Physiology Endocrine - Hormones Structures And Synthesis

Front 1

Hormones falls into three chemical classes:

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1) Amines

2) Peptides and Proteins

3) Steroids

Front 2

The amine hormones are all derivatives of the animo acid __________:

Back 2

Tyrosine

Front 3

Amine hormones include:

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- the tyroid hormones

- catecholamines
- epinephrine
- norepinephrine
- dopamine

Front 4

Norepinephrine is produced by the:

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adrenal medulla

Front 5

Dopamine is produced by the:

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hypothalamus

Front 6

There are _____ adrenal glands, one on top of each ______

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- two

- kidneys

Front 7

Each adrenal gland is comprises two distinct endocrine glands _______ & _______.

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- an inner adrenal medulla

- a surrounding adrenal cortex

Front 8

The adrenal medulla secretes:

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amine hormones

Front 9

the adrenal cortex secretes:

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steroid hormones

Front 10

THe adrenal medulla is really a modified:

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sympathetic ganglion whose cell bodies do not have axons, but instead release their secretions into the blood, thereby fulfilling a criterion for an endocrine gland

Front 11

The adrenal medulla secretes mainly two amine hormones: ____________ & ____________

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- Epinephrine

- Norepinephrine

Front 12

In humans, the adrenal medulla secretes appx _____ epinephrine than norepinephrine

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- 4 times more

Front 13

Why does the adrenal gland secrete more epinephrine than norepinephrine?

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Because the adrenal medulla expresses high amounts of an enzyme called phenyl-N- methyltransferase which catalyzes the step that converts noepinephrine to epinephrine.

Front 14

Epinephrine and norepinephrine exert actions similar to those of the _______, which, because they do not express PNMT, make only ....

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sympathetic nerve

norepinephrine

Front 15

Most hormones are either

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peptides or proteins

Front 16

Peptides are initally synthesized on the

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ribosomes of the endocrine cells as larger proteins known as preprohormones, which are than cleaved to prohormones by proteolytic enzymes in the rough endoplasmic reticulum

Front 17

After preprohormones are cleaved to prohormones by proteolytic enzymes in the rough endoplasmic reticulu, what happens?

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the prohormone is than packaged into secretory vesicles by the golgi apparatus

Front 18

the prohormone is than packaged into secretory vesicles by the golgi apparatus. What happens during this process

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The prohormone is cleaved to yield the active hormone and other peptide chains found in the prohormone

Front 19

When the cell is stimulated to release the contents of the secretory vesicles by exocytosis, the other peptides are..

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secreted along with the hormone

Front 20

when exocytosis happens, instead of just one peptide hormone, the cell may ....

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be secreting multiple peptides hormones that differ in ther effects on target cells

Front 21

Many peptides serve as both _________ & as ____________

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- neurotransmitter (or neuromodulators)

- hormones

Front 22

some hormones secreted by the endocrine glands in the GI tract (like cck) are also produced by:

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neurons in the brain, where they may function as neuromodulators

Front 23

Steroid hormones are primarily produced by the:

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adrenal corex and the gonads (testes and ovaries) as well as by the placenta during pregnancy

Front 24

The step 1 of the general process of steroid hormone synthesis

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- In both the gonads and the adrenal cortex, the cells must be stimulated by binding their respective tropic hormone from the pituitary to plasma membrane receptors

Front 25

The step 2 of the general process of steroid hormone synthesis

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

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The step 3 of the general process of steroid hormone synthesis

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3. The subsequent activation of protein kinase A results in Phosphorylation of numerous cytosolic and membrane

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The step 4 of the general process of steroid hormone synthesis

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4. When the cell is stimulated by a tropic hormone (e.g ACTH or LH), free cholestrol is released from the lipid droplet by the action of the enzyme cholestrol esterase, which is activated by protein kinase A

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The step 5 of the general process of steroid hormone synthesis

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5. A carrier protein called the steroidogenic acute regulatory (StAR) protein then transports the free cholestrol to the mitochondria

Front 29

The step 6 of the general process of steroid hormone synthesis

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6. Peripheral - type benzodiazepine receptor step

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The step 7 of the general process of steroid hormone synthesis

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7. Once at the inner membrane, cholesterolis acted upon by enzymes called cytochrome P450s

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The step 8 of the general process of steroid hormone synthesis

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8. After P450 modifications occur in both the mitochondria and in the smooth E.R , thus the intermediates are shuttled back and forth between the two organelles by an unclear mechanism

Front 32

The step 9 of the general process of steroid hormone synthesis

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9. Once formed, the lipophillic steroid hormones are not stored in the cytosol, but instead diffuse out through the lipid bilayer of the plasma membrane into the interstitial fluid and from there into the circulation

Front 33

What important step of the general process of steroid hormone synthesis facilitates the subsequent steps in the process

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Step 3 - The subsequent activation of protein kinase A results in the phosphorylation of numberous cytosolic and membrane proteins

Front 34

Cells producing steroid hormones synthesize some of their own cholestrol for this purpose from.....

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molecules of acetate, but typically most of the cholestrol enters the cells in the form of low density lipoproteins (LDLs)

Front 35

Receptors on the cell surface bind to circulating LDL; when this occurs, the LDL/receptor complex is

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internalized into the cell cytosol by endocytosis

Front 36

When the LDL/receptor complex is internalized into the cell cytosol by endocytosis, what happens?

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The cholesterol is stored in anesterfied form in large, non-membrane-bound lipid droplets

Front 37

The cytochrome P450s are

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

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As the P450 enzymes modify cholesterol, intermediates form, which must be futher modified before...

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the final steroid hormone is produced

Front 39

The final product of steroid synthesis depends upon

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the cell type and amounts of the enzymes it expresses