Endocrine Intro

Question 1

Hormones and receptors involved in endocrine signaling are usually ____ in concentration and ____ in affinity for their specified hormones, respectively.

Answer 1

low, high

The significance of this is it allows nano molar concentrations of hormones to still be effective.

Question 2

In paracrine signaling, molecules travel a _____ distance and are present at a ____ concentration.

Answer 2

short, high

The significance of this is it allows for rapid and localized communication AND controls the distance over which communication can occur.

Question 3

Contrast the length of signaling for paracrine, neuronal, and endocrine signaling.

Answer 3

endocrine: over minutes to hours
paracrine: intermediate
neuronal: milliseconds

Question 4

Describe and give examples of polypeptide hormones.

Answer 4

encoded by DNA, synthesized by ribosomes, modified by post-translational modifications

examples: oxytocin and insulin

Question 5

Describe and give examples of steroid hormones.

Answer 5

synthesized from parent compound cholesterol by several enzyme-catalyzed reactions

examples: testosterone, estrogen, progesterone

Question 6

Describe and give examples of amino acid/fatty acid hormones.

Answer 6

modified amino acids/fatty acids done by several chemical reactions

examples: epi/norepi, serotonin, prostaglandin

Question 7

Outline the secretion, transport, and uptake of polypeptide and other hydrophilic hormones.

Answer 7

secretion: usually by exocytosis
transport: freely in circulation dissolved in plasma
uptake: by transporters/receptors

Question 8

Outline the secretion, transport, and uptake of fatty acid/amino acid derived hormones.

Answer 8

secretion: diffusion
transport: bound to proteins
uptake: freely diffuse through membrane

Question 9

Contrast the cellular receptors of hydrophilic vs. hydrophobic hormones.

Answer 9

Hydrophilic hormones usually have extracellular receptors, while hydrophobic hormones are able to diffuse through the cell membrane to intracellular targets.

Question 10

Binding of a hormone to an extracellular receptor can generate what kind of intracellular responses?

Answer 10

(1) enzymatic cascades
(2) generation of second messenger molecules
(3) change in membrane potential via opening of ion channels

Question 11

Give examples of receptor tyrosine kinases.

Answer 11

(1) growth factor receptors, EGF/IGF/PDGF

(2) insulin receptor

Question 12

What is the activation process for receptor tyrosine kinases?

Answer 12

(1) ligand binding
(2) dimerization
(3) autophosphorylation
(4) substrate binding

Question 13

What is the name of the domain at which the substrate of a receptor tyrosine kinase binds to the receptor?

Answer 13

SH2 domain

Question 14

Give some general properties of steroid receptors.

Answer 14

(1) intracellular
(2) contain a DNA-binding domain and a hormone binding domain
(3) regulate transcription of specific genes

Question 15

What is a hormone response element (HRE)?

Answer 15

An HRE is a sequence of DNA that interacts with the DNA binding domain of a steroid receptor (in activated dimerized form).

Question 16

Name and describe the two ways by which hormone receptor signaling can be terminated.

Answer 16

(1) halting production of hormone (negative feedback)
(2) halting response of receptor (via desensitization, lowering production, or internalization for recycling/degradation)

Question 17

Which kind of receptors undergo desensitization to terminate signaling? How fast does this occur?

Answer 17

GPCRs, fast

Question 18

Which kind of receptors undergo internalization to halt signaling? How fast does this occur?

Answer 18

Tyr kinases, slower than desensitization, faster than halting transcription

Question 19

Outline the hypothalamic/pituitary/adrenal (HPA) axis.

Answer 19

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.

Question 20

How does the HPA axis display negative feedback?

Answer 20

cortisol release from the adrenal cortex inhibits ACTH release and CRH

Question 21

Define desensitization.

Answer 21

Desensitization is an uncoupling of a GPCR from the signaling cascade it is associated with. It occurs after prolonged stimulation by the ligand.