April 13, 2017 | David F. Coppedge

Walk This Way: Body Designs Head to Toe

When you examine what makes us tick, you find intelligent design from the top down and from the bottom up.

Complementary mechanisms for upright balance during walking (PLoS One). We usually walk without much conscious attention; some of us can chew gum at the same time. Given that the human body is much taller than it is wide, and uses only two legs instead of four, it has a challenge: keeping balance during motion. We actually fall forward with each step, and have to compensate at the right time. Babies learning to walk, and stroke victims in PT (physical therapy), know how hard that can be. Six physiologists tried to figure out the physics and signals involved.

Lateral balance is a critical factor in keeping the human body upright during walking. Two important mechanisms for balance control are the stepping strategy, in which the foot placement is changed in the direction of a sensed fall to modulate how the gravitational force acts on the body, and the lateral ankle strategy, in which the body mass is actively accelerated by an ankle torque. Currently, there is minimal evidence about how these two strategies complement one another to achieve upright balance during locomotion. We use Galvanic vestibular stimulation (GVS) to induce the sensation of a fall at heel-off during gait initiation. We found that young healthy adults respond to the illusory fall using both the lateral ankle strategy and the stepping strategy. The stance foot center of pressure (CoP) is shifted in the direction of the perceived fall by ≈2.5 mm, starting ≈247 ms after stimulus onset. The foot placement of the following step is shifted by ≈15 mm in the same direction. The temporal delay between these two mechanisms suggests that they independently contribute to upright balance during locomotion, potentially in a serially coordinated manner.

Now figure this out for basketball players, hurdlers, and gymnasts.

Atomic resolution of muscle contraction (Osaka University). When you walk or flex a muscle, there are actual pushes and pulls going on at the subcellular level. The molecular motor myosin, which traverses actin membrances, is an “engineering marvel”, these scientists find. This machine is working out hard as you work out:

At the molecular level, muscle contraction is defined by myosin molecules pulling actin filaments. New electron cryomicroscopy images with unprecedented resolution taken by researchers at Osaka University reveal unexpectedly large conformational changes in the myosin molecule during the pull. These findings, which can be seen in Nature Communications, provide new insights into how myosin generates force and a paradigm for the construction of nanomachines.

To biophysicists like Keiichi Namba, professor at Osaka University, the ability of tiny molecules to generate large amounts of force seen in muscle make myosin an engineering marvel.

5 Reasons Why Placentas Are Amazing (Live Science). This series by Mindy Waisberger tells readers amazing things about the life-support organ that nourished and protected us – and all placental mammals from mice to giraffes — in the womb. “It is the only organ that reproductive-age humans grow entirely from scratch,” she says. The organ is constantly adjusting to the baby within it, responding to hormones and secreting others. “Surrounding the placenta is a thin, protective layer known as the amniotic membrane, an intricate scaffold of proteins that carries nutrients and stem cells for fetal development.” Its ability to protect tissues is inspiring technologies for wound healing, she reports. Don’t be tempted to eat placenta, though: there’s no evidence it is healthy, as some claim.

Characterization of the human aqueous humour proteome: A comparison of the genders (PLoS One). You might remember learning the parts of the eye in school, including the humorous parts: the aqueous humor behind the cornea, and the vitrious humor behind the lens. Unless you’re an opththalmologist, you may not have learned how much that aqueous humor does for you:

Aqueous humour (AH) is an important biologic fluid that maintains normal intraocular pressure and contains proteins that regulate the homeostasis of ocular tissues. Any alterations in the protein compositions are correlated to the pathogenesis of various ocular disorders. … A total of 147 proteins were identified with a false discovery rate of less than 1% and only the top 10 major AH proteins make up almost 90% of the total identified proteins. A large number of proteins identified were correlated to defence, immune and inflammatory mechanisms, and response to wounding.

A little inhibition shapes the brain’s GPS (Kings College London): Who needs directions, guys, when you have a GPS system in your brain? “Researchers from King’s College London have discovered a specific class of inhibitory neurons in the cerebral cortex which plays a key role in how the brain encodes spatial information,” this article says. Want to shoot some hoops? ” In their new study, the researchers reveal that one of the main classes of basket cells plays a key role in how the brain represents and remembers our environment, called spatial information coding.”

Chew on this: Physics of chewing in terrestrial mammals (Nature Scientific Reports). No matter how hard or gently you chew, your muscles stay within limits of a power law based on your body mass. This is true for big and small mammals. “All of our experimental data stay within these physical boundaries over six orders of magnitude of body mass regardless of food types.”

Gene analysis adds layers to understanding how our livers function (Weizmann Institute). For your daily Wonder Wander, Weizmann tells about your liver. What does the liver do? It lives, doh! But there’s a lot in that living:

Amazing FactsIf you get up in the morning feeling energetic and clearheaded, you can thank your liver for manufacturing glucose before breakfast time. Among a host of other vital functions, it clears our body of toxins and produces most of the carrier proteins in our blood. In a study reported recently in Nature, Weizmann Institute of Science researchers showed that the liver’s amazing multitasking capacity is due at least in part to a clever division of labor among its cells.

A genetic analysis showed nine different types of cells in this all-purpose organ. They’re arranged in a purposeful way, too: “The scientists also discovered that certain processes, such as the manufacture of bile, proceed across several different layers, in something like a production line.

Isn’t it wonderful what chance can do over millions and millions of years zzzzz… Wake up! That was a nightmare. Time to rise and become energetic and clearheaded. Thank your liver! Now, go live, walk, flex some muscles, and think logically.


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