Endocrine Intro Flashcards
Hormones and receptors involved in endocrine signaling are usually ____ in concentration and ____ in affinity for their specified hormones, respectively.
low, high
The significance of this is it allows nano molar concentrations of hormones to still be effective.
In paracrine signaling, molecules travel a _____ distance and are present at a ____ concentration.
short, high
The significance of this is it allows for rapid and localized communication AND controls the distance over which communication can occur.
Contrast the length of signaling for paracrine, neuronal, and endocrine signaling.
endocrine: over minutes to hours
paracrine: intermediate
neuronal: milliseconds
Describe and give examples of polypeptide hormones.
encoded by DNA, synthesized by ribosomes, modified by post-translational modifications
examples: oxytocin and insulin
Describe and give examples of steroid hormones.
synthesized from parent compound cholesterol by several enzyme-catalyzed reactions
examples: testosterone, estrogen, progesterone
Describe and give examples of amino acid/fatty acid hormones.
modified amino acids/fatty acids done by several chemical reactions
examples: epi/norepi, serotonin, prostaglandin
Outline the secretion, transport, and uptake of polypeptide and other hydrophilic hormones.
secretion: usually by exocytosis
transport: freely in circulation dissolved in plasma
uptake: by transporters/receptors
Outline the secretion, transport, and uptake of fatty acid/amino acid derived hormones.
secretion: diffusion
transport: bound to proteins
uptake: freely diffuse through membrane
Contrast the cellular receptors of hydrophilic vs. hydrophobic hormones.
Hydrophilic hormones usually have extracellular receptors, while hydrophobic hormones are able to diffuse through the cell membrane to intracellular targets.
Binding of a hormone to an extracellular receptor can generate what kind of intracellular responses?
(1) enzymatic cascades
(2) generation of second messenger molecules
(3) change in membrane potential via opening of ion channels
Give examples of receptor tyrosine kinases.
(1) growth factor receptors, EGF/IGF/PDGF
(2) insulin receptor
What is the activation process for receptor tyrosine kinases?
(1) ligand binding
(2) dimerization
(3) autophosphorylation
(4) substrate binding
What is the name of the domain at which the substrate of a receptor tyrosine kinase binds to the receptor?
SH2 domain
Give some general properties of steroid receptors.
(1) intracellular
(2) contain a DNA-binding domain and a hormone binding domain
(3) regulate transcription of specific genes
What is a hormone response element (HRE)?
An HRE is a sequence of DNA that interacts with the DNA binding domain of a steroid receptor (in activated dimerized form).
Name and describe the two ways by which hormone receptor signaling can be terminated.
(1) halting production of hormone (negative feedback)
(2) halting response of receptor (via desensitization, lowering production, or internalization for recycling/degradation)
Which kind of receptors undergo desensitization to terminate signaling? How fast does this occur?
GPCRs, fast
Which kind of receptors undergo internalization to halt signaling? How fast does this occur?
Tyr kinases, slower than desensitization, faster than halting transcription
Outline the hypothalamic/pituitary/adrenal (HPA) axis.
The hypothalamus, in response to low levels of cortisol, releases CRH that travels to the pituitary. The anterior pituitary releases ACTH that it makes. ACTH travels to the adrenal cortex, where cortisol is released into circulation as a response.
How does the HPA axis display negative feedback?
cortisol release from the adrenal cortex inhibits ACTH release and CRH
Define desensitization.
Desensitization is an uncoupling of a GPCR from the signaling cascade it is associated with. It occurs after prolonged stimulation by the ligand.
