NM704 MOD2 EXAM QUESTIONS AND ANSWERS WITH
COMPLETE SOLUTIONS VERIFIED
Phase 0 → Quiescence
Hormones that inhibit labor/contractions:
Progesterone
Prostacyclin
Relaxin
Nitric oxide & others
Phase 1 → Activation
Uterotropins are Estrogen & Prostaglandins
-stimulate up regulation of myometrial receptors for oxytocin & prostaglandins & gap
junctions
Phase 2 → Stimulation
Uterotonins- oxytocin & protiglandins
-promote labor progression
Phase 3 → Involution
Uterine involution after birth
-mediated by oxytocin & possibly thrombin
Progesterone
Uterotropin. Effects the uterus. Dominant in Quiescence and inhibits regular uterine
contractions.
,Estrogen
Uterotropin. Effects the uterus. Dominant in Activation phase.
Prostaglandins
Uterotonin. Effects the contractions. Dominant in activation and stimulation phase. They
facilitate contractions and increase myometrial sensitivity to oxytocin and stimulate gap
junctions.
Oxytocin
Uterotonin. Effects the contractions, maintains labor but does not initiate it. Dominant in
Stimulation Phase. Amount of oxytocin increases and peaks during second stage of
labor and enhanced by fetal oxytocin synthesis. Released in a pulsatile fashion.
Oxytocin receptors
The number of receptors and their sensitivity influences the strength and frequency of
contractions. The affinity of oxytocin for the receptors increases. The number of
receptors present on the myometrium peaks in early labor. Labor and mechanical
stretch increase expression of oxytocin receptors.
Gap junctions
proteins that create a line of communication between two adjacent myocytes. The
action potentials act through gap junctions and cause a
Myometrium
it is the bulk of the uterus. It is located between the decidua and perimetrium and has
four muscle layers and promote and inhibit contractions. The muscle is thickest at the
fundus and has the greatest contraction strength. The muscle is thinner towards the
isthmus. This is the muscle that is made of smooth muscle fibers and connective tissue
, (elastin and collagen). The myocytes have contractile ability. Prostaglandins stimulate
myocytes to depolarize creating a wave of contraction with action potentials being sent
from gap junction to gap junction like a domino effect. Intermittent contractions allow for
reperfusion.
Activation phase
myometrial excitability increases during this stage. Estrogen helps the myometrial cells
to make prostaglandins and oxytocin receptors and develop gap junctions between
muscle fibers.
Stimulation phase
Oxytocin binds to myometrial oxytocin receptors which cause smooth muscle
contractions. Prostaglandin is also stimulated by oxytocin binding. More oxytocin
receptors form on the myometrial membrane. Prostaglandins on the myometrium
predominates during this phase and makes contractions happen.
Oxytocin Receptors
The number of receptors and their sensitivity influences the strength and frequency of
contractions. The affinity of oxytocin for the receptors increases. The number of
receptors present on the myometrium peaks in early labor.
Triple Descending Gradient
contractions start in the fundus, last longer in the fundus, and progress from the fundus
towards the isthmus. This is needed for dilation to happen. The muscle bundles shorten
with contractions and cause the fundus to thicken, and the upper portion to get smaller
which helps the fetus descend.
Hemodynamic adaptation to labor
COMPLETE SOLUTIONS VERIFIED
Phase 0 → Quiescence
Hormones that inhibit labor/contractions:
Progesterone
Prostacyclin
Relaxin
Nitric oxide & others
Phase 1 → Activation
Uterotropins are Estrogen & Prostaglandins
-stimulate up regulation of myometrial receptors for oxytocin & prostaglandins & gap
junctions
Phase 2 → Stimulation
Uterotonins- oxytocin & protiglandins
-promote labor progression
Phase 3 → Involution
Uterine involution after birth
-mediated by oxytocin & possibly thrombin
Progesterone
Uterotropin. Effects the uterus. Dominant in Quiescence and inhibits regular uterine
contractions.
,Estrogen
Uterotropin. Effects the uterus. Dominant in Activation phase.
Prostaglandins
Uterotonin. Effects the contractions. Dominant in activation and stimulation phase. They
facilitate contractions and increase myometrial sensitivity to oxytocin and stimulate gap
junctions.
Oxytocin
Uterotonin. Effects the contractions, maintains labor but does not initiate it. Dominant in
Stimulation Phase. Amount of oxytocin increases and peaks during second stage of
labor and enhanced by fetal oxytocin synthesis. Released in a pulsatile fashion.
Oxytocin receptors
The number of receptors and their sensitivity influences the strength and frequency of
contractions. The affinity of oxytocin for the receptors increases. The number of
receptors present on the myometrium peaks in early labor. Labor and mechanical
stretch increase expression of oxytocin receptors.
Gap junctions
proteins that create a line of communication between two adjacent myocytes. The
action potentials act through gap junctions and cause a
Myometrium
it is the bulk of the uterus. It is located between the decidua and perimetrium and has
four muscle layers and promote and inhibit contractions. The muscle is thickest at the
fundus and has the greatest contraction strength. The muscle is thinner towards the
isthmus. This is the muscle that is made of smooth muscle fibers and connective tissue
, (elastin and collagen). The myocytes have contractile ability. Prostaglandins stimulate
myocytes to depolarize creating a wave of contraction with action potentials being sent
from gap junction to gap junction like a domino effect. Intermittent contractions allow for
reperfusion.
Activation phase
myometrial excitability increases during this stage. Estrogen helps the myometrial cells
to make prostaglandins and oxytocin receptors and develop gap junctions between
muscle fibers.
Stimulation phase
Oxytocin binds to myometrial oxytocin receptors which cause smooth muscle
contractions. Prostaglandin is also stimulated by oxytocin binding. More oxytocin
receptors form on the myometrial membrane. Prostaglandins on the myometrium
predominates during this phase and makes contractions happen.
Oxytocin Receptors
The number of receptors and their sensitivity influences the strength and frequency of
contractions. The affinity of oxytocin for the receptors increases. The number of
receptors present on the myometrium peaks in early labor.
Triple Descending Gradient
contractions start in the fundus, last longer in the fundus, and progress from the fundus
towards the isthmus. This is needed for dilation to happen. The muscle bundles shorten
with contractions and cause the fundus to thicken, and the upper portion to get smaller
which helps the fetus descend.
Hemodynamic adaptation to labor
