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Introduction To The Endocrine System Flashcards

1
Q

What is the purpose of the endocrine system?

A

◦ Regulation of multiple organs to meet growth and reproduction demands

◦ Major role in homeostasis

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2
Q

What are the classical endocrine glands?

A 
Hypothalamus
Anterior/posterior pituitary
Thyroid
Parathyroid
Adrenal cortex/medulla
Gonads
Pancreas
Placenta
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3
Q

What major hormones does the hypothalamus produce?

A
  • ADH (PVN)
    * Oxytocin (SO)
    * TRH
    * GRH
    * GHRH
    * GnRH
    * Somatostatin
    * Dopamine
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4
Q

What major hormones does the anterior pituitary produce?

A
  • ACTH
    * TSH
    * Growth hormone
    * Prolactin
    * FSH
    * LH
    * MSH
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5
Q

What major hormones does the posterior pituitary produce?

A
  • Oxytocin

* ADH

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6
Q

What major hormones does the thyroid produce?

A
  • Thyroxine (T4)
    * Triiodothyronine (T3)
    * Calcitonin (CT)
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7
Q

What major hormones does the Parathyroid produce?

A

• Parathyroid hormone (PTH)

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8
Q

What major hormones does the adrenal cortex produce?

A
  • Cortisol
    * Aldosterone
    * Androgens
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9
Q

What major hormones does the adrenal medulla produce?

A
  • Epi

* Norepinephrine

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10
Q

What major hormones do the Testes produce?

A
  • Androgens (esp. testosterone)

* Inhibin

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11
Q

What major hormones do the Ovaries produce?

A
  • Estrogens (estradiol)
    * Progesterone
    * Inhibin
    * Relaxin
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12
Q

What major hormones do the Pancreatic Islets produce?

A
  • Insulin
    * Glucagon
    * Somatostatin
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13
Q

What major hormones does the Placenta produce?

A
  • HCG
    * hPL
    * Estriol
    * Progesterone
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14
Q

What major hormones does the corpus luteum produce?

A
  • Estradiol

* Progesterone

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15
Q

Where are there endocrine cells in a non-endocrine organ?

A 
Adipose 
Kidneys
Liver
Heart
GI tract
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16
Q

What major hormones do the Kidneys release?

A

◦ Renin

◦ 1,25 Dihydroxycholecalciferol

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17
Q

What can also modify hormones?

Examples?

A

Peripheral conversion

Angiotensin II

Vit. D from sun

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18
Q

What constitutes a proteins?

A

Polypeptide with >100 AAs

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19
Q

What constitutes a peptide?

A

Polypeptide with < or equal to 100 AAs

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20
Q

Are protein/peptide hormones lipid or water soluble?

A

Water soluble

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21
Q

How are protein/peptide hormones synthesized?

A

‣ Synthesized as Non-functional pre-prohormone

‣ Modified in ER —> pro-hormone —> Golgi apparatus s

‣ Packed into vesicles

‣ Cleaved by proteolytic enzymes to form functional hormone

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22
Q

What are protein/peptide hormones stored in?

When are they secreted?
Example?

A

In secretory vesicles

Secreted w/ endocrine stimulus

(Increased intracellular Ca —> increase cAMP —> PKA activation)

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23
Q

What are examples of steroid hormones?

A 
‣ Cortisol
		‣ Aldosterone
		‣ Estradiol
		‣ Estriol
		‣ Progesterone
		‣ Testosterone
		‣ 1,25-dihydroxycholecalciferol
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24
Q

Are steroid hormones lipid or water soluble?

A

Lipid soluble

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25
Q

How are steroid hormones synthesized?

A

‣ From cholesterol
‣ modifications of cholesterol via addition or removal of side chains, hydroxylation or aromatization of the steroid nucleus

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26
Q

Where are steroid hormones synthesized at?

A

• Adrenal cortex, gonads, corpus luteum, placenta

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27
Q

How are steroid hormones stored? Secreted?

A

They are not stored

Secreted by adrenal cortex, gonads, corpus luteum, placenta

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28
Q

What are the 2 groups of amine hormones?

A

Catelcholamines

Thyroid hormones

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29
Q

How are catelcholamine hormones synthesized?

Secreted?

A

‣ Derived from Tyrosine
‣ Synthesized in cytosolic and secretory granules

‣ Secretion: Act thru cell membrane assoc. receptors

30
Q

How are thyroid hormones synthesized? Secreted?

A

‣ Synthesized by Thryoid gland
‣ Stored as thyroglobulin in follicles w/in the gland

‣ Secretion: Cross cell membrane & act thru nuclear receptors

31
Q

What two mechanisms control hormone secretion?

A

Neural and feedback

32
Q

What is the neural mechanism that controls hormone secretion?

A

‣ Neuronal input to endocrine cell increases or decrease hormonal secretion

33
Q

What is an example of neural mechanism of controlling hormone secretion?

A

sympathetic preganglionic innervation to adrenal medulla = causes release of Catecholamines into circulation

34
Q

What mechanism is more common in controlling hormone secretion, neural or feedback

A

Feedback

35
Q

How does the feedback mechanism for controlling hormonal secretion work?

A

element of pathway feeds back, directly or indirectly, on endocrine gland to change secretion rate

36
Q

What is a positve endocrine feedback ?

A

◦ Hormone action causes additional secretion of hormone

◦ Uncommon in biological system

37
Q

What can a positive endocrine feedback lead to?

Example?

A

‣ Can lead to explosive event

• Ovulation or labor contractions

38
Q

What is a Negative Endocrine Feedback?

Purpose?

A

◦ Hormone action inhbits further secretion of the hormone

◦ Confers stability by keeping a physiological parameter (i.e. blood glucose level) w/in a normal range

39
Q

What is the pathway for a LONG feedback loop?

A

‣ Hormone released from peripheral endocrine gland (3rd tier)
—-goes back to —->

1st tier (hypothalamus) and 2nd tier (pituitary)

40
Q

What is the pathway for a SHORT feedback loop?

A

Hormone from 2nd tier (pituitary)

—>

1st tier (hypothalamus)

41
Q

What is the ULTRA SHORT feedback loop?

A

Gland inhibits its own secretions

42
Q

How is the hypothalamus regulated?

A

By descending and ascending neuronal inputs

From Suprachiasmatic nucleus, pineal glands, physiological stress

43
Q

What is the “first tier” of the endocrine axes?

A

Hypothalmus

44
Q

What does the suprachiasmatic nucleus Regulate? How?

A

Hypothalamus

Thru imposing circadian rhythm on secretion of hypothalamic releasing hormone and endocrine axes

45
Q

What does the pineal gland regulate? How?

A

Hypothalamus

Releases melatonin to feed back to SCN re: info about day and night

46
Q

What does physiological stress regulate? How?

A

Hypothalamus

Influences the release of hormones from hypothalamus

47
Q

How is sensitivity defined?

A

[hormone] that produces 50% of maximal response (EC50)

48
Q

What is the dose-response relationship regulate?

A

Responsiveness of target tissue

49
Q

How can you change the responsiveness of tissues to hormones?

A

Change # of receptors

Change affinity of receptors for hormones

50
Q

What are the mechanisms for up-regulation ?

When would you upregulate?

A

◦ Increase # of receptors OR sensitivity of target tissue

when hormone level is low

51
Q

What are the mechanisms for down-regulation ?

When would you downregulate?

A

◦ Reduce # of receptors OR sensitivity of target tissue

when hormone levels are high (Chronic)

52
Q

How would you enact up-regulation?

A

‣ Increasing synthesis of new receptors

‣ Decreasing degradation of old

‣ Activating receptors

53
Q

How do you enact down-regulation ?

A

‣ Decreasing receptor synthesis

‣ Increasing degradation of receptors

‣ Inactivating/desensitizing receptors

54
Q

What are the hormones that act thru adenylyl cyclase pathway?

What is the mechanism?

A

ACTH, LH, FSH, TSH, Glucagon

1st messenger hormone —> receptor

Gs activated —> primary effector-adenylyl cyclase

2nd messenger cAMP —> 5AMP —> PKA active now = secondary effector

PKA —> phosphorylate proteins

—> physiological actions

55
Q

What hormones will act thru Phospholipase C pathway?

A

GnRH, TRH, Oxytocin

56
Q

What is the mechanism of hormone action using the Phospholipase C pathway?

A

1st messenger hormones —> receptor

Gq activated —> Phospholipase C (primary effector)

Phospholipase C —> IP3, DAG, Ca (2nd messenger)

—> PKC or Calmodulin (secondary effector)

57
Q

How do steroid hormones diffuse into target cell?

A

Diffuse UNbound to plasma protein carriers

58
Q

What is the signal transduction pathway for steroid hormones?

A

Steroid diffuses into target cell

Bind steroid hormone r. On cytoplasm or NUCLEUS

If nucl —> binds DNA, activating/repressing 1 or more genes
Activated genes —> new mRNA —> mRNA back to cytoplasm —> Translation at ER —> new proteins made for cell processes

59
Q

What do steroid hormones that bind to membrane receptors do?

A

Use second messenger system to create RAPID response

60
Q

What is Guanylyl Cyclase do when activate?

A

Convert GTP to cGMP

CGMP —> activates cGMP kinase

Relax vascular smooth muscle

61
Q

What are the 2 categories for tyrosine kinases?

A
  1. Receptor tyrosine kinases

2. Tyrosine kinase associated receptors (jak-stat)

62
Q

What are the characteristics of Receptor Tyrosine Kinases?

When active, what will they do?

A

Have intrinsic tyrosine kinase activity

Will phosphorylates downstream proteins

63
Q

What are the characteristics of Tyrosine Kinase Associated Receptors?

What will they do when active?

A

associate non-covalently to proteins that have kinase activity

Active kinase phosphylates downstream proteins

64
Q

What is the relationship to the amount of hormone bound to protein and its half life and clearance?

A

Increase protein binding by hormone

Will

INCREASE 1/2 half

DECREASE metabolic rate (clearance)

64
Q

What are the three tiers of the endocrine system?

A

Tier 1: hypothalamus

Tier 2: pituitary

Tier 3: target of pituitary

64
Q

What are the three general classes of hormones?

A

Proteins and peptides

Amines

Steroids

64
Q

What are endocrine cells?

A

Release hormone thru blood which can act on a DISTANT cell that will then produce an effect

64
Q

What is a paracrine cell?

A

Acts on NEARBY cell using hormone and then that cell will have effect

64
Q

What is an Autocrine cell?

A

Acts on the SIGNALING cell using hormone released by itself

64
Q

What are neuroendocrine cells?

A

Cells that receive neuronal input
(NTRs released by nerve cells or neruocsecretroy cells)
and release hormone into blood to act on distant cell

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