Ch 11: Endocrine System General Flashcards
What organs can secrete hormones?
heart, liver, kidneys, adipose tissue, hypothalamus etc. in addition to endocrine glands
What are hormones secreted by the hypothalamus called?
neuro-hormones
What do hormones do?
regulate metabolism, growth, behavior and reproduction
Chemical classes of hormones
1) Amines
2) Polypeptides & proteins
3) Glycoproteins
4) Steroids
What are amines derived from?
tyrosine & tryptophan
Examples of amines hormones
some hormones of the adrenal medulla, thyroid, pineal gland
Examples of protein hormones
ADH, insulin, GH, oxytocin, glucagon, ACTH, parathyroid hormone
Examples of glycoprotein hormones
FSH, LH, TSH
Examples of steroid hormones
testosterone, estradiol, progesterone, cortisol
Where do steroid hormones originate from?
Derives from cholesterol, secreted by adrenal cortex and gonads
How must polar hormones be administered as a drug
Via injection
Examples of polar hormones
polypeptides, glycoproteins, catecholamines, norep, epinephrine
Examples of nonpolar hormones
steroids, thyroid hormone, melatonin
Prohormones
inactive hormones that must be spliced together to become active
Prehormones
inactive prohormones that must be modified within their target cells
Hormones may act
1) antagonistically, 2) synergistically, and/or 3) permissively
Hormones may act
1) antagonistically, 2) synergistically, and/or 3) permissively
How a cell responds to hormones depends on the _____ of hormone and the ________ of all hormones
amount; combination
Synergistic effects can be
1) additive (producing same effect) or 2) complementary (each contributes different piece to system)
Permissive effects
when one hormone makes target cell more responsive to a second hormone
Example of permissive effects
1) estrogen makes the uterus more receptive to progesterone
2) increased secretion of parathyroid hormone makes intestines more responsive to vitamin D in Ca++ absorption
Duration of hormone half lives
minutes to hours to days
How do hormones get removed from blood
removed by liver and converted to less active products
Higher than normal concentrations of blood hormone levels may result in;
1) binding to receptors of related hormones
2) widespread side effects
Priming effects/upregulation
when target cells respond to hormone by increasing the number of receptors available for hormone binding, resulting in greater response from more hormone release
Example of cells using downregulation
adipose cells reducing receptors available to insulin for binding
How can the body avoid hormone desensitization?
hormones get released in spurts = pulsatile secretion
Hormones bind to receptors with high ______ and low ______
affinity; capacity
Where do we find lipophilic hormone receptors?
in the cytoplasm or nucleus
Where do we find water-soluble hormone receptors?
on the plasma membrane
How do steroid hormones and thyroid hormone travel to the target cell?
attached to carrier proteins; dissoc. once at target
What are hormone receptors in the nucleus called? What do they do?
nuclear hormone receptors; activate genetic transcription via transcription factors
What effects do lipophilic hormones have?
to produce new proteins, usually enzymes, to change metabolism of the cell
What 2 regions are on nuclear hormone receptors?
1) ligand-binding domain for hormone
2) DNA-binding domain for DNA
Where does the DNA-binding protein bind, once the receptor is activated by the hormone?
to a short sequenced hormone response element on the DNA that sits adjacent to the gene to be transcribed
What is an orphan receptor?
A receptor that has no known ligand (yet, to science)
Nongenomic action
action that may occur in the cytoplasm of the cell, involving 2nd mssngrs and cause effects from seconds to minutes
How long does it take to activate genomic effects?
at least 30 minutes
Where are receptors for genomic action?
in the cytoplasm or in the nucleus; once the hormone binds to receptor the complex translocates to the nucleus
How many ligands may be necessary for a hormone response element to activate? What is this called?
2 - dimerization (homodimer, since both complexes are the same)
Coactivators & Corepressors
molecules that are needed in addition to steroid (or thyroid) hormone to bind to nuclear receptor proteins at different sites to change the effect of the hormone on transcription factors
What happens to protein structure when lipophilic hormone binds?
1) removes heat shock proteins that prevented receptors from binding to DNA;
2) coactivators/repressors get recruited (activators modify chromatin to facilitate DNA transcription)
Types of 2nd messngr mechanisms
1) Adenylate cyclase (cAMP)
2) Phospholipase C
3) Tyrosine kinase
cAMP system is used by
epinephrine and norep
What do epine and norep bind to?
b-adrenergic receptor
What happens after epine or norep binds to the B-adrenergic receptor?
g-protein dissociates, activating adenylate cyclase
What does adenylate cyclase use to make cAMP?
ATP
What does cAMP activate?
protein kinase
How does protein kinase work in the cell?
It phosphorylates proteins of target cell to alter cell metabolism
cAMP is inactivated by
phosphodiesterase
Some cells can use ____ in place of cAMP
cGMP
What hormone uses the Phospholipase C system?
epinephrine (in some cells)
In PC system, what does epine bind to?
a-adrenergic receptors, dissociating g-protein
In PC system, g-protein dissociation activates ___
phospholipase C
What does phospholipase C produce?
IP3 and DAG
What do IP3 and DAg do?
release Ca++ from endoplasmic reticulum in cell
What does Ca++ release do in PC system?
Ca activates calmodulin, activating protein kinases to modify enzymes
Which hormones use tyrosine kinase systems?
insulin and growth factors
What is the receptor name for insulin and growth factors?
tyrosine kinase
Where is tyrosine kinase located?
on the plasma membrane, such that the ligand binding site is outside and the enzyme is internal
Tyrosine kinase is activated by
phosphorylation
What does the active tyrosine kinase phosphorylate?
insulin receptor substrate molecules, activating other enzyme cascades
