Posted on 20th October 2007 by Judy Breck in animals | biology | ecology | sciences
bird_migration, butterflies, migration, monarch, wildlife
The bird in this learn node is Crane #722 who is now participating in her first Journey South. She hatched on May 21, 2007 and is a member of 2007 Autumn Release Group III of captive-born whopping cranes who this fall are on their 1st migration, led by ultralight planes . She is part of the Journey North Whooping Crane adventures in which new online participants (you) are invited to take part. The wonder of the many Journey North global studies of wildlife migration and seasonal change in which many thousands of students and nature enthusiasts have participated for more than a decade is that their subjects are real. You can, for example, visit the Journey North monarch butterfly migration map to see where the great winged beauties have been sighted this fall as they are moving toward Mexico to winter there.
Crane #722 is playing a role in efforts to reestablish whooping cranes, who had almost become extinct in the 20th century. We are learning from her more general lessons about migration of birds. For more on that, there is a student project on The Mystery of Bird Migration in these MIT engineering class materials and even more in this lecture on migration and navigation.
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Posted on 19th October 2007 by Judy Breck in biology | design | sciences
motor_unit, muscle, neuroscience
The image for this learn node is from Dr. Emad Eskandar’s Harvard-MIT Health Sciences and Technology Neuroscience course handout (Motor Systems I). Page 2, With the image the handout explains:
We will begin our discussion from the bottom up starting with the physiology of the muscles and the spinal cord. An important concept to grasp is that of the motor unit. The following points should be kept in mind.
- A whole muscle is made up of many muscle fibers
- A muscle fiber is a single mutlinucleated cell
- Each muscle fiber is innervated by only one alpha motor neuron
- Each alpha motor neuron innervates numerous muscle fibers within a muscle
- A single neuron and all the muscle fibers it innervates are a motor unit
- The motor unit is the smallest division that the system can control individually
You can connect the muscle concepts above to another superb academic source by going to the Tufts Dental School course: Histology: Study of Cells, Tissues and Organs. Lecture 9: Muscle, on page 5 of the PDF summarizes the sequence of events of a muscle contraction. This Tufts muscle lecture can flex the most curious young mind � one that wants move past the medium learning fare.
To drop by and look over the shoulders of some scientists learning about muscle motor neurons from the transparent spinal cord of the zebrafish, click into The Journal of Neuroscience, where the articles are freely open online for the benefit of scientists, students and teachers.
For a look at the same information in non-academic, non-medical terms: How Muscles Work at HowStuffWorks.com.
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Posted on 28th September 2007 by Judy Breck in general science | sciences
astronomy, orbit, satellite, space, sputnik
This learn node notes the fiftieth anniversary of satellites. On October 4, 1957, the Soviet Union launched a 23-inch diameter satellite. It was the first object ever launched into Earth orbit by humankind, as a post I wrote for iCommons.org describes in a birthday salute to this object named Sputnik 1.
Although the image above suggests Sputnik satellite in orbit, it is more general. It is from a Connexions tutorial � an open educational resource where you can learn how artificial satellites are the backbone of modern communications system. A lot has happened in the past 50 years as orbiting objects have diversified and become common. The open learning website How Stuff Works’ section on How Satellites Work begins:
Not so long ago, satellites were exotic, top-secret devices. They were used primarily in a military capacity, for activities such as navigation and espionage. Now they are an essential part of our daily lives. We see and recognize their use in weather reports, television transmission by DIRECTV and the DISH Network, and everyday telephone calls. In many other instances, satellites play a background role that escapes our notice.
An interesting place to move out into the online clusters of the adventures and ramifications of the Sputniks is from this Astronomy Picture of the Day salute to Traveling Companion (which is what “sputnik” means). You can even meet Laika, the first dog in space.
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