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 3rd September 2007 by Judy Breck in biology | health | molecules, cells
cells, polio, poliomyelitis, virus
Polio invasion is seen in this learn node illustration. The little purple ball – lower center in this image – is a very scary thing. It is polio entering a person’s gut. Good public health can prevent polio and many other human miseries. Superb learning materials for public health practitioners are available as open education resources OER at Johns Hopkins Bloomberg School of Public Health. The image above combines slides 26-28 from an OPENCOURSEWARE course on Public Health Biology. The exact location for these OER lectures, which are open for you to download, is: Module 2: Pathogens and Host Immunity > Lecture 3: Pathogens: Nature and Transmission. This is the text that accompanies the illustrations above:
Poliovirus Viron (left image):
30 nM diameter virion contains 60 copies each of four proteins (encoded in the viral RNA) – Viral RNA is a single strand mRNA (+) polarityi, is about 8000 bases long, and encodes 11 proteins – Viron is non-enveloped and contains no enzymes
Poliovirus: Intracellular Replication (right image):
1. Attachment to cell via specific receptor (Vpr) on cell membrane 2. Virus entry (endocytosis); extrusion of RNA into cytoplasm 3-5. Translation of viral RNA; processing of polyprotein; formation of RNA replicase protein 8-10. Replication of viral RNA 11. Continued translation and processing; formation of virion proteins 12. Assembly of (+) RNA and rivon proteins into new virions 13. Virion release into the gut
MORE POLIOVIRUS LEARN NODES:
For more about the ongoing fight against polio, the Stony Brook University School of Medicine published an open access article in Virology Journal: “Epidemics to eradication: the modern history of poliomyelitis.”
For a look at sleuths who are tracking the polio viruses as they invade our cells try this open access article from the Public Library of Science BIOLOGY: “Imaging Poliovirus Entry in Live Cells.”
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