Exercise 12: Microscopic Anatomy and Organization of Skeletal Muscle

To successfully complete this assignment, first read the following exercise from the Laboratory Manual: Exercise 12: Microscopic Anatomy and Organization of Skeletal Muscle.

Student Discussion Assignment

Describe the banding pattern of a myofibril, including the Z-disc, H-zone, I-band, A-band, and M-line.
Describe the structure of a neuromuscular junction and explain its role in the control of muscle function.

ORDER NOW FOR CUSTOMIZED SOLUTION PAPERS

Write your responses in a minimum of 250 words in APA format.

As in all assignments, cite your sources in your work and provide references for the citations in APA format. Support your work, using your course lectures and textbook readings. Helpful APA guides and resources are available in the South University Online Library. Below are guides that are located in the library and can be accessed and downloaded via the South University Online Citation Resources: APA Style page. The American Psychological Association website also provides detailed guidance on formatting, citations, and references at APA Style.

Student Discussion Assignment

Describe the banding pattern of a myofibril, including the Z-disc, H-zone, I-band, A-band, and M-line.

Describe the structure of a neuromuscular junction and explain its role in the control of muscle function.

Write your responses in a minimum of 250 words in APA format.

Skeletal muscle is made up of relatively large, long cylindrical cells, called muscle fibers. These cells range from 10 to 100 μm in diameter. Some are up to 30 cm long.

Since hundreds of embryonic cells fuse to produce each muscle fiber, the cells (Figure 12.1a and b) are multinucleate; multiple oval nuclei can be seen just beneath the plasma membrane (called the sarcolemma in these cells). The nuclei are pushed peripherally by the longitudinally arranged myofibrils, long, rod-shaped organelles that nearly fill the sarcoplasm, the cytoplasm of the muscle cell. Alternating light (I) and dark (A) bands along the length of the perfectly aligned myofibrils give the muscle fiber its striped appearance.

Electron microscope studies have revealed that the myofibrils are made up of even smaller threadlike structures called myofilaments (Figure 12.1d). The myofilaments are composed largely of two varieties of contractile proteins— actin and myosin—which slide past each other during muscle activity to bring about shortening or contraction of the muscle cells. The actual contractile units of muscle, called sarcomeres, extend from the middle of one I band (its Z disc) to the middle of the next along the length of the myofibrils (Figure 12.1c and d.) Cross sections of the sarcomere in areas where thick and thin filaments overlap show that each thick filament is surrounded by six thin filaments; each thin filament is surrounded by three thick filaments (Figure 12.1e). Exercise 12: Microscopic Anatomy and Organization of Skeletal Muscle

At each junction of the A and I bands, the sarcolemma indents into the muscle cell, forming a transverse tubule (T tubule). These tubules run deep into the muscle fiber between cross channels, or terminal cisterns, of the elaborate smooth endoplasmic reticulum called the sarcoplasmic reticulum (SR) (Figure 12.2). Regions where the SR terminal cisterns border a T tubule on each side are called triads.

To successfully complete this assignment, first read the following exercise from the Laboratory Manual: Exercise 12: Microscopic Anatomy and Organization of Skeletal Muscle. Student Discussion Assignm 1To successfully complete this assignment, first read the following exercise from the Laboratory Manual: Exercise 12: Microscopic Anatomy and Organization of Skeletal Muscle. Exercise 12: Microscopic Anatomy and Organization of Skeletal Muscle

Exercise 12: Microscopic Anatomy and Organization of Skeletal Muscle