Lab 6: Skeletal Muscle-Structure And Function

Question 1

Where does the organizational hierarchy begin with skeletal muscle?

Answer 1

Begins with muscle organ

Question 2

What is the muscle organ covered with?

Answer 2

Epimysium connective tissue layer

Question 3

The muscle organ is composed of bundles of _________ in which each fascicle is surrounded by connective tissue layer called __________

Answer 3

Fascicles

Perimysium

Question 4

Collections of ________ compose each fascicle?

Answer 4

Muscle fibers

Question 5

Each muscle fiber is enclosed by ________ connective tissue layer

Answer 5

Endomysium

Question 6

________ are the components of muscle fibers and they contain groups of _______, which are arranged one next to each other.

Answer 6

Myofibrils

sarcomeres

Question 7

What do sarcomeres contain that are the basic contractile elements?

Answer 7

Myofilaments

Question 8

What do myofilaments contain and what are they also known as?

Answer 8

Myofilaments contain thick and thin filaments, better known as myosin and actin respectively

Question 9

Describe the hierarchical organization of skeletal muscle?

From outermost to innermost

Answer 9

Periosteum covering the bone –>tendon–>Fascia–> skeletal muscle –>Epimysium–>Perimysium–>Fasciculus–>–>endomysium–>Muscle fiber–>Sarcolemma–>Sarcoplasm–>nuclei–>Striations–>myofibrils–>filaments

Question 10

What are the steps to the sliding filament model of muscle contraction

Answer 10

1. When an action potential arrives at a muscle fiber via motor neuron, acetylcholine is released and the plasma membrane is depolarized
2. The action potential is been transmitted across the entire muscle fiber and delivered to the interior of the cell via transfers tubules
3. Upon arriving at the sarcoplasmic reticulum the action potential stimulates the release of calcium into the cytoplasm
4. Calcium binds with troponin-tropomyosin complex resulting in exposure of the myosin binding site located on the actin molecule
5. In ATP dependent process, the head of the myosin molecule interacts with actin molecule forming a cross-bridge
6. The release of ADP and Pi are a result of ATP hydrolysis and they result in swiveling of the myosin head causing the actin filaments to move toward the center of the sarcomere, with shortening of the sarcomere resulting
7. Relaxation results when a new molecule of ATP binds with myosin head and causes detachment from the actin molecule

Question 11

What is length-tension curve

Answer 11

Look at the figure on page 2 it illustrates the relationship between tension production in sarcomere length

Question 12

What does length tension curve suggest?

Answer 12

That altering the extent of Actin and myosin overlap, tension generated by that muscle is affected

Question 13

What is plateau limb of the length tension curve?

Answer 13

It is the point on the curve in which there is the greatest tension production since the myofilaments are at the most desirable length of overlap

Question 14

What is the optimal length?

Answer 14

Is the region of overlap between actin and myosin, thereby able to generate maximal tension

Question 15

What is ascending limb?

Answer 15

Looking at the length-tension curve, the sarcomere length is small, so the myofilament overlap is too extensive. Unnecessary myofilaments interfere inhibiting proper myofibril overlap resulting in minimal tension production.

Question 16

As the sarcomeres are stretched, the myofibrils are extended past the optimal length so what happens?

Answer 16

There are fewer cross bridges formed therefore decreasing tension generation

Question 17

What is descending limb?

Answer 17

The length tension curve suggests that the muscle fiber’s length relative to its optimal length determines the amount of tension developed by the muscle

Question 18

What is skeletal muscle and what are its functions?

Answer 18

Skeletal muscle is a complex and highly compartmentalized structure consisting of numerous proteins and connective tissue

It’s functions aid in movement and stabilization