please eplan how nerve supply to a skeletal muscle fibre causes it to contract
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Replies(1)
Dr. Nikola Gjuzelov
, MD
replied on February 5th, 2007
Muscular & Nerve Disorders Answer A2264
Every muscle fiber consists of many fibrils (myofibrils) that contain special contractile proteins, actin and myosin, in their cytoplasm. When Calcium ions (Ca2 ) are present in the cytoplasm, actin and myosin cause a shortening of the whole fibril. Calcium ions comes from a special small organ in the cell called the endoplasmatic reticulum. In muscle cells, this organ is called the sarcoplasmatic reticulum. The arcoplasmatic reticulum releases Calcium ions when activated by electrical impulse. After contraction, the Ca2 -ions are pumped back into the sarcoplasmatic reticulum which are waiting for another electrical impulse. Then, the nerves conduct electrical impulses to the muscles.... or more precisely to the myofibrils’ membrane (sarcolema). This membrane is connected with the sarcoplasmatic reticulum so when the nerve carries an electrical impulse, the impulse transfers to the sarcoplasmatic reticulum and causes Ca2 -release and contraction.
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