10. Intro to Endocrinology Flashcards
Homeostasis
maintenance of a constant internal environment
Endocrine hormone
produced by a ductless gland
Paracrine
released from effector cell (E)
interact with a different target cell (T)
Autocrine
secreted by E interact with original E cell or similar cell types
Juxtacrine
expressed on surface of effector cell and interacts with target cell via direct cell-cell contact
Intracrine
Secretes own ligand intracellularly to bind to an internal receptor
Type I NR (nuclear receptor)
monomers in cytosol
When activated form homo-dimers and migrate to nucleus
Bind specific gene signals to activate gene expression
Type II NR
Heterodimers bound to target DNA
When activated they promote gene expression
Steroid hormones
activate Gene Transcription
production of mRNA
Switched off by the action of other proteins or being degraded
Amide and peptide hormones
bind to receptors on the exterior (i.e. on the membrane)
Second messengers
Small molecules, free to diffuse
Allows AMPLIFICATION
Allows CROSS-TALK
G Protein coupled receptors
7 transmembrane proteins (7TMs)
Binding of ligand results in change of conformation within the receptor
external signal is transferred across the membrane
G PROTEIN binding involved
G protein Unactivated state
GDP bound
α subunit
G protein Activated state
GTP bound
Resetting of G-proteins
Reaction is slow
binding of GTP