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physio fall midterm > endocrinology lecture 1 > Flashcards

endocrinology lecture 1 Flashcards

1
Q

what is the route of communication for the endocrine system

A

blood

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2
Q

compared to the nervous system, the endocrine system has a _____ onset of response

A

the endocrine system has a DELAYED onset of response

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3
Q

compared to the nervous system, the duration of the effects for the endocrine system are

A

the endocrine system’s duration of effects are PROLONGED

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4
Q

glands in the e.system are…

A

ductless

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5
Q

specificity of tissue response in the e.system is due to what….

A

due to the presence of receptors that are specific to a particular hormone (in that target tissue)

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6
Q

if you want to regulate/increase a response to a particular hormone you must (3)

A
  1. increase secretion of the hormone
  2. increase the hormone’s availability in the blood
  3. increase the expression of the hormone’s receptors in the target tissue
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7
Q

what are the 3 chemical classes of hormones

A
  1. peptide/protein
  2. steroid
  3. amine
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8
Q

peptide hormones are highly variable in ____

A

size! can be just a few a.a to very large proteins

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9
Q

what can be added to peptide hormones to make them variable in structure

A

sugar residues…aka they can be glycosylated

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10
Q

can peptides fn as both neurotransmitters and hormones?

A

yes! somatostatin and seratonin are examples.

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11
Q

what is a preprohormone

A

stage in peptide hormone synthesis. inactive form of hormone that is synthesized on a ribosome. includes extra a.a and foldings.

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12
Q

what is a prohormone

A

a stage in peptide hormone synthesis following the preprohormone stage. the preprohormone gets cleaved in the RER to remove the extra a.a. the prohormone is then packaged into vesicles in the Golgi.

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13
Q

what is the final stage of peptide hormone synthesis

A

the prohormone is cleaved prior to being in the vesicle OR is cleaved within the vesicle (and when secreted, the hormone is secreted with the fragments)

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14
Q

what is the benefit of packaging peptide hormone in vesicles

A

large quantities can be stored for rapid release

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15
Q

what is the purpose of precursor molecules in peptide hormone synthesis

A
  1. prevents intracellular degradation
  2. limits the feedback effects on the cell
  3. limits hormone having an effect before it leaves the cell
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16
Q

what type of hormones are steroid hormones

A

small lipid hormones

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17
Q

what are the sources (which organs secrete) the steroid hormones

A

-gonads
-adrenal cortex
-placenta
these are the primary steroid producing organs

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18
Q

all steroids are derived from

A

cholesterol (by a series of rxns)

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19
Q

what are the 5 classes of steroid hormones

A
  1. progestagens
  2. androgens
  3. estrogens
  4. glucocorticoids
  5. mineralocorticoids
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20
Q

what are the progestrogens

A

pregnenolone, progesterone, 17-hydroxyprogesterone

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21
Q

what are the androgens

A

dehydroepiandrosterone, androstenedione

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22
Q

what are the glucocorticoids

A

corticosterone and cortisol

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23
Q

what are the mineralocorticoids

A

aldosterone

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24
Q

what are the 2 main sources used for cholesterol synthesis

A

acetyl coA and LDL (made within the cell from these 2 molecules)

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25
Q

what is the process by which steroid hormones are made…

A
  1. LDL binds to LDL receptors on the cell and is endocytosed
  2. fusion of these vesicles into and endosome
  3. w/in the endosome LDL dissociates from the receptor (and the receptor is recycled to surface of cell)
  4. LDL delivered to lysosome
  5. cholesterol ester is cleaved from the LDL to give free cholesterol
  6. this cholesterol is used for membrane synthesis OR is converted to steroid hormones and bile acids
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26
Q

how are cholesterol esters stored within steroidogenic cells

A

w/in lipid droplets in the cell (bc cholesterol is lipid soluble and would otherwise diffuse through the membrane)…this gives the cell a white fatty appearance

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27
Q

what initiates steroid hormone synthesis

A

usually a peptide hormone that binds to a g-protein coupled receptor

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28
Q

what is the cascade for steroid hormone synthesis

A

peptide hormones bind to GPCR–>activate adenyl cyclase–>increase in cAMP–>cAMP activates PKA–>PKA stimulates the activity of cholestrol esterases (which cleave the cholesterol esters from LDL in the lipid droplets)–>free cholesterol is released

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29
Q

what is StAR and what is its purpose

A

StAR=steroid acute regulatory protein. Bc cholesterol is lipid soluble, it is difficult to transport around the “watery” cell. StAR is able to bind to free cholesterol and FACILITATE ITS TRANSPORT TO THE MITOCHONDRIA (crossing both inner and outer membranes)

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30
Q

what happens to cholesterol in the mitochondria

A

it is converted in the mitochondria to steroids

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31
Q

that enzymes modify cholesterol in the mitochondria and that do they add/cleave

A

P450 enzymes. add OH or cleave C-C. the P450 enzymes are located on the inner mitochondrial membrane). **important to note that the type of steroidogenic enzyme present in the cell, determines which steroid is produced from cholesterol (different cells make different steroids)

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32
Q

from the mitochondria, where do steroids move to

A

steroids move from the mitochondria to the SER for further modification and then they DIFFUSE into the blood (across the cell membrane)

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33
Q

bc steroids are lipid soluble they cannot be…

A

stored (or any of the intermediates)

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34
Q

what 3 ways is the synthesis of steroids regulated

A
  1. by regulating the peptide hormone that stimulates the synthesis
  2. regulating the synthesis of the steroidogenic enzymes
  3. the # of the steroidogenic cells
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35
Q

what is the pathway for the different classes of steroid hormones

A

cholesterol–> progestagens–> corticosteroids (glucocorticoids or mineralocorticoids) OR androgens—>androgens to estrogens

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36
Q

amine hormones are derived from what

A

the a.a. tyrosine

37
Q

what are the different amine hormones (4)

A
  1. thyroid hormone
  2. norepinephrine
  3. epinephrine
  4. dopamine
    (2,3,&4 are all catecholamines)
38
Q

thyroid hormone is produced where

A

thryroid gland….duh

39
Q

what are the 2 thyroid hormones

A

triiodothyronine (T3) and thyroxine (T4)….basically iodinated tyrosine molecules

40
Q

where are the catecholamines synthesized

A
  • norepinephrine and epinephrine–> adrenal medulla

- dopamine–>hypothalamus

41
Q

T3 and T4 are _____ like with respect to solubility and receptors

A

steroid like….they are lipophilic and nonpolar (diffuse through the membrane)

42
Q

the catecholamines are _____ like with respect to solubility and receptors

A

peptide like….they are hydrophilic/polar

43
Q

what are the 2 principles of hormone secretion

A
  1. (most) are secreted in short bursts/bursting pattern….where there is a decrease in hormone [ ] due to clearance/metabolism of the hormone after/between bursts
  2. circadian
44
Q

what is the “fourth” class of hormones

A

eicosanoids

45
Q

what are the eicosanoids derived from

A

arachidonic acid…aka they are lipids!

46
Q

why are eicosanoids not typically thought of as a class of hormones

A

bc they are very LOCALLY active and not seen in large amounts in circulation like typical hormones

47
Q

the patterns of hormone secretion can be controlled by what three factors

A
  1. plasma [ ] of a NUTRIENT
  2. neural control (like the brain tells an organ when to secrete the hormone)
  3. hormonal control (other hormones control hormones release…a cascade)
48
Q

how do hydrophilic hormones travel in the blood vs hydrophobic hormones

A

hydrophilic hormones are readily transported, but hydrophobic hormones require a carrier protein to be bound to

49
Q

where are carrier proteins (for hydrophobic hormones) synthesized

A

the liver

50
Q

what affects the availability of hydrophobic hormones

A

the use of carrier proteins

51
Q

when considering a hydrophobic hormone and its carrier protein, what must happen for the hormone to bind to the receptor

A

the hormone must be released from the carrier protein…thus the [ ] of the free hormone is a function of the [ ] of the binding protein

52
Q

what is the fn of carrier proteins (2)

A
  1. transport hydrophobic hormones through the blood

2. prevent the hydrophobic hormones from degradation and clearance (protects steroid and thyroid hormones)

53
Q

where is the main place for hormone metabolism and excretion

A

liver and kidneys….they contain enzymes that breakdown/inactivate a hormone (note that degradation can also occur in blood via circulating enzymes)

54
Q

what are the 2 ways that hormones are brokendown/inactivated in the liver and kidneys

A
  1. hydrolysis

2. sulfation

55
Q

where are the receptors located for peptide and catecholamine hormones

A

bc they are hydrophilic…their receptors are on the cell surface in the membrane

56
Q

what are the 2 types of responses for hydrophilic hormones (catecholamines and peptide hormones)

A
  1. ionotropic

2. metabotropic

57
Q

what is an ionotropic response

A

when the hormone binds, an ion channel opens

58
Q

what is a metabotropic response

A

when a hormone binds, it alters the cell activity (ex. phosphorylation of 2nd messengers)

59
Q

what speed of response is possible with hydrophilic hormones

A

rapid and delayed….delayed responses occur when a 2nd messenger cascade alters transcription/protein synthesis

60
Q

where are the receptors located for steroid and thyroid hormones

A

bc they are lipophilic, their receptors are intracellular or nuclear

61
Q

typically, a lipophilic hormone (thyroid or steroid hormone) and its receptor/ligand form a______

A

DNA binding protein/transcription factor that alters transcription

62
Q

what speed of response is possible with lipophilic hormones

A

delayed only…bc it alters protein synthesis/transcription. (there are exceptions…see notes)

63
Q

where does the anterior pituitary develop from

A

outpocketing of oral ectoderm

64
Q

where does the posterior pituitary develop from

A

buds of the flood of the hypothalamus…remains attached to the median eminence of the hypothalamus via the infindibulum

65
Q

what are the 2 hormones released from the posterior pituitary

A
  1. oxytocin

2. vasopressin

66
Q

where are oxytocin and vasopressin synthesized

A

in the hypothalamus within the:

  1. supraoptic
  2. paraventricular nuclei
67
Q

what does oxytocin do

A

stimulates smooth muscle contraction

68
Q

what does vasopressin/antidiuretic hormone do

A

regulates b.p via the kidney and b.v

69
Q

how is the secretion of the anterior pituitary regulated

A

by the hypothalamus…the hypothalamus secretes hypophysiotropic/releasing hormones that stimulate the ant. pituitary

70
Q

how do hyophysiotropic hormones travel to the ant. pituitary

A

at the base of the median eminence of the hypothalamus, portal blood vessels are present (which axons release into)…and from the portal b.v, the hormones travel to the ant. pituitary

71
Q

there are _____ # of different cells in the ant. pituitary that produce ____ different hormones

A

5 diff cell types producing 6 primary hormones

72
Q

what does GnRH (secreted from the hypothalamus) stimulate the secretion of (from the ant. pituitary)

A

FSH and LH

73
Q

what does GHRH (secreted from the hypothalamus) stimulate the secretion of (from the ant. pituitary)

A

Growth hormone

74
Q

what does SS/somatostatin (secreted from the hypothalamus) INHIBIT the secretion of (from the ant. pituitary)

A

growth hormone

75
Q

what does TRH (secreted from the hypothalamus) stimulate the secretion of (from the ant. pituitary)

A

TSH

76
Q

what does DA/dopamine (secreted from the hypothalamus) INHIBIT the secretion of (from the ant. pituitary)

A

prolactin

77
Q

what does CRH (secreted from the hypothalamus) stimulate the secretion of (from the ant. pituitary)

A

ACTH

78
Q

besides dopamine, what type of hormone are the other 5 releasing hormones from the hypothalamus

A

small peptide hormones

79
Q

what comprises the ‘neuroendocrine system’

A

hypothalamus, pituitary, target…also called an ‘axis’

80
Q

what are the 2 hormones secreted by the ant. pituitary that are products of the proopiomelanocortin gene (POMC)

A
  1. beta-lipotropin

2. beta-endorphin

81
Q

what is the long loop feedback mechanism

A

self-regulation by hormone/product of the ultimate/last target tissue

82
Q

what is the short loop feedback mechanism

A

hormone from 2nd gland in the axis affects the 1st gland’s secretion

83
Q

secretion of hypophysiotropic hormones is controlled by

A

neural signals

84
Q

what is the target tissue of FSH and LH

A

gonads…to secrete hormones

85
Q

what is the target tissue of GH

A

liver/many organs….protein synthesis etc

86
Q

what is the target tissue of TSH

A

thyroid….secretion of T3 and T4

87
Q

what is the target tissue of prolactin

A

breasts…development/milk

88
Q

what is the target tissue of ACTH

A

adrenal cortex…for cortisol secretion

physio fall midterm (12 decks)

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