Ch. 17 - Endocrine System Flashcards
Endocrine system
composed of ductless glands of epithelial tissue within a connective tissue framework that synthesize and secrete hormones to be transported to target cells.
target cells
have specific receptors for a hormone
How do hormones travel
Hormones are released into interstitial fluid and then into the blood where they are transported. They randomly leave the blood and enter into interstitial fluid where they bind to target cells’ receptors.
Nervous system vs. Endocrine
Both are the control systems of the body and release ligands that bind to receptors on particular target cells. Unlike nervous, endocrine is more widespread and transfers hormones everywhere, has longer reaction times and effects
Functions of the Endocrine system
regulating development, growth, and metabolism, maintaining homeostasis of blood comp. and volume, controlling digestive processes and reproductive activities
Regulating development, growth, and metabolism
regulate embryonic cell division and differentiation. Regulate metabolism (anabolism and catabolism.
ligands
chemical messangers
maintaining homeostasis of blood comp & volume
regulate blood solute concentrations, blood volume, cellular concentration, and platelet #
controlling digestive processes
hormones influence secretory processes and movement of materials in digestive tract
controlling reproductive activities
hormones affect development and function of reproductive systems and the expression of sexual behaviors.
Endocrine glands with solely endocrine function
pituitary, pineal, thyroid, parathyroid, adrenal
endocrine cells found in clusters in organs with other functions
hypothalamus, skin, thymus, heart, liver, stomach, pancreas, small in., adipose ct, kidneys, gonads
hormonal stimulation
a gland cell releases its hormone when some other hormone binds to it
humoral stimulation
a gland cell releases its hormone when there is a certain change in levels of a nutrient or ion in the blood.
nervous stimulation
a gland cell releases its hormone when a neuron stimulates it.
Steroids
lipid-soluble made from cholesterol
gonadal steroids (estrogen) adrenal steroids (cortisol)
calcitriol is more accurately a sterol
biogenic amines (monoamines)
modified amino acids, water soluble except for TH.
Includes catecholamines, thyroid hormone, melatonin
Thyroid hormone
a biogenic amine made from a pair of tyrosines. is nonpolar and lipid soluble.
Proteins
most hormones, water-soluble chain of amino acids
Local hormones
signaling molecules that don’t circulate in blood
Eicosanoids
type of local hormone formed from fatty acids within phospholipid bilayer of membrane. Synthesized through an enzymatic cascade; stimulate pain and inflammatory response. NSAIDS block prostaglandins (type of eicosanoid)
Eicosanoid formation
Phospholipase A2 removes arachidonic acid from phospholipid. Other enzymes then convert arachidonic acid to a type of eicosanoid
Water-soluble hormones
are polar and can’t diffuse so must use membrane receptors. Goes through a signal transduction pathway. This works in that the hormone (first messenger) binds to a receptor on cell membrane. this activates a g-protein which causes activation of a membrane enzyme (like adenylate cyclase). This activated enzyme makes the second messenger- the chemical that modifies cellular activity.
Action/Results of water-soluble hormones
with different signal transduction pathways comes different results. Enzymes can be activated/inhibited, muscles contract/relax, membrane permeability changes, cellular secretions released, growth stimulated.
Hormone interactions on target cell
different hormones bind simultaneously and can react as synergistic, permissive, or antagonistic
Synergistic interactions
One hormone reinforces activity of another hormone. ex: estrogen and progesterone.
Permissive interactions
One hormone requires activity of another hormone. ex: for oxytocin to stimulate milk ejection there has to be prolactin to make milk.
Antagonistic interactions
One hormone opposes activity of another hormone. ex: glucagon vs. insulin
Hypothalamus controls the…
pituitary gland.
Pituitary gland controls the…
thyroid, adrenal glands, liver, testes, ovaries
Pituitary gland
known as hypophysis. Lies inferior to hypothalamus in sell turcica of sphenoid. It is pea-sized and connected to hypothalamus via the infundibulum. portioned into anterior and posterior parts.
Posterior Pituitary
neurohypophysis. smaller part of pituitary that has hypothalamic neurons that project through infundibulum and release hormones in post. pit.
Somas in paraventricular nucleus and supraoptic nucleus
Axons in hypothalmo-hypophyseal tract of infundibulum
Synaptic knobs in pars nervosa.
Anterior Pituitary
hypothalmo-hypophyseal portal system of blood vessels connects hypothalamus to ant. pit.
Hypothalamo-hypophyseal portal system
has primary plexus (capillary network near hypothalamus), secondary plexus (capillaries near ant. pit. and hypophyseal portal veins that drain primary plexus to transport to secondary.
Interactions between hypothalamus and posterior pituitary
Posterior pit. stores and releases oxytocin (ot) and antidiuretic H (ADH). These hormones are made in hypothalamus’ neurosecretory cells, packed into vesicles, transported via fast axonal transport and released from synaptic knobs when neurons fire.
Antidiuretic hormone (vasopressin)
made in supraoptic nucleus. Functions to decrease urine production, stimulate thirst, and constrict blood vessels.
Oxytocin
made in paraventricular nucleus. Functions: uterine contraction, milk ejection, emotional bonding.
Interactions between hypothalamus and anterior pituitary
hypothalamus hormonally stimulates anterior pituitary to release hormones. Hypothalamus secretes regulatory hormones that travel via portal blood vessels to pituitary. This causes ant. pit. to secrete hormones into general circulation.
Hormones of the hypothalamus
releasing hormones, inhibiting hormones
Releasing hormones
Increases secretion of ant. pit. hormones. Includes thyrotropin-releasing hormone, prolactin-releasing hormone, gonadotropin RH, corticotropin RH and growth hormone RH.
Inhibiting hormones
decrease secretion of anterior pituitary hormones. Includes Prolactin-inhibiting hormone and growth-inhibiting hormone
Hormones of anterior pituitary
TSH, PRL, adrenocorticotropic hormone (ACTH), gonadotropins (FSH & LH), Growth hormone
Thyroid-stimulating hormone (TSH)
release is triggered by TRH from hypothalamus. Causes release of thyroid hormone from thyroid gland. (released by ant. pit.)
Prolactin (PRL)
release triggered by PRH, inhibited by PIH from hypothalamus. Causes milk production, mammary gland growth in females. (released by ant. pit.)
Adrenocorticotropic hormone (ACTH)
release is triggered by CRH (corticotropin releasing hormone). causes release of corticosteroids by adrenal cortex. (released by ant. pit.)