Body Scan: How Precision Engineering Aids Human Acumen
Often the most interesting science stories are the ones about us– how our bodies and minds function. Actions we perform each day without much thought are made possible by precision engineering, sometimes at the molecular level. Here is a selection of news briefs about human superpowers.
- Electrical engineering: We have untold myriads of electrical voltage sensors in our cells. They are so small, scientists must use extremely delicate techniques of X-ray crystallography to try to determine their structure. Science Now summarizes recent papers by Roderick MacKinnon et al. (see 05/01/2003, 3/12/2002 entries) about potassium channels in the membranes of neurons. The structure of the pores and the adjacent voltage sensors is coming into focus. There are four positively-charged arginine molecules (amino acids) that sit on top of the voltage sensors that surround the channel. “These charged arginines,” the article says, “move in response to changes in the voltage across the cell membrane, pressing up and down on the lever that opens and closes the pore.” Just how this movement takes place is still unknown, but it happens really fast. That’s what makes you cry ouch almost instantly after stubbing your toe: an electrical current, set up by these voltage-dependent ion channels, travelled from neuron to neuron from toe to brain in a fraction of a second.
- Optical engineering: What could be clearer than a cornea? This outer surface of the eye looks simple, like a glass lens, but it is very complex. EurekAlert summarized work by the American Society for Biochemistry and Molecular Biology. The scientists identified 141 distinct proteins in the cornea, 70% of which were previously unknown. (For the structure of protein, see our online book). These complex molecules perform many important roles, such as “antimicrobial defense, heme and iron transport, tissue protection against UV-radiation and oxidative stress,” it lists. “Several other proteins were known antiangiogenic factors, which prevent the formation of blood vessels.” The cornea is not a mere gateway for light, but a lively, active place, constantly undergoing maintenance, repair and cleaning. The September issue of Sky and Telescope recommends that you think carefully before deciding on laser surgery on this delicate, dynamic, living surface.
- Software engineering: Perceiving perception: Your brain uses database technology. A press release from Howard Hughes Medical Institute states that “The brain may interpret the information it receives from sensory neurons using a code more complicated than scientists previously thought.” This “perception code,” studied by experiments with monkeys (which presumably have similar neuronal equipment to humans) found that “most attention to the first 250 milliseconds of neural firing, and that their attention falls off exponentially from there.” Maybe some form of attention deficit is built in to deal with TMUI (too much uninteresting information).
See also a related report on EurekAlert about work at Johns Hopkins, “How the brain understands pictures.” Researchers found that “the system continuously organizes the whole scene, even though we usually are attending only to a small part of it.” Three or four times per second, the brain organizes the chunks of a scene into something like a database, according to a “sophisticated program” to “select and process the information that is relevant at a given moment.” As one researcher visualized it, imagine the challenge of pulling order out of a chaotic jumble of Lego blocks. He said, “the visual system first has to arrange this bag of blocks into useful ‘chunks’ and provide threads by which one or the other chunk can be pulled out for further processing.”
- The Cellular 007: When major threats arise, sometimes you have to give the cops their leash and turn them loose to do whatever is necessary to maintain security. EurekAlert reported on work by Yokoyama et al. at Washington School of Medicine. They found that natural killer cells act like the “James Bond” of the immune system. Under certain circumstances, the body gives them a “license to kill” – “the arsenals of natural killer cells only become fully armed after a receptor on their surfaces interacts with a molecule on the surfaces of other cells.” That’s the warrant to search and destroy. The article says that these natural killer cells are produced in the bone marrow, and that the entire population is replaced in a week’s time. “The molecular details of the process were so unusual,” says the report, “that Yokoyama and his colleagues found themselves struggling to develop terms to describe it to other immunologists.”
- Safe Stem Cells: Scientists at Pittsburgh School of Medicine, reports EurekAlert, have found that discarded placentas apparently contain stem cells with the “same potential as the more controversial counterparts,” embryonic stem cells. If so, then “placentas would no longer be relegated to the trashcan,” but become a lifesaving source of regenerative material. See also the MSNBC News report.
- Navigational Guidance and Control: Those orthogonal semicircular canals in our inner ears do more than just help balance. Because they respond to acceleration and deceleration, reports EurekAlert on work by the Institute of Neurology in London, they provide the brain with inputs for an “on-line movement guidance system” that is crucial when visual cues are absent, such as finding your way in a dark room. Additionally, the otolith organs (see 10/10/2003 entry), part of the vestibular system, are essential for determining which way is up. The article states that “the inner-ear vestibular organs provide what is essentially an on-line movement guidance system for maintaining the accuracy of whole-body movements.” This not only helps those of us lost in the dark, but highly-trained specialists undergoing “complex, high-precision whole-body movements, such as those of the gymnast or circus performer.” Visualize an acrobat balancing and catching a jug on his head and making it spin around, or picture an Olympic gymnast on uneven bars nailing a double twisting dismount, or a skater executing a perfect triple Lutz. You can bet those vestibular organs are working overtime. The full article by Brian L. Day and Richard C. Fitzpatrick, loaded with praise for the vestibular system, can be found on Current Biology, Volume 15, Issue 15, 9 August 2005, pages R583-R586. Here is the opening paragraph:
Small, beautifully formed and locked in the skull, the vestibular organs continuously bombard the brain with messages. The messages are quite unlike any others. They tell of accelerations, how the head is rotating and translating and its orientation in space. The messages never stop and cannot be turned off. Even when we are completely motionless, they signal the relentless pull of gravity. Perhaps because of their constant monologue, the vestibular sensation is different to the other senses. There is no overt, readily recognizable, localisable, conscious sensation from these organs. They provide a silent sense.
A body is a terrible thing to waste (speaking of waist, there can be too much of a good thing). Whether your body is fully functional or afflicted with a malady or two, you have a marvelous set of capabilities, and a dignity underscored by the complexity of the engineering that went into your making. Even if you are completely disabled, there is more complex engineering working properly under the skin than you could possibly realize. Fill in the box you were given. Exercise, eat right, practice. Maintain your machinery in optimum working order. Aim your body at something noble and worthwhile. You have a huge support infrastructure, with a staff of trillions behind the scenes, hoping you will make the right choices.