Lec 39 & 40: Muscle Mechanics I

Question 1

Two functions of muscle are

Answer 1

1. to perform physical work

2. to generate stress/tension/force

Question 2

How is work quantified?

Answer 2

Work=(Force)x(Distance)

Question 3

What is muscle efficiency based on?

Answer 3

muscle efficiency is based on the ratio of mechanical work output to total metabolic cost

Question 4

How is stress quantified?

Answer 4

Stress=Force/(area of muscle)

Question 5

What does force depend on?

Answer 5

force depends on type of muscle, length of muscle, stimulus pattern, and number of muscle cells firing

Question 6

Is movement required for stress?

Answer 6

No

Question 7

What does the contractile element in a muscle cell consist of?

Answer 7

a cross-bridge system that generates muscle force

Question 8

What is the role of the viscous element in a muscle cell?

Answer 8

It resists motion and dissipates energy as heat. Force is only produced while it is in motion

Question 9

What is the series elastic element made of?

Answer 9

Largely tendon and connective tissue, to a small degree titin

Question 10

What is the parallel elastic element made of?

Answer 10

Titin and connective tissue

Question 11

Isometric Contraction

Answer 11

End of muscle is fixed, contraction at a constant length (think of holding a weight but not moving it up or down)

Question 12

Isotonic Contraction

Answer 12

Constant force, muscle shortens until there are just end cross bridges to barely support the load, preload and afterload