Question

MCAT Tutorial: Endocrine System

Answer 1

\({\bf{Basics:}}\)
exocrine glands: release enzymes through ducts
endocrine glands: release hormones into bloodstream

all hormones bind to protein receptors

Three Types of Hormones: peptide, steroids, tyrosine derivatives

Peptide Hormones:
- water soluble, so dissolve in blood easily
- cannot pass through membranes, have to bind to receptors on surface
- made in rough ER, modified into final form in the Golgi Apparatus
- act through second messengers
- peptide hormones you need to know: FSH, LH, ACTH, HGH, TSH, prolactin, ADH, oxytocin,
PTH, glucagon, insulin, calcitonin


Steroid Hormones:
- lipid soluble
- derived from cholesterol
- require a protein carrier
- can dissolve through target membranes
- act on transcription by binding to receptor on nucleus or in cytosol
- steroid hormones you need to know: cortisol, aldosterone, estrogen, progesterone, testosterone

Tyrosine Derivatives:
- formed by enzymes on cytosol or rough ER
- T3, T4, epinephrine, adrenaline
- thyroid hormones are lipid soluble
- epinephrine and norepinephrine are water soluble

Answer 2

\({\bf{Hormones~by~Location:}}\)
Posterior Pituitary
- "storage site" for hormones produced by thalamus
- extension of nervous system
- releases ADH and oxytocin
> ADH - stimulates kidneys to reabsorb water
> oxytocin - involved in labor and nursing

Anterior Pituitary
- regulated by hypothalamus
- regulates secretion of steroid hormones

Parathyroid
- PTH - raises osteoclast activity, and thus increases blood calcium levels

Thyroid
- calcitonin - lowers osteoclast activity, increases calcium deposition on bone

Pancreas
- insulin - responds to high glucose blood levels, signals to store glucose for later use
- glucagon - responds to low glucose blood levels, signals to release glucose for use, acts on liver

Placenta
- HCG - signals for the continued production of estrogen and progesterone during pregnancy

Adrenal Medulla
- adrenaline
- norepinephrine

Adrenal Cortex
- cortisol (glucocorticoid) - long term stress response
- aldosterone - causes reabsoprtion of Na+