Chapter 11, The muscular system

Based on patterns of fascicle organization, name the four classifications of skeletal muscle tissue.

Based on the patterns of fascicle organization, skeletal muscles can be classified as parallel muscles, convergent muscles, pennate muscles, or circular muscles.

Why can swallowing help alleviate the pressure sensations at the eardrum when you are in an airplane that is changing altitude?

Swallowing involves contractions of the palatal muscles, which elevate the soft palate as well as portions of the superior pharyngeal wall. Elevation of the superior portion of the pharynx enlarges the opening to the auditory tube, permitting airflow to the middle ear and the inside of the eardrum. Making this opening larger by swallowing facilitates airflow into or out of the middle ear cavity.

Which facial muscle would you expect to be well developed in a trumpet player?

You would expect the buccinator muscle, which positions the mouth for blowing, to be well developed in a trumpet player.

The muscles that rotate the radius without producing either flexion or extension of the elbow are the ___________ muscles.

pronator teres and supinator

Important flexors of the vertebral column that act in opposition to the erector spinae are the ___________ muscles.

rectus abdominis

The major extensor of the elbow is the ___________ muscle.

triceps brachii

Shrugging your shoulders uses which muscles?

When you shrug your shoulders, you are contracting your levator scapulae muscles.

To what does a "pulled hamstring" refer?

A "pulled hamstring" refers to a strain affecting one or more of the three muscles that collectively flex the knee: the biceps femoris, semimembranosus, and semitendinosus muscles.

If someone hit you in your rectus abdominis muscle, how would your body position change?

A hit in the rectus abdominis muscle would cause that muscle to contract forcefully, resulting in flexion of the vertebral column. In other words, you would "double over."

Define a lever, and describe the three classes of levers.

A lever is a rigid structure—such as a board, a pry bar, or a bone—that moves on a fixed joint called the fulcrum. There are three classes of levers: In a first-class lever, the fulcrum lies between the applied force and load; in a second-class lever, the load lies between the applied force and fulcrum; and in a third-class lever, the applied force or pull exerted is between the fulcrum and the load. Third-class levers are the most common type in the body.

Why can a pennate muscle generate more tension than can a parallel muscle of the same size?

A pennate muscle contains more muscle fibers, and thus more myofibrils and sarcomeres, than does a parallel muscle of the same size, resulting in a contraction that generates more tension.

Define the term synergist as it relates to muscle action.

A synergist is a muscle that helps a larger prime mover (or agonist—a muscle that is responsible for a specific movement) perform its actions more efficiently.

How would a torn calcaneal tendon affect movement of the foot?

A torn calcaneal tendon would make plantar flexion difficult because this tendon attaches the soleus and gastrocnemius muscles to the calcaneus (heel bone).

While unloading her car trunk, Amy strains a muscle and as a result has difficulty moving her arm. The doctor in the emergency room tells her that she strained her pectoralis major. Amy tells you that she thought the pectoralis major was a chest muscle and doesn't understand what that has to do with her arm. What would you tell her?

Although the pectoralis muscle is located across the chest, it inserts on the greater tubercle of the humerus, the bone of the arm. When this muscle contracts, it contributes to flexion, adduction, and medial rotation of the humerus at the shoulder joint. All of these arm movements would be impaired if the muscle were damaged

What is an aponeurosis? Give two examples.

An aponeurosis is a collagenous sheet connecting two muscles. The epicranial aponeurosis and the linea alba are examples.

Describe the location of axial muscles.

Axial muscles arise on the axial skeleton. They position the head, neck, and vertebral column, move the rib cage, and form the perineum.

Why does a pennate muscle generate more tension than does a parallel muscle of the same size?

Contraction of a pennate muscle generates more tension than would contraction of a parallel muscle of the same size because a pennate muscle contains more muscle fibers, and thus more myofibrils and sarcomeres, than does a parallel muscle of the same size.

If you were contracting and relaxing your masseter muscle, what would you probably be doing?

Contraction of the masseter muscle elevates the mandible, and relaxation of this muscle depresses the mandible. You would probably be chewing something.

Identify the physiological effects of exercise on the cardiovascular, respiratory, and integumentary systems, and indicate the relationship between those physiological effects and the nervous and endocrine systems.

Exercise affects the cardiovascular system by increasing heart rate and dilating blood vessels. With exercise, the rate and depth of breathing increases, and sweat gland secretion increases. The physiological effects that result from exercise are directed and coordinated by the nervous and endocrine systems

The bundles of muscle fibers within a skeletal muscle are called

Fascicles

Define fibrosis.

Fibrosis is the development of increasing amounts of fibrous connective tissue. Fibrosis causes muscles to be less flexible, and the collagen fibers can restrict movement and circulation.

Describe general age-related effects on skeletal muscle tissue.

General age-related effects on skeletal muscles include decreased skeletal muscle fiber diameters, diminished muscle elasticity, decreased tolerance for exercise, and a decreased ability to recover from muscular injuries.

A(n) ___________ develops when an organ protrudes through an ab-normal opening.

Hernia

Why does a convergent muscle exhibit more versatility when contracting than does a parallel muscle?

In a convergent muscle, the direction of pull can be changed by stimulating only one group of muscle cells at any one time. When all the fibers contract at once, they do not pull as hard on the tendon as would a parallel muscle of the same size, because the muscle fibers on opposite sides of the tendon are pulling in different directions rather than working together.

An injury to the flexor carpi ulnaris muscle would impair which two movements?

Injury to the flexor carpi ulnaris muscle would im-pair your ability to flex and adduct the wrist.

Which leg movement would be impaired by injury to the obturator muscle?

Injury to the obturator muscle would impair your ability to laterally rotate the hip.

The more movable end of a muscle is the

Insertion

Why is it difficult to lift a heavy object when the elbow is at full extension?

Lifting heavy objects becomes easier as the elbow approaches a 90° angle. As you increase the angle at or near full extension, tension production decreases, so movement becomes more difficult.

Mary sees Jill coming toward her and immediately contracts her frontalis and procerus muscles. She also contracts her right levator labii muscles. Is Mary glad to see Jill? How can you tell?

Mary is not happy to see Jill. Contraction of the frontalis muscle would wrinkle Mary's brow, contraction of the procerus muscle would flare her nostrils, and contraction of the levator labii muscle on the right side would raise the right side of her lip, as in sneering.

The strongest masticatory muscle is the ___________ muscle.

Masseter

The muscle that rotates the eye medially is the ___________ muscle.

Medial rectus

Muscle A abducts the humerus, and muscle B adducts the humerus. What is the relationship between these two muscles?

Muscles A and B are antagonists to each other, because they perform opposite actions.

Identify the kinds of descriptive information used to name skeletal muscles.

Names of skeletal muscles are based on several factors, including location in the body, origin and insertion, fascicle organization, relative position, structural characteristics, and action. Names may also reflect the muscle shape, number of origins, and size.

Which four muscle groups make up the axial musculature?

The axial musculature includes (1) muscles of the head and neck, (2) muscles of the vertebral column, (3) oblique and rectus muscles, and (4) muscles of the pelvic floor.

List the four fascicle organizations that produce the different patterns of skeletal muscles.

The four fascicle organiza-tions are (1) parallel, (2) convergent, (3) pennate, and (4) circular.

What three functional groups make up the muscles of the lower limbs?

The functional muscle groups in the lower limbs are (1) muscles that move the thigh, (2) muscles that move the leg, and (3) muscles that move the foot and toes.

The joint between the occipital bone of the skull and the first cervical vertebra (atlas) is an example of which class of lever?

The joint between the occipital bone and the first cervical vertebra is part of a first-class lever system. The joint between the two bones (the fulcrum) lies between the skull (which provides the load) and the neck muscles (which provide the applied force).

Baseball pitchers sometimes suffer from rotator cuff injuries. Which muscles are involved in this type of injury?

The muscles involved in a rotator cuff injury are the supraspinatus, infraspinatus, teres minor, and subscapularis (SITS) muscles

What three functions are accomplished by the muscles of the pelvic floor?

The muscles of the pelvic floor (1) support the organs of the pelvic cavity, (2) flex joints of the sacrum and coccyx, and (3) control movement of materials through the urethra and anus.

What major function does the muscular system perform for the body as a whole?

The muscular system generates heat that maintains normal body temperature.

What does the name flexor carpi radialis longus tell you about this muscle?

The name flexor carpi radialis longus tells you that this muscle is a long muscle (longus) that lies next to the radius (radialis) and flexes (flexor) the wrist (carpi).

Which type of fascicle arrangement would you expect in a muscle guarding the opening between the stomach and the small intestine?

The opening between the stomach and the small intestine would be guarded by a circular muscle, or sphincter. The concentric circles of muscle fibers found in sphincters are ideally suited for opening and closing passageways and for acting as valves in the body.

The gracilis muscle is attached to the anterior surface of the tibia at one end, and to the pubis and ischium of the pelvis at the other. When the muscle contracts, flexion occurs at the hip. Which attachment point is considered the muscle's origin?

The origin of a muscle is the end that remains stationary during an action. Because the gracilis muscle moves the tibia, the origin of this muscle must be on the pelvis (pubis and ischium).

After spending an afternoon carrying heavy boxes from his basement to his attic, Joe complains that the muscles in his back hurt. Which muscles are most likely sore?

The sore muscles are most likely the erector spinae muscles, especially the longissimus and the iliocostalis muscles of the lumbar region. These muscles would have to contract harder to counterbalance the increased anterior weight when carrying heavy boxes.

On which bones do the four rotator cuff muscles originate and insert?

The supraspinatus, infraspinatus, and teres minor originate on the posterior body of the scapula, and the subscapularis originates on the anterior body of the scapula. All four muscles insert on the humerus.

The muscles of the vertebral column include many dorsal extensors but few ventral flexors. Why?

The vertebral column does not have a massive series of flexors, because many of the large trunk muscles flex the vertebral column when they contract. In addition, most of the body weight lies anterior to the vertebral column, and gravity tends to flex the intervertebral joints.

The muscles of facial expression are innervated by cranial nerve

VII

Which types of movements are affected when the hamstrings are injured?

When the hamstrings are injured, flexion at the knee and extension at the hip are affected.

Of the following actions, the one that illustrates that of a second-class lever is

ankle extension (plantar flexion)

Damage to the external intercostal muscles would interfere with what important process?

breathing.

Mary's newborn is having trouble suckling. The doctor suggests that it may be a problem with a particular muscle. What muscle is the doctor probably referring to?

buccinator

Levers make muscle action more versatile by all of the following

changing the speed of movement produced by an applied force, changing the distance of movement produced by an applied force, changing the strength of an applied force, changing the direction of an applied force.

Compartment syndrome can result from all of the following

compartments swelling with blood due to an injury involving blood vessels, torn ligaments in a given compartment, pulled tendons in the muscles of a given compartment, torn muscles in a particular compartment.

The powerful flexors of the hip are the ___________ muscles.

iliopsoas

Elongated bursae that reduce friction and surround the tendons that cross the dorsal and ventral surfaces of the wrist form ___________.

synovial tendon sheaths

Knee extensors known as the quadriceps consist of the

three vastus muscles and the rectus femoris muscle