Pharmacology Of The Uterus

Question 1

Describe the structure of the myometrium

Answer 1

3 layers: outer longitudinal fibres, middle figure-eight fibres and inner circle fibres

Question 2

Where do the uterine contractions originate from?

Answer 2

The muscle itself (myogenic)

Question 3

What initiates the uterine contractions?

Answer 3

Spontaneous depolarisation of pacemaker cells that spread through gap junctions

Question 4

What is a syncytium?

Answer 4

When lots of cells work together to give an effect

Question 5

What causes contration?

Answer 5

Increase in intracellular calcium concentration

Question 6

What are uterine contractions modulated by?

Answer 6

Hormones and neurotransmitters

Question 7

How do we measure uterine contractions?

Answer 7

Isometric tension recording or ion channel modulators

Question 8

What are the two types of ion channel modulators?

Answer 8

Potassium channel activator and calcium channel blockers

Question 9

What type of innervation does the uterus have?

Answer 9

Sympathetic

Question 10

What types of receptors does the uterus have?

Answer 10

Alpha and beta adrenoreceptors

Question 11

What do alpha adrenoreceptor agonists cause in the uterus?

Answer 11

Contraction

Question 12

What do beta adrenoreceptor agonists cause in the uterus?

Answer 12

Relaxation

Question 13

How does progesterone affect uterine contractions?

Answer 13

Inhibits

Question 14

How does oestrogen affect uterine contractions?

Answer 14

Increases

Question 15

When does a non pregnant uterus contract?

Answer 15

Weak contractions early in the cycle and strong contractions during menstration

Question 16

What are the uterine contractions like at the start of pregnancy and why?

Answer 16

Weak and uncoordinated because of high progesterone

Question 17

How do the uterine contractions become stronger in pregnancy if the progesterone levels stay the same?

Answer 17

Oestrogen increases to overcome the progesterone

Question 18

Where is oxytocin synthesised and released from?

Answer 18

Synthesised in the hypothalamus and released from the posterior pituitary gland

Question 19

What is oxytocin released in response to?

Answer 19

Suckling and cervical dilation

Question 20

How does oestrogen release affect oxytocin?

Answer 20

Causes it to be released and increases the expression of oxytocin receptors

Question 21

What do prostaglandins do?

Answer 21

Induce myometrial contraction and have a role in dysmenorrhea, menorrhagia and pain after labour

Question 22

What does oxytocin stimulate?

Answer 22

Release of prostaglandins

Question 23

What do ergots cause?

Answer 23

Powerful and prolonged uterine contractions and contraction of the blood vessels surrounding the uterus

Question 24

How do ergots work?

Answer 24

Stimulation of the alpha adrenoreceptors and 5-HT receptors

Question 25

What are ergots used for clinically?

Answer 25

Post-Partum bleeding

Question 26

What is exogenous oxytocin used for clinically?

Answer 26

Induce/ augment labour at term and post-partum bleeding

Question 27

What can too much exogenous oxytocin cause?

Answer 27

Sustained contration and foetal distress

Question 28

What are prostaglandins used for clinically?

Answer 28

Induction of preterm labour, induce abortion

Question 29

When are myometrial relaxants used?

Answer 29

In premature labour

Question 30

Why are myometrial relaxants used?

Answer 30

Allows the mother to be transferred to a specialist unit and given antenatal corticosteroids to help with foetal lung maturation

Question 31

What are the different types of myometrial relaxants?

Answer 31

Oxytocin receptor antagonists, anti-prostaglandins, nitric oxide donors, beta adrenergic receptor agonists and calcium channel blockers