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Endocrine Glands
Secrete hormones into the bloodstream
Hormones (AKA Chemicals)
circulate throughout the body to affect target cells which must contain the specific receptor proteins for the hormones
Neurohormones
are secreted by specialized neurons
Hormones
affect the metabolism (chemical reactions) of the target cells/tissues/organs
norepinephrine
act as both a hormone and a neurotransmitter depending on the nervous or endocrine usage
Glucocorticoids
Influence glucose metabolism
Insulin
Promotes cellular uptake of glucose and formation of glycogen and fat
Glucagon
Stimulates hydrolysis of glycogen and fat
Parathyroid hormone
Increases Ca2+ concentration in blood
Antidiuretic hormone
Promotes water retention and vasoconstriction
Oxytocin
Stimulates contraction of uterus and mammary secretory units
Thyroxine (T4) and Triiodothronine (T3)
Promote growth and development; stimulates basal rate of cell respiration (Basal Metabolic Rate ¬タモ BMR)
Calcitonin
May participate in the regulation of blood Ca2+ levels
Amine
hormones are derived from tyrosine and tryptophan
Polypeptide
hormones that are generally less than 100 amino acids longs
Glycoprotein
Hormones that are polypeptide bound to 1 or more carbohydrate group
Steroids
hormones that are lipids and derived from cholesterol
Nonpolar (lipophilic)
hormones are soluble in lipids & thus can cross the plasma membrane (phospholipids) and into cells
Polar
hormones soluble in water; cannot pass through the phospholipids membrane
Prohormones
precursors (early forms) of hormones (e.g. ¬タモ proinsulin)
Prehormones
precursors of prohormones (e.g. ¬タモ preproinsulin)
What is the hormone sequential line for insulin?
Preproinsulin -> Proinsulin -> Insulin
Why can¬タルt hormones made of proteins be taken orally?
Because they would be digested into inactive fragments before being absorbed into the blood.
Both NS & Endocrine system use what to communicate to tissue cells/organs?
some sort of regulatory molecules (either NTs or Hormones)
Targets for both regulatory molecules...
must have specific receptor proteins
Hormones are normally removed by the body through which 2 means?
urine & catabolic breakdown
How does a tissue usually responds to a number of different hormones?
Thru the number of receptors
Two hormones are synergistic if they...
work together to produce a common effect.
antagonistic
If the action of a hormone inhibits the effect of another
A hormone has permissive effects if it...
enhances the responsiveness of a target organ to a 2nd hormone.
Target responds better to hormone 2 if...
it was previously exposed to hormone 1.
Half-life
the time after initial release required for the hormones blood level to be reduced by half (1/2).
Half-life ranges
from minutes to hours for most, but days for thyroid hormones
Normal tissue responses
are produced only when hormones are in physiological range
High (pharmacological) doses
can cause a number of side effects, probably by binding to receptors belonging to other hormones
Primary Effect (Upregulation)
occurs when a hormone induces more of its own receptors on the target cells; Results in a greater response of the target cell
Densensitization (Downregulation)
occurs after long exposure to high levels of poly peptide hormone; Subsequent exposure to this hormone produces a lesser response due to the reduction in receptors
Most peptide hormones have ...
pulsatile secretion (spurts) which prevents down regulation
Receptors show
1) Specificity to a particular hormone; 2) High affinity bonds tightly; 3) Low capacity limited number of cell receptors in/on a cell. Receptors can be saturated.
Lipophilic horomones (non polar)
Have receptors in target¬タルs cytoplasm and/or nucleus b/c they can diffuse through the plasma membrane (lipids can move through other lipids)
genomic action
Lipophilic horomones (non polar) target is the nucleus where they effect transcriptional, translation, leading to poly peptide/protein production. Takes at least 30min.
Water-soluble hormones (polar)
Cannot pass through a membrane. Their receptors are then located on the surface of target cell (membrane)
cascading reactions
Water-soluble hormones (polar) acting through 2nd messengers which are located in the cell.
Signal transduction AKA non-genomic actions
Effects of cascading reactions are quick
Some steroids (lipids)...
also act like a cell surface receptors
Lipid hormones travel in the blood...
attach themselves to carrier proteins. If not, they form globs of lipids.
Hormones that Bind to Nuclear Receptor Proteins...
dissociate from the carriers allowing them to pass through the plasma membrane of target; They then bind to nuclear hormone receptors (cytoplasmic) subsequently causing gene expression.
The hormone/receptor complex...
serves as a transcription factor (activates/causes transcription).
The actual receptor of Nuclear Hormone Receptor
has a ligand (hormone) binding domain & a DNA¬タモbinding domain. A domain is an area/region
Hormone Response Element (HRE)
DNA-binding domain allows the complex to bind to DNA in a specific region
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