Posterior Pituitary and HPL Axis Flashcards Preview

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Flashcards in Posterior Pituitary and HPL Axis Deck (42)
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1

What is the AVP pro hormone comprised of?

AVP + neurophysin II

2

What is the oxytocin pro hormone comprised of?

Oxytocin + neurophysin I

3

What are the two types of cells found in the paraventricular nucleus (PVN)?

Parvocellular
Magnocellular

4

What are the only PVN cells to project to the posterior pituitary?

Magnocellular Neurons

5

Where do parvocellular PVN neurons project to?

Median Eminence

6

When does the cleavage of neurophysin from released hormones occur?

Neurophysin is cleaved from the prohormone in the secretory granules during axonal transport.

7

What are the main targets of AVP?

Kidney and vasculature

8

What is the most potent stimulus for the release of AVP?

Osmolarity

9

What is the effect of AVP on the vasculature?

Causes vasoconstriction

10

What is the effect of AVP on the kidney?

Leads to aquaporin insertion in the distal tubule that leads to increased H2O reabsorption

11

What is the effect of AVP on the sympathetic nervous system?

Increases sympathetic tone

12

What receptor pathways does AVP go through to cause vasoconstriction?

Phospholipase C -> Ca2+ -> Calmodulin -> MLC Kinase

13

What is the major symptom of diabetes insipidus?

Excessive urination

14

What is the most common cause of diabetes insipidus?

Decreased AVP release which is due to a hypothalamic or pituitary defect “central” due to trauma, cancer, or infectious disease.

15

Besides a hypothalamic or pituitary defect, what may be the other cause of diabetes insipidus?

Decreased renal responsiveness to AVP that can be either genetic OR acquired.

16

Besides a hypothalamic or pituitary defect, what may be the other cause of diabetes insipidus?

Decreased renal responsiveness to AVP that can be either genetic OR acquired.

Genetic - X linked mutation in the AVP receptor
Acquired - Li treatment or hypokalemia

AVP levels are NORMAL in BOTH genetic and acquired diabetes insipidus.

17

What is pitocin?

It is artificial oxytocin used to stimulate labor

18

What does the oxytocin receptor activate?

It is a GPCR that activates PLC and IP3 -> Ca2+ signalling

19

What is the function of oxytocin?

Induces smooth muscle contration in breast and uterus for milk ejection and birth

20

How are the structure of AVP and OXY similar?

They are both 9 AAs and only differ by a single AA

21

What is the HPL axis comprised of?

Hypothalamic Arcuate Nucleus - GHRH
Pituitary Somatotroph - GH
Liver - IGF-I

22

What is the function of GHRH?

It is made in the arcuate nucleus and functions to stimulate the release of GH from the anterior pituitary.

23

What are the two forms of somatostatin?

There is SS14 and SS28

SS14 is found in the hypothalamus and SS28 is found in the D cells of the stomach

24

What is the function of somatostatin in the brain?

Inhibits GHRH at the hypothalamus
Inhibits GH and TSH in pituitary

25

Describe the release of somatostatin and its timing.

It has a pulsatile release that occurs normally at night

26

What stimulates IGF-I production in the liver?

GH

27

What is the function of IGF-I?

Insulin-like growth factor mediates the downstream effects of GH and also as negative feedback to INHIBIT GH release.

28

What is the effect of IGF-I on various tissues like muscle/adipose/liver?

IGF-I acts like insulin in muscle but does not in adipose or liver because they do not have the receptors.

29

At what age range does IGF-I reach its peak?

During puberty

30

What are some of the direct effects of GH?

Decreases adiposity
Increases gluconeogenesis/protein synthesis
Increases lean body mass

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