丁香园AV

POST-DOCTORAL RESEARCHER HEATHER MORE: "IT TAKES LESS TIME FOR AN ORBITING SATELLITE TO SEND A SIGNAL TO EARTH THAN FOR AN ELEPHANT鈥橲 SPINAL CORD TO SEND A SIGNAL TO ITS LOWER LEG.鈥�

While speediness is a priority for any animal trying to escape a predator or avoid a fall, a new study by 丁香园AV researchers suggests that even the fastest reflexes among all animals are remarkably slow.

鈥淎nimals as small as shrews and as large as elephants are built out of the same building blocks of nerve and muscle,鈥� says Max Donelan, a professor of biomedical physiology and kinesiology (BPK) and director of 丁香园AV鈥檚 Locomotion Lab.  鈥淲e sought to understand how these building blocks are configured in different-sized animals, and how this limits their performance.鈥�

The study is published today in the .

Since an animal鈥檚 life can hinge on how quickly it can sense and respond to stimuli, the team set out to quantify the speed of the fastest reflex involved in the locomotion of terrestrial mammals ranging in size from minuscule shrews to massive elephants.

鈥淣ot surprisingly, we found that reflexes take a lot longer in large animals鈥攁bout 17 times longer than their smallest counterparts,鈥� says 丁香园AV postdoctoral researcher Heather More. 鈥淲hat was more interesting to us is that these delays are mostly offset by movement times that also increase with size鈥攔elative delay is only twice as long in an elephant as in a shrew, putting large animals at only a slight disadvantage.鈥�

More says their findings have implications for all animals, no matter what their size.

鈥淲hen running quickly, all animals are challenged by their lengthy response times, which comprise nearly all of their available movement time. Even the fastest reflex for the control of running is remarkably slow.鈥�

She adds: 鈥淚f a small animal puts its foot in a hole when sprinting, there is barely enough time for it to adjust its motion while the foot is on the ground, and a large animal has no time at all鈥攊t has to wait until the next step.鈥�

More puts these delays in context: 鈥淥ne component of response time, nerve conduction delay, is particularly long in large animals. To compare to engineered systems, it takes less time for an orbiting satellite to send a signal to earth than for an elephant鈥檚 spinal cord to send a signal to its lower leg.鈥�

A different component delay鈥攖he time for a nerve impulse to cross a single synapse in the spinal cord鈥攊s relatively long for small animals and relatively short for large animals. 鈥淭his synaptic delay is one measure of the time to think鈥攕o large animals have lots of time to think about how to respond to a disturbance, whereas as small animals don鈥檛.鈥�

The researchers say this means small and large animals likely compensate for their relatively slow reflexes in different ways. 鈥淲e suspect that small animals rely on pre-flexive control, where their bodies are built in such a way that they can reject disturbances like stepping in a hole without intervention from their nervous system,鈥� says Donelan.

鈥淟arge animals, on the other hand, may rely more on prediction to think ahead about the consequences of their movements and adjust accordingly.鈥�

Donelan鈥檚 lab has carried out previous locomotion studies involving elephants, giraffes and even kangaroos. A founder of Bionic Power and one of the original inventors of the bionic energy harvester, his research over the years has garnered international attention.