Chapter 6-7 Flashcards
hormones act on their target cells by
- controlling rates of enzymatic runs 2. controlling transport of ions/molecules across membranes 3. controlling gene expression –> protein synthesis
endocrine system acts __ than the nervous system
WAY SLOWER
Arnold Berthold
rooster castration experiment, demonstrated that the testes secreted something in the blood that affected male development
Charles Brown-Sèquard
injected ground up bull testicle into his blood to “reinvigorate his manhood” probably a placebo effect, but paved way for organotherapy
immune system “hormones”
cytokines
nervous system “hormones”
neurohormones
not all hormones are secreted into the blood
ectohormones are secreted in the external environment Pheremones are a prime example of this
traditionally it is thought that hormones are transported to a distant target, but….
growth factors are secreted and act more locally there are autocrine and paracrine factors
eicosanoids
lipid derived signaling molecules
hormones exert their effect at very low concentrations
nM and pM concentrations but some are at way higher concentrations- histamine
Hormones act by
binding to receptors = cellular mechanism of action
Insulin in the muscle and adipose tissue
alters glucose in transport proteins and exzymes for glucose metabolism
insulin in the liver
modulates enzyme activity, no effect on glucose metabolism
insulin in the brain
glucose metabolism is independent of insulin
body will terminate hormone effect by
limiting secretion removing or inactivating secreted hormone terminating activity in target cells
in the bloodstream, hormones are degraded by
liver and kidney enzymes, excreted in bile or urine
hormone half life ___ if bound to protein
increases
enzymatic degradation of hormones bound to receptor can occur
at the membrane or in lysosomes
peptide/protein hormones
composed of linked amino acids
steroid hormones
all derived from cholesterol
amino acid-derived hormones (amine)
modifications of either tryptophan or tyrosine
most hormones are __ or __
proteins or peptides
Preprohormone (inactive
peptide hormone plus signal sequence that directs the protein into the RER
Prohormone (inactive)
Signal sequence cleaved, enzymatic activity in secretory vesicles cleaves prohormone into active hormone + peptide fragments




