1. Every human body has an uncountable number of this basic unit of a muscle known as the: (1 point)
A) muscle fibers
B) ligaments
C) tendons
D) muscle tissues
2. Slow-twitch muscles are needed for: (1 point)
A) Quick, short bursts of energy for high intensity
B) Endurance activities
C) Speed or power activities
D) Low endurance and short duration exercises
3. A group of muscle fibers responsible for a specific movement is called: (1 point)
A) a motor unit
B) a striated group
C) a fast-twitch unit
D) a slow-twitch unit
4. When a muscle fiber contracts as much as it can it is called the _________________. (1 point)
A) Maximum potential principal
B) Contraction principal
C) Muscular capacity principal
D) All or none principal
5. Select the answer below that best fits the following description.
Voluntary
Come in pairs
Attach to the bones through tendons
Made up of long, cylindrical fibers (1 point)
A) Striated muscles
B) Cardiac muscles
C) Smooth muscles
D) Contracted muscles
6. Select the answer below that best fits the following description.

Involuntary
Found in internal organs
Can stretch or maintain tension for long periods of time

(1 point)
A) Striated muscles
B) Cardiac muscles
C) Smooth muscles
D) Skeletal muscles
7. Select the answer below that best fits the following description.
Involuntary
Only found in the heart
(1 point)
A) Striated muscles
B) Cardiac muscles
C) Smooth muscles
D) Skeletal muscles

Option A, muscle fibers. Skeletal muscle is made up of bundles of individual muscle fibers.
Option B, endurance activities. There are two types of muscle fibers; fast-twitch and slow-twitch. Slow-twitch muscle fibers are necessary for aerobic exercises which involve low levels of exertion but with high level of endurance.
Option A, a motor unit. A motor unit consists of one neuron and all of the muscle fibers that it innervates.
Option D, all or none principle. The all or none principle states that the strength by which a muscle fiber responds to a stimulus is independent of the strength of the stimulus. If that stimulus exceeds the threshold potential, the nerve or muscle fiber will give a complete response; otherwise, there is no response.
Option A, striated muscles. It is a muscle tissue in which the contractile fibrils in the cells are aligned in parallel bundles and come in pairs, so that their different regions form stripes visible in a microscope. Muscles of this type are attached to the skeleton by tendons and are under voluntary control.
Option C, smooth muscles. It is a muscle tissue in which the contractile fibrils are not highly ordered, occurring in the gut and other internal organs and not under voluntary control.
Option B, cardiac muscle. Cardiac muscle (also called heart muscle or myocardium) is one of three types of vertebrate muscles, with the other two being skeletal and smooth muscles. It is an involuntary, striated muscle that constitutes the main tissue of the walls of the heart.