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Midwifery Year 1 MCQ > Hormones of Parturition > Flashcards

Hormones of Parturition Flashcards

1
Q

List the four phases of parturition.

A

Quiescence, activation, stimulation and involution.

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2
Q

What is the term for a muscle cell?

A

A myocyte.

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3
Q

What does the cytoplasm of myocytes contain that helps them to contract?

A

Actin and myosin.

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4
Q

Muscle contraction is triggered by raised intracellular levels of what?

A

Calcium.

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5
Q

What are the five substances implicated in quiescence?

A

Progesterone, prostacyclin, relaxin, parathyroid hormone-related peptide, nitric oxide.

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6
Q

Progesterone decreases the expression of what?

A

Contraction related proteins (CAPs)

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7
Q

Progesterone prevents what from binding to its receptors?

A

Oxytocin.

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8
Q

What other hormone might progesterone compete with for the same binding sites?

A

Cortisol.

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9
Q

What does cAMP stand for?

A

Cyclic adenosine monophosphate.

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10
Q

What does cAMP do?

A

Uncouples gap junctions.

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11
Q

What two effects do prostacyclin, nitric oxide, relaxin and parathyroid hormone-related peptide have?

A

They increase cAMP and decrease intracellular calcium concentrations.

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12
Q

What are the two main substances implicated in activation?

A

Oestrogen and gap junction proteins.

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13
Q

What two things cause myometrial receptors and signalling pathways to change so that they respond to contractile stimuli?

A

The mechanical stretch of the uterus, and increased fetal HPA axis activity.

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14
Q

True or false: the fetus can manipulate progesterone : oestrogen ratios and thus precipitate uterine activity?

A

True.

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15
Q

What are the three zones of the fetal adrenal gland?

A

The outer adult zone, the fetal zone and the transitional zone.

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16
Q

What does the outer adult zone of the fetal adrenal gland produce?

A

Aldosterone.

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17
Q

What does the fetal zone of the fetal adrenal gland procude?

A

Dehydroepiandrosterone sulphate (DHEAS)

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18
Q

What does the transitional zone of the adrenal gland produce?

A

Cortisol.

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19
Q

DHEAS is the fetal adrenal precursor for the production of which hormone?

A

Oestrogen.

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20
Q

The production of DHEAS is controlled by what hormone?

A

Adrenocorticotrophic hormone (ACTH).

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21
Q

Where is ACTH released from?

A

The anterior pituitary gland.

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22
Q

What stimulates the release of ACTH from the anterior pituitary?

A

Hypothalamic corticotrophin-releasing hormone (CRH).

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23
Q

Where else can CRH be produced?

A

The placenta.

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24
Q

CRH activity is attenuated by what?

A

CRH-binding protein (CRH-BP).

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25
Q

Where is CRH-BP synthesised?

A

The liver, placenta and brain.

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26
Q

Describe what happens to CRH and CRH-BP levels towards the end of pregnancy.

A

Levels of CRH increase, whilst CRH-BP decreases. This results in an increased mount of physiologically free CRH.

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27
Q

How is the maternal HPA axis protected from overstimulation?

A

Maternal adrenal CRH receptors are down-regulated so the ACTH response to CRH is blunted.

28
Q

Fetal stress (e.g. hypoxia) increases CRH. What physiological effect does this have?

A

CRH acts as a vasodilator in the placental vascular bed, increasing blood flow to the fetus.

29
Q

Describe how a compromised fetus can precipitate labour.

A

Chronic fetal stress increases CRH levels. This increases fetal ACTH production, which increase DHEAS production in turn. Oestrogen synthesis is therefore increased, aiding myometrial activation.

30
Q

CRH receptors can couple with what?

A

Different G-proteins.

31
Q

For most of pregnancy, CRH is coupled to the G-protein involved in increasing what?

A

cAMP

32
Q

Towards term, CRH couples with other G-protein pathways so it now activates what?

A

Phospholipase C (PLC)

33
Q

What does PLC do?

A

It mobilises calcium from intracellular stores = increased myometrial activity.

34
Q

What physiological effect does the cortisol produced the fetal adrenal gland have?

A

It matures the fetal organs in preparation for extrauterine life.

35
Q

Maturing fetal lungs produce what?

A

Surfactant.

36
Q

Inflammation in the fetal membranes and underlying myometrium amplifies signals leading to labour. What three substances cause this inflammation?

A

Surfactant proteins, phospholipids and pro-inflammatory cytokines.

37
Q

Which hormone triggers the up-regulation of CAPs?

A

Oestrogen.

38
Q

Give three CAPs.

A

Connexin 43, prostaglandins and oxytocin receptors.

39
Q

Gap junctions are formed from what?

A

Bundles of proteins (connexins).

40
Q

What do gap junctions allow?

A

The rapid transmission of signals and synchronisation of contractions.

41
Q

Approximately how many gap junctions are present per myocyte towards term?

A

1000.

42
Q

What causes a pre-labour rise in the amount of myometrial oxytocin receptors?

A

Uterine distension.

43
Q

What three factors are implicated in stimulation?

A

Prostaglandins, oxytocin and CRH.

44
Q

Give two examples of cytokines involved in cervical ripening?

A

Interleukin 1-beta and tumour necrosis factor.

45
Q

What inflammatory-like changes occur that cause cervical ripening?

A

Increased synthesis of prostaglandins and cytokines cause an influx of macrophages and neutrophils.

46
Q

What do macrophages and neutrophils do to the cervix?

A

They infiltrate the cervical tissue and produce enzymes, which digest extracellular matrix proteins.

47
Q

Fill the blanks: ___ converts ___________ into prostaglandins.

A

Cyclooxgenase (COX) converts arachidonic acid into prostaglandins.

48
Q

How short are prostaglandins half life?

A

Approximately 3 minutes.

49
Q

Where do prostaglandins exert their influence?

A

At a local or subcellular level.

50
Q

What three hormonal changes trigger the increased synthesis of prostaglandins?

A

Increased DHEAS production. Increased oestrogen production. Decreased progesterone.

51
Q

Synthesis of prostaglandins is up-regulated by which substances?

A

Cortisol, oestradiol, CRH, interleukin 1-beta and tumour necrosis factor.

52
Q

Where are prostaglandins produced?

A

In the fetal membranes, decidua, myometrium and cervix.

53
Q

What does the chorion produce during pregnancy which inactivates prostaglandins?

A

Prostaglandin dehydrogenase (PGDH) - an enzyme.

54
Q

In late pregnancy, PGDH decreases, causing an increase in which prostaglandin?

A

Prostaglandin E2 (PGE2).

55
Q

What are the two most important prostaglandins in labour?

A

PGF2-alpha and PGE2.

56
Q

What is metabolised by the myometrium to produce PGF2-alpha?

A

PGE2.

57
Q

What inhibits PGE2 production during pregnancy, but favours its production in labour?

A

Relaxin.

58
Q

Where is oxytocin synthesised and released from?

A

It is synthesised by the hypothalamus and released from the posterior pituitary gland.

59
Q

At 32 weeks, how many times have the oxytocin receptors in the myometrium and decidua increased by?

A

They have increased 100 fold.

60
Q

At term, how many times have the oxytocin receptors in the myometrium and decidua increased by?

A

They have increased 300 fold.

61
Q

True or false: the fetal posterior pituitary also produces oxytocin during labour?

A

True.

62
Q

Which substance helps to maintain uterine blood flow during labour?

A

Prostacyclin.

63
Q

True or false: catecholamines inhibit uterine activity?

A

False: catecholamine both stimulate and inhibit uterine activity.

64
Q

What effect does noradrenaline have during labour?

A

It increases uterine contractions (contributes to the fetal ejection reflex).

65
Q

What effect does adrenaline have during labour?

A

It causes uterine relaxation, slowing labour.

Midwifery Year 1 MCQ (10 decks)

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