chemical communication: endocrine system Flashcards
(24 cards)
what are the two systems of internal communication and regulation?
(1) A nervous system that involves high speed signaling with specialized cells (= neurons). These rapid messages control movement of body in response to sudden environmental changes (the reflexes we discussed earlier).
(2) an Endocrine System or a system of chemical communication that relies on the production and secretion of chemical messengers, such as hormones. coordinates more slowly, but does have longer acting responses to stimuli, such as stress, dehydration, low blood sugar, etc. Hormones also regulate long-term developmental processes by informing different parts of body how fast to grow or when to develop
what are endocrine glands and hormones?
ductless glands, secrete chemical messages (hormones) directly into extracellular fluid or into the bloodstream. Hormones-chemical signals—molecules that communicate regulatory messages within the body. They can reach all body cells but affect target cells that have appropriate receptor molecules. The hormone and receptor fit similar to a key into a lock—specific hormone for a specific receptor. They can function in extremely low concentrations.
what are the three major types of hormones vertebrates use? what is their chemical make-up?
1) Polypeptides, which are short strings of Amino Acids.
2) Amines, which are derived from the amino acids tyrosine and tryptophan.
3) Steroids, which are lipids.
three major types of hormones vertebrates use: are they water soluble? how do they bind to receptor?
Most polypeptides and Amino acids are water soluble, but not the hormone Thyroxine, which is lipophillic. Steroids are not water soluble, but are lipophilic. can either bind to a receptor on the cell membrane (which is what most polypeptide and amine hormones do), or within the cell cytosol (cytoplasm or nuclear membrane), which is what most lipid hormones do. the receptor hormone complex causes a conformational change, which typically results in the release of a second messenger or a cascade of reactions. a second messenger can either affect a metabolic pathway of the cell, or travel to the nucleus and affect Gene transcription = turn genes on or off. Lipids and a few amines will pass through the cell phospholipid membrane and bind to receptor in the cytoplasm or nucleus where the receptor/hormone complex affects gene transcription, typically by turning on a gene.
what is the major axis in regulating vertebrate hormones and what gland and brain part does it involve?
hypothalamo-hypophyseal axis, which involves a lower section of the brain (the hypothalamus) and the pituitary gland (Hypophysis). information from sensory neurons travels to the central nervous system to the brain, and through the hypothalamus. The hypothalamus monitors environmental (internal and external) changes and adjusts secretion of hormones from the pituitary gland to regulate the various functions of the body. Thus, the pituitary gland affects many other endocrine glands.
hypothalamo-hypophyseal axis-pituitary gland: what are the two parts of the pituitary gland?
posterior pituitary and the anterior pituitary
hypothalamo-hypophyseal axis-pituitary gland-posterior: what hormones are secreted by the post-pit gland?
Oxytocin, and Antidiuretic Hormone (ADH)
hypothalamo-hypophyseal axis-pituitary gland-posterior: what does oxytocin do?
causes smooth muscle to contract. Therefore, Oxytocin is the hormone associated with childbirth or egg-laying in vertebrates. inject a synthetic form of oxytocin to induce birth. Also, in mammals, oxytocin is associated with contraction of smooth muscle in mammary glands; therefore, this hormone also is associated with release of milk during suckling. also a release of oxytocin has been associated with the chemical attraction of people—the feelings experienced as a couple are becoming attached emotionally to each other (pair-bonding). plus the bonding that occurs between a child and a parent. Thus, the feelings that individuals have for each other are based, in part, on secretion of oxytocin.
hypothalamo-hypophyseal axis-pituitary gland-posterior: what does antidiuretic hormone do(ADH)?
ADH affects aquaporins in the collecting ducts of kidneys, causing them to open and allowing water to be conserved. Alcohol inhibits the release of ADH; thus, an individual drinking alcoholic beverages has a tendency to empty their bladder more frequently than an individual not drinking alcoholic beverages.
hypothalamo-hypophyseal axis-pituitary gland-posterior: how is oxytocin and ADH produced?
Both oxytocin and ADH are produced by specialized neurons in the hypothalamus. The telodendria of these neurons, where the hormones (specialized neurotransmitters or neurohormones) are stored until secreted, are located in the posterior pituitary. Structurally, the posterior pituitary is a component of the brain.
hypothalamo-hypophyseal axis-pituitary gland-anterior: relation to brain? neurohormone released to this how? blood supply name? what are the two lobes?
lacks a direct anatomical connection to the brain. Neurohormones secreted from the hypothalamus are released into the blood stream and travel directly to the anterior pituitary, where they regulate (inhibit or stimulate) the secretion of several different hormones. The blood supply connecting the hypothalamus and the anterior pituitary is the hypothalamo-hypophyseal portal system. intermediate lobe and anterior lobe
hypothalamo-hypophyseal axis-pituitary gland-anterior-intermediate lobe: secretes? what does this hormone do?
secretes the hormone Intermedin or Melanophore-stimulating Hormone (MSH). This hormone regulates pigment granules in lower vertebrates, and is associated with memory enhancement in mammals.
hypothalamo-hypophyseal axis-pituitary gland-anterior-anterior lobe: secretes what 6 peptide hormones?
(1) Thyrotropic Hormone (TH), also known as Thyroid-Stimulating Hormone (TSH), 2) Adrenocorticotropic Hormone (ACTH), 3 & 4) Gonadotropins, 5) Growth hormone, and 6) Prolactin (or Lactogenic Hormone, LH)
hypothalamo-hypophyseal axis-pituitary gland-anterior-anterior lobe: what does thyrotropic hormone(TH) aka Thyroid-Stimulating Hormone (TSH) do?
This hormone regulates the production of the thyroid hormones Triiodothyronine (T3) and Tetraiodothyronine (thyroxine or T4). Both T3 and T4 promote normal growth and stimulate metabolic rate (heat production). Also, they are associated with amphibian metamorphosis. under Negative Feedback-Levels of T3 and T4 are monitored by the pituitary gland, and when a certain level is detected, the pituitary gland deceases the secretion of TSH; consequently, less T3 and T4 are secreted. two clinical conditions associated w/ thyroid hormones, goiter and cretinism. Goiter is an enlarged thyroid gland that develops in people who do not have enough iodine in their diet. Cretinism, a condition that produces an individual characterized by intellectual disability, small stature and thickened facial features, occurs because of extreme iodine deficiency during development
hypothalamo-hypophyseal axis-pituitary gland-anterior-anterior lobe: what does Adrenocorticotropic Hormone (ACTH) do?
This hormone secreted by the anterior lobe stimulates the adrenal cortex of the adrenal gland, which is located adjacent to kidneys. The outer or Cortex of the adrenal glands secrete glucocorticoids, such as cortisol and cortisone. These hormone are involved with food metabolism, inflammation, and stress. They are also anti-inflammatory. (athlete injected with cortisone when injured) Also, mineral corticoids are secreted by the cortex of the adrenal gland. These hormones regulate salt balance in the blood. ACTH, from the anterior pituitary, therefore, regulates these responses. But remember, it is under regulation from the hypothalamus of the brain. Although not regulated by ACTH, the adrenal medulla (middle portion of the adrenal glands) produces the hormones epinephrine, which is will be transported though the blood enhancing the neural sympathetic response (and will last longer).
hypothalamo-hypophyseal axis-pituitary gland-anterior-anterior lobe: what does Gonadotropins do? the two types?
Two major hormones secreted from the anterior pituitary regulate the gonads. The gonads, although producing gametes, are also endocrine glands, producing estrogens (ovaries) or testosterone (testes) among others. For example, Follicle-Stimulating Hormone (FSH) is associated with gamete production in ovaries and testes. Lutenizing Hormone (LH) is historically termed Interstitial Cell Stimulating Hormone in males (ICSH) is associated with ovulation in females, and production of the steroid hormones estrogens (females) and testosterone (males).
hypothalamo-hypophyseal axis-pituitary gland-anterior-anterior lobe: what does growth hormones do?
governs body growth by affecting mitosis, cell division, and protein synthesis.
hypothalamo-hypophyseal axis-pituitary gland-anterior-anterior lobe: what does Prolactin (or Lactogenic Hormone, LH) do?
has many functions in vertebrates, including milk production in mammals. Among other functions, prolactin in amphibian larvae stimulate growth of the larva and inhibit metamorphosis (antagonistic to T3 and T4).
how is Ca++ regulated? what are the three ways?
under hormonal control, but not from the axis. The body regulates circulating levels of Ca++, in part because calcium is associated with muscle contraction and blood levels are typically fairly constant. A few endocrine glands and hormones are involved in Ca++ regulation, including (1) Parathyroid gland and Parathyroid Hormone, (2) specialized cells in the thyroid gland secrete Calcitonin, (3) a metabolite of vitamin D (1,25 dihydroxyvitamin D3 )
Ca++ regulation: how does the parathyroid gland/hormone relate to Ca++ regulation?
Bone is used as a Ca++ storehouse. About 98% of the body’s Ca++ is stored in bone. Calcium is removed from bone by specialized cells called Osteoclasts. They breakdown bone and release Calcium into the bloodstream. Other specialized cells, Osteoblasts, build bone, and to do so, remove Ca++ from blood. As Ca++ are removed from the blood, blood Ca++ levels drop slightly, which stimulates the secretion of Parathyroid hormone. Parathyroid hormone stimulates osteoclasts to release Ca++ from bone (and stimulates kidneys to reabsorb Ca++ from the convoluted tubules). As Ca++ levels rise, Parathyroid hormone secretion decreases, which decreases Osteoclast activity.
Ca++ regulation: how does calcitonin relate to Ca++ regulation?
due to parathyroid gland/hormone the thyroid is stimulated to secrete calcitonin, which inhibits osteoclasts and protects the body against rapid increase in circulating Ca++ level; therefore, these hormones work together to regulate circulating levels of Ca++. used in treating osteoporosis sometimes, particularly in advanced cases. Oral, injected, or nasal passages are used.
Ca++ regulation: how does metabolite of vitamin D (1,25 dihydroxyvitamin D3 ) relate to Ca++ regulation?
The metabolite of Vit. D is required to absorb calcium from the intestine, and it also promotes synthesis of a protein that transports Ca++ in the blood. There are two common sources of Vitamin D: diet and sunlight. Sunlight stimulates a reaction in the skin that produces a Vit. D metabolite from a type of cholesterol. Ricketts is a clinical condition that develops when blood levels of Ca++ are low. It results in weak bones, and is most common in northern regions of the earth when winters are long (low sunlight) and since, the industrial age, in polluted cities.
how are the hormones insulin and glucagon involved in glucose metabolism?
from the pancreas. Insulin allows glucose to enter cells. Without insulin, glucose levels in the blood increase and it is eventually eliminated in urine (too much lost in filtrate to be effectively reabsorbed in the convoluted tubules). Insulin also allows Amino Acids to enter muscle cells. Diabetes occurs when either receptor cells do not detect insulin, or insulin is not produced in sufficient quantities. Glucagon raises blood glucose levels by converting glycogen, temporarily stored in the liver and muscle cells, to glucose, which is then released into the blood stream.
how are the hormones gastrin, secretin, and cholecystokinin involved in glucose metabolism?
Gastrin is produced by cells lining the stomach lumen. Gastrin is secreted into the bloodstream, but affect other cells of the stomach lining (parietal cells) to secrete HCl. HCl acid will kill some bacteria ingested, and also decreases the pH of the stomach contents, converting Pepsinogen to pepsin (an enzyme that initiates protein digestion). Secretin is secreted by cells lining the small intestine. It travels through the blood stream and its target cells are in the pancreas. It stimulates the pancreas to release bicarbonate into the lumen to increase the pH form the contents that entered form the stomach. The increase in pH produces an environment conducive for enzymes form the pancreas and intestinal luminal epithelium to function. Cholecystokinin is secreted from cells of the upper reaches of the small intestine and stimulates the pancreas to secrete pancreatic enzymes, and the gall bladder to release bile into the small intestine.
