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Physio II Exam 3 > Endocrine Principles > Flashcards

Endocrine Principles Flashcards

1
Q

Polypeptide and Protein Hormones:

A
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2
Q

Steroids

A
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3
Q

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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4
Q

Receptor Locations

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

Down Regulation of Receptors:

A
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6
Q

Up regulation of receptors

A
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7
Q

Ion-channel-linked receptors:

A
  • Used primarily by neurotransmitters
  • Found in post-synaptic membrane
  • Binding leads to conformation change resulting in opening of ion channels such as sodium, calcium, or potassium
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8
Q

G protein-linked hormone receptors:

A
  • Coupled 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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9
Q

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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10
Q

Enzyme-linked hormone receptor:

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 the leptin receptor (JAKSTAT)

•Transduction pathway requires tyrosine kinase (JAK family) •Activates transducer proteins (STAT)

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11
Q

Feedback Loops

A
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12
Q

Example of positive feedback mechanism:

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.
  • Additional LH results in typical negative feedback.
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13
Q

Periodic variations in hormone release are superimposed on the negative and positive feedback mechanisms

A
  • Seasonal changes
  • Various stages in development and aging
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14
Q

Signal Transduction Mechanisms

A
  • Adenylcyclase—cAMPsecond messenger system
  • Cell membrane phospholipid second messenger system
  • Calcium—calmodulinphospholipid second messenger system
  • Hormones acting directly on DNA
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15
Q

Adenylcyclase—cAMPsecond messenger system

A
  • Binding of hormones with a receptor allows coupling of the receptor to a G protein.
  • A G protein that stimulates the adenyl cyclase—cAMPsystem is called a Gs protein.
  • Adenylcyclase catalyzes ATP → cAMP.
  • cAMPactivates cAMP-dependent protein kinase.
  • Protein kinase phosphorylates specific proteins.
  • This system typically activates a cascade of enzymes.
  • Giproteins reduce the formation of ATP.
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16
Q

Cell membrane phospholipid second messenger system:

A

In this system, hormones activate transmembrane receptors that activate enzyme phospholipase C.

Phospholipase C catalyzes break-down of phospholipids in the cell membrane:

  • Phosphatidylinositol biphosphate PIP2→
  • Inositol triphosphate (IP3):
  • Mobilizes calcium ions from mitochondria and ER
  • Diacylglycerol (DAG):
  • Activates protein kinase C
  • Note that a component of DAG is arachidonic acid
17
Q

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 calmodulininitiates multiple effects:
  • Activation of protein kinases
  • Inhibition of protein kinases
18
Q

Hormones acting directly on DNA:

A

Steroid hormones: •Diffuse across cell membrane •Bind with receptor proteins in cytoplasm •Receptor protein-steroid complex diffuses into nucleus •Complex binds to DNA

Note that this system takes longer than membrane-receptor mediated signaling.

Thyroid hormones: •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.

19
Q

Anterior Pituitary (Adenohypophysis)

A

At least five cell types can be differentiated:

  • Somatotropes(acidophils): HGF
  • Corticotropes: ACTH
  • Thyrotropes: TSH
  • Gonadotropes: LH and FSH
  • Lactotropes: Prolactin
20
Q

Posterior Pituitary (Neurohypophysis)

A

Magnocellularneurons are located in the supraopticand paraventricularnuclei.

  • ADH is formed primarily in the supraopticnuclei.
  • Oxytocin is formed primarily in the paraventricularnuclei: Causes contraction of the pregnant uterus and Aids in milk ejection (milk letdown) by acting on myoepithelial cells of mammary alveoli.
21
Q

Hypothalamus

A

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

  • Conducted to anterior pituitary via hypothalamichypophysealportal system
  • Secreted into median eminence
  • Diffuse into portal system

Collecting center for information concerning internal well-being of body

22
Q

Growth Hormone Functions

A

Growth, protein synthesis, fatty acid mobilization, decreases glucose utilization, Causes liver to form somatomedins (proteins),

23
Q

Growth Function

A
  • Increases deposition of protein by chondrocyticand osteogeniccells
  • Increases rate of reproduction of chondrocyticand osteogeniccells
  • Converts chondrocytes into osteogeniccells
  • Strongly stimulates osteoblasts
24
Q

Protein Synthesis

A
  • Directly enhances transport of amino acids through cell membranes into cytoplasm
  • Increases RNA translation
  • Increases transcription rate
  • Decreases protein catabolism
25
Q

Fatty acid mobilization:

A
  • Causes release of fatty acids from adipose tissue
  • Enhances conversion of fatty acids to acetyl-CoA
26
Q

Decreases glucose utilization:

A
  • 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
27
Q

Causes liver to form somatomedins (proteins)

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 somatomedinC (IGF-I)

Injection into epiphyseal plates causes specific growth of these regions

28
Q

Factors known to stimulate secretion

A
  • Starvation (protein deficiency) -More important under chronic conditions
  • Hypoglycemia -More important under acute conditions
  • Exercise
  • Excitement
  • Trauma
  • Ghrelin
  • First two hours of deep sleep
29
Q

Endocrinology…

A

… is a scientific and medical discipline with a unique focus on hormones and features a multidisciplinary approach to understanding hormones and their diseases.

30
Q

Hormone-secreting cells are designed to …

A

… efficiently synthesize hormones and secrete them in a regulated way.

31
Q

Hormones in the bloodstream often are associated with _______, keep them from degradation and renal excretion, and regulate their ____.

A

binding proteins to allow their solubility

stability in the extracellular space

32
Q

Endocrine diseases fall into three broad categories:

A

hormone over-or underproduction, altered tissue response to hormones, or tumors arising from endocrine tissue

33
Q

Control of hormone secretion involves ___, all leading to complex patterns of _____.

A

multiple inputs from distant targets, nervous system inputs, and local paracrine and autocrine factors

circadian secretion, pulsatile secretion, secretion driven by homeostatic stimuli, or stimuli that lead to secular changes over the lifespan

34
Q

Hormones either act on receptors on the ___ or ____; in either case, the target cell is not a passive recipient of signals but rather has key roles in ____.

A

plasma membranes of target cells

move into cells to bind to intracellular receptors

regulating the responses to hormones

35
Q
A

Physio II Exam 3 (9 decks)

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