Chapter 6 Human Biology

Which type(s) of muscle cells can contract spontaneously?

both smooth muscle cells and cardiac muscle cells

A myogram is a recording of

the activity of muscle cells

Which term describes the subunits of a myofibril?

Sarcomere

What structure is not contained within a muscle fiber?

Tendon

Muscles that oppose each other and produce opposite movements are described as __________.

antagonistic

In a muscle cell, __________ contain __________.

myofibrils; actin and myosin filaments

Activities associated with aerobic training result in an increase in the amount of ________ in the body.

oxygen

Which one of the following is characteristic of cardiac and smooth muscle, but not skeletal muscle?

presence of gap junctions

The process of activating more motor units when more force must be exerted is called ________.

recruitment

The portion of a myofibril from one Z-line to the next is a(n) ________.

sarcomere

When a muscle contracts, shortening of the muscle occurs because __________.

sarcomeres shorten

Which of the following is the site of calcium ion storage within muscles?

sarcoplasmic reticulum

Skeletal muscle groups that work together to create the same movement are referred to as

synergistic

The thin filaments of sarcomeres are composed of _____.

Actin

The thick filaments of sarcomeres are composed of _____.

Myosin

The sliding filament mechanism describes the process during which __________.

actin and myosin slide relative to each other

Following electrical stimulation of a muscle cell, calcium functions to

bind to the protein troponin

Intercalated discs

contain gap junctions that allow the signal to spread quickly through cardiac muscle cells

Tetanic contractions result from __________.

frequent stimulation preventing a muscle from relaxing

When a skeletal muscle contracts, the __________ is pulled toward the __________.

insertion; origin

Which one of the following activities would fast-twitch fibers be most useful for?

lifting weights

What is not a function of the muscular system?

maintenance of body calcium stores