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Module 15 in the Syllabus

The Endocrine System Images
Image gallery for study with links to larger teaching JPEGs for classroom presentation

Question Drill for The Endocrine System
Conceptual Vocabulary Self-Test

Basic Terms Crossword Puzzle

Basic Puzzle Solution

Conceptual Vocabulary
Endocrine systemThe endocrine system is an integrated system of small organs which involve the release of extracellular signaling molecules known as hormones.
HormoneA hormone is a chemical messenger that carries a signal from one cell, or group of cells, to another.
Endocrine glandsEndocrine glands are glands that secrete their product directly into the blood rather than through a duct.
HypothalamusLocated just below the thalamus, the hypothalamus links the nervous system to the endocrine system via the pituitary gland.
Posterior pituitaryThe posterior pituitary gland and is part of the endocrine system, secreting the hormones oxytocin and vasopressin, which are produced in the hypothalamus.
Anterior pituitaryUnder the influence of the hypothalamus, the anterior pituitary produces and secretes several peptide hormones which regulate many physiological processes including stress, growth, and reproduction.
VasopressinArginine vasopressin, also known as antidiuretic hormone, plays a major role in regulating the body's retention of water, being released when the body is dehydrated.
Pituitary glandThe pituitary gland, or hypophysis, is an endocrine gland about the size of a pea that sits in a small, bony cavity covered by a dural fold at the base of the brain.
Growth hormoneGrowth hormone or somatotropin is a protein hormone which stimulates growth and cell reproduction.
ProlactinProlactin is a peptide hormone on the anterior pituitary gland primarily associated with lactation.
OxytocinOxytocin is a hormone that also acts as a neurotransmitter in the brain. In females, it is released in large amounts during labor and it is also released during breastfeeding. It is released in both sexes during orgasm.
ThyroidOne of the largest endocrine glands in the body, the thyroid controls how quickly the body burns energy, makes proteins, and how sensitive the body should be to other hormones.
ThyroxineThyroxine, often abbreviated as T4, is the major hormone secreted by the follicular cells of the thyroid gland.
TriiodothyronineTriiodothyronine (T3) is a thyroid hormone similar to thyroxine but with one less iodine atom per molecule. T3 exhibits greater activity than thyroxine but is produced in smaller quantity.
CalcitoninCalcitonin is a polypeptide hormone produced by the parafollicular cells of the thyroid which participates in calcium and phosphorus metabolism, lowering blood calcium, countering the effects of parathyroid hormone.
Parathyroid glandThe parathyroid glands are small endocrine glands in the neck, usually located behind the thyroid gland.
Parathyroid hormoneParathyroid hormone is secreted by the parathyroid glands, acting to increase the concentration of calcium in the blood, opposite the effect of the thyroid hormone calcitonin.
AngiotensinAngiotensin is an oligopeptide in the blood that causes vasoconstriction, increased blood pressure, and release of aldosterone from the adrenal cortex.
Islets of LangerhansThe endocrine cells of the pancreas are grouped in the islets of Langerhans.
InsulinInsulin is an animal hormone which causes liver and muscle cells to take in glucose and store it in the form of glycogen and causes fat cells to take in blood lipids and turn them into triglycerides.
GlucagonGlucagon is released by the pancreas when the glucose level in the blood is low, causing the liver to convert stored glycogen into glucose and release it into the bloodstream.
AngiotensinAngiotensin is an oligopeptide in the blood that causes vasoconstriction, increased blood pressure, and release of aldosterone from the adrenal cortex.
AldosteroneAldosterone is a steroid hormone produced by the outer-section of the adrenal cortex in the adrenal gland which regulates sodium and potassium balance in the blood.
Adrenal medullaThe adrenal medulla is the part of the adrenal gland located in the center of the gland, being surrounded by the adrenal cortex.
Signal transductionSignal transduction refers to any process by which a cell converts one kind of signal or stimulus into another.
Second messenger systemA secondary messenger system is a method of cellular signalling where the signalling molecule does not enter the cell, but rather utilizes a cascade of events that transduces the signal into a cellular change.
Peptide hormonePeptide hormones are a class of peptides that are secreted into the blood stream and have endocrine functions in living animals.
Adrenocorticotropic hormoneAdrenocorticotropic hormone or corticotropin is a polypeptide hormone produced and secreted by the pituitary gland. It is an important player in the hypothalamic-pituitary-adrenal axis.
Atrial natriuretic peptideAtrial natriuretic peptide is a polypeptide hormone involved in the homeostatic control of body water, sodium, and adiposity.
Beta cellBeta cells are a type of cell in the pancreas in areas called the islets of Langerhans which make and release insulin.
Alpha cellAlpha cells are endocrine cells in the islets of Langerhans of the pancreas which are responsible for synthesizing and secreting the peptide hormone glucagon.
ErythropoietinErythropoietin, also called hematopoietin, is a glycoprotein hormone that acts as a cytokine for erythrocyte precursors in the bone marrow.
ReninRenin is released by the juxtaglomerular apparatus of the kidneys in response to low blood volume or decreased serum NaCl concentration.
Adrenal glandThe adrenal glands are triangle-shaped endocrine glands that sit on top of the kidneys which regulate the stress response through the synthesis of corticosteroids and catecholamines.
Adrenal cortexThe adrenal cortex, situated along the perimeter of the adrenal gland, mediates the stress response through the production of mineralocorticoids and glucocorticoids.
MineralocorticoidMineralocorticoids are a class of steroid hormones that include aldosterone which influence salt and water balance.
GlucocorticoidGlucocorticoids are a class of steroid hormones characterised by an ability to bind with cortisol receptors and trigger events which increase and maintain normal concentrations of glucose in blood.
NorepinephrineEpinephrine and norepinephrine are a fight or flight hormones released from the adrenal glands, and they are also neurotransmitters within the central and sympathetic nervous systems.
ThrombopoietinThrombopoietin is a glycoprotein hormone produced mainly by the liver and the kidney that regulates the production of platelets by the bone marrow.
Thyrotropin-releasing hormoneThyrotropin-releasing hormone is a tripeptide hormone that stimulates the release of thyroid-stimulating hormone and prolactin by the anterior pituitary.
Gonadotropin-releasing hormoneGonadotropin-releasing hormone is a peptide hormone responsible for the release of FSH and LH from the anterior pituitary.
Growth hormone releasing hormoneGrowth hormone releasing hormone is carried by the hypothalamo-hypophysial portal circulation to the anterior pituitary gland where it stimulates somatotropin secretion.
Corticotropin-releasing hormoneCorticotropin-releasing hormone stimulates corticotropes in the anterior pituitary to secrete adrenocorticotropic hormone and other biologically active substances such as beta endorphin.
SomatostatinSomatostatin is a peptide hormone that regulates the endocrine system and affects neurotransmission and cell proliferation.
Tropic hormoneTropic hormones describes as a class the anterior pituitary-secreted hormones which regulate the activity of various endocrine glands.
Thyroid-stimulating hormoneThyroid-stimulating hormone or thyrotropin is a hormone synthesized and secreted by thyrotrope cells in the anterior pituitary gland which regulates the endocrine function of the thyroid gland.
Melanocyte-stimulating hormoneThe melanocyte-stimulating hormones are a class of peptide hormones produced by cells in the intermediate lobe of the pituitary gland which stimulate the production and release of melanin by melanocytes in skin and hair.
HyperthyroidismHyperthyroidism is the clinical syndrome caused by an excess of circulating free thyroxine or free triiodothyronine.
Brain natriuretic peptideBrain natriuretic peptide is a polypeptide secreted by the ventricles of the heart in response to excessive stretching of myocytes in the ventricles.
Renin-angiotensin-aldosterone systemThe renin-angiotensin system is a hormone system that helps regulate long-term blood pressure and extracellular volume in the body.
Hypothalamic-pituitary-adrenal axisThe hypothalamic-pituitary-adrenal axis is a complex set of direct influences and feedback interactions between the hypothalamus, the pituitary gland, and the adrenal gland.
HypothyroidismHypothyroidism is the disease state in humans and animals caused by insufficient production of thyroid hormone by the thyroid gland.
MelatoninMelatonin is a hormone found in all living creatures from algae to humans, at levels that vary in a diurnal cycle.
LipotropinLipotropin is a hormone produced by the cleavage of pro-opiomelanocortin, which also produces adrenocorticotropin in the cleavage.
EndothelinEndothelin is a vasoconstricting peptide that plays a key part in vascular homeostasis. It is one of the strongest vasoconstrictors yet studied.
Pancreatic polypeptidePancreatic polypeptide is secreted by PP cells in the endocrine pancreas. It is a cholecystokinin antagonist, suppressing pancreatic secretion and stimulating gastric secretion.
Advanced terms that may appear in context in MCAT passages
Juxtaglomerular cellThe juxtaglomerular cells are cells in the kidney that synthesize, store, and secrete the enzyme renin.
Paraventricular nucleus of hypothalamusThe paraventricular nucleus (PVN) is an aggregation of neurons in the hypothalamus, which produces many hormones.
Hypophyseal portal systemThe hypophyseal portal system is the system of blood vessels that links the hypothalamus and the anterior pituitary.
PreprohormoneA preprohormone is the precursor protein to one or more prohormones, which are in turn precursors to peptide hormones.
Insulin-like growth factorThe insulin-like growth factors are polypeptides with high sequence similarity to insulin. They are part of a complex system that cells use to communicate with their physiologic environment.
AmylinAmylin is a peptide hormone secreted by pancreatic beta-cells at the same time as insulin
Zona glomerulosaThe zona glomerulosa of the adrenal gland is the most superficial layer of the adrenal cortex, lying directly beneath the adrenal gland's capsule.
Zona fasciculataThe cells of the zona fasciculata sit directly beneath the zona glomerulosa within the adrenal cortex, chiefly producing glucocorticoids.
CorticotropeCorticotropes are cells in the anterior pituitary which produce adrenocorticotrophic hormone and melanocyte stimulating hormone.
SomatotropeSomatotropes are cells in the anterior pituitary which produce growth hormone.
Pituitary stalkThe pituitary stalk (infundibulum) is the connection between the hypothalamus and the posterior pituitary.
Thyroid peroxidaseThyroid peroxidase is an enzyme mainly expressed in the thyroid that liberates iodine for addition onto tyrosine residues on thyroglobulin for the production of thyroid hormones.
DeoxycorticosteroneDeoxycorticosterone is a steroid hormone produced by the adrenal gland that possess mineralocorticoid activity and acts as a precursor to aldosterone.
Magnocellular neurosecretory cellMagnocellular neurosecretory cells are large cells within the supraoptic nucleus and paraventricular nucleus of the hypothalamus which produce oxytocin and/or vasopressin.
Supraoptic nucleusThe supraoptic nucleus is a nucleus of magnocellular neurosecretory cells in the hypothalamus of the mammalian brain.
Herring bodiesHerring bodies are structures found in the posterior pituitary representing the terminal end of the axons from the hypothalamus, where hormones are temporarily stored.
Pars intermediaPars intermedia is the boundary between the anterior and posterior lobes of the pituitary.

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