15. How does the force-velocity relationship in smooth muscles compare to that of skeletal muscles? A. They are identical. B. Increasing the degree of phosphorylation of myosin light chains increases the shortening velocity of both muscle fiber types. C. The maximal shortening velocity in smooth muscles is much less than in skeletal muscles. D. The maximal active tension or force produced by smooth muscles is much less than skeletal muscles. The answer is C. However, i thought the smooth muscle has a greater passive tension and broader active tension, wouldn't it get more "shortening velocity" than skeletal.
See Slide 26 of the Smooth Muscle lecture. This represents the force-velocity relationship and demonstrates the curve for skeletal muscles (in redish-brown) and smooth muscles (in blue). As you can see the maximal shortening velocity for smooth muscles is much less than that for skeletal muscles. Remember as I mentioned in class, this is because it takes many more steps in order for smooth muscles to initiate contraction. In addition, the ATP hydrolysis by the myosin head group is a lot slower event in smooth muscles as well.
Shortening velocity is not the amount of tension produced, but how fast the contractile proteins can work to change the length of the muscles.
15. How does the force-velocity relationship in smooth muscles compare to that of skeletal muscles?
ReplyDeleteA. They are identical.
B. Increasing the degree of phosphorylation of myosin light chains increases the shortening velocity of both muscle fiber types.
C. The maximal shortening velocity in smooth muscles is much less than in skeletal muscles.
D. The maximal active tension or force produced by smooth muscles is much less than skeletal muscles.
The answer is C. However, i thought the smooth muscle has a greater passive tension and broader active tension, wouldn't it get more "shortening velocity" than skeletal.
Thank you,
See Slide 26 of the Smooth Muscle lecture. This represents the force-velocity relationship and demonstrates the curve for skeletal muscles (in redish-brown) and smooth muscles (in blue). As you can see the maximal shortening velocity for smooth muscles is much less than that for skeletal muscles. Remember as I mentioned in class, this is because it takes many more steps in order for smooth muscles to initiate contraction. In addition, the ATP hydrolysis by the myosin head group is a lot slower event in smooth muscles as well.
ReplyDeleteShortening velocity is not the amount of tension produced, but how fast the contractile proteins can work to change the length of the muscles.