Lecture 3 Flashcards

Question

The HT-PT relationship Is it 1-1 or 1 directional?

Answer 1

Hormones of the HT stimulate secretion of hormones from the PT Not one to one relationship (e.g., CRH ≠ ACTH) The small distance from the hypothalamus to the PT gland means you can have very small amounts of CRH etc which cause large amounts of ACTH etc top be released Not unidirectional (PT hormones affect HT) Not only regulated by HT but also by neurotransmitters

Answer 2

Allows for negative feedback, allows homeostatic control

Answer 3

if old, just the areas that never stop growing (like the jaw) if young, all areas eg Andre the giant Usually caused by an adenoma of the PT gland Increased GH

Answer 4

Superior to third ventricle and anterior to cerebellum Produces the hormone melatonin Under control of the suprachiasmatic nucleus (SCN) in the hypothalamus Involved with coordinating sleep/wake cycle Get back to this at the end of the semester with chronobiology

Answer 5

``` Where the trophic pituitary hormones act: Thyroid gland Adrenal gland Gonads Ovaries and testes ``` Pancreas is also an endocrine gland outside of the CNS Not activated by the hypothalamus pituitary connection Can be inhibited by somatostatin, released from the hypothalamus to slow growth process

Answer 6

pineal pancreas

Answer 7

include the catecholamines, the indoleamines and the thyroid hormones Adrenalin + nor Indolaemines: indoleamines consist of serotonin, synthesised from tryptophan in the CNS, and melatonin

Answer 8

Long chains of AAs Small peptide hormones include: oxytocin, vasopressin, thyrotropin-releasing hormone, angiotensin, somatostatin and luteinising hormone-releasing hormone. Large peptide hormones include: secretin, calcitonin, gastrins, glucagon and adrenocorticotropic hormone. Polypeptide (or protein) hormones include: insulin, parathyroid hormone and growth hormone.

Answer 9

Are lipid soluble In blood, often bound to albumin or sex hormone binding globulin

Answer 10

Steroids The key androgens are testosterone (T), dehydroepiandrosterone (DHEA), androstenedione and 5-dihydrotestosterone (DHT) Testosterone is the principal circulating androgen, more than 95% of this steroid being produced by the 350–500 million Leydig cells in the testes. These secrete around 5000 g per day leading to plasma concentrations of around 700 ng/100 ml (Norman and Litwack, 1987). The remainder is produced by the adrenal cortex of the adrenal glands. Testosterone (but not DHT) can be converted into estradiol via the enzyme aromatase Testosterone is also a potent androgen in women, but levels are around a tenth of those in males; testosterone production shows considerable variability in females in that an increase of 20–30% is seen around the middle of the menstrual cycle (Judd and Yen, 1973). Around 50% of circulating testosterone comes from the ovarian production of the testosterone precursor androstenedione, the remainder coming from adrenal activity. As women age, then levels of androstenedione decline, with a reduction in levels after the menopause to around half those of women of reproductive age

Answer 11

In females the two most important steroid hormones are 17-estradiol and progesterone In the ovaries in non-pregnant females, the follicles principally secrete estradiol and estrone; during pregnancy estriol is the principal estrogen secreted by the placenta. Progesterone (the principal progestin and named for its progestational role in maintaining pregnancy) is produced by the follicles in non-pregnant females, and by the corpus luteum in pregnant females. Secretion and plasma concentrations of these steroids are greatly determined by the menstrual cycle, for example levels of estradiol range from around 6 ng/100 ml in the early follicular phase to 60 ng/100 ml in the late follicular phase (Norman and Litwack, 1987). In general the estrogens stimulate the development of the internal reproductive structures and later promote female secondary sexual characteristics (e.g. breast development, fat deposition), and promote water retention, calcium metabolism, the stages of pregnancy, and certain reproductive and maternal behaviours

Answer 12

Made in adrenal gland corticosterone and cortisol (sometimes referred to as hydrocortisone Work on glucose metabolism, they increase glycerol and free fatty acid release from cells; increase muscle lactate release; inhibit glycogen breakdown; alter carbohydrate metabolism; reduce calcium absorption; suppress the immune system; and influence heart rate levels drop in the late evening and then rise sharply before waking to then show a steady decline throughout the day The second type of corticoid are the mineralocorticoids, which consist of aldosterone and 11-deoxycorticosterone (DOC). They principally act to maintain blood pressure and water and salt balance in the body by helping the kidneys retain sodium and excrete potassium. When aldosterone production falls below a certain point, the kidneys are not able to regulate salt and water balance, causing blood volume and blood pressure to drop

Answer 13

Prohormones’ are the precursors to ‘true’ hormones and can consist of modified molecules, or molecules that have split to form a particular hormone. A key prohormone is proopiomelanocortin (POMC), a large molecule which is composed of different sections, each section capable of producing a different hormone. One section forms beta-lipoprotein, which in turn is the precursor for the hormone/neurotransmitter beta-endorphin (an endogenous opiate). Other sections can be synthesized into melanocyte-stimulating hormone (MSH) and adrenocorticotropic hormone (ACTH), both of which are located within the pituitary gland. In fact, testosterone also acts as a prohormone because it serves as the precursor for both dihydrotestosterone (DHT) and estradiol.

Answer 14

Released from the anterior pituitary in response to

Answer 15

In neck Makes t4 and t3 Needs iodate Lack of this causes goiter

Answer 16

They are located on the top of the kidneys and consist of two distinct structures. The adrenal cortex comprises around 90% of the total volume of the adrenal glands and consists of three distinct zones. The zona glomerulosa acts independently of the other zones and produces only aldosterone. The zona fasciculata and the zona reticularis produce cortisol, androgens and small amounts of estrogens, and both work in conjunction under the control of ACTH. ``` The adrenal medulla releases three monoamine hormones, adrenaline, noradrenaline and dopamine; it also releases a class of protein hormones – the enkephalins. ```

Answer 17

the cycle is normally split into three stages: menses (days 1–5), follicular (days 6–14) and luteal (days 15–28). During the follicular phase rising levels of FSH (and small amounts of LH) cause the follicles to mature, and as they do so they release estrogen which thickens the lining of the uterus and alters the composition of the cervical mucus. When estrogen levels reach a certain point this triggers the pituitary to secrete high levels of LH (via stimulation from the hypothalamus), which causes a follicle to release an egg (ovulation). During the luteal phase the ruptured follicle becomes the corpus luteum, and this secretes some estrogen and more progesterone which are necessary for maintaining a pregnancy (should the egg be fertilised). If the egg remains unfertilised, levels of all hormones fall and the uterus lining is discarded during menses

Answer 18

Leydig cells (also called interstitial cells) Principally produce testosterone but also smaller amounts of dihydrotestosterone, dehydroepiandrosterone, estradiol, estrone, progesterone and androstenedione

Answer 19

Interact with cytoplasmic receptors. All polypeptide hormones, as well as monoamines and prostaglandins are this type. Act via metabotropic receptors and their associated G proteins.

Answer 20

Cross and bind to intracellular receptors, enter the nucleus and bind to chromosomal acceptor sites. Affects transcription to exert its effects. Thyroid and steroid hormones, various fatty acids and the eicosanoids work in this fashion

Answer 21

Controlled by less or more secretion typically This is often, though not always, controlled by negative feedback