Endocrine System Flashcards
Endocrine Glands
Pituitary, Hypothalamus, Thyroid, Parathyroids, Adrenals, Pancreas, Testes, Ovaries, Pineal Gland, Kidneys, Gastrointestinal Glands, Heart, and Thymus
Adrenal Glands
-located on top of the kidneys and consist of the adrenal cortex and the adrenal medulla
Adrenal Cortex
in response to stress, ACTH (produced by the anterior pituitary, stimulates the adrenal cortex to produce corticosteroids. Corticosteroids are bound to transport proteins called transcortins
Glucocorticoids
- examples: cortisol & cortisone
- involved in glucose regulation & protein metabolism
- raise blood glucose levels by promoting protein breakdown and gluconeogenesis and decreasing protein synthesis, increase plasma glucose levels and are antageniostic to the effects of insulin
Mineralocorticoids
- examples: aldosterone
- regulate plasma levels of sodium and potassium and consequently the extracellular fluid volume
Cortical Sex Hormones
the adrenal cortex secretes small quantities of androgens
Adrenal Medulla
- produces epinephrine and norepinephrine, which belong to a class of amino-acids derived compounds called catecholamines
- promote release of lipids by adipose tissues “flight or fight” response
Pituitary Glands
-a small, trilobed gland at the base of the brain
Anterior Pituitary
- synthesizes direct hormones, which directly act on their target organs
- sytnhesizes tropic hormones, which stimulate other endocrine glands to release hormones
Follicle-Stimulating Hormone (FSH) - tropic hormone
causes maturation of ovarian follicles - secrete estrogen also causes maturation of the seminiferous tubules to sperm production
Luteunizing Hormone (LH) -tropic hormone
stimulates ovulation and maintenance of the corpos leteum. Stimulates the interstitial cells of the testess to synthesize testosterone
Adrenocorticotropic Hormone (ACTH) -tropic hormone
stimulates the adrenal cortex to synthesize and secrete glucocerticoids and is regulated by CRF
Thyroid-Stimulating Hormone (TSH) -tropic hormone
stimulates the thyroid gland to synthesize and release thyroid hormones
Prolactin - direct hormone
stimulates milk production in female mammary glands
Endorphins - direct hormone
neurotransmitters that have pain-relieving properties
Growth Hormones - direct hormone
promotes bone and muscle growth, protein synthesis and lipid mobilization and ctabolism
Melanocyte-stimulating Hormone (MSH) -direct hormone
secreted by the intermediate lobe of the pituitary
Posterior Pituitary
does not synthesize hormones; it stores and releases the peptide hormones oxytocin and antidiuretic hormone (ADH)
Oxytocin
increases the strength and frequency of uterine muscle contractions
ADH
increases the permeability of the nephron’s collecting duct to water (increases blood pressure)
Hypthalamus
part of the forebrain and is located directly above the pituitary gland
Interactions with the anterior pituitary gland
hypothalamic-releasing hormones stimulate or inhibit the secretions of the anterior pituitary
Interactions with the posterior pituitary gland
nuerosecretory cells in the hypothalamus synthesize both oxytocin and ADH and transport them via their axons into the posterior pituitary for storage and secretion
Thyroid
affect the function of nearly every organ system in the body
Thyroid Hormones
- thyroxine (T4) and triiodothyronine (T3) are formed from the glycoprotein thyroglobulin
- T3 is five times more potent than T4
- T4 and T3 are transported via plasma proteins
- T4 is formed and secreted by the thyroid glands only
- 20% of T3 is produced by the conversion of T4 to T3 by the enzyme 5’ - monodeiodase, found primarily in the peripheral tissues
Pancreas
both an exocrine and endocrine gland
Glucagon
stimulates protein and fat degradation
Insulin
a protein hormone secreted in response to a high blood glucose concentration
Parathyroid Glands
- four small, pea-shaped structures, embedded in the posterior surface of the thyroid
- these glands synthesize and secrete parathyroid hormone (PTH), which regulate plasma Ca2+ concentration
Kidneys
- when blood volume falls, the kidneys produce renin-an enzyme that converts the plasma protein angiotensinogen to angiotensin I
- Angiotensin I is converted to angiotestin II, which stimulates the adrenal cortex to secrete aldosterone (helps restore blood volume by increasing sodium reabsorption by the kidneys
- the kidneys also produce erythroporetin (EPO), a glycoprotein that stimulates red blood cell production
Gastrointestinal Hormones
- ingested food stimulates the stomach to release the hormone gastrin
- gastrin is carried to the gastrin glands and stimulates the glands to secrete HCl in response to food in the stomach
- secretin is released by the small intestine when acidic chyme enters from the stomach
- cholecystokinin is released by the small intestine in response to the presence of fats and causes the contraction of the gall bladder and release of bile into the small intestine
- bile (not a hormone) is involved in the emulsification and digestion of fats
Pineal Gland
a tiny structure at the base of the brain that secretes the hormone melatonin
Mechanism of Hormone Action
- peptide hormones act as first messengers
- cyclic AMP acts as a second messenger (inactivated by cytoplasmic enzyme phosphodiesterase)
