Chapter 10 HW

Place a single word into each sentence to make it correct, and then place each sentence into a logical paragraph order that describes the length-tension relationship. Not all terms will be used.

1. In resting muscle fiber, a sarcomere is normally 2.0 to 2.5 micrometers long. 2. This is the optimum length for producing maximum tension when the muscle contracts. 3. If a muscle fiber is overly contracted, the thick filaments butt against the Z discs. 4. Conversely, if the muscle fiber is overly stretched, there is not enough overlap between the thick and thin myofilaments. 5. Therefore, if the thick and thin filaments do not overlap, very few crossbridges are formed.

Place the organizational level of muscle tissue in order, beginning with the entire muscle and ending with the smallest component.

1. Muscle 2. Fascicle 3. Muscle Fiber 4. Myofibril 5. Myofilament

The area of the muscle fiber where the actin and myosin myofilaments overlap is the

A band

Check all that are proteins of thin filaments.

Actin, Troponin, Tropomyosin

In a relaxed muscle, the ends of the actin filaments overlap.

False

In fully contracted muscles, the actin filaments lie side-by-side

False

During contraction, the actin myofilaments slide toward the

H Zone

Which of the following best describes the role of Ca2+ in muscle contraction?

It binds to troponin, moving tropomyosin, so that myosin heads can bind to actin.

An action potential causes depolarization of the T-tubule membrane.

True

T-tubules are invaginations of the sarcolemma of a muscle cell.

True

All the muscle fibers under the control of a single motor axon are referred to as

a motor unit

The ability of muscle cells to shorten is called _______, a property that allows muscle cells to cause body movement.

contractility

The specialized region of the sarcolemma that has folds and indentations to increase the membrane surface area covered by the synaptic knob is the

motor end plate.

The contractile unit of a myofibril is called the

sarcomere

The distance from one Z disk to the next Z disk is called a(n)

sarcomere

An action potential causes calcium ions to diffuse from the ________ into the ________.

sarcoplasmic reticulum; sarcoplasm

All of the following are filamentous proteins except

troponin