Nav: Home

Stick insect study shows the significance of passive muscle force for fast movements

January 09, 2019

Long, heavy limbs such as arms or legs differ fundamentally from short, light limbs such as fingers in their ability to execute fast movements. While the central nervous system has to actively control fast movements of large limbs, passive muscle force can suffice for the movement velocity and movement amplitude of small and light limbs. That is the result of a study conducted on the stick insect by the zoologists Ansgar Bueschges, Arndt von Twickel and Christoph Guschlbauer at the University of Cologne in cooperation with the visiting scientist Scott Hooper from Ohio University. The paper has now been published under the title 'Swing Velocity Profiles of Small Limbs Can Arise from Transient Passive Torques of the Antagonist Muscle Alone' in Current Biology.

There are different basic speed levels in the course of a movement until the entire motor action has been optimally executed, says Bueschges: 'If we look at the swinging of our legs when we walk, for example, the swinging phase brings the leg back into the starting position for the next step. With this feedback, the swing speed of the leg decreases towards the end, so that the foot does not touch down as quickly. Without the deceleration, the force generated when touching down would be so strong that it would counteract the next step.' Our nervous system produces this deceleration in large limbs such as the human leg.

For smaller limbs such as insect bones, however, the authors have shown that the slowing of the leg during rapid movements such as the swinging phase is independent of the central nervous system. Von Twickel explains that this is due to the intrinsic muscle characteristics of the limb: 'If the extensor muscle of a leg joint is actively shortened to produce rapid movements, the inactive flexor muscle is necessarily lengthened. During this stretching, the flexor muscle develops a previously unknown dynamic passive force, which is so large that it can continuously slow down movements to the functionally necessary level.'

In the study, the authors exposed the flexor muscle of the stick insect leg to various stretching scenarios and measured the dynamic forces exerted by the passive muscle against the different stretches. Then, they used the results to dynamically simulate the functioning of a leg joint. The passive dynamic forces of the flexor generated by extensor activation were able to generate a movement that corresponded to the speed profile of an animal.

These results are quite surprising and contradict widespread notions of how small limbs execute fast movements. Bueschges concludes: 'We have known for a long time that passive muscle forces are important for the movements of small limbs, but we did not expect that their effect is so great that they can determine the speed profile of a movement. This means that the active muscle and its opponent must be perfectly tuned to each other. We are in the process of better understanding this interaction.'
-end-


University of Cologne

Related Central Nervous System Articles:

Zika combats advanced-stage central nervous system tumors in dogs
The viral therapy was tested in three elderly animals with spontaneous brain tumors by a group affiliated with the FAPESP-funded Human Genome and Stem Cell Research Center.
Fewer scars in the central nervous system
Researchers have discovered the influence of the coagulation factor fibrinogen on the damaged brain.
Mayo Clinic discovers a molecular switch for repairing central nervous system disorders
A molecular switch has the ability to turn on a substance in animals that repairs neurological damage in disorders such as multiple sclerosis (MS), Mayo Clinic researchers discovered.
Discovery concerning the nervous system overturns a previous theory
It appears that when our nervous system is developing, only the most viable neurons survive, while immature neurons are weeded out and die.
Nanocapsule reaches cancer that has spread to central nervous system in mice
Researchers developed a drug delivery system that can break through the blood-brain barrier in mice.
Persistent HIV in central nervous system linked to cognitive impairment
Many people with HIV on antiretroviral therapy (ART) have viral genetic material in the cells of their cerebrospinal fluid, and these individuals are more likely to experience memory and concentration problems, according to a NIAID-funded study published in the Journal of Clinical Investigation.
First step to induce self-repair in the central nervous system
Injured axons instruct Schwann cells to build specialized actin spheres to break down and remove axon fragments, thereby starting the regeneration process.
First complete wiring diagram of an animal's nervous system
In a study published online today in Nature, researchers at Albert Einstein College of Medicine describe the first complete wiring diagram of the nervous system of an animal, the roundworm Caenorhabditis elegans, used by scientists worldwide as a model organism.
Scientists unlock new role for nervous system in regeneration
Biologists have developed a computational model of flatworm regeneration to answer an important question in regeneration research - what are the signals that determine the rebuilding of specific anatomical structures?
Microglia, immune cells of the central nervous system, shown to regulate neuroinflammation
A research team at Massachusetts Eye and Ear has shown that microglia, the immune cells of the central nervous system -- including the retina -- serve as 'gatekeepers' of neuroinflammation.
More Central Nervous System News and Central Nervous System Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Reinvention
Change is hard, but it's also an opportunity to discover and reimagine what you thought you knew. From our economy, to music, to even ourselves–this hour TED speakers explore the power of reinvention. Guests include OK Go lead singer Damian Kulash Jr., former college gymnastics coach Valorie Kondos Field, Stockton Mayor Michael Tubbs, and entrepreneur Nick Hanauer.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at Radiolab.org/donate.