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Guyton - unit questions EW > Unit XIV (75-84) - Endocrinology and Reproduction > Flashcards

Unit XIV (75-84) - Endocrinology and Reproduction Flashcards

1
Q

What hormones are secreted by the posterior pituitary gland?

A

ADH

Oxytocin

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2
Q

Where are ADH and Oxytocin synthesized respectively?

A

Supraoptic nuclei - ADH

Paraventricular nuclei - Oxytocin

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3
Q 
Where are these cell types found?
Somatotropes
Corticotropes
Thyrotropes
Gonadotropes
Lactotropes
A

Anterior pituitary

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4
Q

Somatotropes produce _____

A

Growth hormone

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5
Q 
Growth hormone physiologic roles include:
stimulation of:
1.\_\_\_\_\_\_\_\_\_\_\_\_\_\_
2. \_\_\_\_\_\_\_\_\_\_\_\_\_
and inhibition of: 
1.\_\_\_\_\_\_\_\_\_\_\_\_\_\_
2. \_\_\_\_\_\_\_\_\_\_\_\_\_
A 
Stimulates:
1. secretion of insulin like growth factor 1
2. lipolysis
Inhibits:
1. action of insulin on carbohydrates
2. lipid metabolism
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6
Q

Corticotropes produce ______

A

ACTH

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7
Q

ACTH stimulates: ___________

A

Adrenal cortex to produce glucocorticoids and androgens

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8
Q

Thyrotropes produce ______

A

TSH

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9
Q

Where is MSH is produced?

A

Pars intermedia

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10
Q

A cells in the pars intermedia produce _____

A

alpha MSH

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11
Q

B cells in the pars intermedia produce ______

A

ACTH

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12
Q

Lactotropes produce __________

A

Prolactin

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13
Q

Gonadotropes produce _________

A

FSH and LH

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14
Q

GHRH
Source:
Effects:

A

Growth hormone releasing hormone
hypothalamus
stimulates release of GH from anterior pituitary

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15
Q

Somatostatin
AKA:
Source:
Effects:

A

growth hormone inhibitory hormone
hypothalamus
inhibit release of GH from anterior pituitary

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16
Q

CRH
Source:
Effects:

A

corticotropin releasing hormone
hypothalamus
stimulate release of ACTH

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17
Q

GnRH
Source:
Effects:

A

Gonadotropin releasing hormone
hypothalamus
stimulates release of LH and FSH

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18
Q

Examples of protein/polypeptide hormones

A

secreted by pituitary, parathyroids and pancreas

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19
Q

How are protein and polypeptide hormones synthesized and secreted

A

Preprohormone is synthesized in RER and then cleaved to a prohormone
Prohormone goes into the golgi - may be modified
Hormone is packaged into vesicles
The vesicles are stored in the cytoplasm and released via exocytosis when needed.

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20
Q

Method of transport of peptide hormones

A

free in plasma because they are water soluble

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21
Q

Examples of steroid hormones

A

glucocorticoids, androgens

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22
Q

How are steroid hormones synthesized and secreted

A

Made in mitrochondria and ER from cholesterol
Not stored
Since they are lipid soluble they are freely permeable (they are released as they are synthesized)

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23
Q

The receptors for protein hormones are located ________________

A

ON the cell (rely on 2nd messengers)

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24
Q

The receptors for steroid hormones are located _____________

A

IN cytoplasm (do not need 2nd messengers)

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25
Q

Examples of amino acid derivatives

A

Tyrosine derivatives

  1. Thyroid hormones
  2. Catecholamines
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26
Q

Compare and contrast the tyrosine derivative hormones (MOA, secretion, transport in blood)

A
  1. Thyroid hormones - stored in large follicles and released into the blood after amine is split from thyrogloblumin, once secreted they act like steroid hormones (protein bound and has a receptor in the nucleus)
  2. Catecholamines - taken up into preformed vesicles and stored, once secreted they act like protein hormones (water soluble, rely on second messengers)
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27
Q

What hormones are usually involved with ion channel linked receptors? What is the MOA?

A

Catecholamines, ACh - cause a change in the receptor = open or close one or more ion channels

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28
Q

What hormones use G-protein linked receptors?

A

Most hormones (FSH, GnRH, Oxytocin, Glucagon)

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29
Q

Describe the MOA of G-protein linked receptors

A

Inactive G - protein = Alpha, beta and gamma subunits + GDP
Hormone binds on the extracellular part of the receptor and activates G-protein causing:
1. open or close of ion channels
2. change in activity of a cytoplasmic enzyme or
3. activates gene transcription
Active G-protein (after hormone binds) GDP is displaced by GTP and the alpha subunit dissociates from beta and gamma
Alpha subunit associates with other intracellular signaling proteins that can change cell function
When hormone is removed alpha subunit converts the bound GTP to GDP and combines with beta and gamma subunits

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30
Q

What hormones use enzyme linked receptors?

A 
Tyrosine kinase
Leptin
Insulin
Prolactin
ANP
Growth factors (insulin like growth factor 1, VEGF)
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31
Q

Structurally, how are enzyme linked receptors different than G-protein linked receptors

A

G - protein linked receptors go through the membrane 7 times
Enzyme linked receptors go through the membrane once

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32
Q

Describe the MOA of enzyme linked receptors

A

once the hormone binds on the outside of the cell an intracellular enzyme is activated (or inactivated)

33
Q

What hormones use intracellular receptors?

A

Steroids
Thyroid
Retinol
Vit D

34
Q

Describe the MOA of intracellular receptors

A

Hormone just goes into cell (since its lipid soluble) The activated hormone-receptor complex binds to a specific promoter sequence of DNA - called hormone response element

35
Q

What are second messengers involved in intracellular signaling?

A

cAMP
Ca+Calmodulin
Products of membrane phospholipid breakdown

36
Q

Describe the role/MOA of cAMP as a second messenger

A

If a hormone binds to a stimulatory G protein receptor = cytoplasmic ATP catalyzed to cAMP
cAMP can phosphorylate specific proteins and trigger cell response to hormone

If a hormone binds to an inhibitory G protein receptor = adenylyl cyclase is inhibited and cAMP formation is reduced

37
Q

Describe the role/MOA of Ca+calmodulin as a second messenger

A

Ca influx into cell and when 3-4/4 calmodulin sites are bound to Ca calmodulin undergoes a change in shape
change shape can lead to phosphorylation of calmodulin dependent kinases

38
Q

______________ catalyzes breakdown of phospholipids in the cell membrane (ie. phosphatidylinositol biphosphate) into ____________________ and ______________

A

Phospholipase C
Inositol triphosphate - IP3
diacylglycerol - DAG

39
Q

What is the MOA of IP3 as a second messenger?

A

mobilizes Ca ions from mitochondria and ER

Ca then acts as a 2nd messenger itself

40
Q

What is the MOA of DAG?

A

Activates protein kinase C which then phosphorylates other proteins leading to cell responses

41
Q

The cells from the ________ pituitary are epithelial in origin vs the cells from the ___________ are glial in origin.

A

Anterior

Posterior

42
Q

Inhibition of ACTH production in the pars distalis is mediated by _______ and by __________ in the pars intermedius

A

Cortisol

Dopamine

43
Q

Inhibition of ACTH production in the pars distalis is mediated by _______ and by __________ in the pars intermedius

A

CRH

Serotonin

44
Q

The pars ___________ produces the majority of ACTH in dogs

A

Distalis

45
Q

What are the physiologic effects of growth hormone?

A

Increased rate of protein deposition
Increased mobilization of fats
Decrease rate of glucose utilization in the body
Promote cartilage and bone growth

46
Q

What is the role of insulin like growth factor-1?

where is it produced?

A

mediates most of GH actions

produced in the liver

47
Q

What are the physiologic effects of oxytocin?

A

contraction of pregnant uterus

milk let down

48
Q

Secretion of ADH is stimulated by

A

Decreased blood pressure
Decreased blood volume
Increased osmolarity**

49
Q

what is the site of action of ADH?

A

collecting tubules and collecting ducts

50
Q

What is the MOA of ADH

A

binds to V2 receptor –> forms cAMP –> stimulates movement of aquaporin-2 which forms water channels on the luminal side = increased water permeability
also causes vasoconstriction in response to low blood volume

51
Q

List the 4 major steps of thyroid hormone synthesis

A
  1. Iodide trapping
  2. Thyroglobulin synthesis
  3. Oxidation
  4. Organification
52
Q

The the thyroid hormone secreted ____% is T4 and ____% is T3

A

93%

7%

53
Q

Thyroid hormone is found in plasma bound to __________________ , _______________ and ________________

A

Thyroxine binding globulin**
Thyroxine-binding prealbumin
Albumin

54
Q

What 2 classes of hormone are derived from tyrosine?

A

Thyroid and adrenal medullary

55
Q

Where are receptors for protein hormones typically found?

A

Cell membrane

56
Q

Where are receptors for steroid hormones typically found?

A

Cytoplasm

57
Q

Where are receptors for catecholamine hormones typically found?

A

Cell membrane

58
Q

Where are receptors for thyroid hormones typically found?

A

Nucleus

59
Q

What hormones are synthesised from cholesterol?

A

Steroid and thyroid

60
Q

Which hormones are secreted from the anterior pituitary?

A

GH
TSH
ACTH
Prolactin
FSH/LH

61
Q

Which hormones are secreted from the posterior pituitary?

A

ADH
Oxytocin

62
Q

What hormones are secreted from the hypothalamus?

A

GHRH
CRH
TRH
GnRH
Somatostatin (growth hormone-inhibitory protein)
Dopamine (prolactin-inhibitory hormone)

63
Q

What are the metabolic effects of GH?

A

Increased protein synthesis
Increased fatty acid mobilisation
Decreased glucose utilisation

64
Q

What factors stimulate GH release?

A

Decreased BG
Decreased blood FFA
Increased blood amino acids
Starvation
Exercise
Testosterone
Sleep
GHRH
Ghrelin

65
Q

What factors inhibit GH release?

A

Increased BG
Increased FFA
Aging
Obesity
Somatostatin
Exogenous GH
Insulin-like growth factors

66
Q

Describe the structure of the thyroid gland

A

Composed of follicles filled with colloid
Lined with cuboidal epithelial cells

C cells - secrete calcitonin

67
Q

What is the main constituent of colloid?

A

Thyroglobulin

68
Q

What is the main influencer of iodine trapping in the thyroid?

A

TSH

69
Q

How is iodide transported out of the cell across the apical membrane into the follicle?

A

Via iodine/chloride transporter - Pendrin

70
Q

Briefly describe the steps of thyroid hormone formation

A

Thyroglobulin produced in thyroid cells, transported into follicle
Iodide transported into follicle via pendrin
Iodide oxidised by peroxidase and H2O2
Iodide binds with thyroglobulin - produces T4
Stored in follicle
Reabsorbed back into cell by pinocytosis

71
Q

How do T3/T4 circulate in blood?

A

Small free fraction
Bound to thyroxine-binding globulin, thyroxine-binding prealbumin and albumin

72
Q

What layer of the adrenal gland secretes aldosterone?

A

Zona glomerulosa

73
Q

What stimulates aldosterone secretion?

A

AngII and potassium

74
Q

Where is the majority of cholesterol for synthesis of adrenocortical hormones from?

A

LDLs

75
Q

In which organelles are adrenal steroids synthesised?

A

Mitochondria and endoplasmic reticulum

76
Q

Why doesn’t cortisol activate the renal mineralocorticoid receptor?

A

11B-hydroxysteroid dehydrogenase converts cortisol => less potent cortisone

77
Q

Where is the main site of aldosterone action?

A

Principal cells in collecting tubules

78
Q
A

Guyton - unit questions EW (14 decks)

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