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ENDOCRINOLOGY > 3. Principles of Hormone Action > Flashcards

3. Principles of Hormone Action Flashcards

1
Q

what are HORMONES

A
  • one type of FIRST (or PRIMARY) MESSENGER
  • molecules that have an effect on specific organs
  • called TARGET ORGANS
  • only cells with SPECIFIC RECEPTORS for the hormone will respond to the
    hormone
  • called TARGET CELLS
  • organs, tissues or cells lacking the specific receptors do not respond to
    the stimulating effects
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2
Q

what are the 4 CLASSIFICATIONS of HORMONES

A
  1. Lipid-Derived Hormones (Lipid-soluble)
  2. Amino acid derivative hormones
  3. Peptide hormones (hydrophilic)
  4. Chemical messengers derived from fatty acids (eicosanoids)
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3
Q

what is the primary class of LIPID HORMONES

A

STEROID HORMONES

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4
Q

most LIPID HORMONES are DERIVED from…

A

CHOLESTEROL

  • thus have a similar structure to it
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5
Q

examples of LIPID HORMONES

A
  • SEX-HORMONES
    (androgens, estrogens and progesterone)
  • Hormones produced in ADRENAL GLANDS
    (Glucocorticoids and mineralocorticoids)
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6
Q

FUNCTIONS of LIPID HORMONES include (3):

A
  • WATER BALANCE
  • SEXUAL DEVELOPMENT
  • STRESS RESPONSE
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7
Q

AMINO ACID DERIVATIVE HORMONES are SMALL molecules commonly DERIVED from.. (2)

A

TYROSINE &
TRYPTOPHAN

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8
Q

examples of AMINO ACID DERIVATIVE HORMONES (2)

A
  • THYROID hormone (lipid-soluble)
  • CATECHOLAMINES (water-soluble)
    eg noradrenalin, adrenalin
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9
Q

FUNCTIONS of AMINO ACID DERIVATIVE HORMONES include:

A
  • Thyroid hormone regulates the development of organs
    and metabolism.
  • Noradrenaline and adrenaline (catecholamines) increase
    heart rate, dilate blood vessels and cause the release of glucose during times of stress
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10
Q

PEPTIDE HORMONES (hydrophilic) are…

A

CHAINS OF AMINO ACIDS (short or long)

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11
Q

most HORMONES are..

A

PEPTIDE HORMONES

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12
Q

examples of PEPTIDE HORMONES

A

FSH (small)
INSULIN (large)

PROLACTIN
GROWTH HORMONE
VASOPRESSIN
(pituitary)
ANP (which is produced by the heart -regulates homeostasis of the circulatory
system; released in response to high blood pressure and dilation of the atrium.)

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13
Q

CHEMICAL MESENGERS derived from FATTY ACIDS
- EICOSANOIDS
are synthesised from..

A

ARACHIDONIC ACID
- 20-CARBON AMINO ACID

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14
Q

CHEMICAL MESENGERS derived from FATTY ACIDS
- EICOSANOIDS…

A
  • DEGRADE very EASILY
  • do NOT GO FAR from production site
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15
Q

unique characteristic of CHEMICAL MESENGERS derived from FATTY ACIDS
- EICOSANOIDS

A

they are produced and secreted by
NEARLY EVERY CELL in the body instead of just one gland.

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16
Q

example of a CHEMICAL MESENGERS derived from FATTY ACIDS
- EICOSANOIDS

A

PROSTAGLANDIN

  • Prostaglandins have a wide variety of functions ranging from
    uterine contractions to
    bronchodilation, inflammation and fever

(Aspirin acts on prostaglandins to reduce pain and fever)

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17
Q

various roles of EICOSANOIDS include

A

inflammation,
blood pressure
blood clotting

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18
Q

Endocrine, paracrine and autocrine

A

-paracrine signalling is
when NEIGHBOURING CELLS signal to each other

  • Autocrine signalling is
    when a cell sends signals to ITSELF
  • endocrine signalling uses the CIRCULATORY SYSTEM to transport ligands
19
Q

Binding of a ligand to a receptor changes…

A

changes its SHAPE or ACTIVITY

  • allowing it to transmit a SIGNAL or directly
    produce a CHANGE inside of the cell
20
Q

RECEPTORS can be divided into 2 categories:

A
  • INTRACELLULAR RECEPTORS
    (inside of the cell - in the cytoplasm or
    nucleus)
  • CELL SURFACE RECEPTORS
    (embedded in the plasma membrane)
21
Q

What type of molecules reach INTRACELLULAR RECEPTORS

A

HYDROPHOBIC signalling molecules (ligands)

  • DIFFUSE through plasma membrane
22
Q

RECEPTORS function as..

A

ligand-dependent TRANSCRIPTION FACTORS

23
Q

how do RECEPTORS function as ligand-dependent TRANSCRIPTION FACTORS?

hormone-receptor complex binds to…

A
  • the hormone-receptor complex BINDS to PROMOTER REGIONS of responsive GENES and STIMULATE/INHIBIT TRANSCRIPTION
  • SELECTIVELY affecting TRANSCRIPTION of genes
  • CONCENTRATIONS of respective PROTEINS ALTERED
    -CHANGE IN PHENOTYPE OF CELL
24
Q

3 main components of CELL-SURFACE RECEPTORS

A
  1. An external ligand binding domain- extracellular domain
  2. A hydrophobic membrane spanning region
  3. Intracellular domain inside the cell
25
Q

3 types of CELL-SURFACE RECEPTORS

A
  • G PROTEIN-LINKED
  • ENZYME-LINKED
  • ION CHANNEL-LINKED
26
Q

What happens when a ligand binds to a G-PROTEIN COUPLED RECEPTOR

A
  • G-PROTEIN IS ACTIVATED (membrane protein)

eg used by Catecholamines

27
Q

what does an INACTIVE G-PROTEIN have on its ALPHA subunit

A

GDP

28
Q

What happens when a G-Protein is activated

A
  • ALPHA SUBUNIT swaps GDP for GTP

ALPHA subunit dissociates from the BETA and GAMMA subunits and triggers a cellular response

29
Q

What does the GTP-BOUND ALPHA SUBUNIT do after dissociating from other G-protein subunits

A
  • BINDS to and ACTIVATES ADENYLATE CYCLASE
  • activated adenylate cyclase catalyses CONVERSION of ATP to CAMP and PYROPHOSPHATE
  • cAMP ACTIVATES PROTEIN KINASE A (secondary messenger) which PHOSPHORYLATES and activates other proteins and triggers further responses
30
Q

how does the alpha-subunit return to its original place on inactivated G-protein

A

GTP HYDROLYSED to GDP
- signalling molecule comes off the receptor

Alpha subunit comes back together with the receptor and beta and gamma subunits

31
Q

What are ENZYME-LINKED RECEPTORS

A

Cell-surface receptors with intracellular
domains that are associated with an
ENZYME

  • Normally have large extracellular and
    intracellular domains
  • When a ligand binds to the extracellular
    domain, a signal is transferred that
    ACTIVATES THE ENZYME component of the
    receptor which leads to a response

eg. Insulin binding to tyrosine-kinase receptor

32
Q

what happens when a ligand binds to an ION-CHANNEL LINKED RECEPTOR

A

CONFORMATIONAL CHANGE in the STRUCTURE
- allows IONS to PASS THROUGH

eg. neurons

33
Q

what happens when Ions pass through ION CHANNEL- LINKED RECEPTOR

A

Change the ACTIVTY of ION-BINDING ENZYMES and VOLTAGE-SENSITIVE CHANNELS
- to produce a response

34
Q

multiple hormones can…

A

utilize the same second messenger system

35
Q

a single hormone can…

A

utilize more than one second messenger system

36
Q

what do we get in DOWN-REGULATION of RECEPTORS

A

LINGAND-INDUCED DESENSITIZATION
or INTERNALIZATION of receptor

37
Q

How do you get DOWN-REGULATION of RECEPTORS

A

Receptors CHRONICALLY EXPOSED to an EXCESSIVE AMOUNT of a LIGAND

(endogenous mediators or from exogenous drugs)

38
Q

what is UP-REGULATION of RECEPTORS

A

SUPER-SENSITIZED CELLS

  • cell makes extra receptors on the surface (so any small amount of that ligand can bind)
39
Q

how do you get UP-REGULATION of RECEPTORS

A
  • REPEATED EXPOSURE to an
    ANTAGONISTIC DRUG
    or
  • PROLONGED ABSENCE of the
    LIGAND
40
Q

What do RECEPTOR AGONISTS cause

A

DOWN-REGULATION of their respective receptor

41
Q

What do RECEPTOR ANTAGONISTS cause

A

UP-REGULATION of their respective receptor

may also damage receptors faster than they upregulate
(internalization of receptors due to antagonism)

42
Q

How are hormones secreted (pattern)

A

Hormone secretion often follows a
RHYTHM or is PULSATILE

secreted in a burst-like or episodic
manner rather than constantly.

43
Q

how is melatonin secretion (pattern)

A

Melatonin secretion is related to the
length of the NIGHT

Also melatonin profiles show a SEASONAL pattern (increased production in winter)

44
Q

example of DIRECT and INDIRECT EFFECTS of hormones
eg growth hormone

A

DIRECT EFFECTS:
growth hormone binds to GH Receptors on Fat Cells, stimulating break down of triglycerides

INDIRECT EFFECTS:
Insulin-like Growth Factor-I (IGF-I) secreted in response to GH. The majority of the growth promoting effects of
GH are actually due to IGF-I acting on its
target cells.

ENDOCRINOLOGY (11 decks)

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