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Endocrinology > Basic Science > Flashcards

Basic Science Flashcards

1
Q

what are exocrine glands

A

glands that excrete a substance via a duct

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2
Q

does the endocrine system involve ducts

A

mostly ductless

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3
Q

what is bulk transport

A

when hormones are carried in bloodstream to reach a target site passing non target sites along the way/ after

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4
Q

what is responsible for endocrine secretion

A

can be either glands or cells

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5
Q

how does a hormone travel

A

is secreted into ECF, diffuses into capillary system, travels in blood stream, diffuses out of blood stream

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6
Q

how is specificity of signalling achieved in the endocrine system

A

chemically distinct hormones

specific receptors for each hormone

distinct distribution of receptors across target cells

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7
Q

what are the four types of hormones

A

modified amino acids
steroids
peptides
proteins

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8
Q

what are modified amino acid hormones derived from, give examples

A

made via modification of amino acids, especially tyrosine

thyroid hormones, adrenaline

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9
Q

what are steroid hormones derived from and give examples

A

from cholesterol

cortisol, progesterone, testosterone

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10
Q

what are peptide hormones derived from and give examples

A

from larger precursor proteins

ACTH, antidiuretic hormone (AHD), oxytocin

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11
Q

give an example of a protein hormone

A

insulin

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12
Q

what is autocrine

A

when a cell signals to itself

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13
Q

what is paracrine

A

when a cell signals to its close neighbours

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14
Q

what is endocrine signalling

A

when the signalling molecule enters the circulation, molecules transported by the blood to target distant cells

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15
Q

hormones can be in very low concentrations in the blood supply- how do organs still respond to them

A

specific receptors have very high
affinity

hormones also have high potency potency

most hormones have effects on more that one target organ- on hormone may have several targets

signal amplified once it binds with receptors via second messenger signalling (a signal transduction cascade)

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16
Q

how is action of a hormone terminated

A

by enzyme-mediated metabolic inactivation in the liver or locally at site of action or is excreted by the kidney

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17
Q

describe the complementary action of hormones

A

when hormones work together to achieve a combine affect

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18
Q

what is the antagonistic action of hormones

A

when a balance is created via two opposing influences

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19
Q

how are amines made and released

A

pre synthesised, stored in vesicles, released in response to stimuli by Ca2+ dependent exocytosis

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20
Q

how are amines transported

A

are hydrophilic so are transported mainly free in plasma

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21
Q

how are peptides and protein made an released

A

pre- synthesised usually from a longer precursor (synthesised at ribosomes of rough ER) broken down by proteolytic steps (by convertase during intracellular transport),

stored in vesicles, released in response to stimuli by Ca2+ dependant exocytosis

22
Q

how are proteins and peptides transported in the blood

A

are hydrophilic so transported mainly free in plasma

23
Q

how are steroid made and released

A

synthesised and secreted upon demand
made from cholesterol via biosynthetic pathways (all via pregnenolone)

no storage immediately secreted following synthesis

24
Q

how do stimuli cause the production and secretion of steroids

A

increase cellular uptake an availability of cholesterol

increase the rate of conversion to pregnenolone (rate limiting step)

25
Q

how are steroids transported

A

are hydrophobic, transported in plasma mainly bound (90%) to plasma proteins

only ‘free’ unbound steroid is biologically active and can cross capillary wall to enter ECF

26
Q

name 3 hormones that are generally insoluble in plasma

A

steroids, thyroxine (T4), triiodothyronine (T3)

27
Q

what is the role of circulating carrier proteins

A

increased amount transported in the blood

provide reservoir of hormone

extend the half life of the hormone in the circulation (long duration of action)

maintain relatively constant concentrations of free lipophilic hormone in the blood (free and bound hormone are in equilibrium)

28
Q

name 3 important specific carrier proteins

A

cortisol binding globulin (CBG)

thyroxine binding globulin (TBG) (bind T4)

sex steroid binding globulin (SSBG) binds mainly testosterone and oestradiol

29
Q

what do albumin and transthyretin do

A

less specific carrier proteins

albumin- steroids and thyroxine

transthyretin- binds thyroxine and some steroids

30
Q

why do proteins and peptides generally have a short duration of action

A

as do not need carrier proteins- are soluble in plasma

31
Q

what is the biophase

A

when hormones pass through the capillary wall

32
Q

how are surges of hormones buffered

A

by circulating carrier proteins- bind to hormones

33
Q

what is the primary determinant of plasma concentration

A

rate of secretion

34
Q

what is the purpose of negative feedback

A

to maintain plasma concentration at a set level

35
Q

what is neuroendocrine- give an example

A

nervous system influencing endocrine system- when a stimulus elicits a sudden burst in secretion- e.g. stress causing release of cortisol in HPA axis

36
Q

is the rate of hormone excretion constant

A

no- in diurnal rhythm- secretion rate fluctuates as a function of time- is entrained to external clues

37
Q

what is the duration of actions of the different types of hormones

A 
amine seconds (as released locally) 
proteins and peptides minutes (before are broken down) 
steroids and thyroid hormones hours to days (extensive protein binding to suppresses elimination)
38
Q

what are the three types of hormone receptors

A

G protein couple receptors

receptor kinases

nuclear receptors (class 1, 2 and hybrid class)

39
Q

what are g protein coupled receptors activated by

A

amine and some proteins and peptides

40
Q

what hormone receptors are on the cell surface (meaning the ligand is hydrophillic)

A

g protein coupled

receptor kinases

41
Q

what activates receptor kinases

A

some proteins/ peptides

insulin

42
Q

what are class 1 nuclear receptors activated by and where are they found

A

steroid hormones

in absence of ligand found in cytoplasm bound to inhibitory heat shock proteins- move to the nucleus when activated

43
Q

what are class 2 nuclear receptors activated by and where are they found

A

lipids mostly

nucleus

44
Q

what are the hybrid class of nuclear receptors activated by and where are they found

A

activated by thyroid hormone T3 and other

moves in similar way to class 1- found in cytoplasm, HSP, move to nucleus

45
Q

as nuclear receptors are intracellular- what must the ligands be

A

lipophillic- allowing diffusion across the plasma membrane

46
Q

what pathways do Gs and Gi G proteins signal by

A

adenylyl cyclase, cAMP and protein kinase A, phosphorylation, cellular effects

47
Q

what pathways do Gq G proteins signal by

A

phospholipase C, protein kinase C (phosphorylation), IP3, calcium released from ER, ceulluar effects

48
Q

what pathways do receptor kinases signal by

A

binding of ligand causes autophosphorylation, recruitment of adapter proteins (e.g. insulin receptor substrate proteins), Akt/PKB. metabolic effects

49
Q

what are nuclear receptors

A

ligand gated transcription factors

50
Q

how do nuclear receptors signal

A

when binds moves to nucleus, forms a dimer, binds to hormone response elements in DNA, transcription of specific genes (alter mRNA levels and rate of synthesis of mediator proteins)

Endocrinology (46 decks)

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