Endocrine Intro Flashcards
(107 cards)
0
Q
“senders” in endocrine system
A
endocrine pancreas, parathyroid glands, pituitary gland, thyroid, adrenal, gonads, placenta
1
Q
Endocrine System
A
communication system
2
Q
“messages” of endocrine system
A
hormones
3
Q
Functions the Endocrine System Controls
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BP, Blood Volume, ECF [electrolyte], RBC production, Blood [Glucose], Growth & Maturation, Repro, Behavior, Immunomodulation, Senescence
4
Q
Homeostasis maintained by..
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Nervous system, immune system, endocrine system
5
Q
Why study the endocrine system?
A
to better understand endocrine diseases, non-endocrine diseases, and how to use hormones as therapies
6
Q
non-endocrine diseases cause problems via
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inappropriate hormone release
7
Q
Hormone
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substance that travels through blood to cause specific response at site OTHER THAN where it was made
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Q
Endocrine Hormone Conveyance
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Bloodstream
9
Q
Neurotransmitter conveyance
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axonal (ie norep)
10
Q
Neuroendocrine conveyance
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bloodstream and axonal
ie. norep
11
Q
Paracrine hormones effect
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neighboring cells
12
Q
Autocrine hromones effect
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the cell that secreted it
13
Q
Endocrine hormones effect
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various target organs at other locations
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Q
Paracrine hormones secreted into
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ECF
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Q
Autocrine hormones secreted into
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ECF
16
Q
Endocrine hormones secreted into
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bloodstream
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Q
Hormones can be…
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paracrine, autocrine or endocrine
ex: insulin
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Q
Insulin’s paracrine effects
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inhibit glucagon secretion by alpha cells
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Q
Insulin’s autocrine effect
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regulates growth and function of beta cells
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Q
Insulin’s endocrine effect
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glucose uptake for systemic organs
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Q
3 Classifications of Hormones
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- Proteins
- Steroids
- Amines (‘exceptions’)
22
Q
Amines are
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tyrosine derivatives.
“exceptions”/”hybrids of steroids & proteins”
-catecholamines & thyroid hormones
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Q
Protein Hormone Structure
A
chains of specific amino acids
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Protein/Peptide Solubility
hydrophilic
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Protein/Peptide Synthesis
rough ER and packaged in Golgi
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Protein/Peptide Storage
cytoplasmic secretory granules
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Clinical significance of protein/peptide storage in granules
can't regulate synthesis but can regulate release etc.
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Protein/Peptide Secretion
exocytosis of granules
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Protein/Peptide Transport in Blood
unbound, free hormone
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Protein/Peptide Receptor Site
surface of target cell b/c can't pass through alone
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Protein/Peptide Mechanism of Action
channel changes or activation of 2nd messenger systems
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Protein/Peptide Hormones
include those made in hypothalamus, pituitary, pineal, pancreas, parathyroid, GIT, liver, kidneys, heart
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Protein/Peptide Half-Life
short!
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Protein/Peptide Clearance
- small mount of small proteins in urine (degraded in kidney)
- endocytosis of receptor-hormone complexes & lysosomal degradation
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Protein/Peptide Route of Administration
injection! b/c it'll be degraded in GI w/ other proteins you eat
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Steroid Hormone Structure
cholesterol derivative
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Steroid Hormone Solubility
hydrophobic (lipophilic)
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Steroid Hormone Synthesis
ovaries, testes, placenta, adrenal CORTEX
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Steroid Hormone Storage
not stored in cell (cholesterol precursor is stored), meaning we can regulate their synthesis
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Steroid Hormone Secretion
can cross cell membrane
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Steroid Hormone Transport in Blood
bound to transport proteins, albumin
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Steroid Hormone receptor site
inside a target cell b/c don't need a receptor outside the cell
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Steroid Hormone Mechanism of Action
alters gene expression
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Steroid Hormone Types
progestins, androgens, estrogens, testosterone, minceralocorticoids (aldosterone), glucocorticoids, active Vit. D
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Steroid Hormone Half-life
long!
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Steroid Hormone clearance
liver and kidney
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Steroid Hormone Route of Administration
can give orally b/c they're lipids
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Why are Steroid Hormone half lives so long?
because they're bound to transport proteins which inactivates them and makes them harder to break down
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Types of Amine Hormones
1. Catecholamines
| 2. Iodothyronines
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Catecholamine Structure
tyrosine derivative
| protein like
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Catecholamine Solubility
hydrophilic
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Catecholamine synthesis
adrenal MEDULLA or neurons
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Catecholamine storage
cytoplasmic secretory granules
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Catecholamine secretion
exocytosis of granules
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Catecholamine transport in blood
unbound or loosely bound to albumin
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Catecholamine receptor site
surface of target cell
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Catecholamine mechanism of action
channel changes or activation of 2nd messenger systems
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Catecholamine types
epinephrine, norepinephrine, dopamine
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Catecholamine half-life
short
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Catecholamine clearance
uptake (w/ receptor into cell), enzymatic conversion
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Catecholamine route of administration
injection
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Iodothyronines structure
iodinated tyrosine derivative
| steroid-like
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Iodothyronines solubility
hydrophobic (lipophilic)
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Iodothyronines synthesis
thyroid
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Iodothyronines storage
in thyroid as colloid, acts as a reservoir
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Iodothyronines secretion
can cross cell membrane
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Iodothyronines transport in blood
bound to transport proteins (TBG) & inactive when bound, and to albumin
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Iodothyronines receptor site
inside target cell
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Iodothyronines mechanism of action
alters gene expression
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Iodothyronines types:
T3, T4
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Iodothyronines half-life
long (relatively speaking) with species differences
- in dog, T3 = 6 hrs, and T4 = 10-16 hrs
- in ppl, T3 = 6 hrs, and T4 = 7 days
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Iodothyronines clearance
deiodination, liver & kidney
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Iodothyronines route of administration
can give orally
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Endocrine Axis (cascade)
stress signal -> hypothalamus -> hormone released -> pituitary gland -> tropic hormone released -> peripheral endocrine gland -> hormone (cortosol +) released -> hormone goes to target organ - physiologic effect
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Negative feedback in endocrine system
occurs from [HORMONE] not physiologic response
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Patterns of secretion
circadian, ultradian, seasonal,
| -some pituitary hormones are secreted in PULSE that cycle every 2-20 min (esp protein ones)
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What determines patterns of hormone secretion?
genetically encoded or acquired.
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circadian rhythms
once daily
| endogenously generated by cues like light, feeding, activity, sleep
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ultradian rhythms
occurs multiple times a day
| (diurnal rhythms are day-night)
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seasonal rhythms
control breeding, hybernation, & migration behaviors
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The types of secretion patterns and knowing which hormones are pulsatile and important to know because
hormone levels can help us diagnose but we need to know these levels change throughout the day
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Relative Plasma Concentrations of Hormones
Cortisol and ADH (Vasopressin) are present in very low amounts and still can cause big effects
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Lipid Soluble Hormones (steroids and thyroid hormones) & entering cells
must dissociate with plasma protein to enter cells
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protein bound lipid soluble hormones serve as
a RESERVOIR to replenish free hormone when it enters a cell & binds to receptor
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Methods of Hormone Clearance
- metabolism in tissues
- binding in tissues
- excretion by liver (bile)
- excretion by kidney (urine)
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Hormone Clearance
"cleaning the plasma"
| rate of removal of hormone from the blood
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Hormone receptors
- VERY SPECIFIC for one and only 1 hormone
| - the amount changes constantly
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Ligand-Receptor Interaction
- one hormone binding to one receptor can cause enough amplification of signaling to achieve maximum effect
- one hormone-receptor binding can activate MULTIPLE pathways & cause multiple effects
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Peptide Hormones and Catecholamines
act as extracellular signals generating altered cellular processes
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Steroid hormones and Iodothyronines act
as intracellular signals and change gene expression
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Hormone Receptor Types
1. Ion Channel-Linked
2. G Protein-Linked
3. Enzyme-Linked
4. Intracellular
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Ion channel-linked receptors
open or close an ion channel when activated
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G Protein-Linked Receptors
- activated receptors cause activation of a G protein in cell membrane which initiates intracellular signals leading to physiologic effect
- G proteins can be stimulatory or inhibitory
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Enyzme-Linked Receptors
when activated, function directly as enzymes
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Intracellular Receptors
located in cytoplasm or nucleus & when activated cause protein synthesis or gene transcription
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After a receptor is activated,
the second messenger systems are activated
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Types of 2nd Messenger Systems
Adenylyl Cyclase-cAMP
Cell Membrane Phospholipid
Caclium-Calmodulin
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Adenylyl Cyclase cAMP Steps
1. Hormone binds to G protein-linked receptor
2. Stimulatory G protein activates adenylyl cyclase
3. Adenylyl cyclase converts ATP to cAMP
4. cAMP activates enzyme cascade in cell
5. Cell's response to hormone is achieved
(opposite for inhibitory G protein from Steps 2-5)
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Cell Membrane Phospholipid Steps:
1. Hormone binds to enzyme-linked receptor
2. Phospholipase C is activated
3. Phospholipase C catalyzes breakdown of membrane phospholipids into IP3 and DAG
4. IP3 mobilizes Ca2+
5. DAG activates Protein Kinase C which activates many proteins
6. Cell's response to hormone is achieved by steps 4 & 5
(how a receptors work)
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Calcium-Calmodulin Steps as 2nd Messenger:
1. Hormone binds to ion channel-linked receptor (or voltage channel opens ion channel)
2. Ca enters cell & binds to Calmodulin
3. Calmodulin activated
4. Calmodulin activates/inhibits protein kinases
5. Cell's response to hormone is achieved.
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What influences receptor expression numbers on a cell
- genetically controlled expression
- other factors (disease, ligand binding, etc) that alter sensitivity of cell by altering number of expressed receptors
- tissue type
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Pathologic Up regulation of receptors
adrenergic receptors in hyperthyroidism
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Pathologic Down regulation of receptors
insulin receptors in Type 2 Diabetes
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Decreased responsiveness
decreased response at same CONCENTRATION as normal response
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Normal response
gives maximum response with hormone concentration
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decreased sensitivity
same response at a HIGHER concentration than normal
