Endocrinology Flashcards
General functions of endocrine system
- regulate cellular metabolism (TH)
- maintain water, electrolyte, and nutrient balance (insulin, aldosterone, ADH)
- promote growth and development (GH,TH)
- control reproduction (estrogen, testerone)
- help the body cope with stress (cortisol)
- regulate digestion and adsorption of food (GI hormones)
hormone imbalance
- hypo/hyper
- weight gain/loss
- increase/decrease BP
- infertility, etc.
endocrine glands
secrete substances into the bloodstream
hormones
chemical messengers of the endocrine system
paracrine agent
in the same tissue
ex: histamine, nitric oxide (NO), cytokines
nervous system
- fast/wired
- APs (electrical) and NTs at synapses (chemical)
- short duration
- local effects
endocrine system
- slow/wireless
- hormones into blood (chemical)
- long duration
- widespread effects
Peptides/Proteins
- amino acids
- range in size from 3 amino acids to full proteins
- more of these than the other two
Amines
- derivatives of tyrosine
- TH
- Epi
- NE
steroids
made from cholesterol
- 85% from liver
- 15% from diet
peptide hormones
- composed of amino acids
- most hormones are proteins/peptides
ex: GH, insulin, ADH, LH, FSH
peptide hormone synthesis
peptide hormones are processed and packaged into secretary vesicles for exocytosis
- transcription –> DNA –> mRNA
- translation
- synthesis –> rough ER
- packaging –> Golgi
- storage –> vesicle
cells that secrete lots of peptides have:
- increased rough ER
- increased Golgi
- increased secretory vesicles
properties of peptides hormones
- hydrophilic
- vesicle storage
- soluble in blood
- extracellular receptors (use 2nd messengers)
- fast effect (modify existing proteins)
- short 1/2 life (rapidly degraded)
vesicle storage
release is controled
soluble in blood
no transport needed
rapidly degraded
because unbound in blood
signaling transduction pathway
- hormone-receptor binding activates a G protein
- G protein activates adenylate cyclase
- adenylate cyclase produces cAMP
- cAMP activates protein kinases
- -> 2 nd messenger - protein kinases phosphorylate enzymes. This activates some enzymes and deactivates others
- activated enzymes catalyze metabolic reactions with a wide range of possible effects on the cell
steroid synthesis occurs in
mitochondria and smooth ER
steroid synthesis depends on
- cell type
- enzymes expressed
ex: ovaries express aromatase
testes do NOT
cells that synthesize steroid hormone have:
- increase mitochondria
- increase smooth ER
- increase specific enzyme
properties of steroid hormones
- hydrophobic
- membrane permeant
- need binding/transport proteins
- intracellular receptors
- slow effect (synthesize proteins)
- long 1/2 life
binding proteins of steroid hormones
- transport hydrophobic / lipophilic substances
- hormones inactive when bound
- creates storage pool
- reduce metabolic clearance rate
cellular response to steroid hormone
- dissociates from transport protein
- diffuses into target cell
- binds to receptor complex
- complex binds to DNA (hormone response elements)
- -> alter gene expression