Physiology - Principles Of Hormone Control Systems

Front 1

Hormones fall into three chemical classes

Back 1

- Amines
- Peptides and proteins
- Steroids

Front 2

The amine hormones are all derivates of the amino acid ?

Back 2

tyrosine

Front 3

The amine hormones include

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-the thyroid hormones
- the catecholamines epinephrine and norepinephrine
- Dopamine

Front 4

Epinephrine and norepinephrine is produced by

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The adrenal medulla

Front 5

Dopamine is produced by the

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Hypothalamus

Front 6

Hormones fall into three chemical classes

Back 6

- Amines
- Peptides and proteins
- Steroids

Front 7

The amine hormones are all derivates of the amino acid ?

Back 7

tyrosine

Front 8

The amine hormones include

Back 8

-the thyroid hormones
- the catecholamines epinephrine and norepinephrine
- Dopamine

Front 9

Epinephrine and norepinephrine is produced by

Back 9

The adrenal medulla

Front 10

Dopamine is produced by the

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Hypothalamus

Front 11

The adrenal glands are located where?

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On the top of each kidney

Front 12

Each adrenal gland comprises of two distinct endocrine glands...

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- An inner adrenal medulla, which secretes amine hormones
and a surrounding adrenal cortex, which secretes steroid hormones

Front 13

The adrenal medulla is really a ...

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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

Front 14

The adrenal medulla secretes mainly two amine hormones, ..

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epinephrine and norepinephrine

Front 15

In humans, the adrenal gland secretes approx. ___ ____ ____ epinephrine than norepinephrine

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four time more

Front 16

In humans, the adrenal gland secretes approx. four time more epinephrine than norepinephrine. This is because

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the adrenal medulla expresses high amounts of an enzyme called PNMT, which catalyzes the step that converts norepinephrine to epinephrine

Front 17

Epinephrine and norepinephrine exert action similar to ...

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those of the sympathetic nerves, which because they do not express PNMT, make only norepinephrine

Front 18

Most hormones are either

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peptides or proteins

Front 19

Peptides are initially synthesized on ..

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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

Front 20

In peptides after they are initially synthesized, The prohormone is then packaged into

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secretory vesicles by the golgi apparatus

Front 21

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 .

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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

Front 22

Instead of just one peptide hormone, the cell may be secreting ...

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multiple peptide hormones that differ in their effect on the target cells

Front 23

Many peptides serve as both

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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

Front 24

Steroid hormones are primarily produced by

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the Adrenal corex and the gonads as well as by the placenta during pregnancy

Front 25

The general process of steroid hormone synthesis

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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

Front 26

The cytochrome P450s are

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a large family of related proteins that can attach hydroxyl groups to carbons atoms and that participate in cleaving carbon-carbon bonds

Front 27

As the P450 enzymes modify cholesterol, intermediates form, which must ...

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be futher modified before final steroid hormone is produced

Front 28

Because of their lipid nature, steroid hormones are not greatly soulbe in blood, and thus they are largely transported

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bound to carrier proteins (such as Albumin)

Front 29

The five hormones normally secreted in physiologically significant amounts by the adrenal cortex are

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- aldosterone
- cortisol
- corticosterone
- dehydroepiandrosterone (DHEA)
- Androstenedione

Front 30

aldosterone is known as a ____________ because....

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- Mineralocorticoid

- its effects are on salt (mineral) balance, mainly on the kidney's handling of sodium, potassium, and hydrogen ions

Front 31

Production of aldosterone is under the control of the circulating hormone called ________, which acts on

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- angiotensin II

- plasma membrane receptors in the adrenal cortex to activate the inositol trisphosphate second messenger pathway

Front 32

Once synthesized, aldosterone enters the circulation and acts on

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- cells of the kidneys to stimulate sodium and water retention, and hydrogen excretion in the urine

Front 33

Cortisol and corticosterone are called ________ because they

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- Glucocorticoids

- have important effects on the metabolism of glucose and other organic nutrients

Front 34

Which of the glucocorticoids is the most important of the two in humans?

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Cortisol

Front 35

DHEA and Androstenedione belong to the class of hormones known as ____________ which includes

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- Androgens

- the major male sex hormones, testosterone

Front 36

All androgens have actions similar to

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those of testosterone

Front 37

Because the adrenal androgens are much less potent than testerone, they are of

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little physiological significance in the adult male but play roles in female adults. Used by both sexes in the fetus and at puberty

Front 38

The adrenal cortex is not a homogeneous gland but is composed of

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Three distint layers

- Outer layer: Zona Glomerulosa

- Middle layer: Zona Fasciculata

- Inner layer: Zona Reticularis

Front 39

Facts about Zona Glomerulosa

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- 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

Front 40

What does the Zona Fasciculata and the
Zona Reticularis have in common?

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- Opposite enzyme profile than Zona Glomerulosa

- They secrete no aldosterone but much Cortisol and Androgen

Front 41

In certain disease states, the adrenal cortex may secrete ...

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decreased or increased amount of various steroids

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Compared to the adrenal cortex, the gonads have very different concentrations of

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key enzymes in their steroid pathways

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Endocrine cells in both testes and ovaries lack the enzymes needed to

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produce aldosterone and cortisol

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Endocrine cells possess high concentrations of enzymes in the adrogen pathways leading to ..

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androstenedione, as in the adrenal cortex

Front 45

Endocrine cells in the testes contain a high concentration of the enzyme that converts _______________ to testosterone

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androstenedione

Front 46

What is the major androgen secreted by the testes

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testosterone

Front 47

The ovarian endocrine cells that synthesize the female sex hormones collectively known as

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- estrogens
- estone and esteadiol

Front 48

What estogen is the most important in Ovarian endocrine cells

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Estradiol

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Estrogens have a high concentration of the the enzyme, aromatase, required to transform

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androgens to estrogens

Front 50

What is the major steroid hormone secreted by the ovaries

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Estradiol

Front 51

Very small amounts of __________ do leak out of ovarian endocrine cells and very small amounts of _________ are produced from testosterne in the testes

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- testosterone

- estradiol

Front 52

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

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Progesterone

- critically important for maintaining a pregnancy