Flashcards in Pharmacology of the Uterus Deck (69)
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1

What are the three layers making up the smooth muscle of the uterus?

→ Outer longitudinal fibres
→ Middle figure eight fibres
→ Inner circular fibres

2

What are the three layers of the uterus?

→ endometrium
→ Myometrium
→ perimetrium

3

What do uterine contractions do?

→ Increase uterine pressure
→ Forces content towards the cervix
→ acts as a natural ligature to prevent blood loss

4

What is the activity of the myometrium like?

→ Spontaneously active basal electrical activity

5

What kind of contractions are there in parturition?

→ Rhythmic

6

What is the myometrium sensitive to?

→ Neurotransmitters
→ Hormones

7

What type of cells are in the myometrium?

→ ICC pacemaker cells

8

How is synchronous contraction achieved?

→ Electrical communication between gap junctions
→ electrical activity is transmitted to adjacent cells

9

Where is electrical activity transmitted between in the myometrium?

→ Between ICCs
→ between ICC and smooth muscle
→ between smooth muscle cell

10

How do the myometrium cells function as?

→ A syncytium

11

Describe how contraction occurs?

→ ICC periodic activation of inward currents
→ depolarisations
→ Ca2+ entry through VGCC
→ Intracellular calcium leads to contraction

12

What are the slow waves of ICCs and smooth muscle responses modulated by?

→ Neurotransmitters and hormones

13

Describe how calcium is increased inside the cell?

Slow wave of depolarisation
↓
Ca2+ channels get activated
↓
Ca2+ entry increases Ca2+
↓
Ca2+ binds to calmodulin
↓
This phosphorylates myosin light chain kinase
↓
actin interaction lead to contractions

14

Describe how oxytocin leads to increased Ca2+?

Oxytocin is Gq couples
↓
Activation of phospholipase C
↓
PIP2 → DAG + IP3
↓
IP3 binds to IP3 receptors in the SR
↓
Causes Ca2+ from the store to be released into the cytosol
↓
Ca2+ increases

15

What are smooth muscle cells joined by?

→ Gap junctions

16

How can intracellular calcium be reduced?

→ Na+/Ca2+ exchanger
→ Ca2+ pump
→ some Ca2+ gets taken into the mitochondria

17

What is the effect of low concentrations of stimulants on ICCs?

→ Increase in slow wave frequency producing
→ Increase in frequency of contractions

18

How is the myometrium similar to other smooth muscle tissues?

→ There is a graded response - no threshold
→ increases in Ca2+ lead to increases in force of contraction

19

What is the effect of higher concentrations of stimulants on ICCs?

→ Increased frequency of action potentials on top of slow waves
→ Increased frequency and force of contractions

20

What is the effect of even higher concentrations of stimulants on ICCs?

→ plateau of slow wave producing prolonged sustained contractions

21

What is the effect of large concentrations of stimulants on ICCs?

→ hypertonus (incomplete relaxation)
→Ca2+ extrusion process is not as effective
→ interferes with blood flow - fetal distress

22

What innervation does the myometrium have?

→ Sympathetic

23

What receptors does the myometrium express?

→ alpha and beta adrenoceptors

24

What is the effect of alpha 1 adrenoceptor agonist?

→ contraction

25

What is the effect of beta 2 adrenoceptor agonist?

→ relaxation

26

What are alpha 1 adrenoceptors coupled with?

→ Gq

27

What are beta 2 adrenoceptors coupled with?

→ Gs

28

How does the Gs transduction mechanism work?

→ Stimulates the formation of cAMP
→ cAMP inhibits myosin light chain kinase
→ less contractile force

29

What effects do progesterone and estrogen have on contraction?

→ Progesterone - inhibits contraction
→ Estrogen - increases contraction

30

What contractions does a non-pregnant uterus have?

→ Weak contractions early in the cycle
→ Strong during menstruation (increased prostaglandins