Hormone Synthesis, Regulation, and Mechanisms of Action Flashcards
Name some endocrine glands
hypothalamus anterior pituitary posterior pituitary thyroid parathyroid pancreas adrenal medulla kidney
Which endocrine gland is the core of the endocrine system?
pituitary gland
Endocrine
hormone travels to a distant target
ex: insulin is secreted by beta islet cells and acts on skeletal muscle to increase glucose uptake
Paracrine
hormone acts on neighboring target
ex: insulin acts on nearby alpha islet cells to suppress secretion of glucagon
Autocrine
hormone acts on its own releasing cell
ex: insulin acts on beta islet cells to inhibit release of insulin
Name the 3 classes of hormones
peptides and proteins
amino acid derivatives
steroids
Name the biosynthetic pathways for the 3 classes of hormones
peptides and proteins - amino acids
amino acid derivatives - tyrosine and tryptophan
steroids - cholesterol
How are peptide and protein hormones synthesized?
mRNA - translation to preprohormone - ER, conversion from prepro to prohormone - Golgi, pro packaged for secretion - enzymes in package break pro to hormone
Name the amine hormones
catecholamines (NE, E, and DPA)
thyroid hormones
Characteristics of steroid hormone synthesis
lipid derivative of cholesterol
very rapidly secreted from cells
all steroids bind to plasma proteins produced by the liver
What are eicosanoids?
large group of molecules derived from polyunsaturated fatty acids
Name some eicosanoids
prostaglandins
prostacyclins
leukotrienes
thromboxanes
What is the primary precursors for eicosanoids?
arachodonic acid
How are hormones regulated?
system of control based on stimulation and inhibition of secretory cells
Negative feedback
output of a pathway inhibits inputs to the pathway
some feature of hormone action, either directly or indirectly, inhibits further secretion of the hormone
Positive feedback
hormone action causes more secretion, elevating concentration
some feature of the hormone action causes more secretion of the hormone
Is positive feedback homeostatic?
no
What is a great example of negative feedback?
Glucose causes release of insulin - insulin facilitates entry of glucose into cells - glucose levels in blood fall - insulin not released anymore
What 3 factors determine the concentration of hormone?
rate of production
rate of delivery
rate of degradation and elimination
Receptor
a protein that contains hormone recognition sites that bind their hormone with high affinity and selectivity
Sensitivity
hormone concentration that produces 50% of the maximal response
(if more hormone required to produce 50% of maximal response, then target tissue has decreased sensitivity)
A target tissue’s responsiveness or sensitivity to a hormone can be changed by what 2 factors?
change the affinity of the receptors for the hormone
change the number of receptors
Down-regulation
number of receptors or the affinity of the receptors for the hormone has decreased
Reasons for down-regulation
decreasing synthesis of new receptors
increasing degradation of existing receptors
inactivating receptors
Up-regulation
number of receptors or the affinity of the receptors for the hormone has increased
Reasons for up-regulation
increasing synthesis of new receptors
decreasing degradation of existing receptors
activating receptors
How do hormones change their target cells? (2)
activation of enzymes and other molecules via 2nd messengers
modulation of gene expression via gene transcription
What are the 2 types of hormone receptors?
cell surface receptors
intracellular receptors
What hormones bind to cell surface receptors?
proteins
peptides
catecholamines
eicosanoids
What hormones bind to intracellular receptors?
steroids
thyroid hormones
Name some second messengers
adenylyl cyclase (cAMP)
phospholipase C
tyrosine kinase
guanylate cyclase (cGMP)
