Although we have not quite covered the musculoskeletal system in class, I thought I would make a post on the topic since I will be leaving early this quarter. Thus, I will be writing about pregnancy.
The myometrium - the smooth muscle of the uterus - is a key player in the maintenance of pregnancy. Throughout pregnancy, the myometrium is kept in a relaxed state by the steroidal hormone progesterone. However, unbeknownst to most of the world, there is battle going on during pregnancy, a viscous brawl between progesterone (which would like to maintain pregnancy) and estriol (which would like to violently end it by stimulating the myometrium to contract). Once estriol overtakes progesterone, labor begins and pregnancy soon terminates. Once this begins, there really is no stopping the process.
This presents an issue when mothers go into labor prematurely - if the mother goes into labor too early, the fetus will be underdeveloped when born. Being born prematurely presents a host of potential medical issues to the newborn baby. Thus, we would like to prevent this from occurring. Much research has therefore been done on the matter.
Smooth muscle contracts when an action potential is generated by the muscle cell after signaling from a neuron - calcium enters the smooth muscle cell which facilitates the binding of phosphate groups to the myosin filaments in the cell. This causes a shape change in the myosin which pulls on the actin filaments of the muscle cell- causing the cell to contract.
Therefore, if we want to stop the contraction of the myometrium, we must stop this process from occurring in some way - and, as you can see, there are multiple places at which we could do this. Nitric oxide (NO) and androgens (such as testosterone) have recently been shown to stimulate relax of the myometrium by blockage of these processes. Both molecules have been shown to somehow alter the ion channels which facilitate the entry of Ca2+ and other ions into the cell. Androgens may also regulate at the level of the phosphorylation of the myosin, preventing it from occurring.
Hopefully, not too long from now, these chemicals will find applicable use in preventing premature labor in humans, but more research needs to be done before human trials can begin.
If you want to read more on the matter, here are a couple papers: