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PCAT: BIOLOGY > Endocrine system > Flashcards

Endocrine system Flashcards

1
Q

what is the purpose of the endocrine system

A
  • internalized communication, coordinating the activities of the organ systems
  • endocrine glands synthesize and secrete hormones dircetly into circulatory system
  • exocrine glands like gall bladder secrete substances transported by ducts
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2
Q

what oragans or glands secrete hormones

A
  • pituitary, hypothalamus, thyroid, parathyroid, andrenals, pancreas, testes, ovaries, pineal gland, kidneys, gastrointestinal, heart, thymus

*some hormones regulate a single type of cell or organ while others have more widepsread actions

*thats usually determined by presence of specific receptors on or in target cells

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3
Q

what are the adrenal glands, where are they located

A
  • on top of kidneys and consist of adrenal cortex and adrenal medulla
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4
Q

what does the adrenal cortex secretes and what triggers this secretion and how does it work

A
  • secretion occurs in response to stress, andrenocorticotropic hormone (ACTH) produced by anterior pituitary stimulates adrenal cortex to produce more than 2 dozen steorid hormones (adrenocortical steroids or corticosteroids)
  • corticosteroids are bound to transport proteins called tanscortins
  • corticosteroids exert their action by determining which genes are trnascribed in nuceli of target cells and at what rate
  • subsequent changes in the nature and concentration of enzymes produced in target cells will affect cellular metabolism
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5
Q

what are the 3 major classes of corticosteroids

A
  • glucocorticoids, mineral and cortical sex hormones
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6
Q

what are glucocorticoids

A
  • include cortisol and cortisone: secreted by adrenal cortex
  • involved in glucose regulation and protein metabolism, raise blood glucose levels by promoting protein breakdown and gluconeogenesis and dec protein synthesis
  • inc plasma glucose levels and are antagonistic to the effects of insulin
  • release amino acids from skeletal muscle as well as lipids from adipose tissue

*also promote peripheral use of lipids and have anti-inflammatory effects

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7
Q

what are mineralocorticoids

A
  • ex is aldosterone: secreted by adrenal cortex
  • regulate plasma levels of sodium and potassium which also results in reg of extracellular water volume
  • causes active reabsorption of sodium and passive reabsorption of water in the nephron of the kidney
  • causes inc in blood volume and blood pressure
  • excess production of aldosterone results in excess retention of water causing hypertension (high blood pressure)

**mineralocorticoids are stimulated by angiotensin II and inhibited by ANP (atrial natriuretic peptide)

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8
Q

what are cortical sex hormones

A

adrenal cortex secretes small quantities of androgens like androstenedione and dehydroepiandrosterone in both men and women

* in men most androgens are produces in the testes so effect of adrenal gland is small

  • in women overproduction of andrenal androgens may have masculinizing effects such as excessive facial hair

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9
Q

what does the adrenal medulla secrete

A
  • epinephrine (adrenaline) and norepinephrine (noradrenaline)
  • both belong to a class of amino acid derived compounds called catecholamines

*both are neurotransmitters, secretion is stimulation during sympathetic activation by sympathetic pregnaglion fibers

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10
Q

what does epinephrine and norepinephrine do

A

epinephrine inc conversion of glycogen to glucose in the liver and muscle tissue

causes an inc in blood glucose levels and basal metabolic rate

  • both ep and norep inc rate and strength of heart beat and dilate, constrict blood vessels to inc blood supply to heart, skeletal muscles and brain while dec supply to kidneys, skin and disgestive tract
  • promote release of lipids in adipose
  • inhibts vegetative functions like digestive not immediately required for survival

*fight or lfight response

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11
Q

what is the pituitary gland where is it located

A
  • also called hypophysis, located at the base of the brain hanging below the hypothalamus and is connected by infundibulum
  • contains anterior and posterior lobe
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12
Q

what does anterior pituitary sectrete

A

*synthesizes direct hormones to directly stimulate target organs or cell types and trophic hormones which stimulate endocrine glands to relase hormones

Direct hormones:

  • Growth hormone
  • Prolactin
  • Endorphine
  • Melanocyte-stimulating hormone (MSH)

Trophic Hormones:

  • Adrenocorticotropic hormone: ACTH
  • Thyroid stimulating hormone
  • lutenizing hormone
  • follicle stimulating hormone
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13
Q

what is it called when the hypothalamus regulates the secretions of hormones in antirior pituitary

A
  • releasing/inhibiting hormones or factors
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14
Q

what is growth hormone

A
  • secreted by antirior pituitary
  • promotes bone and muscle growth, protein synthesis, lipid metabolism and catabolism
  • in children a GH deficiency can lead to stunted growth (dwarfism) while voer production of GH results in gigantism
  • over production of GH in adults causes acromegaly characterized by disproportionate overgowth of bone, localized esecially in skull, jaw, feet and hands
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15
Q

what is prolactin

A
  • secreted by antiorior pituitary
  • stimulates milk production and secretion in female mammary glands
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16
Q

what are endorphins

A
  • secreted by anterior pituitary
  • neurotransmiters that have pain relieving properties
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17
Q

what is melanocyte-stimulating hormone

A
  • secreted by the intermediate lobe of the pituitary and stimulates the release of melanin

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18
Q

What does the anterior pituitary secrete

A
  • trophic hormones
  • adrenocorticotropic hormone
  • thyroid stimulating hormone
  • lutinizing hormon
  • follicle stimulating hormone
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19
Q

what does adrenocorticotropic hormome do

A
  • ACTH
  • secreted by anterior pituitary
  • stmiulates the adrenal cortex to synthesize and secrete glucocorticoids
  • regulated by the releaseing hormone corticotropin- releasing factor (CRF)
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20
Q

what does thyroid stimulating hormone do

A
  • secreted by anterior pituitary
  • stimulates the thyroid gland to synthesize and release thyorid hormones including thyroxine
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21
Q

what does luteinizing hormone do

A
  • secreted by anterior pituitary
  • in women stimulates ovulation and formation of he corpus luteum
  • LH is also responsible for regulating progesterone secretion in women
  • in men it stimulates interstitial cells of testes to synthesize testosterone
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22
Q

what does follicle stimulating hormone do

A
  • secreted by anterior pituitary
  • in women causes maturation of ovarian follicles that begin secreting estrogen
  • in men stimulates maturation of the seminiferous tubules and sperm production
23
Q

What is the posterior pituitary and what does it secrete

A
  • also called neurohypophysis
  • does not synthesize hormones

stores and releases the peptide hormones oxytocin and antidiuretic hormone produced by neurosecretory cells of hypothalamus

  • hormone secretion is stimulated by action potentials descending from the hypothalamus
24
Q

what is oxytocin

A
  • secreted during childbirth
  • inc the strenght and frequency of uterine uscle contractions
  • release also caused by suckling stimualting milk secretion in mammary glands
25
Q

what is antidiuretic hormone

A
  • secreted by posterior pituitary
  • also caled vassopressin
  • inc the permeability of nephron’s collecting duct to water
  • promotes water reabsorption and inc blood volume resulting in inc bp
  • secreted when plasma osmolarity inc (sensed by osmoreceptors in hypothalamus), or when blood volume bc sensed by barorecepotrs in circulatroy system
26
Q
A
27
Q

what is the hypothalamus

A
  • part of the forebrain, located directly above the pituitary gland
  • hypothalamus receives neural transmissions from other parts of the brain and from peripheral nerves to trigger response from neurosecretory cells
  • these cells regualte pituitary gland secretions via negative feedback mechanisms and through actions of inhibiting and releasing hormones
28
Q

what are the interactions between the hypothalamus and the anterior pituitary

A
  • hypothalamus releasing hormones stimulate or inhibit the secretions of the anterior pituitary
  • ex: GnRH stimulates ant pit secretion of FSH and LH
  • releasing hormones ae secreted into hypothalamic-hypophyseal portal system
  • blood from the capillary bed in hypothalamus flow through protal vein into ant pit where it goes into secondary cap network so releasing hormones can immediately reach ant pit
29
Q

what regulates the secretions of the endocrine system

A
  • complicated feedback system
30
Q

what are the interactions of the hypothalamus with the posterior pituitary

A
  • neurosecretory cells in the hypothalamus synthesize oxytocin and ADH and transport them via their axons into posterior pituitary for storage and secretion
31
Q

what is the thyroid

A
  • thyroid hormones affect the function of nearly every organ system in the body
  • in chrildren they are essential for growth and neurological development
  • in adults essential for maintenance of metabolic activity
  • inc the rate of metabolism throughout the body
32
Q
  • what are the thyroid hormones
A
  • thyroxine (T4) and triiodothyronine (T3) formed by the glycoprotein thyroglobulin which is syn by thyroid cells
  • =specific teritary structure, iodinate tyrosine residues present in thyroglobulin are able to bind together to forma ctive thyorid hormones
  • T3 is 5x more potent than t4
  • T4 and T3 are transported vis plasma proteins, apporx 99.5% of hormone are bound to proteins but only unbound can enter cell and elicit a response
  • all T4 in body formed are secreted by thyroid gland, only 20% of T3 is produced by thyroid gland
  • majority of T3 is produved by conversion of T4 to T3 by 5’-monodeiodase found primarily in periphereal tissues
33
Q

explain hypothyroidism

A
  • thyroid hormones are under secreted or not secreted at all
  • can cause slowed HR and resp rate, fatigue, cold intolerance and weight gain
  • in infants its called cretinism characterized by mental retardation and short stature
  • treated with supplimented thyroid hormones via synthetic or animal derived products
34
Q

explain hyperthyroidism

A
  • thyroid is overstimulated
  • symptoms include inc metabolic rate, feelings of excessive warmth, profuse sweating, palpitations, weight loss and protruding eyes

0 can be treated with antithyroid medications to suppress the thyroids release of excess hormone or ablation of thyroid with radiotherapy

  • after ablation the thyroid no longer produces thyroid hormone and pateints must take thyorid supplementation for the rest of life
35
Q

what is calcitonin

A
  • antagonistic parathyroid hormone
  • decreases plasma Ca2+ conc by inhibiting the relase of Ca from bone
  • secretion is regulated by plasma Ca levels
36
Q

what is the role of the pancreas

A
  • exocrine organ and endocrine organ
  • exocrine functions is performed by cells that secrete digestive enzymes into the small intestine via series of ducts
  • endocrine function is performed by small glandular structures called islets of langerhand composed of alpha and beta cells
  • alpha cells secrte glucagon and beta cells produce and secrete insulin
37
Q

what is glucagon

A
  • secreted by alpha cells of islets of langerhand of pancreas
  • stimulates protein and fat degredation, conversion of glycogen to glucose and gluconeogenesis

*all serve to inc blodo glucose levels

  • actions are antagonistic to insulin
38
Q

what is insulin

A
  • protein hormone secreted by beta cells of islets of langerhans in pancreas
  • secreted in response to high blood glucose conc
  • stimulates glucose uptake by muscle and adipose cells and the storage of glucose as glycogen in muscle and lvier cells to lower blood glucose levels
  • it also stimulates synthesis of fats from glucose and the uptake of amino acids
  • actions are antagonistic to glucagon and glucocorticoids
39
Q

what happens if insulin is under produced

A
  • diabetes mellitus, characterized by hyperglycemia (high blood glucose levels)
40
Q
A
41
Q

what are the parathyroid glands

A
  • four, pea - shaped structures embedded in the posterior surface of the thyorid
  • synthesize and secrete parathyroid hormone which regualtes plasma Ca concentration
  • PTH raises the Ca concentration in the blood by stimulating Ca release from the bone and decreasing excretion in the kidneys
  • calcium in the bone is bonded to phosphate and breakdown of bone releases phos and cal
  • parathyroid compensates for inc phos conc by stimulating the excreation of phos by the kidneys
42
Q

what do the kidneys secrete

A
  • renin and eryhtroprotein
43
Q

what is Erythropoietin

A

glycoprotein that stimualtes RBC production normally produced by kidneys

stimulation of the stem cells to differentiate into rubtiblasts

  • increases rate of mitosis
  • increased release of reticulocytes from the bone marrow
  • increased hemoglobin formation which creates the critical HgB concentration necessary for maturity to eb reached at a more rapid rate
44
Q

what is renin

A
  • secreted by kidneys
  • when blood voluem falls the kidneys produce renin an enzyme which converts the plasma protein angiotensinogen to angiotensinogen I

angiotensinogen I -> angiotensinogen II which stimualtes the adrenal cortex to secrete aldosterone

alsdosterone helps to restore blood volume by increasing sodium reabsorption at the kidney leading to an inc in water

removes intial stimulus for enin production

45
Q

what are the gastrointestinal hormones

A
  • gastrin, secretin, cholecystokinin
46
Q

what is gastrin

A
  • ingested food stimulates the stomach to release gastrin
  • is carried to the gastric glands and stimulates secretion of HCl
47
Q

what is secretin

A
  • released by the small intestine when acidic food material enters from the stomach
  • stimulates the secretion of alkaline bicarbonate solution from the pancreas
48
Q

what is cholecystokinin

A
  • released frmo the small intestine in response to the presence of fats and causes the contraction of the gallbladder and release of bile into the small intestile
  • bile involved in the emulsification of fats
49
Q

what is the pineal gland, what does it secrete

A
  • tiny structure at base of the brain that secretes melatonin
  • role of melatonin is unclear but is believed to pay role in regulation of circaidan rhythms
  • melatonin secretion is regulated by light and dark cycles in environment
50
Q

what are the ways in which hormones affect the activities of their target cells

A

via extracellular receptors or intracellular recepotrs

51
Q

describe peptide hormones

A
  • range from simple short peptides like ADH or complex like insulin
  • act as first messengers binding to specfic receptors on surface of target cells
  • trigger series of enzymatic rxns, first may be conversion of ATP to cAMP catalyzed by membrane ound adenylate cyclase
52
Q

what does cAMP do

A
  • acts as a secondary messanger relaying messages from the extracellular peptide hormone to cytoplasmic enzymes to initiate a series of seccessive rxns in the cell
  • ex of casacde efect: with each step the hormoens effects are amplified
  • cAMP acitivty is inactivated by the cytoplasmic enzyme phosphodiesterase
53
Q

decribe steroid hormones

A
  • like estrogen and aldosterone
  • belong to lipid derived molecules with characteristic ring structure
  • produces by testes, ovaries, placenta and adrenal cortex
  • bc lipid soluble they can cross the phospholipid bilayer and enter the target cells directly to bidn to receptor in cytoplasm
  • receptor-hormone complex enters the nucleus and directly activates the expression of specific genes by binding to receptors on chromatin
  • induces a change in mRNA transcription and protein synthesis

PCAT: BIOLOGY (18 decks)

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