Lab 10 Exercise 12 Study Sheet

Discuss the similarities and differences between concentric and eccentric muscle contractions

In a concentric contraction, the muscle tension exceeds the load and the muscle shortens, producing movement. In an eccentric contraction, the muscle lengthens and does not move the load. Typically, eccentric contractions oppose concentric contractions and help maintain muscle tone.

Describe the relationship between muscle tension and muscle load

Muscle tension is the force generated by the muscle. Load is the force the muscle is trying to overcome. The muscle tension must exceed the load in order for the muscle to move the object.

Discuss the relationship between muscle function and motor unit size

Muscles used for highly specialized motor skills, such as the intrinsic hand muscles, have motor units with fewer than 10 muscle fibers. Conversely, large, weight-bearing muscles, such as the gluteus maximus, contain motor units with hundreds of muscle fibers.

contractions of a muscle at various levels of strength

graded contractions

force that is exerted by an object and resists muscle tension

load

motor nerve fiber and all the muscle fibers it innervates

motor unit

condition of a muscle characterized by its inability to generate a force

muscle fatigue

force exerted by a muscle when it contracts

muscle tension

state of muscle contraction while at rest

muscle tone

period of smooth, sustained muscle contraction

tetanus

minimum stimulus required to initiate a muscle fiber contraction

threshold stimulus

The muscle fibers in a motor unit are dispersed throughout a muscle and intermingle with muscle fibers of other motor units. What is the functional significance of such an arrangement?

By having the motor units dispersed throughout the muscle, even recruitment of a small number of motor units produces some contraction throughout the whole muscle, instead of a contraction of just one small part of it.

From a functional standpoint, discuss the difference between isotonic and isometric muscle contractions

During an isotonic contraction, the muscle tension exceeds the load, the muscle changes in length, and movement occurs. In an isometric contraction, the muscle tension does not exceed the load, so the muscle does not change in length and no movement is produced.