Module 3 Flashcards
(101 cards)
1
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Endocrinology
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The study of hormones
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Endocrine system components
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Endocrine glands that produce hormones and target cells
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What is a hormone
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a specific chemical substance (molecule) secreted into circulation by an endocrine gland (ductless) and carried in blood to other area of the body eliciting a response from target cells
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What is a target cell .
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A cell with a Specific receptor for a hormone
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Hormone function
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Influence cell function and maintain homeostasis
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What other body System communicates with organs and works closely with endocrine system
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Nervous system
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The three categories of hormones
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steroid, peptide (protein) , Amino acid derived
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Steroid hormones
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<Steroid hormones are fat-soluble molecules derived from cholesterol. These include sex hormones (testosterone and estrogen) cortisol and aldosterone from the adrenal gland cortex.
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peptide (protein) hormone
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produced by the pituitary gland (growth hormone and prolactin), hypothalamus (Antidiuretic hormone, ADH, oxytocin, and releasing factors), and the Islets of Langerhans in the pancreas (insulin and glucagon)
Synthesized in rough ER
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Amino acid derived
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such as thyroxine (T4) and triiodothyronine (T3) derived from tyrosine in the thyroid gland
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The major endocrine glands
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Anterior pituitary gland
Posterior pituitary gland
Thyroid gland
Parathyroid gland
Adrenal gland
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Organs that perform endocrine functions
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Hypothalamus
Pancreas
Ovaries
Testes
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Feedback Mechanism
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The regulation of hormonal output by the concentration of another hormone
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What is negative feedback
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Too much of one hormone produced so an influencing hormone reduces production to reduce the hormone that’s too high
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positive Feedback
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An increase of influencing hormone to start a biological process/ hormone release
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TRH
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Thyrotropin releasing hormone - > Stimulates TSH release
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GHRH
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Growth hormone releasing hormone - Stimulates GH release (hypothalamus)
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SS
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Somatostatin - GH-release inhibiting factor (hypothalamus)
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CRH
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.Corticotropin releasing hormone - Stimulates ACTh release (hypothalamus)
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GnRH
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Gonadotropin releasing hormone-Stimulates LH and FSH release (hypothalamus)
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ADH
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Antidiuretic Hormone (Vasopressing) - Antidiuretic and Vasoconstrictor (posterior pituitary-made in hypothalamus)
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Oxytocin
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Uterine contraction and milk letdown
(posterior pituitary-made in hypothalamus)
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TSH
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Thyroid stimulating hormone-Stimulates T4 and T3 release from thyroid gland (anterior pituitary)
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GH
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Growth hormone - Muscle and bone growth ( Anterior Petunitary )
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ACTH
Adrenocorticotropic - Stimulates cortisol and aldosterone release from adrenal glands (Anterior Petuitary)
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FSH
Follicle stimulating hormone-Spermatogenesis in male, follicle growth in female (Anterior petuitary)
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LH
Lutenizing hormone-Stimulates testosterone production in male and female and development of corpus lute (Anterior pituitary)
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PRL
Prolactin - Stimulates milk production (Anterior Pituitary )
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T2 and T4
(Follicles) Triiodothyronine and thyroxine - Stimulates an increase in basal metabolic rate (Thyroid)
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(C-cells) Calcitonin
Promotes a decrease in ECF and palm levels of calcium (Thyroid)
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PTH
Parathyroid (Parathyroid hormone) - Promotes an increase in ECF and plasma levels of calcium (Thyroid)
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Zona Glomerulosa
Promotes water and sodium balance (Adrenal Gland (cortex))
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Zona Fasciculata
Influences fat, carbohydrates, and protein metabolism (Adrenal Gland (cortex))
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Zona Reticularis
Promotes reproduction and development of sexual behavior (Adrenal Gland (cortex))
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Norepinephrine
Promotes vasoconstriction of arterioles in the skin, GI tract, kidney, and spleen (Adrenal gland (medulla))
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Epinephrine
Promotes an increase in heart rate and blood pressure (Adrenal Gland (Medulla))
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Follicle (Estrogen)
Promotes development of female reproduction and sexual behavior (Ovary)
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Corpus Luteum Progesterone
Stimulates development of mammary gland and uterus; maintains pregnancy (ovary)
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Beta cells Insulin
Promotes a decrease in blood glucose (Pancreas)
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Alpha cells Glucagon
Promotes an increase in blood glucose (pancreas)
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Testes (Leydig cells) Testosterone
Promotes development of male reproduction and sexual behavior
(Ovary)
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Hormonal transmission
Mechanism of cell-to-cell signaling
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Delta cells Somatostatin
Inhibits secretion of insulin and glucagon (Pancreas)
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F cells (Pancreatic peptide)
Inhibits gall bladder contraction and secretion of pancreatic enzymes (Pancreas)
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Endocrine Hormone Transmission
a hormone is released from the endocrine gland into the blood to act on a distant target tissue
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epicrine transmission
the hormone travels through gap junctions between the cells and never enters the extracellular fluid.
This system does not include the blood in its route of transmission.
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exocrine transmission
A hormone is secreted from the body by duct glands.
This includes hormones that are secreted into the intestine to affect other portions of the gastrointestinal tract
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Paracrine Transmission
cells release hormones into the extracellular fluid. The hormone acts on adjacent or nearby cells. An example of a paracrine hormone is prostaglandin.
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Autocrine Hormone Transmission
cells release hormones or a chemical messenger (autocrine substance) that binds to receptors of the cell that secretes it.
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Neuroendocrine transmission
involves hormone signals that originate from neurons
An example of direct neurohormonal transmission is when the sympathetic system stimulates the adrenal medulla cells to release epinephrine into the bloodstream. The hormone's release is a direct effect of the autonomic nervous system.
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How do hormones interact with cells to elicit responses?
Target cells have specific receptors that recognize different hormones. A single receptor will only recognize one specific hormone, and it has a great affinity for this hormone.
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inositol triphosphate (IP3) pathway
the hormone binds to a cell membrane receptor (PIP2).
After the hormone binds, PIP2 is hydrolyzed into IP3 by phospholipase C. IP3 then acts on the endoplasmic reticulum to open Ca ligand-gated channels
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What can peptide hormones activate (second messengers)
Cyclic AMP (cAMP)
Inositol triphosphate (IP3)
Calcium pathway
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The cyclic amp pathway
the hormone binds to the cell membrane receptor and activates the enzyme adenylate cyclase in the membrane
Cyclic AMP then activates another enzyme called a protein kinase
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What types of hormones are secreted by the anterior pituitary
Hormones that have direct effects on the body (growth hormone and prolactin)
Trophic hormones, which control other endocrine glands.
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The two parts of the pituitary gland
the anterior pituitary (Adenohypophysis)
posterior pituitary (Neurohypophysis)
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Calcium Pathway
When the hormone binds to the plasma membrane receptor, calcium is directly released from extracellular fluid into the cytoplasm.
In the cytoplasm, calcium then binds to calmodulin, stimulating enzyme activation
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what types of hormones are secreted by the anterior pituitary
Hormones that have direct effects on the body (growth hormone and prolactin)
Trophic hormones, which control other endocrine glands.
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Trophic hormones
secreted by the anterior pituitary to stimulate other endocrine glands to secrete their own hormones
For example, adrenocorticotropic hormone (ACTH) stimulates the adrenal cortex to secrete cortisol.
The other trophic hormones secreted by the anterior pituitary are thyrotropin (thyroid stimulating hormone - TSH) and the gonadotropins, which are follicle stimulating hormone (FSH) and luteinizing hormone (LH).
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what are the three layers of the adrenal cortex
the zona glomerulosa, the zona fasiculata, and the zona reticularis
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What is the function of ACTH
acts on both the zona glomerulosa and the zona fasciculata. The zona glomerulosa produces mineralocorticoids (e.g. aldosterone); the zona fasciculata produces glucocorticoids (e.g. cortisol); and the zona reticularis produces a small amount of sex steroids.
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what is the function of THS
stimulates the thyroid gland to release more T4 and T3(thyroid hormones)
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function of FSH and LH in females
SH acts on granulosa cell receptors to promote follicular growth and development (oogenesis). It also activates an enzyme called aromatase, which acts on testosterone to produce estradiol. LH acts on internal theca cell receptors to produce testosterone, which diffuses across the cell membrane into granulosa cells. LH also promotes ovulation, growth of the corpus luteum, and progesterone secretion.
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function of FSH and LH in males
FSH acts on Sertoli cell receptors in the seminiferous tubules to start the process of sperm production (spermatogenesis).
LH stimulates the detachment of spermatozoa from Sertoli cells (spermiation). LH also acts on Leydig cell receptors in the interstitium of the seminiferous tubules to stimulate testosterone production.
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GH function
causes the body to grow. It acts on the liver to produce somatomedins, which cause bone growth. GH affects carbohydrate and fat metabolism and increases lean body mass. It enhances transportion of amino acids across cell membranes, formation of RNA, and activation of ribosomes. All of these effects will increase protein synthesis.
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How does the hypothalamus control the anterior pituitary?
The hypothalamic-hypophyseal-portal system is a bed of capillaries that delivers hormones from the hypothalamus straight to the anterior pituitary, circumventing the systemic circulation. The hormones that are released from the hypothalamus have either a stimulatory effect or an inhibitory effect on the anterior pituitary hormones.
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what hormones are released from the hypothalamus
TRH (thyroid releasing hormone)
GRH (growth releasing hormone) and GIH (growth inhibiting hormone-somatostatin)
CRH (cortisol releasing hormone)
PRL-RH (prolactin releasing hormone) and PRL-IH (prolactin inhibiting hormone-dopamine)
GnRH (gonadotropin releasing hormone), and GnIH (gonadotropin inhibiting hormone)
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What are the hormones synthesized by the hypothalamus and stored in the posterior pituitary?
ADH and oxytocin.
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function of the posterior pituitary
posterior lobe of the pituitary gland is not a true endocrine gland; rather, it is an extension of the hypothalamus that serves as a storage place for oxytocin and ADH, which are synthesized by two nuclei (cluster of neurons bodies) in the hypothalamus.
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what is colloid
a gel-like, cohesive fluid that is made primarily of the protein thyroglobulin (TGB)
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What hormone regulates the production of T4 and T3 by the thyroid gland
TSH or thyrotropin (thyroid stimulating hormone)
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How is thyroxine produced in the follicles of the thyroid gland?
Thyroxine is made by coupling iodine with the amino acid tyrosine
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Important actions of thyroid hormones
Increase heart rate and cardiac output
Increase the activity of the nervous system (more excitable reflexes)
Increase the activity (motility and secretion) of the gastrointestinal tract
Growth and maturation of bones
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Hyperthyroidism
occurs when T3 and T4 levels are above normal. Hyperthyroidism will lead to an increase in metabolic rate
most common thyroid disturbance in cats
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Hypothyroidism
T3 and T4 levels drop below normal. Hypothyroidism will lead to a decrease in metabolic rate
most common thyroid deficiency in dogs
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Goiter
In some parts of the world, animals eat cruciferous plants (cabbage, rutabaga, turnip, kale, and rapeseed) that can cause hypothyroidism. The plants contain a goitrogenic agent that inhibits the binding of iodine to tyrosine, thus interfering with T3 and T4 production
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calcitonin
Produced by C Cells. Calcitonin is important for regulation of blood calcium levels
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parathyroid glands
sensitive to plasma calcium levels. The parathyroid glands secrete parathyroid hormone (PTH), and the parafollicular cells of the thyroid gland secrete calcitonin. PTH and calcitonin perform opposite tasks to maintain a relatively constant blood calcium level.
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why is calcium homeostasis important
Calcium is important for muscle contraction, transmission of impulses in the nervous system, and blood clotting. Calcium is the major mineral in bones and teeth. It also serves many functions in the cell.
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What is the major function of PTH?
increase calcium levels in extracellular fluid (ECF) and plasma.
increases osteoclast activity and bone resorption, which causes free calcium to be released into the ECF and the plasma. It also acts on the intestines and kidneys to increase absorption and resorption of calcium, respectively.
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How does PTH increase plasma calcium?
It stimulates calcium mobilization from the bone.
It increases calcium reabsorption in the kidney.
It indirectly enhances calcium absorption in the intestines through vitamin D.
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adrenal glands
paired organs situated cranial to the kidneys and next to the caudal vena cava and the aorta. Each adrenal gland has an outer cortex and an inner medulla.
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what are the three layers of the adrenal cortex
the zona glomerulosa, the zona fasciculata and the zona reticularis.
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aldosterone
steroid hormone secreted by the zona glomerulosa in the adrenal glands, it is a mineralocorticoid important in the regulation of sodium, potassium, blood pressure, and blood volume.
main function on the distal tubules and the collecting ducts of the kidneys to increase the rate of sodium absorption into the blood, and potassium excretion in the urine. When sodium (a positively charged ion) is absorbed, absorption of chloride (a negatively charged ion) and water will follow
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the most important long term regulator of aldosterone secretion
increased ECF potassium concentration
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The zona fasciculata of the adrenal gland
secretes glucocorticoids, mainly cortisol. Cortisol is a steroid hormone that has a diverse range of effects on the body
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Effect of cortisol on glucose metabolism
Cortisol stimulates muscle protein breakdown and amino acid mobilization in the liver. These actions stimulate hepatic gluconeogenesis, which results in an overall increase of hepatic glycogen; this will be used to increase serum glucose levels.
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short term regulation of aldosterone secretion
provided by cells in the juxtaglomerular apparatus in the kidneys. when blood pressure is low these cells secrete renin which converts angiotensinogen to angiotensin I, which is quickly converted to angiotensin II by angiotensin converting enzyme (ACE) in the lung capillaries.
Angiotensin II causes vasoconstriction of the arterioles, including the efferent arteriole of the kidney, and this directly increases blood pressure in the glomerulus
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What are the functions of cortisol in the body?
plays an integral role in the long-term response to stress.
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Effect of cortisol on protein metabolism
involved in the breakdown of protein for amino acid mobilization. The amino acids are taken to the liver, where they are made into glucose or blood proteins, or they can be taken to damaged tissue where they are used for tissue repair.
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Effect of cortisol on fat metabolism
Cortisol breaks fat down and mobilizes it from storage so that it can be used for energy. With chronic high levels of cortisol, fat is redistributed to the liver and abdominal area, giving a classic “pot-bellied” appearance.
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How is cortisol secretion regulated?
ACTH from the anterior pituitary gland stimulates the release of cortisol. The anterior pituitary secretes ACTH in response to corticotropin releasing factor (CRF) from the hypothalamus.
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The zona reticularis
the innermost layer of the adrenal cortex. Its main function is to produce sex steroids. The sex steroids include androgens (testosterone) and estrogen, which are secreted in trace amounts.
secretes a great amount of the precursors of sex steroid hormones with weak androgenic activity; namely, androstenedione, dehydroepiandrosterone (DHEA) and DHEA -sulphate. These are important precursors that can be converted to androgens and estrogen in peripheral tissues.
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The adrenal medulla
secretes a class of hormones called catecholamines, which are derived from the amino acid tyrosine. The adrenal medulla is considered by be functionally part of the sympathetic nervous system. It has modified postganglionic neural cells.
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