Endocrine Physiology: Pituitary and Adrenals Test 3 Flashcards
feedback mechanisms generally involves 4 features. What are they?
- system variable
- Set point
- Detector
- Corrective mechansim
what is endocrinology?
the study of the endocrine system and hormone action
hormones act by binding receptors on or in target cells by controlling what? there are 3 things
rates of enzymatic reactions
controlling the movement of ions or molecules across membranes
controlling gene expression and protein synthesis
the secretion of hormones into the blood stream by neurons is called?
neurocrine
the secretion of hormones into the bloodstream by endocrine glands is called?
endocrine
hormone molecules secreted by one cell affects adjacent cells is what?
paracrine
hormone molecule secreted by a cell affects the secreting cell
autocrine
T/F bound forms of hormones are considered inactive?
true
bound forms of hormones can act as what?
reservoirs
what are the 3 chemical classifications for hormones?
amines (tyrosine derivatives)
peptide hormones
steroid hormones
which type of hormones are lipophilic (non-polar)? and where are the receptors on or in cells?
steroid hormones and thyroid hormones
receptors are intracellular
what type of hormones are hydrophilic (polar)? and where are the receptors on or in cells?
peptide hormones and catecholamines
receptors are extracellular cell membrane receptors
what are the two types of amine hormones and describe their characteristics regarding receptor sites and such?
- thyroid: lipophilic and bind to nuclear receptors. example: triiodothryonine (T3) and thyroxine (T4). Long half lives
- catecholamines: hydrophilic and bind to cell surface receptors. examples: epinephrine and norepinephrine. short half lives
how do what soluble hormones(peptides and catecholamines) affect transcription of target genes or how does signal transduction occur with these types of hormones?
they act as a first messenger that binds to a G-protein receptor on the surface and then a second messenger that is inside the cell (usually cAMP) then initiates the signal cascade.
what are the most numerous type of hormones in the body?
peptide hormones
Peptide hormones are water soluble and are often produced as what?
precursors called preprophormones that are proteolytically cleaved post-translationaly to an active form.
T/F peptide proteins must be exocytosed and secreted from the cell and transported in the blood bound to carrier proteins?
true
where is the preprohormone formed with in the cell?
the endoplasmic reticulum
where does the preprohormone get broken down into a prohormone?
golgi apparatus
what are all steroid hormones derived from?
cholesterol and the are all lipid-soluble
what do steroid hormones need to do before they can be transported in the blood?
must be carried by a plasma hormone-specific plasma binding globulins.
*these bound steroid hormones serve as a reservoir for rapid release.
what type of hormones can cross the cell membrane and bind directly to intracellular receptors?
steroid hormones and thyroid hormones
what is the complex called that the lipid soluble hormone binds to? and what do they do?
hormone-receptor complex
they act as a transcription factor regulating transcription of the target gene.
what is aromatase and what does it do?
it is an enzyme that converts androgens to estrogens.
this is done by trophoblastic tumors and by some normal adipose tissue, liver and brain
what is a tropic hormone?
a hormone released from the pituitary gland
involve in short-loop feedback to the hypothalamus
what is the anterior pituitary gland?
classical gland that secretes protein hormones that stimulate/inhibit target organs and may feedback to hypothalamus
what is the posterior pituitary gland?
it is not a separate organ, but an extension of the hypothalamus.
composed of axons of hypothalamic neurons
what connects the posterior pituitary gland to the hypothalamus?
infundibular stalk
what is the hypothalamic-pituitary-adrenal (HPA) axis?
responsible for the adaption component of the stress response.
Has regulatory implications on many body processes including digestion, the immune system, mood and emotions.
how does vasopressin (antidiuretic hormone) ADH regulate serum osmolality?
it produced by neurosecretory cells in the hypothalamus and secreted at the posterior pituitary gland.
Main control is by hypothalamic osmoreceptors
what does ADH (vasopressin) do?
increases the water permeability of the renal collecting duct by inserting aquaporins to increase water reabsorbtion from urine into circulation.
-makes hypertonic urine (concentrated)
T/F all adrenocortical hormones are steroid compounds?
true
the zona glomerulosa of the adrenal gland secretes what steroid compound?
mineralocorticoids (aldosterone)
the zona fasciculata secretes what steroid compound?
glucocorticoids (cortisol)
the zona reticularis secretes what steroid hormone?
adrenal androgens (dehydroepiandrosterone) DHEA
what does the adrenal medulla secrete?
catecholamines (epinephrines EPI, and norepinephrine NE)
what do mineralcorticoids (aldosterone) effect?
- promotes sodium reabsorption and potassium excretion by the renal tubular epithelial cells of the collecting and distal tubules.
- leads to an increase in extracellular fluid volume
what is aldosterone escape?
presistently elevated extracellular fluid volumes causes pressure diuresis in the kidney.
if levels of aldosterone are increased what happens to muscles?
hypokalemia occurs and muscle weakness is observed
if levels of aldosterone are decreased what happens?
leads to hyperkalemia with cardiac toxicity.
how do glucocorticoids (cortisol) effect the body?
stimulates gluconeogenesis in the liver while decreasing glucose use by extrahepatic cells in the body
- leads to an increase in serum glucose(adrenal diabetes) and increased glycogen stores in the liver
- clinically significant anti-inflammatory effects by stabilizing membrane, preventing release of proteolytic enzymes.
- immunity is adversely affected
effects of adrenal androgens on body?
sex hormones:(DHEA), androstenedione, and 11-hydroxyandrostenedione
small quantities of progesterone and estrogen via aromatization
-most effects result from extra-adrenal conversion of androgens to testosterone
-parallels secretion of cortisol
effects of the adrenal medulla on the body/
80% epinephrine, 20% norepinephrine into blood stream due to Ach.
- short term stress response
- acute stress (fight or flight)
- longer stress (metabolic changes and immune suppression)
cortisol regulation by HPA axis
hypothalamus signaled by circadian rhythm, stress, pro inflam cytokines to increase corticotropin releasing hormone (CRH) from hypothalamus
- Ant. Pitu. increases release of andrenocorticotropic hormone (ACTH) to increase cortisol synthesis and secretion from the adrenal gland.
- glucocorticoid, cortisol suppresses both CRH and ACTH at the pituitary and hypothalamus in a negative feedback loop.
what are three types of endocrine disorders?
endocrine hyposecretion (hormone deficiency)
- hormone resistance
- hormone excess
type I diabetes myelitis is what type of endocrine disorder?
hyposecretion (hormone deficiency)
beta cells are destroyed
type II diabetes myelitis is what type of endocrine disorder?
hormone resistance due to signal transduction uncoupling
acromegaly (gigantism) and graves disease are what type of endocrine disorder?
hormone excess
adrenal insufficiency leads to what disease?
addison’s disease
what is acromegaly?
gigantism due to hormone excess of growth hormone
what causes cushing’s syndrome
excess ACTH which leads to an over production of cortisol.
hypothyroidism symptoms
and a disease
fatigue, constipation, dry skin, depression infertility, weight gain, heavy menstral periods.
-Hashimoto’s disease
hyperthyroidism symptoms and a diseasea
due to too much thyroid hormone
weight loss, fast heart rate, sweating, infertility, nervousness
Graves disease
Grave’s disease is caused by what? and what is the most common symptom?
caused by overactive thyroid, which is an autoimmune disorder.
-Exopthalmos (bulging eyes)
