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Repro Phys > Pharmacology Of The Uterus > Flashcards

Pharmacology Of The Uterus Flashcards

1
Q

Myometrium

A

smooth muscle layer(s) of the uterus

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2
Q

Gap junctions

A

connections between cells that allow transfer of (electrical) signal

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3
Q

VGCC

A

voltage-gated calcium channels

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4
Q

Parturition

A

childbirth

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5
Q

Ergometrine

A

a potent contractor of the uterus found in ergot

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6
Q

Functional syncytium

A

a mass of cells that function as one

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7
Q

STRUCTURE OF MYOMETRIUM

A 
diagrams 
Smooth muscle of the uterus 
•Outer longitudinal fibres
•Middle figure-eight fibres
•Inner circular fibres
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8
Q

MECHANICAL PROPERTIES OF

MYOMETRIUM

A 
Rhythmic contractions
Spontaneously active 
Vary during menstrual cycle and 
pregnancy
Force content towards the cervix
 Contractions originate in the 
muscle itself
Doesn’t require neuronal or 
hormonal input
BUT highly sensitive to e.g. sex 
hormones
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9
Q

SO WHAT INITIATES THE

CONTRACTION?

A 
Spontaneous depolarisation of ‘pacemaker’ cells
 Give rise to action potentials
 Electrical communication between cells
 Gap junctions spread depolarisation
 Myometrium can function as a syncytium
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10
Q

EXCITATION-CONTRACTION

COUPLING

A

Slow waves of pacemakers and smooth muscle responses are modulated
by neurotransmitters and hormones
diagrams

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11
Q

BASAL AND ELEVATED [CA2+]I

A

Similar to other smooth muscle tissues
• [Ca2+]i  contraction
•Graded response: incremental increases in [Ca2+]i  incremental
increases in force of contraction
•Mechanisms for lowering [Ca2+]i: e.g. Ca2+ extrusion
diagram

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12
Q

CONTRACTION MODULATED BY

HORMONES AND NEUROTRANSMITTERS

A

diagram

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13
Q

HOW TO MEASURE UTERINE

CONTRACTION?

A

• E.g. Isometric tension recording
Measure tension generated with diameter of the muscle ring remains constant
• Y1 practicals: Large organ baths – aortic ring experiments
• Widely used techniques to investigate the functional properties of uterine, vascular, airway and bladder smooth muscle segments

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14
Q

OXYTOCIN-INDUCED CONTRACTIONS

A

diagrams

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15
Q

ION CHANNEL MODULATORS

A

diagram

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16
Q

REGULATION BY NEUROTRANSMITTERS

A

Sympathetic (not parasympathetic) innervation
Expression of α- and β- adrenoceptors
α-adrenoceptor agonist – contraction
β2-adrenoceptor agonist – relaxation

17
Q

REGULATION BY SEX HORMONES

A

Progesterone inhibits contraction
Oestrogen increases contraction
Both act at nuclear and membrane receptors

Non-pregnant uterus
Weak contractions early in cycle
Strong contractions during menstruation
(progesterone low)

Pregnant uterus
Weak and uncoordinated contactions in early pregnancy (high
progesterone)
7 month till term – Oestrogen increases, progesterone stays constant
Oestrogen / progesterone ratio increases throughout last trimester culminating with strong, coordinated contractions for delivery

diagrams

18
Q

REGULATION BY OXYTOCIN

A

Non-peptide hormone synthesised in hypothalamus and released from the posterior pituitary gland
Released in response to suckling and cervical dilatation
Oestrogen (released at later stages of pregnancy) causes:
oxytocin release, increase expression of oxytocin receptors
Oxytocin also increases synthesis of prostaglandins

19
Q

REGULATION BY PROSTAGLANDINS

A

Prostaglandins induce myometrial contraction (PGE and PGF)
Role in dysmenorrhoea (severe menstrual pain), menorrhagia (severe menstrual blood loss), pain after parturition
NSAIDs are effective – reduce contraction and pain
Oxytocin stimulates release of prostaglandins

20
Q

Contractile Agents

A

diagram

21
Q

Ergot to ergometrine

A

• Ergot - fungus that grows on some cereals (e.g. rye) and grasses
• Contains ergometrine
Action• Powerful and prolonged uterine contractionMechanism• Stimulation of -adrenoceptors, 5-HT receptors?
Uses• Post-partum bleeding - NOT induction

22
Q

Oxytocin and Prostaglandins

A 
Oxytocin
 Used to induce/augment labour at 
term
 Dose dependent increases in 
contraction – but too much can 
cause sustained contraction and 
fetal distress
 Also used in postpartum 
haemorrhage

Prostaglandins
Induction of labour – before term
Induce abortion
Postpartum bleeding

23
Q

Myometrial Relaxants

A

Relaxants may be used in premature labour
• Important: Delay delivery by 48 hrs, so Mother can be transferred to specialist unit, and given antenatal corticosteroids to aid foetal lung maturation and increase survival

  • 2-adrenoceptor stimulants e.g. ritodrine
  • Relax uterine contractions by a direct action on the myometrium
  • Used to reduce strength of contractions in premature labour
  • May occur as a side effect of drugs used in asthma
  • Ca2+ channel antagonists e.g. nifedipine (used in hypertension) or Mg Sulfate
  • Oxytocin receptor antagonists e.g. Retosiban
  • COX inhibitors e.g. NSAIDs
  • ( prostaglandin) – why NSAIDS are useful to treat dysmenorrhoea and menorrhagia

Repro Phys (12 decks)

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