones are formed from iodide (I-) and tyrosine.
Q: where is thyroglobulin (TG) synthesized and processed in follicular cells?
A: Thyroglobulin (TG) is synthesized in follicular cells and exported into the colloid of the thyroid follicle.
Q: How is iodide involved in the synthesis of thyroid hormones?
A: Iodide is actively taken up by follicular cells, oxidized to its active form, and then diffuses into the colloid.
Q: What happens when iodide attaches to tyrosine residues in thyroglobulin (TG)?
A: When iodide attaches to tyrosine residues in TG, it forms monoiodotyrosine (MIT) and diiodotyrosine (DIT).
Q: How are Tri-iodothyronine (T3) and Tetra-iodothyronine (T4) formed?
A: The coupling of MIT and DIT forms Tri-iodothyronine (T3), while the coupling of two DIT molecules forms Tetra-iodothyronine (T4).
Q: Where are T3 and T4 stored before release?
A: T3 and T4 are attached to thyroglobulin (TG) and stored in the colloid until they are released.
Q: What stimulates the release of thyroid hormones (T3 and T4)?
A: The release of T3 and T4 is stimulated by Thyroid-stimulating hormone (TSH).
Q: What happens during the release of thyroid hormones from the follicular cells?
A: The colloid containing synthesized thyroglobulin (TG) undergoes endocytosis by follicular cells, where TG is digested proteolytically to release T3 and T4.
Q: What happens to MIT and DIT after the release of thyroid hormones?
A: MIT and DIT undergo deiodination, with iodide being removed and recycled for further thyroid hormone synthesis.
Q: How are T3 and T4 transported in the bloodstream?
A: T3 and T4 are secreted into the blood and transported in a carrier-bound form, primarily bound to Thyroxine-binding globulin (TBG).
Q: How does thyroid hormone affect normal growth?
A: Thyroid hormone affects normal growth by mediating its effects through Growth Hormone (GH) and Insulin-like Growth Factor 1 (IGF-1). It stimulates GH secretion and hepatic production of IGF-1.
Q: Where is T4 converted to its active form, T3?
A: T4 is converted to active T3 in the liver and kidneys.
Q: How does thyroid hormone promote protein synthesis and skeletal growth?
A: Thyroid hormone promotes the effects of GH and IGF-1 on protein synthesis and skeletal growth.
Q: Why is thyroid hormone important for the development of the nervous system?
A: Thyroid hormone is required for normal development of the nervous system in infants and children.
Q: What effect does thyroid hormone have on the CNS in adults?
A: Thyroid hormone promotes normal CNS activity in adults.
Q: What is the effect of thyroid hormone on metabolic rate and heat production?
A: Thyroid hormone increases the overall basal metabolic rate and heat production, known as the “calorigenic effect.” It is the main regulator of resting oxygen consumption and energy expenditure.
Q: What is the effect of thyroid hormone on intermediary metabolism?
A: Thyroid hormone has biphasic effects on carbohydrate, fat, and protein metabolism, meaning it can stimulate or inhibit these processes depending on the context.
Q: How does thyroid hormone affect sympathetic activity?
A: Thyroid hormone increases cellular responsiveness to catecholamines (such as adrenaline) by up-regulating β-receptor activity, which enhances myocardial contractility and heart rate (HR).
Q: Where are the adrenal glands located?
A: The adrenal glands are paired organs located on top of the kidneys (hence the name “adrenal,” meaning “next to the kidney”).
Q: What are the two distinct secretory organs of the adrenal glands?
A: The adrenal glands consist of two distinct secretory organs: the outer adrenal cortex and the inner adrenal medulla.
Q: What hormones are secreted by the adrenal cortex?
A: The adrenal cortex secretes three types of steroid hormones:
Mineralocorticoids (e.g., aldosterone)
Glucocorticoids (e.g., cortisol)
Sex hormones (e.g., Dehydroepiandrosterone, DHEA)
Q: What hormones are secreted by the adrenal medulla?
A: The adrenal medulla secretes catecholamines, specifically adrenaline (AD) and noradrenaline (NA).
Q: What are the three layers or zones of the adrenal cortex?
A: The adrenal cortex consists of three layers or zones:
Zona glomerulosa
Zona fasciculata
Zona reticularis
Q: What hormone is secreted by the zona glomerulosa, and what is its function?
A: The zona glomerulosa secretes mineralocorticoids, primarily aldosterone, which regulates sodium (Na⁺) and potassium (K⁺) balance and helps maintain blood pressure (BP) homeostasis.
Q: What hormone is secreted by the zona fasciculata, and what are its functions?
A: The zona fasciculata secretes glucocorticoids, primarily cortisol, which is involved in long-term control of metabolism and adaptation to stress.
Q: What hormones are secreted by the zona reticularis, and what is their function?
A: The zona reticularis secretes sex hormones, primarily Dehydroepiandrosterone (DHEA), which supplement gonadal sex steroids.
