Archive: Eyes, Ears, Clocks, and Cold Dinosaurs
CEH has been reporting on science for a long time. These entries from February 2002 are still worth reading. Enjoy!
Note: some links may no longer work.
Third Eye Sets Biological Clock 02/08/2002
A third light-detecting mechanism in the eye, independent of rods and cones, has been discovered, reports Feb 8 Science. The cells and their photoreceptors appear to send their signals to the brain’s clock that governs circadian rhythms and day/night cycles.
The surprising finding is the culmination of a “burst of papers published in the past 2 months” that resulted in two reports in the current issue. The system responds primarily to the luminance, or brightness, of the light, rather than the details of an image, as do the rods and cones.
The scientists believe this new light-detection system not only affects the body’s biological rhythms, but also controls pupil constriction and emotions: “The impact of this light-sensing system may go far beyond pupil size and the clock. In humans, light levels can modulate mood and performance. ‘This photoreceptor system may be incredibly important in our general physiology and well-being,’ says [Russell] Foster” of Imperial College, London.
The study of biological clocks is just coming into its heyday. The field is not getting any less complex. If scientists are just now finding out about new “eyes”, what other wonders remain to be discovered?
Dinosaur Bones Abundant in Arctic 02/08/2002
Finding dinosaur bones in the frozen north is a job for Roland Gangloff of the Alaska Museum, who says, “These dinosaurs were doing quite well in high latitudes in both hemispheres 110 – 65 million years ago. They were well adapted and the evidence is so overwhelming it cries out to be understood.”
His paper published in the Feb 8 Science puzzles over how allegedly cold-blooded creatures survived in such a habitat. He sees deposits along the Colville River as most promising for research.
There have been reports of unfossilized dinosaur bones found in Alaska, some even with blood protein traces in them that should have decayed long ago. If true, they could not be as old as claimed by evolutionary theory. Keep your eye on the anomalies, not on the conventional wisdom, which assumes evolution and geological time scales.
How Your Ear Electronic Organ and Mixing Console Works 02/07/2002
The cover article in the Feb 8 issue of Cell describes a new motor found in your ear. Inside the ear is a very complex and sophisticated system that, for all practical purposes, can be described as an electronic organ and mixing console. Have you ever been at a meeting where the sound system went berserk and feedback sent a shriek through the room? Well, the ear has a mechanism to prevent that, and a motor called myosin is apparently involved, according to Jeffrey R. Holt and a team of eight cell biologists.
The inner ear needs to convert (transduce) mechanical signals to electrical signals – pressure waves in the fluid of the inner ear to nerve pulses that go to the brain. The way it does this is to use “hair bundles” of about 50 hairs that look for all the world like organ pipes (a picture is on the cover). These hairs are tied together and bend over in response to vibrations (sound). This bending opens up channels in the cell to which they are attached, allowing electrical ions to flow in and start nerve signals. This is the act of transduction. But there has to be a way to shut off the flow or tame it down, else you would have a stuck note: a flood of irritating messages hitting the brain.
That’s where adaptation comes in. The ear has two kinds of adaptation: fast and slow, and they involve very different mechanisms. In fast adaptation, a calcium ion enters the channel and blocks the flow; this happens within a few thousandths of a second. A few tens of milliseconds later, slow adaptation kicks in. In this process, a motor climbs up the hair cells and adjusts the tension of “gating springs” and relaxes the tension so that the ion channels close.
These scientists proposed myosin-1c, a member of the the myosin superfamily of motor proteins, as the probable motor that climbs up the actin filaments. Their diagram shows actual springs (not that they are like metal springs we know, but proteins that function like them) with myosin-1c like a little ratchet motor that can climb up the hairs and adjust the tension in the springs, to relax the hair and close the channel. In effect, the myosin acts like a mixing board operator with his fingers on sliders, adjusting the volume level on each line. … only even more elaborate, and quicker. Another analogy would make this like an automatic compressor-limiter.
And this study was done on mice, turtles and bullfrogs. Human ears are no less wonderful; probably more so. When you listen to speech or music, two million of these hair cells go into operation, with the mixing console adapting to intensities of 10 billion to one. You can distinguish up to 300,000 pitches, far more than needed for mere survival, but abundantly adequate to enjoy music.
The motorized compressor-limiter described by these scientists is just one part of an elaborate system that converts nearly infinitesimal pressure waves in the air into the joy of music. Inside your head right now is one of the most complex and sophisticated sound systems imaginable: a combination microphone, electronic organ, mixing console, sound processor and stereo receiver, all automatic, all self-adjusting, able to respond to a jet takeoff or the footsteps of a cat, able to pick out a familiar voice in a crowd, able to pinpoint the direction of a sound, all self-servicing for up to a lifetime. Don’t be deaf to the shouts of “Design!”