introduction to endorinology Flashcards

1
Q

exocrine

A

epithelial lining forms ducts

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2
Q

endocrine

A

sheets of cells secrete hormones into the bloodstream

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3
Q

how is communication between glands & other tissues achieved?

A

but the secretion of a hormone into the blood stream & transport to a target site

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4
Q

how is specificity of signalling achieved?

A
  • chemically distinct hormones
  • specific receptors for each hormone
  • distinct distribution of receptors across target cells
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5
Q

hypothalamus

A

highest level of the endocrine system, major centre of pituitary control

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6
Q

parathyroid

A

calcium

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7
Q

adrenal gland

A

aldosterone

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8
Q

testes

A

steroid precursors & testosterone

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9
Q

thyroid

A

thyroxine

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10
Q

what are the 3 main classes of chemical natural hormones?

A
  • glycoproteins & peptides
  • steroids
  • tyrosine & tryptophan derivatives
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11
Q

which is the most diverse class of the chemical natural hormones?

A

glycoproteins & peptide

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12
Q

what does the glycoprotein & peptides class encompass?

A

amino acid chains of variable length, can be simple or contain disulphide bonds or be multiple chains

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13
Q

give an example of the glycoproteins & peptides

A

oxytocin

insulin

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14
Q

what are steroids derived from?

A

cholesterol

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15
Q

give an example of tyrosine & tryptophan derivatives

A

adrenaline
thyroid hormones
melatonin

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16
Q

describe the synthesis, storage and attitude to water of amines?

A

pre-synthesised stored in vesicles

hydrophilic

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17
Q

when are amines released from their vesicles?

A

in response to stimuli by calcium dependent exocytosis

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18
Q

how are amines mainly transported?

A

“free” in plasma

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19
Q

what’s special about the vesicles that store hormones?

A

usually protected from effects of that hormone

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20
Q

describe the synthesis, storage and attitude to water of peptides & proteins?

A

pre-synthesised usually from a longer precursor & stored in vesicles, hydrophilic

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21
Q

when are peptides & proteins usually released from their vesicle?

A

in response to stimuli by calcium dependant exocytosis

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22
Q

how are peptides & proteins transported?

A

“free” in plasma

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23
Q

what is the major trigger for the release of insulin?

A

the sensing of glucose in the intracellular space between beta cells of the pancreas

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24
Q

describe the synthesis, storage and attitude to water of steroids?

A

synthesised & secreted upon demand, hydrophobic

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25
Q

what do the stimuli of steroid synthesis increase?

A

increase cellular uptake & availability of cholesterol & increase the rate of conversion of cholesterol to pregnenolone

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26
Q

what is the rate limiting step of steroid synthesis?

A

the conversion of cholesterol to pregnenolone

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27
Q

how are steroids transported?

A

mainly found to plasma proteins

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28
Q

are steroids active when bound to plasma proteins?

A

no, only “free” is biologically active

29
Q

how soluble are steroids & thyroxine in plasma?

A

relatively insoluble

30
Q

what do carrier proteins do for steroids & thyroxine?

A

increase the amount transported in blood

prevent rapid excretion

31
Q

how do plasma proteins prevent rapid excretion of steroids & thyroxine?

A

prevent filtration at the kidney

32
Q

what does cortisol-binding globulin do?

A

binds cortisol in a selective manner & some aldosterone

33
Q

what does thyroxin-binding globulin do?

A

binds thyroxine selectively & some triiodothyronine

34
Q

what does sex steroid-binding globulin do?

A

binds manly testosterone & estradiol

35
Q

what does albumin do in terms of being a carrier protein?

A

binds many steroids & thyroxine

36
Q

what does transthyretin do?

A

binds thyroxine & some steroids

37
Q

why do proteins & peptides not require carrier proteins for transport?

A

they are soluble in plasma

38
Q

what do carrier proteins do altho helps maintain relatively constant concentrations of free lipophilic hormone in the blood?

A

act as buffer & reservoir, free & bound hormone are in equilibrium

39
Q

can free or bound hormone cross the capillary wall to activate receptors in target tissue?

40
Q

how are surges in hormone secretion buffered?

A

by binding to carriers, free concentration then doesn’t rise abruptly

41
Q

how is free hormone removed from plasma & what is it replaced by?

A

removed by elimination & replaced by bound hormone dissociating from carrier protein

42
Q

what is the primary determinant of plasma concentration?

A

rate of secretion

43
Q

what does negative feedback do?

A

maintains plasma concentration at a set level

44
Q

what does tropic mean?

A

a hormone that acts upon another endocrine gland to regulate its secretion of hormone

45
Q

what does a neuroendocrine mechanism do?

A

elicits sudden burst in secretion to meet a specific stimulus

46
Q

what does diurnal (circadian) rhythm mean?

A

secretion rate fluctuates up & down as a function of time, entrained to external cues

47
Q

how does elimination occur?

A

several routes

48
Q

where does metabolism tend to take place?

49
Q

where does excretion tend to take place?

50
Q

how can the plasma concentration of a hormone be described in terms of secretion & elimination

A

secretion - elimination

51
Q

when should cortisol levels be checked if a deficiency is suspected?

A

9am, should be at optimum level

52
Q

when should cortisol levels be checked if an excess (cushing’s syndrome) is suspected?

A

midnight, should be very low

53
Q

name some hormones other than cortisol that exhibit diurnal variation

A

growth hormone

testosterone

54
Q

when are testosterone levels highest in men?

A

in the morning

55
Q

what are the 3 types of hormone receptor?

A
  • G-protein coupled receptors (GPCR)
  • receptor kinases
  • nuclear receptors
56
Q

which of the 3 types of hormone receptor is found intracellularly?

A

nuclear receptors

57
Q

how are nuclear receptors reached by hormones?

A

the ligand of the hormone is lipophilic so can diffuse across the plasma membrane of cells

58
Q

what are GPCRs activated by?

A

amines & some proteins/peptides

59
Q

which GPCRs are involved in major signalling pathways?

60
Q

what are receptor kinases activated by?

A

some proteins/peptides

61
Q

what are nuclear receptors divided into?

A
class 1 
class 2
hybrid class
62
Q

what are class 1 nuclear receptors activated by?

A

many steroid hormones

63
Q

in the absence of activating ligand, where are class 1 nuclear receptors mainly located?

A

in the cytoplasm bound to inhibitory heat shock proteins

64
Q

where do class 1 nuclear receptors move to in the presence of an activating ligand?

A

the nucleus

65
Q

where are class 2 nuclear receptors found?

A

constitutively present in the nucleus

66
Q

what are class 2 nuclear receptors activated by?

A

mostly by lipids

67
Q

what are hybrid class nuclear receptors activated by?

A

thyroid hormone & other symptoms

68
Q

hybrid class nuclear receptors function is similar to which other class?