Posts Tagged ‘biology’

The Most Powerful Movements in Biology » American Scientist

Sunday, March 27th, 2016

The Most Powerful Movements in #Biology,y.2015,no.5,content.true,page.1,css.print/issue.aspx How nature uses the latched bow-&-arrow construct in many contexts

Just like the bow and arrow example, mantis shrimp raptorial appendages contain a spring and a latch to generate extreme power amplification. Their mechanism for power amplification is just a tweak to the standard antagonistic muscle contractions that characterize most animals’ motor systems. Just like the extensor and flexor muscle pairs that extend and flex our limbs, mantis shrimp raptorial appendages use extensor muscles to swing out their hammer and flexor muscles to fold appendage segments toward the body during normal, daily activities. However, when they need to do a high-powered blow, they contract the flexor and extensor muscles simultaneously (similar to the antagonistic leg muscle contractions that we do prior to a jump). When they co-contract these muscles, the large, bulky extensor muscles compress an elastic system and tiny flexor muscles pull latch-like mineralizations of their apodemes (tendons) over a small lump inside the appendage, thus providing effective mechanical advantage over the high forces of the large extensor muscles. The result is no movement at all! The system is primed to strike as soon as the flexor muscles relax, release the latches, and permit the stored elastic energy to release over an extremely short time period to push the hammer forward with extreme power output.

“To varying degrees, this is the trick that all high-power systems use: They temporally and spatially separate slow loading and energy storage from the rapid release of energy that confers power
amplification. Trap-jaw ants release tiny latches that block their preloaded mandibles (watch a video on Patek’s research on trap-jaw ants). Two droplets slowly grow until the point at which they fuse over exceedingly short time scales to yield the power to launch a fungal ballistospore. The jellyfish’s stinger waits within a slowly pressurizing cell; a trigger hair dramatically releases the stored pressure and ejects the stinger toward its target. Thus, whether a muscle-based movement or a fluid-driven motion, the underlying mechanisms of ultrafast systems are all about power amplification.” “}}