chapter 11 The muscular System

Question 1

skeletal muscles

Answer 1

Skeletal muscles produce movements by pulling on bones. Bones serve as levers, and joints act as fulcrums for the levers

Question 2

origin

Answer 2

Ordinarily, the attachment of a muscle’s tendon to the stationary bone is called the origin

the origin is usually proximal and the insertion distal

Question 3

insertion

Answer 3

the attachment of the muscle’s other tendon to the movable bone is
called the insertion

the origin is usually proximal and the insertion distal

Question 4

belly

Answer 4

The fleshy portion of the muscle between the tendons is called the belly
(body)

Question 5

actions

Answer 5

the main movements that occur when the muscle contracts

Question 6

reverse muscle action
(RMA).

Answer 6

This means that during specific movements of the body the
actions are reversed; therefore, the positions of the origin and insertion of a specific muscle are switched

Question 7

lever systems and leverage

Answer 7

bones act as levers, and joints function as the fulcrums of these levers

Question 8

lever

Answer 8

is a rigid structure that can move around a fixed point called a fulcrum (ex joint)

A lever is acted on at two different points by two different forces:

1) effort - which causes the movement, force exerted by muscular contraction
2) load (resistance ) - which opposes movement. (weight)

Levers are categorized into three types according to the positions
of the fulcrum, the effort, and the load:

Question 9

mechanical disadvantage

Answer 9

If the load is farther from the fulcrum and the effort is
applied closer to the fulcrum, then a relatively large effort is required

Question 10

first class levers

Answer 10

The fulcrum is between the effort and the load
(Scissors and seesaws)

A first-class lever can produce either a mechanical
advantage or a mechanical disadvantage depending on whether
the effort or the load is closer to the fulcrum

Question 11

second-class levers

Answer 11

The load is between the fulcrum and the effort in second-class
levers

They always produce a mechanical advantage because the load is always closer to the fulcrum than the effort this type of lever produces the most force

an example is standing up on your toes

Question 12

third-class levers

Answer 12

The effort is between the fulcrum and the load in third-class levers

Third-class levers always produce a mechanical disadvantage because the effort is always closer to the fulcrum than the load. In the body, this arrangement favors speed and range of motion over force

Question 13

fascicles (5 patterns)

Answer 13

the skeletal muscle fibers (cells) within a
muscle is arranged in bundles known as fascicles

Fascicular arrangement affects a muscle’s power and range of
motion

5 patterns with respect to the tendons:

parallel
fusiform (spindle-shaped, narrow toward the ends and
wide in the middle),
circular
triangular

pennate (shaped like a feather) (oblique)
have a large number of short-fibered fascicles distributed
over their tendons, giving them greater power but a smaller range of
motion.

In contrast, parallel muscles have comparatively fewer
fascicles, but they have long fibers that extend the length of the
muscle, giving them a greater range of motion but less power

the power of a muscle depends on the cross-sectional area. so the more
fibers per unit of the cross-sectional area a muscle has, the more power
it can produce

Question 14

antagonistic

Answer 14

(against)
the muscle stretches and yields to the effects of the prime mover

Question 15

prime mover

Answer 15

agonist ( leader) contracts to cause an action of the muscle

if a prime mover and its antagonist contract at the same time with equal force,
there will be no movement

Question 16

synergists

Answer 16

synergists (SIN-er-jists; syn- = together; -ergon
= work) contract and stabilize the intermediate joints

Synergists are usually located close to the prime mover.

Question 17

fixators

Answer 17

Some muscles in a group also act as fixators, stabilizing the
origin of the prime mover so that the prime mover can act more
efficiently

Question 18

compartment

Answer 18

a compartment is a group of skeletal muscles, their
associated blood vessels, and associated nerves, all of which have a
common function.

Question 19

Maximus Largest Gluteus maximus
Minimus Smallest Gluteus minimus
Longus Long Adductor longus
Brevis Short Adductor brevis
Latissimus Widest Latissimus dorsi
Longissimus Longest Longissimus capitis
Magnus Large Adductor magnus
Major Larger Pectoralis major
Minor Smaller Pectoralis minor
Vastus Huge

Question 20

occipitofrontalis
1) front belly

2) occipital belly

Answer 20

frontal belly - Draws scalp anteriorly,
raises eyebrows which
wrinkles skin of the forehead horizontally as in a look of surprise.

occipital belly - draws scalp posteriorly

Question 21

orbicularis oris

Answer 21

Closes and protrudes lips, as in kissing

compresses lips against teeth

shapes lips during speech.

Question 22

Zygomaticus major

Answer 22

Draws angle of mouth superiorly and laterally, as in smiling

Question 23

Buccinator

Answer 23

Presses cheeks against teeth and lips,
as in whistling, blowing, and sucking;

draws corner of mouth laterally

Assists in mastication (chewing) by keeping food between the teeth (and
not between teeth and cheeks

Question 24

orbicularis oculi

Answer 24

Closes eye

Question 25

muscles of mastication (chewing)

Answer 25

The muscles that move the mandible (lower jawbone) at the temporomandibular joint (TMJ) are known as the Of the four pairs of muscles involved in mastication, three are powerful closers of the jaw and account for the strength of the bite 1) Masseter, (strongest one) Elevates mandible, as in closing mouth 2) Temporalis - Elevates and retracts mandible 3) Medial pterygoid - (movers the mandible from side to side to help grind food) lateral pterygoid- protract (protrude) the mandible.

Question 26

sternocleidomastoid

Answer 26

Sternal head: manubrium of sternum; clavicular head: medial third of clavicle Mastoid process of temporal bone and lateral half of superior nuchal line of occipital bone. Acting together (bilaterally), flex cervical portion of vertebral column, extend head at atlanto-occipital joints; acting singly (unilaterally), laterally flex neck and head to same side and rotate head to side opposite contracting muscle. Laterally rotate and flex head to opposite side of contracting muscle. Posterior fibers of muscle can assist in extension of head. RMA: elevate sternum during forced inhalation

Question 27

Masseter

Answer 27

Elevates mandible, as in closing mouth origin - Maxilla and zygomatic arch Insertion - Angle and ramus of mandible

Question 28

Temporalis

Answer 28

Elevates and retracts mandible origin- Temporal bone insertion - Coronoid process and ramus of mandible

Question 29

Rectus abdominis

Answer 29

Flexes vertebral column, especially lumbar portion, and compresses abdomen to aid in defecation, urination, forced exhalation, and childbirth. RMA: Flexes pelvis on the vertebral column ORIGIN - Pubic crest and pubic symphysis Insertion - Cartilage of ribs 5–7 and xiphoid process.

Question 30

External oblique external = closer to surface

Answer 30

Acting together (bilaterally), compress abdomen and flex vertebral column; acting singly (unilaterally), laterally flex vertebral column, especially lumbar portion, and rotate vertebral column

Question 31

Internal oblique (internal = farther from surface, deep within)

Answer 31

Acting together, compress abdomen and flex vertebral column; acting singly, laterally flex vertebral column, especially lumbar portion, and rotate vertebral column

Question 32

Transversus abdominis (inner abbs)

Answer 32

Compresses abdomen insertion- Xiphoid process linea alba, and pubis

Question 33

The aponeuroses

Answer 33

(sheathlike tendons) of the external and internal oblique, and transversus abdominis muscles form the rectus sheaths, which enclose the rectus abdominis muscles. The sheaths meet at the midline to form the linea alba (= white line)

Question 34

linea alba

Answer 34

linea alba (= white line), a tough, fibrous band that extends from the xiphoid process of the sternum to the pubic symphysis. In the latter stages of pregnancy, the linea alba stretches to increase the distance between the rectus abdominis muscles

Question 35

diaphragm 1

Answer 35

The peripheral muscular portion of the diaphragm originates on the xiphoid process of the sternum, the inferior six ribs and their costal cartilages, and the lumbar vertebrae and their intervertebral discs and the twelft rib. From their various origins, the fibers of the muscular portion converge and insert into the central tendon, a strong aponeurosis located near the center of the muscle. The central tendon fuses with the inferior surface of the pericardium (covering of the heart) and the pleurae (coverings of the lungs) Contraction of diaphragm causes it to flatten and increases vertical dimension of thoracic cavity, resulting in inhalation; relaxation of diaphragm causes it to move superiorly and decreases vertical dimension of thoracic cavity, resulting in exhalation.

Question 36

External intercostals

Answer 36

Contraction elevates ribs and increases anteroposterior and lateral dimensions of thoracic cavity, resulting in inhalation; relaxation depresses ribs and decreases anteroposterior and lateral dimensions of thoracic cavity, resulting in exhalation.

Question 37

Internal intercostals

Answer 37

Contraction draws adjacent ribs together to further decrease anteroposterior and lateral dimensions of thoracic cavity during forced exhalation.

Question 38

central tendon

Answer 38

From their various origins, the fibers of the muscular portion converge and insert into the central tendon, a strong aponeurosis located near the center of the muscle (Figure 11.11b–d). The central tendon fuses with the inferior surfaceof the pericardium (covering of the heart) and the pleurae (coverings of the lungs).