Stimulating Muscle contraction in Glycerinated skeletal Musc

Stimulating Muscle contraction in Glycerinated skeletal Muscle Tissue Put the following events of the sliding filament theory into their proper sequence: 1. power stroke of the cross bridge, causing sliding of the thin filaments 2. influx of calcium ions into the sarcoplasm 3. hydrolysis of ATP, leading to reenergizing and repositioning of cross bridges 4. binding of myosin to actin 5. transport of calcium ions back into the sarcoplasmic reticulum 6. binding of ATP to a cross bridge, resulting in the cross bridge disconnecting from actin a. 2, 4, 1, 6, 3, 5 b. 2, 6, 1, 4, 3, 5 c. 2, 4, 1, 3, 6, 5 d. 2, 1, 4, 6, 3, 5 e. 2, 4, 3, 1, 6, 5 What happens to each of the following components of a sarcomere during muscle contraction? a. Z-discs b. H zone c. A band d. I bands Describe the effect of glycerin on skeletal muscle fibers.

Solution

1. ANS: C. 2, 4, 1, 3, 6 and 5.

Explanation:

Sliding filament theory steps

Step 1: The sarcoplasmic reticulum stimulated to release calcium ions

Step 2: Calcium ions bind to troponin. Then it causes troponin to drag tropomyosin off cross bridge binding sites and cross bridges bind to actin

Step 3: Cross bridges on myosin pull on actin (power stroke). Then Actin filaments slide to middle of sarcomere and finally muscle shortens and contracts

Step 4: Cross bridges detach from binding sites on actin

Step 5: Muscle fiber lengthens and relaxes

Step 6: Calcium ions activley pumped back into endoplasmic reticulum. So troponin released from tropomyosin and tropomyosin covers cross bridge binding sites.

2. ANS:

a. Z discs: It is a protein dense area, which separates the sarcomers.

b. H zone: It is present in the center place of A band and it only contains the thick filament.

c. A band: It is a strated zone of the sarcomere composed of thick and thin filaments of myosin. (dark bands)

d. I band: Strated zone of the sarcomere only composed with the thin filaments of actin, troponin and tropomyosin. (light bands)