Endocrinology intro Flashcards
1
Q
define and features: hormones features
A
- first messengers
- released from endocrine cells into interstitial fluid -> diffuse into blood
- alter function of target cells, which have receptor proteins for particular hormone
2
Q
define and features: receptors
A
- maybe transmembrane protein (hydrophilic hormone)
- or cytoplasm/ nucleus (lipophilic hormone)
3
Q
define and features: agonists
A
- ligands (chemicals) that bind to receptors
- produce SAME effect as hormone
4
Q
define and features: antagonists
A
- bind to receptor
- prevent function of hormones
5
Q
define and features: signal transduction and eg.
A
- binding of hormone to receptor initiates 2˚ messenger sys within cells
- 2˚ messengers (Ca ions, cAMP etc.) constituents of cellular pathways producing hormonal effects within cell
6
Q
hormone function: main functions
A
- along w ANS maintain homeostasis
- growth
- reproduction
7
Q
hormone function: controlling plasma glucose eg (5)
A
- also aa, free fatty acids by
- insulin
- glucagon
- Ad
- cortisol
- growth hormone
8
Q
hormone function: control BP eg. (4)
A
- Ad
- angiotensin II
- aldosterone
- atrial natriuretic peptide (ANP)
work w ANS
9
Q
hormone function: plasma osmolarity eg. (1)
A
- aka water balance
- antidiuretic peptide
10
Q
hormone function: GIT eg. (3)
A
- ANS
- enteric NS
peptide hormones:
- gastrin
- secretin
- cholecystokinin (CCK)
- many more
11
Q
hormone function: appetite eg. (3) and affect what part (3)
A
- leptin
- ghrelin
- CCK
- etc
- arcuate nucleus
- nucleus accumbens (hypothalamus)
- nucleus of solitary tract (NTS) in brain stem
12
Q
hormone function: physical stress response eg. (2) and hormones (4)
A
- Ad
- cortisol
- glucagon
- growth hormone
eg. hypoglycaemia, physiological
13
Q
hormone function: long term stress
A
cortisol
14
Q
hormone function: growth and dev eg. (2)
A
- growth hormone
- somatomedins (IGF1)
15
Q
hormone function: production of sperm, ova (5)
A
- oestrogen
- progesterone
- testosterone
- follicle stimulating hormone
- luteinising hormone
16
Q
hormone secretion as 2˚ function of organ eg. (4)
A
- heart
- kidneys
- adipose tissue
- skeletal mm
17
Q
peptide hormones: features
A
- usually produced in series of steps from precursor protein
18
Q
peptide hormones: eg. insulin
A
- produced from preproinsulin (2x internal sulphide bonds for 3˚ structure)
- signal sequence removed = proinsulin
- internal portion of protein molecules removed = insulin
19
Q
peptide hormones: sig of signal sequence for insulin
A
- directs proteins that are to be secreted to endoplasmic reticulum for further processing
20
Q
peptide hormones: POMC eg.
A
- precursor of many peptide hormones (pro-opiomelanocortin) POMC
- found in pituitary cells, various cels in hypothalamus
- cleaved to prod diff biologically active peptides
- product depends on proteases/peptidases in cell
21
Q
peptide hormones: POMC inside ant pituitary cell result
A
- produce ACTH
- causes cortisol release from adrenal gland
22
Q
peptide hormones: POMC inside hypothalamus prod
A
- å MSH (appetite control)
23
Q
peptide hormones: POMC released in other areas of brain prod
A
- endogenous opioid ß endorphin
24
Q
peptide hormones: stored in
A
- membrane bound vesicles
- when triggered released by exocytosis (fusing of vesicle membrane w plasma membrane)
- peptides r hydrophilic, transported dissolved in plasma
25
peptide hormones: growth hormone (GH) sig
- hydrophilic peptide
| - travels to plasma bound to protein cleaved from membrane-bound GH receptor, acts like carrier protein
26
peptide hormones: function of GH carrier
- bound in circulation
- reg conc fo free (active form) and bound GH
- prolong GH half life in plasma
- modulate GH bioactivity through competition w membrane bound receptors
27
catecholamines:
- hormones prod from peptide tyrosine
- incl dopamine, Ad, NAd
- like peptide hormones: stored in membrane bound vesicles
- released by exocytosis
- hydrophilic
- transported dissolved in plasma
28
mechanism for control of cell function by hormones: features
- can't cross cell membranes
- act by binding to receptor inserted within plasma membrane of target cells
- activation and initiates chain of reaction within cell (signal transduction)
- eg. peptide hormones regulate transcription of particular genes in nucleus, therefore alter rate of prod of specific proteins
29
mechanism for control of cell function by hormones: message generation involves
- activation of enzymes within cytoplasm = prod biological response
30
mechanism for control of cell function by hormones: ligand gated ion channels features
- hormone receptors can be ion channels (eg. transporting Na, K, Cl, Ca) inserted into cell membrane, binding of hormone open/closes channel
- affects cell by changing electrical properties of cells
31
mechanism for control of cell function by hormones: eg. Ca ligand gated channels
- allow influx of EC Ca and increase in cytoplasmic Ca is cellular signal
- when enter cell, many effects: change electrical properties of cells, causing mm contraction
- secretion by exocytosis
32
mechanism for control of cell function by hormones: protein kinases (Ca bound)
- Ca bound to cellular protein calmodulin also activate class of enzymes: protein kinases
- they add phosphate groups (HPO4-) cont from ATP to enzymes
- activate/ inhibit function of particular enzymes, alter cell metabolism
33
mechanism for control of cell function by hormones: kinase enzymes incl tyrosine kinase receptor
- vital part of membrane receptor protein in plasma membrane
- eg. tyrosine kinase receptor
- hormone binds to receptor, kinase phosphorylates tyrosine aa = cause multiple effects
34
G proteins: mechanism
- peripheral proteins (INNER surface)
- no hormone present: guanosine disphosphate (GDP) bound to G protein
- hormone attached to receptor: 'regulatory' subunits (ß and gamma) detach,
- guanosine triphosphate (GPT) bind to active å subunit
- activated subunit will alter function of another membrane bound protein (channel, or adenylate cyclase)
35
G proteins: adenylyl/ adenylate cyclase features
- converts cytoplasmic ATP into cyclic AMP (cAMP)
| - cAMP activates kinase enzyme (protein kinase A)
36
phospholipase C: features and activated mechanism
- å subunit GPT complex also bind to phospholipase C: integral protein embedded in plasma membrane
- when activated breaks membrane phospholipid PIP2 into IP3: dissolves cytoplasm
- DAG retains 2 hydrophobic C-H chains
- remains within lipid bilayer of membrane
37
phospholipase C: when IP3 binds to Ca channels
- in membrane of endoplasmic reticulum (SR in mm) opens and releases Ca stored within organelle
- increased Ca conc. many cell metabolism effects
38
phospholipase C: DAG activates
- in membrane activates protein kinase C
| - will phosphorylate to alter functional state of cell
39
phospholipase C: Ad and glucagon in G protein mediated pathway
- in liver cell
- increase conc glucose in plasma
- Ad binds to ß adrenergic receptors , G protein dissociates, å subunit binds GTP activates adenylate cyclase
- cAMP prod activating protein kinase A, phosphorylates glycogen phosphorylase (enzyme converting glycogen (stored glucose) to glucose)
40
peptide hormones, catecholamines, gene transcription: list peptide hormones (3)
- insulin
- glucagon
- GH
- others
41
peptide hormones, catecholamines, gene transcription: features
- peptide hormones, catecholamines change lvls of cell proteins (enzymes, transport proteins) by altering DNA transcription in nucleus
42
peptide hormones, catacholamines, gene transcription: glucagon release eg.
- released due to low plasma glucose
- glucagon binds to receptors on plasma membrane of liver cells
- initiates sequence ultimately activating protein kinase A
43
peptide hormones, catacholamines, gene transcription: protein kinase A for glucagon
- activates enzymes already in cytoplasm, releasing glucose from glycogen
- cAMP also releases catalytic subunits from PKA
- enter nucleus and phosphorylate transcription factors esp cAMP response element binding protein (CREB)
- transcription of genes for enzymes needed: gluconeogenesis
44
peptide hormones, catacholamines, gene transcription: sig of glucagon
- increases plasma glucose rapidly through glycogenesis
- by activating enzymes already present in plasma
- slowly upreg prod of proteins that produce glucose via gluconeogenesis
45
peptide hormones, catacholamines, gene transcription: gluconeogenesis general
- making new glucose from substances such as lactate and certain aa
46
peptide hormones, catacholamines, gene transcription: why need intermediate reactions- hormone binding to effects?
- multiple steps
- control many diff functions and pathways within one cell by 1 hormone
- amplify signal initiates by binding of hormones
- so messenger molecules lead to phosphorylation of millions of proteins
47
steroid hormones: features
- hormones prod from cholestrol: hydrophobic, lipophillic
- can cross lipid bilayers/ cell membranes
- can't be stored in vesicles
48
steroid hormones: rate of release
- depends on rate of synthesis from cholesterol
- derived directly from LDLs (low density lipoproteins) in plasma or
- stockpiled cholesterol esters that are lipophobic = can be stored in vesicles within cells
49
steroid hormones: bound hormones
- can't dissolve in plasma, carried bound to protein (binding globulins)
- bound hormone buffers conc of free hormone (active form)
- amount of free hormone depends on conc of hormone, conc of carrier, affinity of carrier for hormone
50
thyroid hormones: features
- hydrophobic, lipophilic containing iodine
- 90% output in form of T4 (thyroxin, tetra iodothyronine), remainder= T3 (triiodthryonine)
- thyroxine binding globulin binds T3/4 to allow hormones be dist by plasma
- maintains lrg reservoir of T4 and prevent loss through kidney (preserves iodine)
- active form T3 9even T4 changed to this) converted in periphery usually by target cells
51
steroid/thyroid hormones: mechanism for cell function- features
- hormone diffuses through lipid bilayer and bind to receptor molecules in cytoplasm/ nucleus
- hormone receptor complex (HR) bind to hormone response element (HRE) where specific DNA sequence located near promoter region of gene
- once bound to HRE, HR recruits co-activators: alter chromatin structure to unravel DNA from histones, expose it to transcription factors
- co-activator activates transcription factor to increase pord of mRNA required for prod of desired protein
52
steroid/thyroid hormones: mechanism for cell function- eg. aldosterone
- most aldosterone carrier bound in plasma
- crosses plasma membrane of cells of distal tubule, connecting duct to kidney
- once inside, binds to carrier protein
- hormone receptor complex enters nucleus where binds to HRE in DNA
- complex upreg transcription of mRNA for mitochondrial enzymes (more ATP), Na/K exchange pump proteins, luminal Na and K channels
= more Na reabsorbed by kidney while more K is excreted
