Question

skeletal muscle activity
stimulation and contraction of single skeletal muscle fibers
muscle fibers have several special functional properties that enable them to perform their duties. the first of these is irritability, also termed responsiveness, which is the ability to receive and (1. ) to a stimulus. the second, contractility, is the ability to forcibly shorten when adequately stimulated. this property sets muscle apart from all other tissue types. extensibility is the ability of muscle fibers to stretch, whereas elasticity is their ability to recoil and resume their resting length after being stretched.
the nerve stimulus and the action potential
to contract, skeletal muscle fibers must be stimulated by nerve impulses. one motor neuron (nerve cell) may (2. ) a few muscle fibers or hundreds of them, depending on the particular muscle and the work it does. a motor unit consists of one neuron and all the skeletal muscle fibers it stimulates (figure 6.4, p. 188). when a long, threadlike extension of the neuron, called the axon, reaches the muscle, it branches into a number of axon terminals, each of which forms junctions with the (3. ) of a different muscle cell (figure 6.5, p. 189). these junctions, called neuromuscular (literally,
erve - muscle\) junctions, contain synaptic vesicles filled with a chemical referred to as a neurotransmitter. the specific neurotransmitter that stimulates skeletal muscle fibers is acetylcholine (as\e - til - kolen), or ach. although the nerve endings and the muscle fiber (4. ) are very close, they never touch. the gap between them, the synaptic cleft, is filled with interstitial fluid.
homeostatic imbalance 6.1
in some cases, a motor nerve impulse is unable to reach the muscle. in als, or amyotrophic lateral sclerosis (also called lou gehrigs disease), motor neurons degenerate over time, resulting in paralysis that gradually worsens. the cause of als is unknown, but common characteristics include (5. ) mitochondria, inflammation, and the generation of free radicals that damage dna and tissue much like intense uv light. the prognosis for patients with als is generally death within three to five years because the breathing muscles will eventually be affected, resulting in suffocation

o 1. membranes 2. malfunctioning 3. respond 4. stimulate 5. sarcolemma
o 1. respond 2. stimulate 3. sarcolemma 4. membranes 5. malfunctioning
o 1. malfunctioning 2. respond 3. stimulate 4. sarcolemma 5. membranes
o 1. stimulate 2. sarcolemma 3. membranes 4. malfunctioning 5. respond
o 1. sarcolemma 2. membranes 3. malfunctioning 4. respond 5. stimulate

Explanation:

1. Irritability is the ability to receive and respond to a stimulus.
2. A motor neuron stimulates muscle fibers.
3. Axon terminals form junctions with the sarcolemma of muscle cells.
4. Nerve endings and muscle fiber membranes are close but don't touch.
5. In ALS, there are malfunctioning mitochondria among other issues.

Answer:

1. respond 2. stimulate 3. sarcolemma 4. membranes 5. malfunctioning