Endocrine I Flashcards
what are the functions of the endocrine system?
regulation of body processes such as reproduction, growth and development
water, electrolyte and nutrient balance
regulation of cellular metabolism/ energy balance
mobilization of body defenses
how fast does nervous system work
within millliseconds with electorchemical impulses through neurons
how fast does endocrine system work
minutes, hours, days.
influences metabolic activity through hormones
what are endocrine glands
small masses of secreting epithelial cells, ductless, release hormones
specifics of endocrine glands
rich vascular supply and lymphatic drainage to distribute hormones
how do exocrine and endocrine glands differ
exocrine glands have ducts carrying non-hormones secretions to a membrane surface
definition of hormones
chemicals produced by one set of cells that travel through the body to change the metabolic activity (up or down) of a different set of cells which are called the target cells
what are autocrines
chemicals produced by a set of cells that effect the same kind of cell
what are paracrines
chemicals produced by a cell that effect neighboring cell populations
amino acid based hormones
derived from the AAs themselves. water soluble. faster acting by binding with a surface receptor
short chain of AAs
peptide
long chain of AAs
protein
steroid based hormones
assembled using a cholesterol component (lipids can penetrate cell membranes
slower acting by binding to internal cell receptors and activating genes
eicosanoids
non-steroid lipids which signal nearby cells to action (localized reactions)
mechanisms of hormone action
target cells
tissue response
plasma membrane receptors and second messenger systems
intracellular receptors and direct gene activation
target cells
while hormones will circulate throughout the body, only cells with the appropriate internal or external receptor for that specific hormone will be targeted for effect
example of tissue response
the tissue response is dependent upon the tissue type
common target cell responses for specific hormones
opens/closes ion channels which may increase or decrease plasma membrane potential
stimulates synthesis or activity of proteins or regulatory molecules like enzymes within cell
stimulates mitosis
summary of the second messenger signaling mechanisms
hormone (first messenger) binds to external receptor
engaged external recpetor activates internal G proteins which trigger seconday messengers, eventualy producing intracellular changes in metabolic activites
quick on & of - repeated surgace receptor stimulation needed to prolong a response
2 common intracellular secondary messengers
cAMP signaling mechanism
PIP2-Calcium signaling mechanism
cAMP signaling mechanism
cAMP -> activates protein kinases -> activates enzymes triggering cells internal responses
PIP2-Calcium signaling mechanism
PIP2-Calcium -> activates enzymes triggering cells internal responses
what response does Ca++ trigger in muscles cells?
contraction
summary of internal receptor and direct gene activation
being lipid soluble, steroid hormones diffuse through the plasma membrane and bind to internal receptors
receptor hormone complex then enters nucleus and activates “recipes” stred on molecules as “genes”
then transcription -> mRNA -> translation -> protein synthesis
what happens after internal receptor and direct gene activation
the products made may turn on (enhance) or turn off (inhibit) cellular/tissue responses in the body but slower to start & stop then surface receptor hormones
what determines whether or not a hormone will bind to & activate it
what receptors a cell has
target cell hormone interaction is dependent on 3 things
circulating blood levels of a hormone
number or receptors on or in target cells available for binding
affinity
affinity
strength of binding between hormone and receptor
what is up-regulation
response by a cell to produce more receptors for a certain hormone so its response increases
what is down regulation
response by a cell to decrease # of receptors for a certain hormone leads to a decreased response
hormones circulating in the blood are either…
free form
bound
free form hormones
easily removed from circulation by kidneys on a daily basis
bound hormones
bound to a protein which increases time available in the body before removal by the kidneys
what is half-life
the time it takes to remove 1/2 of the amount of something like a hormone from your blood
how to increase half life
bind a hormone to a protein
forms of interaction of 2 or more hormones on the same cell populations
permissiveness
synergism
antagonism
permissiveness
one hormone must be present to allow another hormone to work properly
ex of permissiveness
thyroxine must be present for the fetal growth hormone to produce the normal amount of growth activity in the baby
synergism
more response from 2 hormones together than both separately
antagonism
2 hormones work to achieve opposite goals from one another
homeostasis
the right amount of something that your body needs at a given time
system of hormone regulation
negative feedback system
positive feedback system
negative feedback system
too little of something produces a response to increase synthesis or cell activity
too much of something produces a response to decrease synthesis or cell activity
positive feedback system
rare in cases like child birth
humoral stimuli
endocrine glands secrete hormones in direct response to changing blood levels. this uses a negative feedback system to regulat the use of hromones
example of humoral stimuli
the parathyroid gland and the regulation of Ca2++ levls
neural stimuli
when nerve fibers stimulate hormone release
ex of neural stimuli
sympathetic nervous system stimulation of the adrenal medulla
hormonal stimuli
when hormonal glands release hormones in response to other hormones produced by other organs
ex of hormonal stimuli
anterior pituitary gland hormones are release by hormones created by the hypothalamus
