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52 Cards in this Set

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Hormones fall into three chemical classes
- Amines
- Peptides and proteins
- Steroids
The amine hormones are all derivates of the amino acid ?
tyrosine
The amine hormones include
-the thyroid hormones
- the catecholamines epinephrine and norepinephrine
- Dopamine
Epinephrine and norepinephrine is produced by
The adrenal medulla
Dopamine is produced by the
Hypothalamus
Hormones fall into three chemical classes
- Amines
- Peptides and proteins
- Steroids
The amine hormones are all derivates of the amino acid ?
tyrosine
The amine hormones include
-the thyroid hormones
- the catecholamines epinephrine and norepinephrine
- Dopamine
Epinephrine and norepinephrine is produced by
The adrenal medulla
Dopamine is produced by the
Hypothalamus
The adrenal glands are located where?
On the top of each kidney
Each adrenal gland comprises of two distinct endocrine glands...
- An inner adrenal medulla, which secretes amine hormones
and a surrounding adrenal cortex, which secretes steroid hormones
The adrenal medulla is really a ...
modified sympathetic ganglion whose cell bodies do not have axons but instead release their secretions into the blood thereby fulfilling a critrion for an endocrine gland
The adrenal medulla secretes mainly two amine hormones, ..
epinephrine and norepinephrine
In humans, the adrenal gland secretes approx. ___ ____ ____ epinephrine than norepinephrine
four time more
In humans, the adrenal gland secretes approx. four time more epinephrine than norepinephrine. This is because
the adrenal medulla expresses high amounts of an enzyme called PNMT, which catalyzes the step that converts norepinephrine to epinephrine
Epinephrine and norepinephrine exert action similar to ...
those of the sympathetic nerves, which because they do not express PNMT, make only norepinephrine
Most hormones are either
peptides or proteins
Peptides are initially synthesized on ..
the ribosomes of the endocrine cells as larger proteins known as preprohormones, which are then cleaved to prohormones by proteolytic enzymes in the rough ER
In peptides after they are initially synthesized, The prohormone is then packaged into
secretory vesicles by the golgi apparatus
In peptides after they are initially synthesized, The prohormone is then packaged into secretory vesicles by the golgi apparatus. In this process, the prohormone is .
cleaved to yield the active hormone and other peptide chains found in the prohormone. Therefore, when the cell is stimulated to release the contents of the secretory vesicles by exocytosis, the other peptides are secreted along with the hormone
Instead of just one peptide hormone, the cell may be secreting ...
multiple peptide hormones that differ in their effect on the target cells
Many peptides serve as both
neurotransmitters ( AKA neuromodulators) and as hormones

ex. Some of the hormones secreted by the endocrine glands in the GI tract (e.g., cholecystokinin) are also produced by neurons in the brain, where they may function as neuromodulators
Steroid hormones are primarily produced by
the Adrenal corex and the gonads as well as by the placenta during pregnancy
The general process of steroid hormone synthesis
1) The cells must be stimulated by binding their respective tropic hormone from the pituitary to plasma membrane receptors

2) These receptors are linked to G-proteins, which activate adenylyl cyclase and thus cAMP production

3) The subsequent activation of protein kinase A results in Phosphorylation of numberous cytosolic and membrane proteins

4)Receptors on the cell surface bind to circulating LDLs; when this occurs, the LDL/receptor complex is internalized into the cell cytosol by endocytosis. Once inside the cell, the cholesterol is stored in an esterified form in large, non-member-bound lipid droplets. When the cell is stimulated by a tropic hormone (e.g. ACTH or LH), free cholesterol is released from the lipid droplet by the action of the enzyme cholesterol esterase, which is activated by protein kinase A

5) A carrier protein then transports the free cholesterol to the mitochondria

6)The production of the LDL receptors and StAR protein are stimulated by the actins of the tropic hormone. Once at the mitochondria, the cholesterol must be transported across the outer membrane to the inner mitochondrial membrane, which contains the enzymes required to process cholesterol into steroid hormones. This transport is mediated by another protein called the peripheral-type benzodiazepine receptor

7) Once at the inner membrane, cholesterol is acted upon by enzymes called cytochrome P450s

8)the shuttling of intermediates btwn smooth ER and Mitochondria by a unknown mechanism

The final product depends upon the cell type and the types and amounts of the enzymes

9)Once formed, the lipophilic steroid hormones are not stores in the cytosol, but instead diffuse out through the lipid bilayer of the plasma membrane into the inerstitial fluid and from there into the circulation
The cytochrome P450s are
a large family of related proteins that can attach hydroxyl groups to carbons atoms and that participate in cleaving carbon-carbon bonds
As the P450 enzymes modify cholesterol, intermediates form, which must ...
be futher modified before final steroid hormone is produced
Because of their lipid nature, steroid hormones are not greatly soulbe in blood, and thus they are largely transported
bound to carrier proteins (such as Albumin)
The five hormones normally secreted in physiologically significant amounts by the adrenal cortex are
- aldosterone
- cortisol
- corticosterone
- dehydroepiandrosterone (DHEA)
- Androstenedione
aldosterone is known as a ____________ because....
- Mineralocorticoid

- its effects are on salt (mineral) balance, mainly on the kidney's handling of sodium, potassium, and hydrogen ions
Production of aldosterone is under the control of the circulating hormone called ________, which acts on
- angiotensin II

- plasma membrane receptors in the adrenal cortex to activate the inositol trisphosphate second messenger pathway
Once synthesized, aldosterone enters the circulation and acts on
- cells of the kidneys to stimulate sodium and water retention, and hydrogen excretion in the urine
Cortisol and corticosterone are called ________ because they
- Glucocorticoids

- have important effects on the metabolism of glucose and other organic nutrients
Which of the glucocorticoids is the most important of the two in humans?
Cortisol
DHEA and Androstenedione belong to the class of hormones known as ____________ which includes
- Androgens

- the major male sex hormones, testosterone
All androgens have actions similar to
those of testosterone
Because the adrenal androgens are much less potent than testerone, they are of
little physiological significance in the adult male but play roles in female adults. Used by both sexes in the fetus and at puberty
The adrenal cortex is not a homogeneous gland but is composed of
Three distint layers

- Outer layer: Zona Glomerulosa

- Middle layer: Zona Fasciculata

- Inner layer: Zona Reticularis
Facts about Zona Glomerulosa
- outer layer of the adrenal cortex

- possesses very high concentrations of the enzymes required to convert corticosterone to aldosterone, but lacks the enzymes required for the formation of cortisol and androgens

- synthesizes and secretes aldosterone but not other major adrenal cortical hormones
What does the Zona Fasciculata and the
Zona Reticularis have in common?
- Opposite enzyme profile than Zona Glomerulosa

- They secrete no aldosterone but much Cortisol and Androgen
In certain disease states, the adrenal cortex may secrete ...
decreased or increased amount of various steroids
Compared to the adrenal cortex, the gonads have very different concentrations of
key enzymes in their steroid pathways
Endocrine cells in both testes and ovaries lack the enzymes needed to
produce aldosterone and cortisol
Endocrine cells possess high concentrations of enzymes in the adrogen pathways leading to ..
androstenedione, as in the adrenal cortex
Endocrine cells in the testes contain a high concentration of the enzyme that converts _______________ to testosterone
androstenedione
What is the major androgen secreted by the testes
testosterone
The ovarian endocrine cells that synthesize the female sex hormones collectively known as
- estrogens
- estone and esteadiol
What estogen is the most important in Ovarian endocrine cells
Estradiol
Estrogens have a high concentration of the the enzyme, aromatase, required to transform
androgens to estrogens
What is the major steroid hormone secreted by the ovaries
Estradiol
Very small amounts of __________ do leak out of ovarian endocrine cells and very small amounts of _________ are produced from testosterne in the testes
- testosterone

- estradiol
The endocrine cells of the corpus luteum, an ovarian structure that arises following ovulation, secrete another major steroid hormone called....
Progesterone

- critically important for maintaining a pregnancy