Pharmacology Of The Uterus Flashcards
Describe the structure of the myometrium
3 layers: outer longitudinal fibres, middle figure-eight fibres and inner circle fibres
Where do the uterine contractions originate from?
The muscle itself (myogenic)
What initiates the uterine contractions?
Spontaneous depolarisation of pacemaker cells that spread through gap junctions
What is a syncytium?
When lots of cells work together to give an effect
What causes contration?
Increase in intracellular calcium concentration
What are uterine contractions modulated by?
Hormones and neurotransmitters
How do we measure uterine contractions?
Isometric tension recording or ion channel modulators
What are the two types of ion channel modulators?
Potassium channel activator and calcium channel blockers
What type of innervation does the uterus have?
Sympathetic
What types of receptors does the uterus have?
Alpha and beta adrenoreceptors
What do alpha adrenoreceptor agonists cause in the uterus?
Contraction
What do beta adrenoreceptor agonists cause in the uterus?
Relaxation
How does progesterone affect uterine contractions?
Inhibits
How does oestrogen affect uterine contractions?
Increases
When does a non pregnant uterus contract?
Weak contractions early in the cycle and strong contractions during menstration
What are the uterine contractions like at the start of pregnancy and why?
Weak and uncoordinated because of high progesterone
How do the uterine contractions become stronger in pregnancy if the progesterone levels stay the same?
Oestrogen increases to overcome the progesterone
Where is oxytocin synthesised and released from?
Synthesised in the hypothalamus and released from the posterior pituitary gland
What is oxytocin released in response to?
Suckling and cervical dilation
How does oestrogen release affect oxytocin?
Causes it to be released and increases the expression of oxytocin receptors
What do prostaglandins do?
Induce myometrial contraction and have a role in dysmenorrhea, menorrhagia and pain after labour
What does oxytocin stimulate?
Release of prostaglandins
What do ergots cause?
Powerful and prolonged uterine contractions and contraction of the blood vessels surrounding the uterus
How do ergots work?
Stimulation of the alpha adrenoreceptors and 5-HT receptors
What are ergots used for clinically?
Post-Partum bleeding
What is exogenous oxytocin used for clinically?
Induce/ augment labour at term and post-partum bleeding
What can too much exogenous oxytocin cause?
Sustained contration and foetal distress
What are prostaglandins used for clinically?
Induction of preterm labour, induce abortion
When are myometrial relaxants used?
In premature labour
Why are myometrial relaxants used?
Allows the mother to be transferred to a specialist unit and given antenatal corticosteroids to help with foetal lung maturation
What are the different types of myometrial relaxants?
Oxytocin receptor antagonists, anti-prostaglandins, nitric oxide donors, beta adrenergic receptor agonists and calcium channel blockers
