Anatomy

Chaper 11 1. Define responsiveness, conductivity, contractility, extensibility, and elasticity. State why each of these properties is necessary for muscle function. a. Responsiveness- is a property of all living cells- Muscle and nerve cells have developed this property to the highest degree. When stimulated by chemical signals, stretch, and other stimuli, muscle cells respond with electrical changes across the plasma membrane. b. Conductivity- Stimulation of a muscle cell produces more than a local effect- The local electrical change triggers a wave of excitation that travels rapidly along the cell and initiates processes leading to contraction. c. Contractility-Muscle cells are unique in their ability to shorten substantially when stimulated.-This enable them to pull on bones and other organs to create movement. d. Extensibility- In order to contract, a muscle cell must alson be extensible able to stretch again between contractions.- Most cells rupture if they are stretched even a little, but skeletal muscle cells can stretch to as much as three times their contracted length. e. Elasticity- When a muscle cell is stetched and then released, it recoils to a shorter length.- If it were not for this elastic recoil, resting muscles would be too slack. 2. How is skeletal muscle different from the other types of muscle? f. Skeletal muscle may be defined as voluntary striated muscle that is usually attached to one or more bones. A skeletal muscle exhibits alternating light and dark transverse bands, or striations that result from an overlapping arrangement of their internal contractile proteins. Skeletal muscle is called voluntary because it is usually subject to conscious control. The other types of muscle are involuntary (not usually under conscious control ), and they are never attached to bones. 3. Name and define the three layers on collagenous connective tissue in a skeletal muscle. g.