Muscular System Worksheet
Key Terms
acetylcholine
antagonists
aponeurosis
atrophycardiac muscle
belly
compartmentorcrush syndrome
contracture
fascia
hypertrophy
insertion
myosin
neuromuscular junction (NMJ)
nonstriated muscle
origin
prime mover
recruitment
sarcomere
sarcoplasmic reticulum (SR)
skeletal muscle
smooth muscle
spasm
striated muscle
synergists
tetanus
tonus
twitch
visceral muscle
What are the function(s) of muscle?
How are muscles attached?
What is Myasthenia Gravis?
How Skeletal Muscles are Named
The names of the various skeletal muscles are generally based on one or more of the following characteristics: size, shape, orientation of the fibers, location, number of origins, identification of origin and insertion, and muscle action.
Size
These terms indicate size: vastus (huge), maximus (large), longus (long), minimus (small), and brevis (short). Examples of skeletal muscles include the vastus lateralis and gluteus maximus.
Shape
Various shapes are included in muscle names, such as deltoid (triangular), latissimus (wide), trapezius (trapezoid), rhomboideus (rhomboid), and teres (round). Examples include the trapezius muscle, latissimus dorsi, and teres major.
Orientation of Fibers
Fibers are oriented, or lined up, in several directions: rectus (straight), oblique (diagonal), transverse (across), and circularis (circular). Examples include the rectus abdominis and the superior oblique.
Location
The names of muscles often reflect their location in the body, such as pectoralis (chest), gluteus (buttock), brachii (arm), supra (above), infra (below), sub (underneath), and lateralis (lateral). Examples include the biceps brachii, pectoralis major, and vastus lateralis.
Number of Origins
A muscle may be named according to the number of sites to which it is anchored: biceps (2), triceps (3), and quadriceps (4). Examples include the biceps brachii, triceps brachii, and quadriceps femoris.
Origin and Insertion
Some muscles are named for sites of attachment both at their origin and insertion. The sternocleidomastoid, for example, has its origin on the sternum and clavicle and its insertion on the mastoid process of the temporal bone. This information allows you to determine the function of the muscle. The sternocleidomastoid flexes the neck and rotates the head. As noted here, many muscles have multiple points of origin and insertion.
Muscle Action
The action of the muscle may be included in the name. For example, an abductor muscle moves the limb away from the midline of the body, whereas an adductor moves the limb toward the midline. In the same way, a flexor muscle causes flexion, whereas an extensor muscle straightens the limb. A levator muscle elevates a structure, and a masseter muscle enables you to chew. Examples include the adductor magnus, flexor digitorum, and levator palpebrae superioris.