Endocrine system Flashcards
Endocrine glands
synthesize and secrete chemical substances called HORMONEs directly into the circulatory system
-include: pituitary, hypothalamus, thyroid, parathyroids, adrenals, pancreas, testes, ovaries, pineal glands, kidneys, gastrointestinal glands, heart and thymus
Exocrine Glands
such as the gallbladder,
-secrete substances transported by ducts
Adrenal Glands
located on the top of the Kidneys and consists of the adrenal cortex and the adrenal medulla
What stimulates the adrenal cortex and what is the result of the stimulation?
-ACTH (adrenocorticotropic mormon which is produced by the anterior pituitary stimulates the adrenal cortex to produce more than 2 dozen different steroid hormones called ADRENOCORTICAL STEROIDS or CORTICOSTEROIDS
Transcortins
the complex that is formed in the blood, when the corticosteroids are bound to transport proteins \
What are the three major classes of corticosteroids?
1) Glucocorticoids
2) Mineralocorticoids
3) Corticol Sex Hormones
Glucocorticoids
-such as cortisol and cortisone are involved in glucose regulation and protein metabolism
- raise blood glucose levels by promoting protein breakdown and gluconeogenesis and decreasing protein synthesis
- increase plasma glucose levels
- antagonistic to the effects of insulin
- release amino acids from skeletal muscle as well as lips from adipose tissue
- also promote the peripheral use of lipids and have anti-inflammatory effects
Mineralcorticoids
- ALDOSTERONE-
- regulate plasma levels of sodium and potassium and consequently the total extracelular fluid volume
- Aldosterone causes active reabsorption of sodium and passive reabsorption of water in the nephron of the kidney. This results in an increase in BLOOD VOLUME AND BP
- stimulated by angiotensen II and inhibited by ANP (Atrial natriuretic peptide)
Excess production of Aldosterone causes?
results in excess retention of water with resulting hypertension (High BP)
Corticol Sex hormones
-in both men and some the adrenal cortex secretes small amounts of ANDROGENS (male sex hormones) like andiostenedioine and dehydroplandrosterone
- in men, most of the androgens are produced by the testes
- in women, overproduction of the adrenal androgens may have maculating effects, such as excessive facial hair
Adrenal Medulla
-produces EPINEPHRINE (adrenaline) and noreepinephrine (noradrenaline)
What class does epinephrine and norepinephrine belong to?
CATECHOLAMINES
Epinephrine
- increases the conversion of glycogen to glucose in the liver and muscle tissue causing an increase in blood glucose levels and an increase in the basal metabolic rate
- inhibits other functions, such as digestion, that are not immediately important for survival
Epinephrine and Norepinephrine SImiliarities
both increase the rate and strength of the heartbeat and dilate and constrict blood vessel in such as way to increase the blood supply to the kidneys, skin, and digestive tract
- also promote the release of lipids by adipose tissue
- THese effects are known as the “fight or flight response”
- both are also NEUROTRANSMITTERS
Pituitary Gland
hypophysis
- a small, trilled gland at the basis of the brain
- the two main lobes are anterior and posterior
- Pituitary gland hangs below the hypothalamus and is connected to it by a slender cord call infundibulum
Anterior Pituitary
- synthesize both direct hormones which directly acts on their target organs
- also synthesize tropic hormones which stimulate other endocrine glands to release hormones
what regulates the hormonal secretion of the anterior pituitary?
regulated by the hypothalamic hormones called releasing/inhibiting hormones or factors
Direct hormones of the anterior pituitary
- Growth Hormone (GH, somatotropin)
- Prolactin
Growth Hormone
- (GH, somatotropin)
- promotes bone and muscle growth
- promotes protein synthesis and lipid mobilization and catabolism
In children what can a deficiency in growth hormone result in?
stunted growth (Dwarfism)
In children what can an excess of growth hormone result in?
Gigantism
In adults what can overproduction of Growth Hormone cause?
Acromegaly, a disorder characterized by disproportionate overgrowth of bone, especialy in the skull, jaw, feet, and hands
Prolactin
stimulates milk production in female mammary glands
Tropic hormones of the Anterior Pituitary
- adrenocorticotropic Hormone (ACTH)
- Thyroid Stimulating Hormone (TSH)
- Lenteinizing Hormone (LH)
- Follicle-stimulating hormone (FSH)
- Melanocyte-stimulating hormone (MSH)
- Endorphins
Adrenocorticotropic Hormone
ACTH
- stimulates the adrenal cortex to synthesize and secrete gulcocorticoids
- regulated by corticotrophin-releasing-factor (CRF)
Thyroid Stimulating Hormone
stimulates the thyroid gland to synthesize and release thyroid hormone, including thyroxine
Lenteinizing Hormone
LH
- in women, LH stimulates ovulation and maintenance of the CORPUS LUteum
- responsible for regulating progesterone secretion in women
- In men, LH stimulates the interstitial cell soy the testes to synthesize testosterone
Follicle-stimulating hormone
FSH
- in women, FSH causes maturation of ovarian follicles, which secretes estrogen
- in men, FSH stimulates maturation of the seminiferous tubules and sperm production
Melanocyte-stimulating Hormone
MSH
- secreted by the intermediate lobe of the pituitary
- in mammals the function is unclear but in frogs, MSH causes darkening of the skin via the induced dispersion of molecules of pigment in melanophore cells
Posterior Pituitary
Neurohypophysis
- doesn’t synthesize hormones
- it stores and releases the peptidehormone, OXYTOCIN and ANTIDURETIC HORMONE
Where are oxytocin and ADH produced?
produced on the neurosecretory cell of the hypothalamus
Oxytocin
secreted during childbirth
- increases the strength and frequency of uterine muscle contractions
- oxytocin secretion is also induced by suckling
- stimulates milk secretion in mammary glands
Antiduretic Hormone
ADH
- increases the permeability of the nephron’s COLLECTING DUCTS to water, thereby promoting water reabsorption and increasing blood vole which increases Blood pressure
- is secreted when plasma osmolarity increases, which is sensed by osmoreceptors in hypothalamus or when Blood volume decreases is sense by baroreceptors in circulatory systems
Hypothalamus
- part of the forebrain and dis located directly above the pituitary gland
- receives neural transmissions from other parts of the brian and form peripheral nerves that trigger specific responses from its neurosecretory cells
Neurosecretory cells
regulate pituitary gland secretions via negative feedback mechanisms and through the actions of inhibiting and releasing hormones
Hypothalamus interactions with posterior pituitary
-neurosecretory cells in the hypothalamus synthesize both oxytocin and ADH and transport them via their axons into the posterior pituitary for secretion
Thyroid
thyroid hormones affect the function of nearly every organ system in the body
Thyroid hormones in children
-thyroid hormones are essential for growth and neurological development
Thyroid Hormones in adults
-thyroid hormones increase the rate of metabolism throughout the body and are essential for maintenance of metabolic stability
What are the thyroid hormones?
Thyroxine (T4) and Triiodothyronine (T3)
How are the thyroid hormones formed?
formed from the glycoprotein (THYROGLOBULIN), which is synthesized in thyroid cells
-because of the specific territory structure of the glycoprotein, iodinated tyrosine residues present in thyroglobulin are able to bind together to form active thyroid hormones
What are some of the characteristics of the thyroid hormones?
- T3 is 5 times more potent than T4
- T4 and T3 are transported via plasma proteins. Approximately 99.5% of these hormones are bound to proteins, but only an unbound hormone is able to enter a cell and elicit a cellular response
- All of the T4 in the body is formed and secreted by the thyroid gland, however only 20% of T3 is produced by the thyroid gland
- The majority of T3 is produced by the conversion of T4 to T3 by the enzyme 5-monodeiodase, found primarily in the peripheral tissues
Hypthyroidism
- thyroid hormones are under secreted or not secreted at all
- common symptoms: slowed heart rate and respiratory rate, fatigue, cold tolerance, and weight gain
in infants what is hypothyroidism called?
Cretinism- characterized by mental retardation and short stature
Hypothyroidism treatment
-supplementation of thyroid hormones via synthetic or animal derived products
Hyperthyroidism
- the thyroid is overstimulated, resulting in over secretion of thyroid hormones
- symptoms: increased metabolic rate, feelings of excessive warmth, produce sweating, palpitations, weight loss, and protruding eyes
Hyperthyroidism treatment
can be treated by antithyroid medications that suppress the thyroids release of excess hormones
OR
ablation of the thyroid with radiation. After ablation, the thyroid no longer produces thyroid hormone, and the patient must take thyroid supplementation for the rest of his/her life
Calcitonin
- decreases plasma Ca2+ concentration by inhibiting the release of Ca2+ from bone
- Calcitonin secretion is regulated by plasma Ca2+ levels
- antagonistic to parathyroid hormone
Pancreas
- both an exocrine organ and endocrine organ
- exocrine function is performed by the cells that secrete digestive enzymes into the small intestine via a series of ducts
-endocrine function is performed by small glandular structures called ISLETS OF LANGERHAS
Islets of langerhas
composed of alpha and beta cells
- alpha cells produce and secrete glucagon
- beta cells produce and secrete insulin
Endocrine hormone secreted by the pancreas
Glucagon
Insulin
Glucagon
stimulates protein and fat digestion, the conversion of glycogen to glucose, and glucogenesis—-all of which serve to INCREASE blood glucose levels
-actions are antagonistic to insulin
Insulin
- protein hormone secreted in response to a high blood glucose concentration
- stimulates the uptake of glucose by muscle and adipose cells and the storage of glucose as glycogen in muscle and liver cells—THUS LOWERING BLOOD glucose levels
- also stimulates the synthesis of fats from glucose and uptake of amino acids
- antagonisitic of glucagon and glucocorticoids
What does underproduction of insulin/insensitivity of insulin lead to?
Diabetes mellitus- characterized by hyperglycemia (high blood glucose levels)
What is the most common endocrine disorder?
diabetes and if not treated can lead to long term complications involving the eyes, nerves, kidneys, and blood vessels
Parathyroid Glands
are four small, pea-shaped structures embedded in the posterior surface of the thyroid
-these glands synthesize and secrete parathyroid hormone PTH
Parathyroid Hormone
regulates the plasma Ca2+ conc.
-PTH raises the Ca2+ conc. int eh blood by stimulating Ca2+ release from the bone and decreasing Ca2+ excretion in the kidneys
Kidneys
- when the blood volume falls the kidneys produce renin
- also produce erythropoietin
Renin
an enzyme that converts the plasma protein angiotenstrogen to angiotensin I. Angiotensin is then converted to angiotensin II, which stimulates the adrenal cortex to secrete ALODSTERONE.
-aldosterone helps restore blood volume by increasing sodium reabsorption of the kidneys, leading to an increase in fluid retention. This removes the initial stimulus for renin production
erythropoietin
-a glycoprotein that stimulates RBC production. It is normally produced in the kidneys
causes the following:
- stimulation of the stem cells to differentiate into rubriblasts
- increased rate of mitosis
- increased rate of reticulocytes front eh bone marrow
- increased hemoglobin formation, which results int eh critical HgB (hemoglobin) conc. necessary for RBC maturity to be reacted at a more rapid rate
Gastrointestinal hormones
-ingested food stimulates the stomach to release the mormon Gastrin
Gastrin
is carried to the gastric glands and stimulates the glands to secrete HCL in the response to food in the stomach
Secretin
released by the small intestine, when acidic chyme enters from the stomach
-secretion stimulates the secretion of an alkaline bicarbonate solution form the pancreas that neutralizes the acidity of the chyme
Cholecystokinin
is released by the small intestine in response to the presence of fats and cause the contraction of the gallbladder and release of bile into small intestine
Bile
not a hormone but is involved in the emulsification and digestion of fats
Pineal Gland
tiny structure at the base of the brain that secretes the hormone melatonin
melatonin
the role in humans is unclear but it is believed to play a role in regulation of the CIRCADIAN RHYTHM
-secretion is relegated by dark and light cycles
