C16 17-21 Flashcards
How is growth hormone regulated?
Hypothalamus (GHRH) –> Ant.Pit (GH) –> Liver and other tissues (IGFs) –> Skeletal/Extraskeletal.
IGF and GH feedback stimulate the release of GHIH and inhibit the release of GHRH from the hypothalamus. GH release is then inhibited.
Growth hormone has both ________ systems?
Direct and indirect. Works directly (metabolic/anti-insulin) to break down fat and increase blood glucose. Indirectly (IGF/liver) growth.
Pathway to target cells of TH
Hypothalamus –> Anterior pituitary –> Thyroid gland –> Target cells (stimulates)
High TH levels inhibit the ant pituitary and hypothalamus.
Effects of TH?
- Increase metabolism: Increase basal metabolic ratewhich increases heat production (calorigenic).
- Many permissive effects: ie TH promotes the synthesis of beta adregenic permitting tissues to respond to E/NE.
- Increase Cardio/gastro/nueromuscular function.
Regulate tissue growth and development.
Maintain BP by increasing the number of adregenic receptors in blood vessels.
Note: TH does not raise the metabolic rate of the retina/spleen/testes/lungs.
Why the release of 90% T4 vs. 10% T3?
So each tissue can self-regulate - tissues can convert T4 to T3 if they need the more powerful version (T3 binds more avidly and is 10x more active.)
T3 binds to a nuclear receptor resulting in transcription of specific thyroid responsive genes.
Calcitonin?
Inhibits osteoclasts.
Is produced by C cells/parafollicular cells of thyroid.
Response to high levels of Ca2+.
How is TH transported and regulated?
Transport: carrier proteins produced by the liver. Immediately binds to TGBs when released.
Regulation: Falling TH levels stimulate the release of TSH. Rising levels shut off the stimulus for TSH.
Where are the adrenal glands?
Superior and medial to the kidneys (aka suprarenal glands)
Structure of the adrenals?
Comprised of adrenal medulla/20%/neural tissue and adrenal cortex/80%/3 layers epithelial
3 layers of adrenal cortex?
Zona glomerulosa - fascisulata - reticularis. Aldosterone in glomer, cortisol and adrogens in fasc and retic.
Function of adrenals? (release)
Medulla - release E/NE/Dop.
Cortex - Corticosteroids (mineralcorticoids, glucosteroids, gonadocorticoids).
Cortisol?
Raises blood glucose, fatty acid and amino acid levels in attempt to resist stress and help repair injured tissues.
PTSD associated with?
Increased cortisol release and activation of ANS.
Mineralcorticoids
Regulation of extracellular electrolytes. ALDOSTERONE
Glucocorticoids
Energy metabolism and stress responses. CORTISOL Help the body negotiate crisis.
Gonadocorticoids
Sex hormones, primarily androgens (little sig in males, may stim sex drive in fem). TESTOSTERONE, ESTROGEN
Aldosterone?
Regulates Na+, K+, reduces excretion of Na+ from kidney tubules - stimulates Na+ resorption and water retention along with elimination of K+.
Accounts for 95% of mineralcorticoids.
Short term stress vs. long term stress
Short term - dealt with by NE/E from adrenal medulla.
Long term stress -
mineralcorticoids/aldosterone increase Na+/H2o retetion resulting in increased BV and BP.
Glucocorticoids/Cortisol converts proteins/fats in glucose 4 energy, increase blood glucose, suppress immune system.
Stress response stages?
(GAS general adaptive syndrome)
- ALARM STAGE - sympNS/adrenal medulla/release E/NE
- RESISTANCE PHASE - Body shifts into endocrine response (cortisol)
- EXHAUSTION PHASE - Lipolysis of all fat, start to break down muscle.
How is cortisol regulated?
Neg FB. Low levels - Hypothalamus (CRH) –> anterior pituitary (ACTH) –> adrenal cortex (Cortisol).
High levels fb to turn off CRH production.
