Oxytocin and ADH Flashcards Preview

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Flashcards in Oxytocin and ADH Deck (44):
1

What is the difference between OT and AVP?

Two different AA side chains

2

Where are both AVP and OT synthesized?

Supraoptic nucleus (mainly AVP)
Paraventricular nucleus (mainly OT)

3

How is OT transported?

Created in the paraventricular nucleus and sent in vesicles down the magnocellular axon to the posterior pituitary

4

When does OT have a burst in males?

At ejaculation to produce contractions for sperm release

5

Mechanism which OT binds and causes smooth muscle contraction?

OT bind OTR-> GPCR-> IP3 (Ca channels open) and DAG-> Prostaglandin (PGF2a)-> uterine and smooth muscle contraction

6

What is the Ferguson reflex?

1.) Head of baby pushes against cervix
2.) Nerve impulses from cervix transmitter to brain
3.) Brain stimulates release of oxytocin (hypothalamus)
4.) Oxytocin carried in bloodstream to uterus
5.) Oxytocin simulates uterine contractions and pushes baby towards cervix

7

What is the secretory unit of the breast?

The alveolus

8

What surrounds the alveolus of the breast?

Myoepithelial cells

9

What does OT cause contraction of to cause the let down reflex?

Myoepithelial cells

10

Characteristics of the four stages of labor:

0: Uterine tranquility and refractoriness
1: Uterine awakening, extending to complete cervical dilation
2: Active labor, from complete cervical dilation to delivery of newborn
3: From delivery of fetus to expulsion of placenta

11

What physiologically is occurring during each of the four stages of labor?

0: Progesterone and relaxin promote inactivity
1: Estrogens increase OT receptors by 80x at 36 weeks
2: Oxytocin, prostaglandins, estrogen increases OT receptors 200X during early labor
3: Oxytocin increases especially in last stage of labor

12

What effect does estrogen have in the OT cycle?

It up regulates OT

13

What affect does progestogens have in the OT cycle?

Decreases response of smooth muscle from OT

14

How does suckling cause OT release?

Suckling stimulates PRL release by removing the inhibition of DA

15

How does suckling affect the menstrual cycle?

GnRH is inhibited by suckling reducing LH and FSH release inhibiting the ovarian menstrual cycle

16

When is relaxin released and what are its affects?

It is released during pregnancy to keep the uterus in a quiet state also during labor in the cervix to dilate it

17

What is the half-life of OT?

3-6 minutes

18

Where is ADH mainly produced?

Supraoptic nucleus

19

What is ADH produced as?

A preprohormone

20

What does the preprohormone of ADH consist of?

Signal peptide
ADH
Neurophysin II

21

What causes the most cases of hereditary hypothalamic diabetes insipidus?

A point mutation in neurophysin II

22

What is neurophysin II?

A carrier of ADH

23

What is the primary signal for secretion of ADH?

An increase in ECF osmolality

24

What inhibits ADH release?

High fluid volume or blood pressure

25

What transports AVP from hypothalamus to neurohypophysis?

Magnocellular neurons

26

What are the receptors for AVP?

V2R in the renal collecting duct

27

Sequence of events for AVP action in renal tubules?

1.) ADH binds V2R
2.) Activates PKA
3.) Phosphorylation of CREB stimulates transcription of mRNA to produce more AQP2

28

What is the threshold at which ADH can be released?

When osmolality increases as little as 1% from 280 mEq/L

29

ADH is also released when blood volume is decreased by what percent and what senses this?

Reduced by 10% by baroreceptors in the atria

30

ADH half-life:

18 minutes

31

What breaks down ADH and what can occur in this organ failure?

Kidneys and Liver
Failure in these organs can lead to high ADH levels

32

In pregnancy, what hormone causes the changes in osmolarity and volume?

Relaxin

33

What occurs to ADH in aging adults?

The kidneys become less sensitive to nocturnal plasma levels of ADH

34

Two types of diabetes insipidus:

Central
Nephrogenic

35

What causes central DI?

Failure of AVP secretion

36

What causes nephrogenic DI?

Kidneys not adequately responding to ADH levels

37

What is the differential diagnosis following water deprivation in DI?

Central: decreased plasma ADH low urine osmolality
Nephrogenic: increased plasma ADH extremely low urine osmolality

38

What does SIADH stand for?

Syndrome of inappropriate ADH secretion

39

What is SIADh essentially?

The opposite of DI

40

What occurs in SIADH?

Secretion of inappropriately high levels of ADH

41

What is the sign of SIADH?

Any urine with greater than 100 Osm with hyponatremia is SIADH

42

Why is urine Na osmolality so high in SIADH?

Because the volume expansion causes a release of ANP increasing natriuresis

43

Treatment of SIADH?

Fluid restriction

44

Drug treatment of SIADH?

V2 receptor antagonists: Conivaptan and Tolvaptan