9. Muscle Tissue

The sites where the motor nerve impulse is transmitted from the nerve endings to the skeletal muscle cell membranes are the

a. neuromuscular junctions

b. sarcomeres

c. myofilaments

d. Z discs

Contraction elicited by a single brief stimulus is called:

a. A twitch

b. Temporal summation

c. Multiple motor unit summation

d. Fused tetanus

A smooth, sustained contraction resulting from very rapid stimulation of the muscle, in which no evidence of relaxation is seen, is called:

a. A twitch

b. Temporal summation

c. Multiple motor unit summation

d. Fused tetanus

During muscle contraction, ATP is provided by:

a. a coupled reaction of creatine phosphate with ADP

b. aerobic respiration of glucose, and

c. anaerobic glycolysis.

______ (1) Which provides ATP fastest?

______  (2) Which does (do) not require that oxygen be available?

______  (3) Which provides the highest yield of ATP per glucose molecule?

______  (4) Which results in the formation of lactic acid?

______  (5) Which has carbon dioxide and water products?

______  (6) Which is most important in endurance sports?

The neurotransmitter released by somatic motor neurons is:

a. Acetylcholine

b. Acetylcholinesterase

c. Norepinephrine

The ions that enter the skeletal muscle cell during the generation of an action potential are

a. Calcium ions

b. Chloride ions

c. Sodium ions

d. Potassium ions

Myoglobin has a special function in muscle tissue. It:

a. Breaks down glycogen

b. Is a contractile protein

c. Holds a reserve supply of oxygen in the muscle

Aerobic exercise results in all of the following except:

a. More capillaries surrounding muscle fibers

b. More mitochondria in muscle cells

c. Increased size and strength of existing muscle cells

d. More myoglobin

What is the importance of acetylcholinesterase in muscle cell contraction?

Explain what is meant by the term excitation-contraction coupling.

Define and draw a motor unit.

a. Describe the structure of a sarcomere and indicate the relationship of the sarcomere to myofilaments.

b. Explain the sliding filament model of contraction using appropriately labeled diagrams of a relaxed and a contracted sarcomere.

Explain how a slight (but smooth) contraction differs from a vigorous contraction of the same muscle. Use the concepts of multiple motor unit summation.

Muscle-relaxing drugs are administered to a patient during major surgery. Which of the two chemicals described next would be a good skeletal muscle relaxant and why?

• Chemical A binds to and blocks ACh receptors of muscle cells.

• Chemical B floods the muscle cells' cytoplasm with Ca²⁺.

What is the basic mechanism of contraction at the level of myofilaments?