Introduction to endocrinology Flashcards
Endocrine gland?
group of cells which secrete messenger molecules directly into the bloodstream
Hormone?
bioactive messenger molecule secreted by endocrine gland into blood (not a metabolite of energy substrate)
effects a change
What did Bayliss and Starling demonstrate?
pancreatic secretion not under neural control, hormonal control important
secretin released from duodenal S cells stimulated pancreas to secrete HCO3
What did Banting and Best demonstrate?
extracted and purified insulin from the pancreas
Endocrine?
hormone acts on target cells at a distance from source via bloodstream
Paracrine?
hormone acts on nearby target cells
Autocrine?
hormone acts on own immediate source
Differences between endocrine and NS messengers?
release of chemical into bloodstream vs across a synapse
effect generalised vs localised to innervated target cells
long time span (s to days) vs milliseconds because NT broken down very quickly
What are the 3 classifications of hormones?
protein/polypeptide
steroid
miscellaneous
What are protein polypeptide hormones?
more complex structure
complex (LH -200aa) intermediate (insulin) small (TRH-3aa) dipeptides (T4 derived from 2 iodinated tyrosine residues) derived from single aa (catecholamines)
What are steroid hormones?
derived from steroid cholesterol
- intact steroid nucleus (adrenal/gonadal steroid)
- broken steroid nucleus (Vit D and metabolites)
What are miscellaneous hormones?
hormone with protein structures (e.g. thyroid hormones have iodine incorporated - not protein specific)
What provides amino acids to synthesise protein hormones?
blood supply
Describe the synthesis, storage and secretion process of a protein hormone (ACTH) ?
pro-hormone transcribed from DNA
mRNA moves into cytoplasm and binds to rER
mRNA is translated on ribosome of rER and endocytosed into Golgi
proteolytic enzymes added to pro-hormone vesicles to cleave pro-hormone into its active form
vesicles containing hormone accumulate near cell surface and when signal arrives they are exocytosed and released into blood
Why are polypeptide hormones short lasting?
quickly metabolised in the blood when unbound
broken down in the liver
What is ACTH?
produced by anterior pituitary
from POMC pro-hormone
stored in pituitary corticotroph cells
What are hormones produced by anterior pituitary?
polypeptide hormones
What is POMC?
pro-opiomelanocortin
241 amino acids
pro hormone of ACTH