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