Endo 6131 Flashcards
The endocrine system consists of an _______________ that secretes a hormone, the hormone itself, and a target tissue that responds to the hormone
endocrine gland
is a chemical substance produced by a ductless endocrine gland that is secreted into the blood
Hormone
Hormone-producing glands:
- pituitary
- thyroid
- parathyroid
- adrenals
- gonads
- pancreas
Three chemical classes of hormones
- amino acid derivatives (catecholamines and thyroid hormones)
- peptide hormones (pancreatic)
- steroids (derivatives of cholesterol)
are sensing and signaling devices that are
capable of responding to changes in the internal and external environments and coordinating multiple activities that maintain homeostasis.
endocrine glands
Two major subdivisions of pituitary gland
- pars distalis
- pars nervosa
adenohypophysis or anterior pituitary, is
the largest subdivision
pars distalis
neurohypophysis or posterior pituitary,
has its cell bodies in the hypothalamus with their axons stretching to the posterior lobe of the pituitary
pars nervosa
it receives peptides from the
hypothalamus through a capillary portal system (hypothalamo–hypophyseal vessels)
pars distalis
has its cell bodies in the hypothalamus with their axons stretching to the posterior lobe of the pituitary; therefore,
functionally and anatomically, the posterior pituitary is an extension of the hypothalamus
pars nervosa
releasing and release-inhibiting hormones are synthesized by neurons in the __________, transported by
axonal processes, and released into capillary plexus.
hypothalamus
Secreted by the anterior pituitary gland
- growth hormone (GH)
- somatotropic hormone (SH)
- prolactin (PRL)
- luteinizing hormone (LH)
- follicle-stimulating hormone (FSH)
- thyrotropic hormone (TTH)
- adrenocorticotropic hormone (ACTH)
- melanocyte-stimulating hormone (MSH)
Secreted by the pars narvosa
ADH and oxytocin
this hormone enhances reabsorption of water by the kidney and causes
contraction of vascular smooth muscle
ADH
this hormone stimulates contraction of smooth muscle or parturition and
milk let-down
oxytocin
To maintain appropriate homeostasis, the endocrine organ must constantly monitor systemic hormone concentrations accomplished in the form of ___________________
negative feedback loops
- inhibits prolactin, LH, and FSH secretion
- exposure increases ACTH levels in rodents exposed during puberty and decreases ACTH levels in animals exposed
during adulthood - acute exposure decreases circulating GH levels, while longer period treatment increases
circulating GH levels
Cadmium
decrease LH and FSH
Lead and mercury
Environmental contaminants inhibit release of LH and FSH as well as TSH
polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers
increases LH and PRL levels
Methoxychlor, dieldrin, and endosulfan
Reduces reduces pulsatile LH and suppresses the pituitary response to exogenous GnRH
coumestrol
stimulate proliferation of a pituitary cell line
Flame retardants tetrabromo- and tetrachlorobisphenol A
can come into contact with drinking water and cause pituitary tumors in chronically exposed rats and mice
2-Mercaptobenzothiazole
a chemical used in the treatment of alcoholics, increases the ACTH precursor mRNA in the anterior
pituitary when co-administered with ethano
cynamide
are two small glands situated on the superior poles of the kidneys
adrenal glands
Major psychological role of adrenal glands
management of stress
Each adrenal gland is divided into two morphologically and
functionally distinct regions:
outer cortex and interior medulla
The adrenal cortex regulates many physiological functions
such as the
- immune system
- inflammation
- water
- electrolyte balance
- carbohydrate
- protein metabolism
The outer region (cortex) synthesizes and secretes
________________________
adrenocorticosteroid hormones
The cortex consists of three zones:
- Zona Glomerulosa
- Zona Fasciculata
- Zona Reticularis
which zone of the adrenal cortex produces the mineralocorticoid
aldosterone
Zona Glomerulosa
which zone/s produce
glucocorticoids, corticosterone, and cortisol, as well as
adrenal androgens.
inner zones, fasciculata and reticularis
appear to be the principal targets of xenobiotic chemicals in the adrenal cortex leading to necrosis
zona fasciculata and reticularis
toxic xenobiotics that target zona fasciculata and reticularis
- 7,12-dimethylbenz[a]
- anthracene
- acrylonitrile
- thioacetamide
- basic polyglutamic acid
______, _____, and various _____directly
target glucocorticoid secretion
- spironolactone
- ketoconazole
- various PCBs
The compounds that affect the functional integrity of
lysosomes include:
- chloroquin
- triparanol, and
- chlorphentermine
Adrenocortical toxicity can also involve increased secretion of
endogenous glucocorticoids due to compounds such as:
- ethanol
- cannabinoids
- Cocaine, and
- cytotoxic anticancer drugs
have been widely used as anti-inflammatory agents can produce symptoms that resemble Cushing’s syndrome
pharmacological treatment with glucocorticoid agonists
it is classified as a specialized postganglionic neuron, is a functional extension of the nervous system
Adrenal medulla
It is composed of _____________, which are the site of
catecholamine synthesis and secretion
chromaffin cells
These are true neuroendocrine cells, which provide a direct
interface between the two systems
chromaffin cells
___________ stimulation of the cell bodies results in secretion of catecholamines, which behave as
hormones
sympathetic, cholinergic
Release of catecholamines is stimulated by __________ from
cholinergic preganglionic neurons
acetylcholine
The adrenal medulla is the major site of _____________
production with a tyrosine precursor and dopamine
intermediate.
(nor)epinephrine
Examples of specific chemicals that target chromaffin cells
include toxins that block _______________ and
bacterial toxins that block ____________,
thereby preventing catecholamine release.
- voltage-gated ion channels
- exocytosis of secretory granules
The most common pathological changes seen in the adrenal
medulla in toxicological studies involve proliferative lesions
classified as _______________
nodular hyperplasia
Large benign adrenal medullary proliferative lesions are
designated __________
pheochromocytomas
In humans, pheochromocytomas are uncommon except in
patients with ___________
multiple endocrine neoplasia (MEN)
is the most powerful mitogenic stimulus to cause chroma in cell proliferation in the adrenal medulla in rats
Vitamin D
In long-term animal studies, pheochromocytomas often are
accompanied by ________ or toxic effects in other organs.
tumors
The thyroid gland is located below the ________-
larynx
The thyroid secretes
two hormones known as
thyroxine (T4) and triiodothyronine
(T3)
are important regulators of overall metabolism with
their primary target tissues including the liver, kidney, heart,
brain, pituitary, gonads, and spleen
(thyroid gland)
T4 and T3
-are some of the best
characterized thyroid disrupting chemicals
- are known to interfere with the thyroid system in a manner that leads to serious neurocognitive defects
- decrease the level of
thyroid hormone by inhibiting synthesis and/or increasing the
metabolism
Polychlorinated biphenyls (PCBs)
are structurally similar to that of PCBs. Thus, it is not surprising that many of the toxic effects between the two are similar leading to neurocognitive defects
Polybrominated diphenyl ethers (PBDEs)
inhibits thyroid hormone levels, possibly leading to hypothyroid-like outcomes
Perchlorate
mixtures containing dichlorodiphenyltrichloroethane
(DDT) have been shown to increase thyroid volume and to
induce antibodies that attack the thyroid gland, resulting in
autoimmune thyroid disease
pesticides
decrease T3 and T4 levels by
potentially upregulating phase II enzymes in liver and
deiodinases in the thyroid
Perfluorinated Chemicals
(perfluorooctane sulfonate and
perfluorooctanoic acid)
- blocks T3 action by antagonizing the binding of T3 to its receptor
- inhibits T3-mediated gene expression in cell lines
- leads to symptoms of hypothyroidism or thyroid
resistance syndrome in animal models
Bisphenol A
- may alter the levels of T3 and T4 in adult men and pregnant women
- result in low thyroid hormone levels and to symptoms of
hypothyroidism
Phthalates
Humans have ______ parathyroid glands that are embedded in
the surface of the thyroid gland
four
They are composed of mainly _______ that produce
parathyroid hormone (PTH)
chief cells
When the parathyroids are removed or damaged, PTH levels
drop, causing a major drop in circulating calcium levels. In
turn, this can lead to __________ and death
tetanic convulsions
The parathyroid glands are critical for life largely because PTH helps maintain normal plasma ____________.
calcium levels
PTH is a polypeptide hormone that is derived from a precursor
molecule called __________
preproparathyroid hormone
xenobiotic exposures have been shown to increase the
size of the parathyroid gland often leading to parathyroid cancer:
- lead
- rotenone
- malathion,
- hexachlorobenzene
has been shown to decrease
PTH levels in pregnant rats
alcohol consumption
have been shown to
inhibit PTH secretion
aluminum and cadmium
has been associated with a rise in PTH levels as well as abnormally high calcium levels
Lithium
main physiological role of the parathyroid gland is to
control circulating _________
calcium levels
PTH works in concert with _____________ and ___________
calcitonin (CT) and vitamin D
PTH serves to increase circulating calcium levels by increasing
the release of calcium from bone through __________________
demineralization
PTH inhibits the renal reabsorption of _____________, which aids in increasing the solubility of calcium
phosphate
PTH also enhances ________reabsorption, inhibits
bicarbonate ion reabsorption, and blocks exchange of sodium
ions by the tubules
magnesium
actions of PTH result in _________, which favors removal of calcium from plasma proteins and bones
metabolic acidosis
serves to prevent hypercalcemia by shutting down efflux of
calcium from bone, and it negatively regulates PTH to prevent kidney calcification
CT
also serves to inhibit PTH actions and build bone
Vitamin D
can cause excessive PTH secretion by the parathyroid gland and lead to hyperparathyroidism.
pesticides and fungicides
may cause low PTH secretion and lead to hypoparathyroidism
heavy metals
Scattered among the pancreatic acini are the endocrine units
of the pancreas, the __________
Islets of Langerhans
The major physiological function of the endocrine pancreas is
to serve as the
primary homeostatic regulator on fuel metabolism, particularly circulating glucose
are sensors on glucose homeostasis that respond to
changes in their nutrient and hormonal environment
Islet cells
is the primary contributor to
increasing blood glucose levels
liver
stimulate anabolic
processes (energy storage)
insulin
functions to lower blood levels of glucose, fatty acids, and amino acids and to promote their conversion to the storage form of each: glycogen, triglycerides, and protein
insulin
is the primary hormone with action counterregulatory to insulin, because it stimulates catabolic processes to prevent hypoglycemia
glucagon
glucagon is stimulated by ___________ and __________, and by the amino acids, _________, _________. and __________
epinephrine and
norepinephrine;
arginine, leucine, and alanine
role of ______________ is its role in regulation of neuroendocrine function to inhibit secretion of growth hormone in the anterior pituitary
somatostatin
The generalized function of somatostatin appears to be as a ___________
hormone release inhibitor
clinical consequences of insulin deficiency are physiologically less severe than those that would result from glucagon deficiency (t or f)
F; more
Two chemicals that have been widely used to generate animal
models of diabetes are ___________ and __________. A common
target of these in pancreatic beta cells is DNA.
alloxan and streptozotocin
Insulin resistance and defective function of pancreatic beta
cells usually occur sometime before the development of type
2 diabetes. (t or f)
T
In a study investigating nondiabetic residents living near a deserted pentachlorophenol and chloralkaline factory in Taiwan, insulin resistance was associated with increasing circulating levels of ___________ and ________
dioxins and mercury
In addition,________ exposure of pregnant mice resulted in
increased insulin, leptin, triglyceride, and glycerol levels
BPA
