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Flashcards in introduction to endorinology Deck (68):
1

exocrine

epithelial lining forms ducts

2

endocrine

sheets of cells secrete hormones into the bloodstream

3

how is communication between glands & other tissues achieved?

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

4

how is specificity of signalling achieved?

- chemically distinct hormones
- specific receptors for each hormone
- distinct distribution of receptors across target cells

5

hypothalamus

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

6

parathyroid

calcium

7

adrenal gland

aldosterone

8

testes

steroid precursors & testosterone

9

thyroid

thyroxine

10

what are the 3 main classes of chemical natural hormones?

- glycoproteins & peptides
- steroids
- tyrosine & tryptophan derivatives

11

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

glycoproteins & peptide

12

what does the glycoprotein & peptides class encompass?

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

13

give an example of the glycoproteins & peptides

oxytocin
insulin

14

what are steroids derived from?

cholesterol

15

give an example of tyrosine & tryptophan derivatives

adrenaline
thyroid hormones
melatonin

16

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

pre-synthesised stored in vesicles
hydrophilic

17

when are amines released from their vesicles?

in response to stimuli by calcium dependent exocytosis

18

how are amines mainly transported?

"free" in plasma

19

what's special about the vesicles that store hormones?

usually protected from effects of that hormone

20

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

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

21

when are peptides & proteins usually released from their vesicle?

in response to stimuli by calcium dependant exocytosis

22

how are peptides & proteins transported?

"free" in plasma

23

what is the major trigger for the release of insulin?

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

24

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

synthesised & secreted upon demand, hydrophobic

25

what do the stimuli of steroid synthesis increase?

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

26

what is the rate limiting step of steroid synthesis?

the conversion of cholesterol to pregnenolone

27

how are steroids transported?

mainly found to plasma proteins

28

are steroids active when bound to plasma proteins?

no, only "free" is biologically active

29

how soluble are steroids & thyroxine in plasma?

relatively insoluble

30

what do carrier proteins do for steroids & thyroxine?

increase the amount transported in blood
prevent rapid excretion

31

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

prevent filtration at the kidney

32

what does cortisol-binding globulin do?

binds cortisol in a selective manner & some aldosterone

33

what does thyroxin-binding globulin do?

binds thyroxine selectively & some triiodothyronine

34

what does sex steroid-binding globulin do?

binds manly testosterone & estradiol

35

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

binds many steroids & thyroxine

36

what does transthyretin do?

binds thyroxine & some steroids

37

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

they are soluble in plasma

38

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

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

39

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

only free

40

how are surges in hormone secretion buffered?

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

41

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

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

42

what is the primary determinant of plasma concentration?

rate of secretion

43

what does negative feedback do?

maintains plasma concentration at a set level

44

what does tropic mean?

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

45

what does a neuroendocrine mechanism do?

elicits sudden burst in secretion to meet a specific stimulus

46

what does diurnal (circadian) rhythm mean?

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

47

how does elimination occur?

several routes

48

where does metabolism tend to take place?

liver

49

where does excretion tend to take place?

kidneys

50

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

secretion - elimination

51

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

9am, should be at optimum level

52

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

midnight, should be very low

53

name some hormones other than cortisol that exhibit diurnal variation

growth hormone
testosterone

54

when are testosterone levels highest in men?

in the morning

55

what are the 3 types of hormone receptor?

- G-protein coupled receptors (GPCR)
- receptor kinases
- nuclear receptors

56

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

nuclear receptors

57

how are nuclear receptors reached by hormones?

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

58

what are GPCRs activated by?

amines & some proteins/peptides

59

which GPCRs are involved in major signalling pathways?

Gs
Gi
Gq

60

what are receptor kinases activated by?

some proteins/peptides

61

what are nuclear receptors divided into?

class 1
class 2
hybrid class

62

what are class 1 nuclear receptors activated by?

many steroid hormones

63

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

in the cytoplasm bound to inhibitory heat shock proteins

64

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

the nucleus

65

where are class 2 nuclear receptors found?

constitutively present in the nucleus

66

what are class 2 nuclear receptors activated by?

mostly by lipids

67

what are hybrid class nuclear receptors activated by?

thyroid hormone & other symptoms

68

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

class 1