Fundamentals of Anatomy and Physiology

The Muscular System

The Function and Location
of Selected Skeletal Muscles

1. Facial muscles around the eyes and mouth assist in

nonverbal communication like smiling.^

2. Muscles around the upper and lower jaw assist in

chewing or mastication.^

3. Six muscles attach to the eye and move the eye in all

directions.^

4. The main muscle that moves the head is the

sternocleidomastoid.^

5. The upper arm is moved mainly by the deltoid,

pectorals, and rotator cuff muscles.^

6. The forearm can be flexed and extended; the
   supinators and pronators supinate and pronate the

forearm and move the hand.^

7. The wrist and fingers can be flexed, extended,

abducted, and adducted.^

8. The thumb does opposition and can grasp implements,

resulting in all the unique abilities of the hand.^

9. Three layers of trunk muscle compress our abdominal
   contents laterally, while the rectus abdominus in the

front produces the washboard effect from sit-ups.^

10. Breathing is accomplished by the diaphragm

muscle and the intercostal muscles of the ribs.^

11. Muscles of the hip flex, extend, abduct, and adduct

the thigh.^

12. Muscles of the thigh, like the hamstrings, flex the

knee; the quadriceps femoris extends^ the knee.^

13. Muscles of the foot and toes produce plantar flexion
    and dorsiflexion as in walking, eversion and inversion
    of the sole of the foot, and flexion and extension of
    the toes.

Review Questions

*1. Explain muscle contraction based on neuroelectrical

factors, chemical interactions, and energy sources.^
*2. Compare the anatomy of a skeletal muscle cell with

that of a smooth and cardiac muscle cell.^
*3. Compare isometric contraction with isotonic

contraction.^

4. Define muscle tone.

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5. What are some symptoms of muscle disorders?^
   6. Explain why disorders of muscles can be caused by a
   number of problematic areas in tissue other than
   muscles.
   Critical Thinking Questions

Fill in the Blank

Fill in the blank with the most appropriate term.

1. 
   

   Myofibrils have dark bands known as the (^)
   (^) bands composed of the (^)
   (^) protein. (^)

   
   


2. 
   

   Myofibrils also have light bands known as the (^)
   (^) bands composed of the (^)
   protein. (^)

   
   


3. 
   

   A dark line in the light band is known as the^

   
   

(^) line, and the area be- (^)
tween two of these adjacent lines is called a (^)
(^). (^)

4. Electron microscopy has revealed that muscle fibrils
   are surrounded by the sarcotubular system. Part^
   of that system is the sys-tem that functions in the rapid
   transmission of the stimulus to all fibrils in the muscle
   via the release of^
   ions from the sarcoplasmic^
   reticulum.^


5. All of the muscle fibers that are innervated by the
   same nerve fiber are called a^
   unit.^


6. ions have a greater con-^

centration inside the resting muscle cell, whereas (^)
(^) ions have a greater concen- (^)
tration outside the resting muscle cell. (^)

7. A nerve impulse causes^ to^

be released at the neuromuscular junction, which (^)
(^) causes ions to rush inside (^)
the muscle cell, changing its polarity.^

8. Two inhibitor substances surrounding the
   myofilaments of actin and myosin are^
   and^.^


9. Smooth and cardiac muscles are under the
   control of the nervous system.


10. The source of energy for muscle contraction is
    molecules.