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Human Physiology 2 - Unit 3 - Zach H. > Lecture 20: Endocrine Principals > Flashcards

Lecture 20: Endocrine Principals Flashcards

1
Q

Why is negative feedback important for hormone systems?

A

Negative feedback prevents over-activity of hormone systems.

controlled variable is sometimes not the secretory rate of the hormone itself but the degree of activity of the target tissue

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2
Q

List the different levels in which feedback loop regulation controls hormones.

A

> gene transcription
gene translation
processing of hormones
releasing of steroid hormones

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3
Q

Give an example of a positive feedback mechanism of hormone control.

A

LH surge prior to ovulation.

> prior to ovulation, estrogen stimulates the surge of LH.
LH acts on ovaries to secrete more estrogen.
secreted estrogen stimulates the release of more LH.

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4
Q

List periodic variations in hormone release that are superimposed on the negative and positive feedback mechanisms.

A

> seasonal changes (more common in other animals, not as much in humans)

> various stages in development and aging (effects humans more)

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5
Q

Where are receptors typically found?

A

> in or on the surface of cell membrane
in the cell cytoplasm
in the cell nucleus

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6
Q

Define “down regulation” of hormone receptors.

A

Number of active receptors may decrease because of increased hormone concentration and increased binding to receptors.

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7
Q

Under what conditions may down regulation of hormone receptors occur?

A

> Inactivation of some of the intracellular protein signaling molecules.

> Temporary sequestration of the receptor inside the cell.

> Inactivation of some of the receptor molecules.

> Destruction of the receptors by lysosomes after they are internalized.

> Decreased production of receptors.

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8
Q

What is the effect of down regulation of hormone receptors?

A

Down regulation decreases the target tissue’s responsiveness to the hormones.

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9
Q

Define “up regulation” of hormone receptors.

A

Number of active receptors or intracellular signaling molecules may increase.

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10
Q

Under what conditions may up regulation of hormone receptors occur?

A

> The stimulating hormone may induce greater than normal formation of receptor or intracellular signaling molecules.

> The stimulating hormone may induce greater availability of the receptor for interaction with the hormone.

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11
Q

What is the effect of up regulation of hormone receptors?

A

Up regulation increases the target tissue’s responsiveness to the hormones.

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12
Q

What are the two types of receptors we are covering?

A

> Ion-channel-linked receptors
G protein-linked hormone receptors
Enzyme-linked hormone receptors
Intracellular hormone receptor

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13
Q

What type of signaling molecule primarily uses ion-channel-linked receptors?

A

Neurotransmitters

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14
Q

What are the characteristics of ion-channel-linked receptors?

A

used primarily by neurotransmitters

not talking too much about

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15
Q

What are the characteristics of G protein-linked hormone receptors?

A

> Couple with groups of cell membrane proteins called heterotrimeric GTP-binding proteins.

> All of these receptors have 7 transmembrane segments.

> Some G proteins are inhibitory (Gi) and some are stimulatory (Gs).

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16
Q

What are the characteristics of enzyme-linked hormone receptors?

A 
> single-pass trasmembrane receptors
> receptor part is extracellular 
> intracellular enzyme:
  - may be part of the receptor
  - may be separate from the receptor
> example is the leptin receptor (JAK-STAT) transduction pathway:
  - requires tyrosine kinase (JAK family)
  - activates transducer proteins (STAT)
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17
Q

What are the characteristics of intracellular hormone receptors?

A

> Intracellular receptors for lipid soluble hormones.

 - adrenal and steroidal hormones 
 - thyroid hormones 
 - retinoid hormones 
 - vitamin D

> Activated hormone-receptor complex binds to promoter sequence of DNA:
- hormone response element

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18
Q

What are the 3 classes of hormones?

A

> Polypeptide and Protein Hormones
Steroids
Amine Hormones

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19
Q

What are the characteristics of polypeptide and protein hormones?

A
  • polypeptide 100 amino acids
  • stored in secretory vesicles until needed
  • usually synthesized as preprohormones
  • released via exocytosis:
    > usually mediated via Ca2+ ions
  • release for some may involve cAMP
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20
Q

What are the characteristics of steroids (hormones)?

A
  • usually synthesized from cholesterol
  • lipid soluble and diffuse readily across cell membranes
  • consist of three cyclohexyl rings and one cyclopentyl ring
  • large quantities of cholesterol esters stored rather than hormones themselves
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21
Q

List some example of common steroid hormones.

A

> cortisol
aldosterone
testosterone
estradiol

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22
Q

What are the characteristics of amine hormones?

A
  • derived from tyrosine
  • include thyroid and adrenal medullary hormones
  • formed by actions of enzymes in cytoplasmic compartments of glandular cells
  • thyroid hormones are incorporated into macromolecules of thyroglobulin and stored in thyroid gland follicles
  • catecholamines (epinephrine and norepinephrine) are formed in adrenal medulla and stored in vesicles until needed
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23
Q

What are the four signal transduction mechanisms?

A

> Adenyl cyclase - cAMP second messenger system.

> Cell membrane phospholipid second messenger system.

> Calcium - calmodulin phospholipid second messenger system.

> Hormones acting directly on DNA.

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24
Q

In the adenyl cyclase - cAMP second messenger system, what effect does Gi proteins have on ATP formation?

A

Reduces the formation of ATP.

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25
Q

In the adenyl cyclase - cAMP second messenger system, which G protein stimulates this system?

A

Gs protein

26
Q

What is the general mechanism in the cell membrane phospholipid second messenger system?

A

Hormones activate transmembrane receptors that activate enzyme phospholipase C (catalyzes break-down of phospholipids in the cell membrane).

Phospholipase C then cleaves PIP2 into IP3 + DAG.

DAG activates PKC, resulting in cell response.
component of DAG is arachidonic acid

IP3 mobilizes calcium ions from mitochondria and ER, resulting in cell response.

27
Q

What is the general mechanism in the calcium - calmodulin phospholipid second messenger system?

A

> Calcium entry may be initiated by:

  • changes in membrane potential that open calcium channels
  • a hormone interacting with membrane receptors that open calcium channels

> Calcium ions bind with calmodulin.

  • When 3-4 binding sites are filled calmodulin initiates multiple effects:
    • activation of protein kinases
    • inhibition of protein kinases
28
Q

What type of hormones act directly on DNA?

A
  • steroid hormones

- thyroid hormones

29
Q

What are the characteristics of steroid hormone signal transduction acting directly on DNA?

A

> Diffuse across cell membrane.
Bind with receptor proteins in cytoplasm.
Receptor protein-steroid complex diffuses into nucleus.
Complex binds to DNA.

30
Q

What are the characteristics of thyroid hormone signal transduction acting directly on DNA?

A

> Bind directly with receptors in nucleus.
Activate genetic mechanisms for many (up to 100+) kinds of proteins, many of which enhance metabolic activity.
Note that thyroid hormones, once bound to DNA, remain bound for days to weeks and continue to function.

31
Q

True or False:

Thyroid hormones, once bound to DNA, remain bound for a short period of time.

A

False - thyroid hormones, once bound to DNA, remain bound for days to weeks and continue to function.

32
Q

True or False:

Hormones acting directly on DNA take longer than membrane-receptor mediated signaling to occur.

A

True

33
Q

What are the 5 cell types that are found in the anterior pituitary (adenohypophysis)?

A 
> Somatotropes (acidophils)
> Corticotropes 
> Thyrotropes 
> Gonadotropes 
> Lactotropes

Remember: troph (tropic) means that they will activate/trigger the release of another hormone.

34
Q

In the anterior pituitary, what do somatotrope cells secrete?

A

HGF (human growth factor)

35
Q

In the anterior pituitary, what do corticotrope cells secrete?

A

ACTH (adrenocorticotropic hormone)

36
Q

In the anterior pituitary, what do thyrotrope cells secrete?

A

TSH (thyroid stimulating hormone)

37
Q

In the anterior pituitary, what do gonadotrope cells secrete?

A

LH (luteinizing hormone) and FSH (follicle stimulating hormone)

38
Q

In the anterior pituitary, what do lactotrope cells secrete?

A

Prolactin

39
Q

Review figure 76-2 and text for metabolic functions of the anterior pituitary hormones.

A

Keep working hard! You’ve almost made it!!

40
Q

Which two hormones released from the anterior pituitary gland will directly or indirectly increase blood glucose levels?

A
  • Human Growth Factor (HGF - from somatotropes) (directly)
  • Adrenocorticotropic Hormone (ACTH - from corticotropes) (indirectly - stimulates adrenal cortex to release ACH, which increases blood glucose level)
41
Q

In the posterior pituitary (neurohypophysis), in which nuclei are magnocellular neurons located?

A
  • supraoptic nuclei

- paraventricular nuclei

42
Q

Which two hormones are released from the posterior pituitary?

A
  • ADH

- Oxytocin

43
Q

In which nuclei is ADH formed?

A

Supraoptic Nuclei

44
Q

In which nuclei is oxytocin formed?

A

Paraventricular Nuclei

45
Q

What does oxytocin cause?

A

> Causes contraction of the pregnant uterus.

> Aids in milk ejection (milk letdown) by acting on myoepithelial cells of mammary alveoli.

46
Q

What type of cells does oxytocin act on to aid in milk ejection (milk letdown)?

A

Myoepithelial cells of mammary alveoli.

47
Q

Which nuclei primarily makes oxytocin?

A

paraventricular nucleus

48
Q

Which nuclei primarily makes ADH?

A

supraoptic nucleus

49
Q

What does the hypothalamus control?

A

Controls anterior pituitary via hormones called hypothalamic releasing and inhibitory hormones (factors).

> conducted to anterior pituitary via hypothalamic-hypophyseal portal system
secreted into median eminence
diffuse into portal system

hypothalamus is the collecting center for information concerning internal well-being of the body

50
Q

What is the hypothalamus?

A

A collecting center for information concerning internal well-being of the body.

51
Q

List sequentially the components of the hypothalamic-pituitary axis.

A

artery -> primary capillary plexus (in the median eminence) -> hypothalamic-hypophysial portal vessels -> sinuses (in the anterior pituitary) -> veins

52
Q

How does growth hormone function to increase growth?

A

> Increases deposition of protein by chondrocytic and osteogenic cells.

> Increases rate of reproduction of chondrocytic and osteogenic cells.

> Converts chondrocytes into osteogenic cells.

> Strongly stimulates osteoblasts.

53
Q

How does growth hormone function to increase protein synthesis?

A

> Directly enhances transport of amino acids through cell membranes into cytoplasm.

> Increases RNA translation.

> Increases transcription rate.

> Decreases protein catabolism.

54
Q

What effect does growth hormone have on fatty acid mobilization?

A

> Causes release of fatty acids from adipose tissue.

> Enhances conversion of fatty acids to actyl-CoA.

55
Q

What effect does growth hormone have on glucose?

A

Decreases glucose utilization

> Decreases glucose uptake in tissues such as skeletal muscle and fat.

> Increases glucose production by liver.

> Increases insulin secretion.

> Note: GH’s effects are diabetogenic.

56
Q

What does growth hormone cause the liver to do, besides increase glucose production?

A

Causes liver to form somatomedins (proteins).
> powerful effect on all aspects of bone growth
> similar to effects of insulin on growth
> also called insulin-like growth factors (IGFs)
> most important is somatomedin C (IGF-I)

57
Q

What is the most important somatomedin (IGFs) formed by the liver after stimulation by growth hormone?

A

Somatomedin C (IGF-I)

58
Q

True or False:

Injection of growth hormone in to epiphyseal plates causes specific growth of these regions.

A

True

59
Q

List factors that are known to stimulate secretion of growth hormone.

A

> Starvation (protein deficiency)

> Hypoglycemia

> Exercise

> Excitement

> Trauma

> Ghrelin (the “hunger hormone”, also known as lenomorelin (INN), is a peptide hormone produced by ghrelinergic cells in the gastrointestinal tract[1][2] which functions as a neuropeptide in the central nervous system.[3] Besides regulating appetite, ghrelin also plays a significant role in regulating the distribution and rate of use of energy).

> First two hours of deep sleep

60
Q

What does kwashiorkor mean?

A

Malnutrition produced by a severely inadequate amount of protein in the diet.

Human Physiology 2 - Unit 3 - Zach H. (9 decks)

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