endocrine system Flashcards
what is the biggest difference between the nervous system and the endocrine system?
the nervous system utilizes neurotransmitters to control body functions and the endocrine system utilizes hormones to control body functions
what is the difference between neurotransmitters and hormones when it comes to where their actions are performed?
neurotransmitters perform their action close to the site of release and hormones usually perform their action far from their site of release
what type of structures does the nervous system act upon?
muscle cells (smooth, cardiac, and skeletal), glands, and other neurons
what type of structures does the endocrine system act upon?
virtually all cells of the body
what is the difference between the nervous system and the endocrine system in regards to the time it takes them to act
nervous system-action typically occurs within milliseconds of neurotransmitter release
endocrine system-action can take seconds to days to occur after release of the hormone
in regards to the duration of actions set off by the endocrine system and nervous system, which tend to be longer?
the actions tend to be briefer in duration in the nervous system and longer in duration in the endocrine system
definition of a hormone
a mediator molecule that is released in one part of the body but regulated activity of cells in other parts of the body
can a neurotransmitter also be a hormone?
yes, several of them are including norepinephrine
what is the travel passage of a hormone
most enter the interstitial fluid and then the bloodstream. They travel through the bloodstream to cells throughout the body
what are the functions of hormones?
- help regulate: chemical composition and volume of the internal environment, metabolism and energy balance, contraction of smooth and cardiac muscle fibers, glandular secretions, and some immune system activities
- control growth and development
- regulate operation of reproductive systems
- help establish circadian rhythms
what structures make up the endocrine system?
all endocrine glands and hormone secreting cells (ie: pituitary, thyroid, and adrenal glands)
which organs in the body contain endocrine tissue but are not endocrine glands exclusively
hypothalamus, thymus, pancreas, stomach, skin, heart
what does it mean that the nervous system and endocrine system act as a coordinated supersystem (neuroendocrine system)?
parts of the neurons stimulate or inhibit the release of hormones and hormones can promote or inhibit the release of nerve impulses
which type of gland secrete their products into ducts that carry secretions into body cavities, into the lumen of an organ, or to the outer surface of the body
exocrine glands
which type of glands secrete their hormones into the interstitial fluid surrounding the secretory cells
endocrine glands
which type of glands are sudoriferous glands
exocrine glands
*sudoriferous (sweat)
which type of glands are pituitary glands?
endocrine glands
which type of glands are sebaceous glands
exocrine glands
*(oil)
which tyoe of glands are thyroid glands?
endocrine glands
which type of glands are mucous and digestive?
exocrine glands
which type of glands are parathyroid glands?
endocrine glands
which type of glands are adrenal and pineal?
endocrine glands
what is endocrinology
the study of the science of endocrine glands, function of endocrine glands, diagnosis of endocrine disorders and treatment of endocrine disorders
how does the binding of hormones to receptors work
hormones affect only certain target cells. Only target cells for a given hormone have specific receptors that bind and recognize that hormone. Target cells for a particular hormone are those cells that have the appropriate receptor mlecules (protiens or glycoproteins) that can bind to the hormone.
if a hormone is present in excess, the number of target cell receptors may _____
why?
What is this called?
decrease, in order to decrease the sensitivity of that target cell to a particular hormone. (Down-regulation)
explain up-regulation
when a hormone (or neurotransmiter) is deficient, the number of receptors may increase in order to make a target cell more receptive to a specific hormone
synergistic effects of hormones
the sum of the actions of the 2 hormones is greater than either hormone individually (ie: estrogens and FSH promote the development of oocytes)
antagonistic effects of hormones
one hormone opposes the actions of another (ie: insulin promotes synthesis of glycogen and glucagon which stimulates the breakdown of glycogen)
what structure serves as a major integrating link between the nervous system and the endocrine system?
hypothalamus
T/F, painful, stressful, and emotional experiences cause changes in hypothalamic activity
T
what structure regulates and exerts control over the pituitary gland?
hypothalamus
what are the five types of anterior pituitary cells & the 7 hormones they secrete?
- Corticotrophs - secrete adrenocorticotropic hormone (ACTH) or corticotropin, which stimulates the adrenal cortex to secrete glucocorticoids
- Gonadotrophs - secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH) which act on the gonads by stimulating the secretion of estrogen, progesterone, and testosterone
- Lactotrophs - secrete prolactin (PRL), which initiates milk production
- Somatotrophs - secrete human growth hormone (hGH) or somatotropin, which stimulates tissues to secrete insulin-like growth factors (IGFs) to stimulate body growth and some regulation of metabolism
- Thyrotrophs - secrete thyroid-stimulating hormone (TSH) or thyroptropin; regulating activites of the thyroid gland
hormones that influence another gland are called _____.
tropic hormones or tropins
what is the difference between anterior pituitary glands and posterior pituitary glands in regards to secreting and synthesizing hormones?
- the secretion of anterior pituitary hormones is regulated by releasing hormones and inhibiting hormones that are delivered from the neurosecretory cells of the hypothalamus by a hypophyseal portal system of blood vessels
- the posterior pituitary does not synthesize hormones, but it does store and release two hormones synthesized in the hypothalamus. (oxytocin & antidiuretic hormone ADH, aka vasopressin)
what is the purpose of oxytocin?
to enhance contraction of smooth muscle cells in the wall of the uterus during delivery and stimulate milk ejection from mammary glands in response to the suckling infant after delivery
what is the purpose of antidiuretic hormone (ADH)?
to decrease urine production and increase blood pressure
describe the anatomy of the thyroid gland
it is butterfly-shaped and located inferior to the larynx and anterior to the trachea. It has right and left lateral lobes connected by an isthmus that lies in front of the upper end of the trachea. It is highly vascular and consists of thyroid follicles
each of the walls of thyroid follicles consists of two types of cells. What are they?
- numerous follicular cells that secrete: thyrocine (tetraiodothyronine or T4), and triiodothyrronine (T3)
- these two hormones are collectively called the thyroid hormones
- these hormones regulate the rate of metabolism, growth, and developement - less numerous parafollicular cells, or C cells, that secrete calcitonin
- calcitonin influences calcium homeostasis by decreasing blood calcium concentration
what are the actions of thyroid hormones?
- increase basal metabolic rate (BMR)
- calorigenic effect (helps regulate body temperature)
- regulate metabolism by stimulating protein synthesis, increasing the use of glucose and fatty acids for ATP, and increasing lypolysis
- accelerate body growth, especially of the nervous system
where can you find parathyroid glands?
embedded into the posterior surface of the lateral lobes of the thyroid gland
what are the two kinds of cells found in the parathyroid glands?
- chief (principal) cells - produce parathyroid hormone (PTH) or parathormone (increase blood calcium and magnesium levels, decreases blood phosphate levels, and promotes the formation of calcitriol, which is the active form of vitamin D)
- oxyphil cell - function unknown
where can we find the adrenal glands?
two adrenal glands lie superior to the two kidneys
is it the adrenal cortex or the adrenal medulla that secretes norepinephrine, epinephrine and dopamine?
adrenal medulla
which two hormones have a sympathomimetic effect?
epinephrine (adrenaline) and norepinephrine (noradrenaline) augment the fight or flight response
what organ is both an endocrine and an exocrine gland?
pancreas
what is the location of the pancreas?
it is a flattened organ located posterior and slightly inferior to the stomach
the tiny clusters of endocrine tissue called pancreatic islets (islets of Langerhans) contain what four types of cells?
- Alpha (A) cells secrete glucagon
- Beta (B) cells - secrete insulin
- Delta (D) cells - secrete somatostatin (identical to growth hormone inhibiting hormone secreted by hypothalamus)
- F cells - secrete pancreatic polypeptide
glucagon raises or decreases blood glucose levels?
raises
insulin raises or decreases blood glucose levels?
lowers
somatostatin promotes or inhibits both glucagon and insulin release?
inhibits
pancreatic polypeptide promotes or inhibits somatostatin secretion, gallbladder contraction and secretion of digestive enzymes by the pancreas?
inhibits
female sex hormones that ovaries secrete:
- estrogens and progesterone, which are responsible for the development and maintenance of female sexual characteristics
- inhibin, which inhibits the secretion of follicle-stimulating hormone (FSH)
- relaxin (during pregnancy), which relaxes the pubic symphysis and helps dilate the cervix just before the birth of a baby
male sex hormones that testes secrete:
- testosterone, which regulates the production of sperm and stimulates the growth and development of male sexual characteristics
- inhibin, which inhibits the secretion of FSH
what hormones are secreted via the endocrine cells of the GI tract?
- gastrin
- glucose-dependent insulinotropic peptidee (GIP)
- secretin
- cholecystokinin (CCK)
what hormones are secreted by the endocrine cells of the placenta?
- human chorionic gonadotropin (hCG)
- estrogens and progesterone
- human chorionic somatomammotropin (hCS)
what hormones are secreted by the endocrine cells of the kidney
- renin
- erythropoietin (EPO)
- calcitriol (active form of vitamin D)
what hormone is secreted by the endocrine cells of the heart
atrial natriuretic peptide (ANP), which decreases blood pressure
what hormone is secreted by the endocrine cells of adipose tissue
leptin
why is the hypothalamus the “master” gland?
bc it is the major link bw the nervous & endocrine systems, and secretes hormones that control other hormones
the pituitary gland is attached to the hypothalamus via a stalk called the _______.
infundibulum
release of anterior pituitary hormones is stimulated by ______ hormones and suppressed by ______ hormones from the hypothalamus.
- releasing hormones
- inhibiting hormones
what is the hypophyseal portal system?
blood flows from capillaries in the hypothalamus into portal veins that carry blood to capillaries of the anterior pituitary
what is the function of neurosecretory cells?
they synthesize the hypothalamic releasing & inhibiting hormones in their cell bodies and package the hormones inside vesicles, which reach the axon terminals by axonal transport
what is the function of human growth hormone (hGH)?
stimulates liver, muscle, cartilage, bones, and other tissues to synthesize & secrete insulin-like growth factors (IGFs)
what is the function of IGFs?
promotes growth of body cells, protein synthesis, tissue repair, lipolysis and elevation of blood glucose concentration
low blood glucose (hypoglycemia) stimulates release of growth hormone-releasing hormone (GHRH). what is the function of GHRH?
- GHRH promotes secretion of hGH
- therefore hGH & IGFs speed up breakdown of liver glycogen into glucose, and blood glucose level rises
high blood glucose (hyperglycemia) stimulates release of growth hormone-inhibiting hormone (GHIH). what is the function of GHIH?
- GHIH suppresses secretion of HGH
- low level of hGH & IGFs decreases rate of glycogen breakdown in liver, and blood glucose level falls
what stimulates the release of follicle-stimulating hormone (FSH) and the release of luteinizing hormone (LH) from the anterior pituitary?
gonadotropin-releasing hormone (GnRH) from the hypothalamus stimulates release of FSH and LH
what is the function of follicle-stimulating hormone (FSH)?
- in females: FSH initiates development of oocytes/ovarian and also stimulates follicular cells to secrete estrogens
- in males: FSH stimulates testes to produce sperm
what is the function of luteinizing hormone (LH)?
- in females: LH triggers ovulation, the formation of the corpus luteum in the ovary, the secretion of progesterone by the corpus luteum, and (together with FSH) stimulates secretion of estrogens by ovarian cells
- in males: LH stimulates cells in testes to secrete testosterone
what hormones are the key players in milk secretion & ejection?
- prolactin (PRL), together with other hormones, initiates and maintains milk secretion by the mammary glands
- oxytocin, which is released from the posterior pituitary, initiates milk ejection
what is the function of thyroid-stimulating hormone (TSH) (or thyrotropin)?
stimulates the synthesis & secretion of thyroid hormones by the thyroid gland
what is the function of adrenocorticotropic hormone (ACTH) (or corticotropin)?
stimulates secretion of glucocorticoids (mainly cortisol) by the adrenal cortex
what is the function of oxytocin (OT)?
- during childbirth, enhances contraction of smooth muscle cells in walls of uterus
- after childbirth, stimulates milk ejection (“letdown”) from the mammary glands
T or F: both males & females secrete oxytocin
true
what stimulates the release of T3 (triiodothyronine) and T4 (thyroxine) from follicular cells?
thyrotropin-releasing hormone (TRH) from the hypothalamus, which stimulates the release of thyroid stimulating hormone (TSH) from the anterior pituitary in response to low thyroid hormone levels, low metabolic rate, cold, pregnancy, and high altitudes
(TRH & TSH secretions are inhibited by high thyroid hormone levels. T3/T4 secretion is inhibited by high iodine levels.)
what stimulates the release of calcitonin (CT) from parafollicular cells?
high blood calcium levels stimulate secretion of calcitonin (CT)
(low blood calcium levels inhibit secretion of calcitonin)
with respect to regulation of blood calcium level, explain why calcitonin (CT) and parathyroid hormone (PTH) are antagonists
- parathyroid hormone (PTH) increases blood calcium levels by promoting the release of calcium from bone and slowing loss of calcium in urine
- calcitonin (CT) decreases blood calcium levels by inhibiting osteoclasts
name the 3 zones of the adrenal cortex and their secretions:
1) zona glomerulosa (outer zone) secretes mineralcorticoids that affect mineral homeostasis including: aldosterone
2) zona fasciculata (middle zone) is the widest and secretes glucocorticoids that affect glucose homeostasis including: cortisol, corticosterone, and cortisone
3) zona reticularis (inner zone) synthesize small amounts of weak androgens including: dehydroepiandrosterone (DHEA)
what is the function of aldosterone?
- increase blood levels of sodium and water
- decreas blood level of postassium
what is the function of glucocorticoids (cortisol, corticosterone, and cortisone)?
regulate metabolism & resistance to stress:
- increase protein breakdown (mainly in muscle fibers)
- increase glucose formation (by stimulating liver cells to convert amino acids or lactic acid to glucose)
- increase lipolysis (the breakdown of triglycerides and release of fatty acids from adipose tissue into blood)
- provide resistance to stress (and raising blood pressure)
- dampen inflammation (and thus retarding tissue repair)
- depress immune responses
which of the glucocorticoids (cortisol, corticosterone, or cortisone) is the most abundant?
cortisol, which accounts of about 95% of secretions by zona fasciculata
what stimulates the secretion of glucocoticoids (cortisol, corticosterone, and cortisone)?
when there is a low level of cortisol in the blood:
- corticotropin-releasing hormone (CRH) is secreted by neurosecretory cells in the hypothalamus
- CRH promotes the release of ACTH from the anterior pituitary
- ACTH stimulates glucocorticoid secretion by adrenal cortex
what is unique about the adrenal medulla (the inner region of the adrenal gland)?
the autonomic nervous system exerts direct control over chromaffin cells in the adrenal medulla, so hormone release can occur very quickly
does the adrenal medulla secrete equal amounts of epinephrine and norepinephrine (aka adrenaline & noradrenaline)?
no - about 80% epinephrine and 20% norepinephrine
T or F: indirectly, human growth hormone (hGH) and adrenocorticotropic hormone (ACTH) stimulate the secretion of insulin because they act to elevate blood glucose.
true
where is the pineal gland located?
part of the epithalamus, it is a small endocrine gland attached to the roof of the third ventricle of the brain at the midline
what does the pineal gland secrete?
melatonin
what is the function of melatonin?
- appears to contribute to the setting of the body’s biological clock (low levels are secreted during the day, and higher levels are secreted at night)
- also a potent antioxidant
what hormones are produced by the thymus?
thymosin, thymic humoral factor (THF), thymic factor (TF), and thymopoetin (role in immunity)
stressors stimulate the hypothalamus to secrete CRH, GHRH, and TRH, which stimulate the anterior pituitary to secrete TSH, hGH, and ACTH. what are the targets for ACTH, hGH, and TSH?
- ACTH targets adrenal cortex & stimulates cortisol secretion, which increases lipolysis, gluconeogenesis, protein catabolism, sensitized blood vessels, and reduced inflamation
- hGH targets liver & stimulates IGF secretion which increases lipolysis & glycogenolysis
- TSH targets thyroid gland & stimulates T3/T4 secretion which increases use of glucose to produce ATP
