What are the chemical messengers secreted to target cells?
What are the functions of the endocrine system?
Maintain internal environment, regulation of growth and development, control and instigation of sexual reproduction and development
What are the categories of hormones?
Peptides and proteins (polypeptides); amino acid derivatives; steroids (cholesterol based); fatty acid derivatives - eicosanoids
Which hormones are chains of amino acids that are water soluble and make up the largest number of hormones?
What are the types of amino acid based hormones?
tyrosine derivatives; tryptophan derivatives; glutamic acid
What are the tyrosine derivatives?
thyroid hormones (T3 and T4); catecholamines/adrenal medulla (epinephrine, norepinephrine)
What type of hormone is a derivative of cholesterol, consists of four covalently bonded rings, and is lipid soluble?
What are examples of steroids?
glucocorticoids, mineralocorticoids, androgens, estrogens, progestogens
What are large groups of molecules derived from polyunsaturated fatty acids?
What are the principal groups of eicosanoids?
prostaglandins, prostacyclins, leukotrienes, thromboxanes
What type of hormones diffuse through the plasma membrane, enter the nucleus, forms hormone-receptor complex, and then binds to transcription factors to chromosome to activate/inactivate genes?
lipid soluble steroids and thyroid hormones
What type of hormone action is: binds to receptor on cell surface, actives g-protein, actives adenylate cyclase, converts ATP to cAMP, cAMP actives protein kinases which produce the final effect?
peptides and water-soluble amines
Hormones circulate in the blood but only affect cells that have a receptor for that hormone. What are these cells called?
How to endocrine hormones signal cells?
travel via the bloodstream to target cells
How do neurohormones signal cells?
release via synapses and travel via the bloodstream
What do paracrine hormones act on?
What do autocrine hormones act on?
released and act on the cell that secreted them
What do intracrine hormones act on?
within the cell that produces them
the hormone is distributed in blood and binds to distant target cells
the hormone acts locally by diffusing from its source to target cells in the neighborhood
the hormone acts on the same cell that produced it
Unlike the nervous system, the endocrine system is ____________?
in response to changing blood levels
in response to nerve fibers
in response to other hormones
What are the inputs to endocrine cells?
neuron, hormone, ion, organic nutrients
The concentration of hormone as seen by target cells is determined by?
rate of production, rate of delivery, rate of degradation and elimination
type II, melitus
Negative feedback occurs when?
a change in a physiological variable triggers a response that counteracts the initial fluctuation
Example of negative feedback
LH from pituitary stimulates the testes to produce testosterone which in turn feeds back and inhibits LH secretion
Example of positive feedback
LH stimulation of estrogen which stimulates LH surge at ovulation