Chapter 6

Cardiac muscle fibers are joined by special gap junctions called intercalated discs; these discs allow heart activity to be closely coordinated.

True

The mechanical force of contraction is generated by ________.

a sliding of thin filaments past thick filaments

What condition results if muscles are not used, such as when immobilized in a cast for healing a broken bone?

atrophy

Neurotransmitters are released upon stimulation from a nerve impulse from the ________.

axon terminals of the motor neuron

Which muscle forms the curved calf of the posterior leg?

gastrocnemius

Anaerobic glycolysis requires ________ to make ATP.

glucose only

One neuron and all the skeletal muscles it stimulates is known as a ________.

motor unit

The gap between the axon terminal of a motor neuron and the sarcolemma of a skeletal muscle cell is called the ________.

neuromuscular junction

Which of the following is an example of an isometric contraction?

pushing against an immovable wall

The plasma membrane of a skeletal muscle cell is called the ________.

sarcolemma

What organelle wraps and surrounds the myofibril and stores calcium?

sarcoplasmic reticulum

Creatine phosphate (CP) functions within the muscle cells by ________.

storing energy that will be transferred to ADP to resynthesize ATP as needed

A sarcomere is ________.

the contractile unit between two Z discs

Why are calcium ions necessary for skeletal muscle contraction?

Calcium ions trigger the binding of myosin heads to actin filaments.

According to the sliding filament theory, how does muscle contraction occur?

Myosin heads form cross bridges and pull thin filaments, causing them to slide.

Striated involuntary muscle tissue is classified as ________ muscle.

cardiac

The heads of the myosin myofilaments are called ________ when they link the thick and thin filaments together during skeletal muscle contraction.

cross bridges

The formation of cross bridges requires both calcium ions and ATP.

true