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Physiology II Exam III > Endocrine Pnciples > Flashcards

Endocrine Pnciples Flashcards

1
Q

What levels can feedback occur?

A
  • gene transcription
  • gene translation
  • processing of hormones
  • releasing of stored hormones
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2
Q

What is an example of positive feedback loops?

A

-LH surge prior to ovulation

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3
Q

What are two examples of changes in feedback loops?

A
  • seasonal changes

- various stages in development and aging

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4
Q

Where can receptors be found?

A
  • in or on the surface of cell membrane
  • in the cell cytoplasm
  • in the cell nucleus
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5
Q

What cause down regulation of receptors?

A
  • increased hormone concentration

- increased binding to receptors

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6
Q

What can down regulation of receptors result in? How does this occur?

A
  • decreases the tissue’s responsiveness to the hormones
  • inactivation so some of the intracellular protein signaling molecules
  • temporary sequestration of the receptor inside the cell
  • inactivation of the some the receptor molecules
  • destruction of the receptors by lysosomes after they are internalized
  • decreased production of receptors
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7
Q

What does up regulation of receptors result in? How does this happen?

A
  • increases the target tissue’s responsiveness to the hormones
  • stimulating hormone may induce greater than normal formation of receptor or intracellular signaling molecule
  • the stimulating hormone may induce greater availability of the receptor for interaction with the hormone
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8
Q

What are the different types of receptors?

A
  • ion channel linked receptors -> neurotransmitters
  • G protein linked hormone receptors
  • enzyme linked hormone receptor

Intracellular hormone receptor and Gene activation

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9
Q

What are some 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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10
Q

What are some characteristics of enzyme linked hormone receptors?

A
  • single pass transmembrane receptors
  • receptor part is extracellular

-intracellular enzyme
+may be part of the receptor (intrinsic)
+may be separate from the receptor

-example is JAK-STAT transduction pathway

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11
Q

What are some characteristics of intracellular hormone receptor and Gene activation?

A 
-intracellular receptors for lipid soluble hormones:
   \+adrenal and steroidal hormones
   \+thyroid hormones
   \+retinoic hormones
   \+vitamin D

-activated hormone-receptor complex binds to promoter sequence of DNA:
+hormone response element

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12
Q

What are the three classes of hormones?

A
  • polypeptide and protein hormones
  • steroids
  • amine hormones
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13
Q

Characteristics of polypeptide and protein hormones.

A
  • polypeptide : less than 100 aa
  • proteins: more than 100 aa
  • stored in secretory vesicles until needed
  • usually synthesized as preprohormones
  • released via exocytosis (usually mediated via Ca+2)
  • release for some may involve cAMP
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14
Q

Characteristics of steroids.

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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15
Q

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 (epi and NE) are formed in adrenal medulla and stored in vesicles until needed
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16
Q

What are the 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
17
Q

What do negative feedback systems prevent?

A
  • 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
18
Q

Outline the events of the adenyl cyclase-cAMP second messenger system.

A
  • binding of hormones with a receptor allows coupling of the receptor to a G protein
  • a G protein that stimulates adenyl cyclase-cAMP system is called a Gs protein
  • adenyl cyclase ATP -> cAMP
  • cAMP activates cAMP dependent protein kinase
  • protein kinase phosphorylates specific proteins
  • Gs proteins reduce the formation of ATP
19
Q

How do cell membrane phospholipid second messenger systems work?

A

-hormones activate transmembrane receptors that activate enzyme phospholipase C

-phospholipase C catalyzes breakdown of phospholipids in the cell membrane
+phosphatidylinositol biphosphate PIP2 -> IP3 (mobilizes Ca+2 from mitochondria and ER)
+DAG -> activates protein kinase C, component is arachidonic acid

20
Q

How does the calcium-calmodulin phosphate second messenger system function?

A

-calcium entry may be initiated by:
+changes in membrane potential that open Ca channels
+a hormone interacting with membrane receptors that open Ca channels

-calcium ions bind with calmodulin
+when 3-4 binding sites are filled, calmodulin initiates multiple effects: Activation or inhibition of protein kinases

21
Q

How do steroid hormones function?

A
  • diffuse across cell membrane
  • bind with receptor proteins in cytoplasm
  • receptor protein-steroid complex diffuses into nucleus
  • complex binds to DNA
  • this system takes longer than membrane receptor mediated signaling
22
Q

How do thyroid hormones function?

A
  • bind directly with receptors in the nucleus
  • activate genetic mechanisms for many kinds of proteins, many of which enhance metabolic activity
  • once bound to DNA, remain bound for days to weeks and continue to function
23
Q

In the anterior pituitary, what do somatotropes/acidophils secrete?

A

-HGF

24
Q

In the anterior pituitary, what do corticotropes secrete?

A

-ACTH

25
Q

In the anterior pituitary, what do thyrotropes secrete?

A

-TSH

26
Q

In the anterior pituitary, what do gonadotropes secrete?

A

LH ad FSH

27
Q

In the anterior pituitary, what do lactotropes secrete?

A

Prolactin

28
Q

The posterior pituitary consists of magnocellular neurons. Where are these located?

A

-supraoptic and paraventricular nuclei

29
Q

Where is ADH formed?

A

-formed primarily in the supraoptic nuclei

30
Q

Where is oxytocin formed? What does it do?

A

-formed primarily in the paraventricular nuclei

+causes contraction of the pregnant uterus
+aids in milk ejection by acting on myoepithelial cells of mammary alveoli

31
Q

What controls the anterior pituitary?

A

-hypothalamus via hormones called hypothalamic releasing and inhibitory hormones
+conducted to anterior pituitary via hypothalamic-hypophyseal portal system
+secreted into median eminence
+diffuse into portal system

-collecting center for information concerning internal well being of body

32
Q

What functions do growth hormones have for growth functions?

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
33
Q

What are the functions of growth hormones in terms of protein synthesis?

A
  • directly enhances transport of aas through cell membranes into cytoplasm
  • increases RNA translation
  • increases transcription rate
  • decreases protein catabolism
34
Q

What are the functions of growth hormones in terms of FA mobilization?

A
  • causes release of FAs from adipose tissue

- enhances conversion of FAs to acetyl CoA

35
Q

What are the functions of growth hormones in terms glucose utilization?

A
  • decreases glucose uptake in tissues such as skeletal muscle and fat
  • increases glucose production by liver
  • increases insulin secretion
  • GHs effects are diabetogenic
36
Q

Growth hormones causes liver to form somatomedins (proteins). What does this actually do?

A
  • 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-C)
  • injection into epiphyseal plates causes specific growth of these regions
37
Q

What factors stimulate growth hormone secretion?

A
  • starvation (more important under chronic conditions)
  • hypoglycemia (more important under acute conditions)
  • exercise
  • excitement
  • trauma
  • ghrelin
  • first two hours of deep sleep

Physiology II Exam III (9 decks)

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