Myometrium Physiology: Smooth Muscle: Young Flashcards
Life is the maintenance of an ionic gradient. What is the dominant ion on the inside of the cell?
K
How does K get into the cell?
Na/K exchanger ATPase
What is the dominant member of a membrane?
Lipid
How thick is the membrane relative to the cell?
Like a basketball rubber thickness relative to cell
What causes shortening of the cell?
Actin and myosin shortening
What ion causes actin and myosin to shorten?
Ca+2
What is concentration of Ca+2 within the cell?
100 nanomolar Ca+2
What goes over the actin and interacts with Ca?
Calmodulin
Where does Ca come from to flood the cell?
Sarcoplasmic reticulum
What other mechanism raises intracellular calcium?
L type Dihydropyrodine Ca Channel: Ca Channel on membrane
What clinical drug inhibits L type Dihydropyridine Ca channel?
NIfedipine: Dihydropyridine blocker
What agonist modulates the 7 transmembrane receptor of the myometrial smooth muscle cell?
- Epi
2. Oxytocin
What is the 7 TM receptor coupled to?
G protein on inside
What is the name of the signaling compound activated by G protein?
IP3
Where does IP3 act?
Sarcoplasmic reticulum
What receptor does IP3 act on in SR?
IP3 receptor
What is the resting potential of a smooth muscle cell?
-40
What is the maximum voltage of a smooth muscle cell?
+10
Where does Ca begin to enter cell in action potential curve?
Phase 2
How does Ca get removed from cytoplasm?
- (SCRCA pump) ScR Ca ATPase pumps it back into SR
- Pumped out of cell by CaATPase on membrane
- Na/Ca Exchanger on membrane
How does cell A communicate with cell B?
CONNEXIN 43: gap junction for electrical communication
What is the stretch activated K channel?
When you stretch a cell, K leaves
What happens with K leaves the cell?
Hyperpolarizes cell
Cell naturally depolarizes to threshold
What is the threshold of the AP in the smooth muscle cell?
-35
What happens when AP reaches threshold in sm cell?
Ca rushes in
What is activated to release Ca from SR?
Ryanodine receptor
How high does the Ca concentration increase from 100 nm resting concentration?
700-800 nm
What happens when Ca concentration increases in cell?
Binds calmodulin
Reveals actin binding site, myosin slides across with ATP binding: CONTRACTION
What pumps Ca back into the SR?
SRCA
What allows Ca to exit cell?
Ca ATPase
Na/Ca exchanger
How does smooth muscle relax?
Ca is pumped out of cell
What causes tissue to contract?
Stretching
How do you maintain membrane potential?
Leak and pumps
Is there a DK channel in the uterine smooth muscle to allow Ca in and out of cell?
No… must be another one
What is ROMK?
Volatage activated K channel
What depolarizes membrane potential?
K channel: DK channel (delayed
What starts all of these contractions?
Oxytocin!
Does the uterine sm act as a syncytium?
Yes! Gap junctions: CONNEXIN 43
What has to happen for myometrium to be ready to contract?
Make CONNEXIN 43
Make Calmodulin
etx… make the players
How long does it take for myometrium to be activated?
7-10 days
What from the baby goes to the myometrium of the mother to start activation of structural proteins there?
Protein A from surfactant
increases sex hormones in myometrium
The relationship of the funduus to the cervix is almost exclusively due to?
Prostaglandins
Inflammation
(oxytocin in labor)
This stuff is important… will you know it in your 3rd year?
Yes. Memorize it. Especially the attack points. And that it is redundant. There are 3 ways for Ca get out . Why? So that if one breaks, the others continue life on.
