The Endocrine System I Flashcards
What is the function of the endocrine system?
Acts with the nervous system for communication & coordination to produce homeostasis
hormones are the product of this system
Where do hormones of once released?
Released into interstitial fluid and then diffuse directly into the blood or lymph
Where do hormones go after their in the blood/lymph
They are carried by the blood/lymph to the target cells
Compare hormone action & the NS
Hormone action is slower & longer lasting then actions produced by the nervous system
Why do only target cells respond to the hormone?
Due to specificity
What contributes to the sensitivity of hormones?
The # of receptors present on a target cell
What is down regulation
A decrese in the # of receptors cell that is produced when the (hormone) is consistently very high
What is the result of down regulation?
Decreased sensitivity
What is up regulation
An increase in the # of receptor cells produced when the (hormone) is low
What is the result of up regulation
Increased sensitivity of target cells
What are the 2 things hormones can do to rxn’s?
Inhibit
Stimulate
What are the major types of hormones?
2
Circulating
Lingering
What are circulating hormones?
They are released from their gland into the lymph/blood to be sent to all body areas
Have more lingering effects.
They are eventually metabolically inactivated by the liver & excreted by the kidneys
Describe local hormones
They have an effect on the cells that secreted them & nearby cells before entering the blood circulation
They tend to have a shorter action due to rapid inactivation
What are the types of hormones (by general function)?
3
Tropic hormones
sex hormones
anabolic hormones
Describe tropic hormones
Act by causing other endocrine glands to grow and/or secrete products
What are sex hormones?
Act on reproductive tissue specifically
What are anabolic hormones?
Cause tissue-building (anabolic) reactions to occur in their target cells
How do we classify hormones (by chemical nature)
2
steroid hormones
Non-steroid hormones
Describe steroid hormones
All contain cholesterol
They are hydrophobic
Travel in blood bound to transport & proteins which increase the stability of the hormone in the blood
What are examples of steroid hormones?
Cartisol, aldosterone, estrogen, testosterone, progesterone, thyroid hormone & nitric oxide
What is the purpose of transport proteins?
Prevent small hormone molecules from being filtered out of the blood into the urine (where they would be lost
Allow hormone levels in the blood to build up & provide a ready supply of additional hormones.
What happens once a steroid hormone reaches the target cell?
It readily crosses the plasma membrane & the nuclear membrane to reach it’s receptor, in the nucleus
Describe non-steroid hormones
Protein & amino acid derivatives
They are hydrophilic so they do not cross membranes easy
They travel in the blood freely (no proteins)
What are some examples of steroid hormones?
Protein hormones (insulin, parathyroid growth hormones Peptide hormones (oxytocin, antidioretic AA derivatives (norepinephrine, thyroxinel)
What are second messengers?
Used in non-steroid hormones
The hormone binds to the plasma membrane & the second messenger is activated so the hormone itself never has to enter the cell