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Phys II Unit II > 1 Intro To Endo > Flashcards

1 Intro To Endo Flashcards

1
Q

What are the functions of the endocrine system?

A

Regulate the internal environment of the organism

Regulate the functioning of cells, tissues, and organs

May act alone or may be integrated with nervous system

Is essential in maintaining homeostasis

Accomplishes this by releasing substances from endocrine glands known as hormones

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2
Q

What is the classic definition of a hormone?

A

The product of an endocrine gland that is released directly into the blood stream to act peripherally at a distant specific target cell.

Exerts a biological effect (or pleiotropic effects).

May exert a trophic effect (meaning it regulates hormone secretion by another gland or growth and integrity of the endocrine gland)

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3
Q

Hormones that regulate processes in neighboring cells

A

Paracrine

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4
Q

Hormones that “act back” to regulate processes within cell of origin

A

Autocrine

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5
Q

Hormone that regulates processes within the cell of origin without being secreted

A

Intracrine

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6
Q

Hormone that originates in the neuron, and after axonal transport, is carried dismally either by a blood vessel or synaptic transmission

A

Neurocrine

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7
Q

What are the classic endocrine glands?

A 
Hypothalamus
Pituitary
Pineal
Thyroid
Parathyroid
Pancreas
GI tract
Placenta
Ovaries
Testes
Thymus
Adrenal cortex
Adrenal medulla
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8
Q

What are the “novel” endocrine glands?

A

Heart (epicardial fat)

Adipose tissue (adipokines)

Skeletal muscle (myokines)

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9
Q

What are the three ways of classifying hormones?

A

By Chemical structure

By Signal transduction pathways

By Solubility in plasma

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10
Q

What are the three chemical structure classifications of hormones?

A

Peptide hormones (produced from gene for hormone that is transcribed into mRNA)

Amine hormones (derived from tyrosine)

Steroid hormones (derived from cholesterol)

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11
Q

What are the two classifications of hormones based on solubility in plasma?

A

Hydrophilic

Hydrophobic

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12
Q

Hormones that are derived from amino acids

A

Peptides

The majority of hormones are peptides

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13
Q

Hormones that are derived from tyrosine

A

Amines

Includes hormones form the adrenal medulla (Dopamine, NE, Epi) and thyroid (Thyrosine T4 and Triiodothyronine T3)

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14
Q

Hormones derived from cholesterol

A

Steroid hormones

Includes cortisol (glucocorticoid), aldosterone, and androgens

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15
Q

Subset of peptide hormones with a carbohydrate moiety

A

Glycoproteins

FSH, TSH, LH, and Human chorionic gonadotropin (hCG)

The carbohydrate moiety is important in assemby, secretion and biologically activity

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16
Q

_________ hormones are transported dissolved in the blood stream

A

Hydrophilic

Includes peptides and catecholamines

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17
Q

_________ hormones are transported bound to binding proteins

A

Hydrophobic (or lipophilic)

Includes thyroid and steroid-based hormones

More than 99% of the hormone is bound, less than 1% is free

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18
Q

Why are binding proteins important?

A

Provide a RESERVE than can be called upon to replenish the free pool

Keeps the hormone in the blood in the inactive state

Increases the hormone HALF-LIFE (time required for the hormone to decrease by 50% in the plasma)

Binding proteins are involved in hormone turnover - rate at which a hormone is released into the plasma and removed from the plasma

19
Q

Hormone turnover depends upon…

A

Secretion of the hormone from gland

Binding to plasma protein

Inactivation and excretion

Activation or peripheral conversion

Internalization in peripheral tissue

20
Q

Site of synthesis for peptides

A

Multiple sites: Ribosomes, ER, golgi

21
Q

Site of synthesis for amines

A

Catecholamines: enzymatic synthesis in CYTOSOL (intracellular)

Thyroid: CYTOSOL of follicular cell and in the colloid (both intra and extracellular)

22
Q

Site of synthesis for Steroid hormones

A

Multiple sites: CYTOSOL, ER, mitochondria

23
Q

Which types of hormones are stored after synthesis?

A

Peptides (in granules), amines (in granules), T3/T4 (inside follicular cells)

Steroids are synthesized and released upon stimulation - NOT stored in granules

24
Q

Steps in the synthesis of hormones

A

1) Gene for hormone is transcribed into a mRNA
2) mRNA in the ER binds amino acids into a peptide chain called a preprohormone
3) In the ER, the preprohormone is cleaved to a prohormone
4) Prohormone is cleaved to hormone (ie - in Golgi apparatus)
5) Storage in secretory vesicles
6) Secretion is initiated by a stimulus that increases cytosolic cAMP and Ca2+

25
Q

Vitamin D3 is produced in the _________, undergoes peripheral conversion in ___________, to the active form ____________.

A

Skin

Liver and Kidney (hydroxylations)

1,25-dihydroxyvitamin D3

26
Q

_________ is produced in the thyroid, undergoes peripheral conversion in ___________, to the active form ____________.

A

Thyroxine (T4)

Most tissues

Triiodothyronine (T3)

27
Q

Testosterone is produced in the _________, undergoes peripheral conversion in ___________, to the active form ____________.

A

Testes

Androgens formed in androgen-dependent tissues (ie prostate —> Dihydrotestosterone (DHT)

Conversion to E2 in brain and testes —> Estradiol (E2)

28
Q

In ________ secretion, hormone release is triggered by a blood born substrate

A

Humoral

Ex: Low plasma calcium triggers PTH release from parathyroid —> PTH acts on various tissues to raise blood Ca2+ back to normal

29
Q

In ________ secretion, hormone release is triggered by an extension of the CNS that signals the gland to secrete

A

Neural

Examples of stimuli: Psychic and/or emotional, Fight response, Altered physiologic status (ie hypoglycemia, exercise, shock, stress, illness)

30
Q

In ________ secretion, hormones regulate the secretion of other hormones

A

Hormonal (duh)

It’s basically negative feedback loop; most hormones work this way

Ex: TRH stimulates pituitary to secrete TSH, which stimulates thyroid to produce and secrete T4/T3

31
Q

Examples of hormones that are regulated by positive feedback

A

Estrogen and Oxytocin

Hormone action stimulates MORE secretion of hormone

32
Q

Where do hydrophilic hormones bind?

A

To a receptor or channel located on the outer cell membrane of the target cell (includes peptides and catecholamines)

33
Q

Where do hydrophobic hormones bind?

A

Diffuse through the lipid bilateral and bind to a nuclear receptor (includes steroid and thyroid hormones)

34
Q

What is “threshold” on the dose-response curve for a hormone?

A

The minimal hormone concentration required to achieve a response

35
Q

What is “Maximal response” on the dose-response curve for a hormone?

A

Effect of a saturating dose of the hormone (the concentration at which the curve plateaus)

36
Q

What is “sensitivity” on the dose-response curve for a hormone?

A

The hormone concentration that produces 50% of the maximum response (half-maximal concentration)

37
Q

A downward shift in the dose-response curve indicates…

A

Down-regulation

A decrease in target cells/receptors and decreased signal transduction mechanisms and activity of enzymes within the cell

Increasing the [H] does not increase the maximal response

38
Q

A rightward shift in the dose-response curve indicates…

A

Decrease in sensitivity (ie insulin resistance)

More hormone is needed to get the same response

Explained by a decrease in the hormone-receptor affinity and decrease in receptor number

39
Q

Mechanism by which hormones have low effect when present alone but when combined the overall effect is greater than the sum of their separate effects

A

Synergism (ie - Testosterone + GH during growth spurts)

40
Q

Mechanism by which one hormone cannot exert its full effect without another hormone being present

A

Permissiveness - hormone MUST be present to exert full effect of another hormone

Ex: BP regulation (need cortisol for catecholamines to have effect on BP)

41
Q

Mechanism by which one hormone reduces or antagonizes the effect of another hormone

A

Antagonism

42
Q

Mechanism by which a hormone regulates number and/or affinity of its own receptor

A

Autologous up- or down-regulation

43
Q

Mechanism by which a hormone regulates number and/or affinity of another hormone’s receptor

A

Heterologous up- or down-regulation (ie progesterone effect on oxytocin)

Phys II Unit II (9 decks)

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