Endocrinology Flashcards
endocrine system
acts as means of internal communication, coordinating the activities of organ systems
hormones
chemical substances synthesized and secreted by endocrine glands directly into the circulatory system.
Exocrine glands
secrete substances that are transported by ducts
two chemical structures of hormones
peptide hormones and steroid hormones.
Peptide hormones
act as first messengers binding to specific extracellular receptors on the surface of their target cells, they rigger a series of enzymatic reactions within the cell. causing a cascade effect usually fast acting and short lived
Cyclic AMP
acts a second messenger from the enzymatic conversion of ATP, which was catalyzed by membrane bound enzyme adenylate cyclase.
it relays messages from the extracellular peptide hormone enzymes.
-inactivated by cytoplasmic enzyme phosphodieterase.
Steroids hormones
belong to a class of lipid derived molecules, because the are lipid soluble, steroid hormones enter their target cells directly and bind to intracellular receptor proteins in cytoplasm -this complex enter the nucleus and directly activates expression. longer and longer effect
endocrine glands
pituitary, hypothalamus, thyroid, parathyroid, adrenals, pancreas, testes, ovaries, pineal, kidneys, gastrointestinal glands, heart and thymus
adrenal glands
are situated on top of the kidneys and consist of the adrenal cortex and adrenal medulla
adrenal cortex
in response to stress ATCH stimulates the adrenal cortex to synthesize and secrete the steroid hormones which are collectively known as corticosteroids.
corticosteroids
derived from cholesterol include glucocorticoids, mineralcorticoids and cortical sex hormones.
glucocorticoids
cortisol and cortisone, involved in glucose regulation and protein metabolism. Rasing blood glucose levels by promoting protein breakdown and using the products in gluconeogenesis. also raises the plasma glucose levels and decreases protein synthesis
gluconeogenesis
a metabolic pathway that generates glucose from non carbohydrates
mineralcorticoids
particularly aldosterone regulates plasma levels of sodium and potassium and the total extracellular water volume.
aldosterone
causes active re-absorption of sodium and passive re-absorption of water in the nephron. results in the rise in both blood volume and blood pressure. this excess retention leads to hypertension
corical sex hormones
the adrenal cortex secretes small quantities fo androgens (male hormones) like androstendione and dehydropieandrosterone in males and females. has no real effect in males due to its already present. but over production in females leads to masculinizing effects
adrenal medulla
produces epinephrine and norepinephrine both of which belong to a class of amino acid derived compounds called catecholamines
epinephrine
increases the conversion of glycogen to glucose in liver and muscle tissue, causing a rise in blood glucose levels and increase in basal metabolic rate. along with norepinephrine it increases the strength of the heart beat to assist in “fight or flight”
control of adrenal hormones
release of adrenal cortical hormones is under the control of ACTH, aldosterone is controlled by renin angiotensisn mechanism.
Pituitary gland
(hypophysis) small trilobed gland lying at the base of the brain. the two main lobes, anterior and posterior are functionally distinct.
anterior pituitary
synthesizes both direct and tropic hormones. the hormonal secretions of this portion of the pituitary is regulated by hypothalamic secretion called releasing and inhibiting hormones or factors.
direct hormones
anterior pituitary hormones that directly synthesize their target organs. (PEG) prolactin, endorphins, growth hormone
Growth Hormone
GH (somatotrophin) promotes the bone and muscle growth
acromegaly
a disorder caused from GH over production in humans that have disproportionate over growth
prolactin
stimulates mile production and secretion in female mammary glands.
endorphins
neurotransmitters that behave like opoids, providing internal pain relief and production of pleasure sensations
Tropic hormones
from the anterior pituitary, which stimulate other endocrine glands to release hormones. (FLAT) follicle stimulating hormone, luteinizing hormone, thyroid stimulating hormone, adrenocorticotropic hormone
ACTH
adrenocorticotropic hormone stimulates the adrenal cortex to synthesize and secrete glucocorticoids and is regulated by the releasing hormone CRF
TSH
thyroid stimulating hormone- stimulates the thyroid gland to synthesize and release thyroid hormones
LH
lutenizing hormone- in females LH stimulates ovulation and formation of the corpus luteum. in males LH stimulates the interstitial cells of the testes to synthesize testosterone.
corpus luteum secretes
progesterone and estrogen
FSH
follicle stimulation hormone- in females causes maturation of ovarian follicles which secrete estrogren. in males it stimulates maturation of the seminiferous tubules and sperm production.
Posterior pituitary
neurohypophysis) does not synthesize hormones its stores and releases the peptide hormones oxytocin and ADH which is produced by the hypothalamus. secretion occurs when action potentials descend from the hypothalamus
Oxytocin
secreted during child birth, increases the strength and frequency of uterine muscle contractions. Oxytocin release causes uterine contractions and uterine contractions stimulates oxytocin release. also induced by suckling as it also stimulates milk in the mammary glands.
ADH
anti duiretic hormone or vasopressin. increases the permeability of the collecting duct of the nephron (in kidney) to water. which promotes water absorption and increases blood volume. sensed by baroreceptors in the circulatory system.
Hypothalamus
part of the forebrain and is located directly above the pituitary gland. receives neural transmissions from other parts of the brain and peripheral nerves from its neurosecretory cells.
how do neurosecretary cells regulate pituitary secretions
via negative feedback mechanisms and through actions of inhibiting and releasing hormones.
hypothalamic interaction with the anterior pituitary
the hypothalamic releasing hormones stimulate or inhibit the secretions of the anterior pituitary. Releasing hormones are secreted into the hypothalamic-hypophyseal protal system. this way releasing hormones can immediately reach the anterior pituitary.
hypothalamic 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 storage and secretion.
thyroid
the thyroid gland is a bi-lobed structure located on the ventral surface of the trachea. It produces secretes thyroxine and triiodothyronine and calcitonin
thyroid hormones
thyroxine (t4) and triiodothyronine (T3) are derived from the iodination of the amino acid tyrosine. they are necessary for growth and neurological development of children. they also increase the rate of metabolism. malfunctions cause goiters.
hypothyroidism
thyroid hormones are undersecreted or secreted at all. symptoms include slowed heart rate, and respiratory rate, fatigue, cold intolerance and weight gain.
hyperthyroidism
thyroid is over stimulated, resulting in the over secretion of thyroid hormones. symptoms are increased metabolic rate, excessive warmth, profuse sweating, palpation, weight loss and protruding eyes.
calcitonin
decreases plasma Ca2+ concentration by inhibiting the release of Ca2+ from bone. Calcitonin is regulated by Ca+ levels. antagonistic to parathyroid hormone.
Pancreas
both an exocrine and endocrine organ. exocrine function performed by cells that secrete digestive enzymes into the SI. the endocrine is performed by small glandular structures called islets of langerhans which is composed of beta and alpha cells.
Glucagon
produced by the alpha cells of the pancreas, stimulates protein and fat degradation, the conversion of glycogen to glucose and gluconeogenesis, all serving to increase blood glucose levels.
Insulin
produced by the beta cell of the pancreas. a protein hormone secreted in response to high levels of glucose in the blood. stimulates the uptake of glucose by muscle and adipose cells and the storage of glucose and glycogen. to lower blood glucose levels.
diebetes mellitus
under production of insulin or insensitivity to insulin that leads to hyperglycemia
parathyroid glands
four small pea-shaped structures embedded in the posterior surface of the thyroid. that synthesize and secrete parathyroid hormone
PTH
parathyroid hormone raises the CA2+ concentration in the blood by increasing bone re-absorption and decreasing Ca2+ excretion in the kidneys.
Kidneys
when blood volume falls the kidney produces renin. which leads to the release of aldosterone from the adreanal cortex.
Renin
an enzyme that converts the plasma protein andiotensinogen to andiotensin I. angiotensin I is converted to angiotensin II which stimulates the adreanal cortex.
Gastrointestinal hormones
- Ingested food stimulates gastrin. Gastrin stimulates the glands to secrete HCl.
- secretin is released by the small intestine stimulating pancreatic fluids which neutralize the acidity of the acidic chyme.
- cholecystokinin is released from the SI in response to fats
cholecystokinin
causes the contraction of the gall bladder and realeas of bile into the small intestine. it also travels to the brain’s satiation center to indicate a full sensation
pineal gland
tiny structure at the base of the brain that secretes the hormone melatonin. role of melatonin is unclear but believed to play a role in light and dark rhythms. in primitive vertebrates it lightens the skin by concentrating pigment.
plant hormones
they are primarily involved in the regulation of growth. produced by actively growing parts of plant.
auxins
an important class of plant hormones associated with several types of growth patterns
Phototrophism
the tendency of the shoots of plants to bend towards light sources (sun). When light strikes the tip of the plant from one side the auxin supply on that side is reduced. thus the illuminated side grows slower than the shaded side.
geotrophism
the growth of portions of plants towards or away from gravity
negative geotropism
causes shoots to grow upward away from the acceleration of gravity. gravity increases the concentration of auxin on the lower side of a horizontally placed plant.
positive geotropism
causes roots t grow towards the pull of gravity. cells exposed to a higher concentration of auxin are inhibited from growing, while cells with lower concentration continue to grow. Causing the root to go down.
gibberellins
stimulate the rapid stem elongation, particularly in plants that do not grow tall. they inhibit the formation of new roots and stimulate the production of new pholem cells by cambium.
-terminate the dormacy of seeds and buds
kinins
promote cell division. Kinetin is an important type of cytokinin. The ratio of kinetin to auxin is of particular importance in the determination of the timing of differentiation of new cells. action of kinetin is enhanced when auxin is present
ethylene
stimulates fruit ripening. ethylene also induces senescence of aging
inhibitors
block cell division and serve an important role in growth regulation. important to the maintenance of dormancy in the lateral buds and seed of plants.
abscisic acid
is one of the most important inhibitors
anit auxins
regulate the activity of auxins
