Muscles

What helps determine the function and location of muscles in the skeletal system?

1. direction of the muscle fibers 2. relative size of the muscle 3. location of the muscle 4. number of origins 5. location of the origin and insertion 6. action of the muscle 7. shape of the muscle

What are the common types of body movement?

1. flexion 2. extension 3. rotation 4. abduction 5. adduction 6. circumduction

What are the Five Golden Rules of the skeletal muscular system?

1. With a few exceptions, all skeletal muscles cross at least one joint. 2. Typically, the bulk of a skeletal muscle lies proximal to the joint crossed. 3. All skeletal muscles have at least two attachments: the origin and the insertion. 4. Skeletal muscles can only pull; they never push. 5. During contraction, a skeletal muscle insertion moves toward the origin.

What are the common arrangements of fascicles?

1. circular 2. convergent 3. fusiform 4. parallel 5. multipennate 6. bipennate 7. unipennate

fusiform

A modification of the parallel arrangement, called fusiform, results in a spindle-shaped muscle with an expanded belly (midsection); an example is the biceps brachii muscle of the arm

abduction

Abduction is moving a limb away (generally on the frontal plane) from the mid- line, or median plane, of the body (Figure 6.13d). The terminology also applies to the fanning movement of your fingers or toes when they are spread apart.

adduction

Adduction is the opposite of abduction, so it is the movement of a limb to- ward the body midline (Figure 6.13d). Think of adduction as "adding" a body part by bringing it closer to the trunk.

circumduction

Circumduction is a combination of flexion, extension, abduction, and adduction commonly seen in ball-and-socket joints, such as the shoulder. The proximal end of the limb is stationary, and its distal end moves in a circle. The limb as a whole outlines a cone as when you do big arm circles.

extension

Extension is the opposite of flex- ion, so it is a movement that increases the angle, or distance, between two bones or parts of the body (straightening the knee or elbow).

Hyperextension

Extension that is greater than 180° (as when you move your arm posteriorly beyond its normal anatomical position, or tip your head so that your chin points toward the ceiling) is called hyperextension

Primary action: sartorius

Flexes thigh on hip

flexion

Flexion is a movement, generally in the sagittal plane, that decreases the angle of the joint and brings two bones closer together (Figures 6.13a and 6.13b). Flexion is typical of hinge joints (bending the knee or elbow), but it is also common at ball-and-socket joints (for example, bending forward at the hip).

opposition

In the palm of the hand, the saddle joint between metacarpal 1 and the carpals allows opposition of the thumb (Figure 6.13h). This is the action by which you move your thumb to touch the tips of the other fingers on the same hand. This unique action makes the human hand a fine tool for grasping and manipulating objects.

inversion and eversion

Inversion and ever- sion are also special movements of the foot (Figure 6.13f). To invert the foot, turn the sole medially, as if you were looking at the bottom of your foot. To evert the foot, turn the sole laterally.

antagonists

Muscles that oppose or reverse a movement -When a prime mover is active, its antagonist is stretched and relaxed. Antagonists can be prime movers in their own right. For example, the biceps brachii and brachialis muscles of the arm

rotation

Rotation is movement of a bone around its longitudinal axis (Figure 6.13c). Rotation is a common movement of ball-and- socket joints and describes the movement of the atlas around the dens of the axis (as in shaking your head "no").

location of the muscle

Some muscles are named for the bone with which they are asso- ciated. For example, the temporalis and fron- talis muscles overlie the temporal and frontal bones of the skull, respectively.

shape of the muscle

Some muscles have a distinctive shape that helps to identify them. For example, the deltoid muscle is roughly tri- angular (deltoid means "triangular").

relative size of the muscle

Such terms as maximus (largest), minimus (smallest), and lon- gus (long) are sometimes used in the names of muscles—for example, the gluteus maximus is the largest muscle of the gluteus muscle group.

prime mover

The muscle that has the major responsibility for causing a particular movement

the movement of a limb away from the body

abduction

Primary action: deltoid

abducts arm

Primary action: adductor muscles

adduct and medial rotate thigh

primary action of the adductor muscles

adduction

the movement of the body toward the midline

adduction

Primary action: pectoralis major

adducts and flexes humerus

Primary action: quadriceps group (vastus medialis, intermedialis, and lateralis, and the rectus femoris)

all extend the knee, rectus femoris also flexes hip on thigh

Muscles that perform opposite actions to one another are termed

antagonists

origin

attachment of a muscle that remains relatively fixed during muscular contraction

insertion

attachment to movable bone -leverage point

Which of the following muscles are antagonists?

biceps brachii and triceps brachii

Primary action: orbicularis oculi

blinks and closes eye

Where do skeletal muscles attach?

bone or other connective tissue -have at least 2 points of attachment

Like the biceps brachii muscle, which muscle is a prime mover in elbow flexion?

brachialis

A nursing infant develops a powerful sucking muscle that adults also use for whistling or blowing a trumpet called the ________.

buccinator

What are fascicles?

bundles of muscle fibers

The arrangement of fascicles in orbicularis oris is

circular

Primary action: orbicularis oris

closes and protrudes lips

Primary action: masseter

closes jaw

Primary action: temporalis

closes jaw

Primary action: buccinator

compresses cheek and holds food between teeth during chewing

The prime mover of arm abduction is the ________ muscle.

deltoid

Primary action: tibialis anterior

dorsiflexes and inverts foot

Primary action: extensor digitorum longus

extends toes

primary action of the erector spinae

extension

Which muscle is named for the arrangement of its fascicles?

external oblique

Primary action: occipitalis

fixes aponeurosis and pulls scalp posteriorly

Primary action: external oblique

flexes and rotates vertebral column

Primary action: brachialis

flexes elbow

Primary action: biceps brachii

flexes elbow and supinates forearm

Primary action: iliopsoas

flexes hip

Primary action: sternocleidomastoid

flexes neck, laterally rotates head

Primary action: rectus abdominis

flexes vertebral column

Primary action of the rectus abdominis

flexion

The type of movement that decreases the angle of the joint

flexion

Which muscle group includes the biceps femoris, semimembranosus, and semitendinosus?

hamstring group

synergists

help prime movers by producing the same movement or by reducing undesirable movements. When a muscle crosses two or more joints, its contraction will cause movement in all the joints crossed unless synergists are there to stabilize them. For example, the flexor muscles of the fingers cross both the wrist and the finger joints. You can make a fist without bending your wrist because synergist muscles stabilize the wrist joints and allow the prime mover to act on your finger joints.

type of movement that turns the sole of the foot medially

inversion

What is the main function of the quadriceps group?

knee extension

Which of the following consists of two large, flat muscles that cover the lower back?

latissimus dorsi

Which of these muscles moves the upper limb?

latissimus dorsi

Which one is NOT a criterion generally used in naming muscles?

method of attachment to the muscle to the bone

Location of the muscle's origin and insertion

muscles are named for their attachment sites. For example, the sternocleidomastoid muscle has its origin on the sternum (sterno) and clavicle (cleido) and inserts on the mastoid process of the temporal bone.

The point of muscle attachment to an immovable or less movable bone is known as the

origin

How many skeletal muscles are there?

over 600

pennate

pattern, short fascicles attach obliquely to a central tendon. In the extensor digitorum muscle of the leg, the fascicles insert into only one side of the tendon, and the muscle is unipennate. If the fascicles insert into opposite sides of the tendon, the muscle is bipennate. If the fascicles insert from several different sides, the muscle is multipennate

Which of these muscles is located on the ventral (anterior) side of the body?

pectoralis major

Primary action: fibularis muscles

plantar flex and evert foot

type of movement that points the toes

plantar flexion

Primary action: zygomaticus

raises corner of mouth

Primary action: frontalis

raises eyebrows

Primary action: trapezius

raises, retracts, and rotates the scapula

What term refers to a muscle that aids another muscle by producing the same the movement or reducing undesirable movements?

synergist

Which of the following muscles acts as a synergist to masseter and closes the jaw?

temporalis

Primary action: platysma

tenses skin of neck (shaving)

action of the muscle

terms such as flexor, extensor, and adductor appear in their names. For example, the adductor muscles of the thigh all bring about its adduction, and the extensor muscles of the wrist all extend the wrist.

A muscle inserts on what?

the bone that moves when the muscle contracts

circular

the fascicles are arranged in concentric rings. Circular muscles are typically found surrounding external body openings which they close by contracting, creating a valve. A general term for such muscles is sphincters ("squeezers"). Examples are the orbicularis muscles surrounding the eyes and mouth.

convergent

the fascicles converge toward a single insertion tendon. A convergent muscle is triangular or fan-shaped, such as the pectoralis major muscle of the anterior thorax

parallel

the length of the fascicles run parallel to the long axis of the muscle, as in the sartorius of the anterior thigh. These muscles are straplike

What does the type of movement depend on?

the mobility of the joint and the location of the muscle in relation to the joint -muscles on limbs and within the vertebrae are affected

Which muscles has an interchangeable origin and insertion point?

the rectus femoris -muscle of the ante- rior thigh crosses both the hip and knee joints. Its most common action is to extend the knee, in which case the proximal pelvic attachment is the origin. However, when the knee bends (by other muscles), the rectus femoris can flex the hip, and then its distal attachment on the leg is considered the origin.

What is the only way muscles can move?

they can only pull- no pushing - movements often result of two or more muscles or groups working together in order to maintain a balance of forces -one group makes the movement and the other reduces it

Jason injured his hamstring muscle group during football practice. He will be unable to perform ________.

thigh extension and knee flexion

Which of these muscles is the prime mover of elbow extension?

triceps brachii

Which facial muscle is considered the "smiling" muscle since it raises the corners of the mouth?

zygomaticus

supination and pronation

The terms supination (soo′′p ̆ı-na′shun; "turning back- ward") and pronation (pro-na′shun; "turning forward") refer to movements of the radius around the ulna (Figure 6.13g). Supination occurs when the forearm rotates laterally so that the palm faces anteriorly (or up) and the radius and ulna are parallel, as in anatomical position. Pronation occurs when the forearm rotates medially so that the palm faces poste- riorly (or down). Pronation brings the radius across the ulna so that the two bones form an X. A helpful memory trick: If you lift a cup of soup up to your mouth on your palm, you are supinating

dorsiflexion and plantar flexion

Up-and- down movements of the foot at the ankle are given special names. Lifting the foot so that its superior surface approaches the shin (pointing your toe toward your head) is dorsi- flexion, whereas pointing the toes away from your head is plantar flexion (Figure 6.13e). Dorsiflexion of the foot corresponds to exten- sion and hyperextension of the hand at the wrist, whereas plantar flexion of the foot cor- responds to flexion of the hand.

direction of the muscle fibers

When a muscle's name includes the term rectus (straight), its fibers run parallel to that imaginary line. For example, the rectus femoris is the straight muscle of the thigh. Similarly, the term oblique in a muscle's name tells you that the muscle fibers run obliquely (at a slant) to the imaginary line.

number of origins

When the term biceps, triceps, or quadriceps forms part of a muscle name, you can assume that the muscle has two, three, or four origins, respectively. For example, the biceps muscle of the arm has two heads, or origins, and the triceps muscle has three.

Primary action of the deltoid

abduction

While doing "jumping jacks" during an exercise class, your arms and legs move laterally away from the midline of your body. This motion is called

abduction

What does the fascicle arrangement determine?

range of motion and power -The longer and the more nearly parallel the fascicles are to a muscle's long axis, the more the muscle can shorten, but such muscles are not usually very powerful. Muscle power depends more on the total number of muscle fibers in the muscle. The stocky bipennate and multipennate muscles, which pack in the most fibers, shorten very little but are very powerful.

Which muscle helps compress the abdominal contents during defecation or childbirth?

rectus abdominis

Which muscle extends the knee?

rectus femoris

The movement of a bone around its longitudinal axis

rotation

What term describes the rotation of a bone around its longitudinal axis?

rotation

fixators

specialized synergists. They hold a bone still or stabilize the origin of a prime mover so all the tension can be used to move the insertion bone. The postural muscles that stabilize the vertebral column are fixators, as are the muscles that anchor the scapulae to the thorax.

Which movement is associated with the hand but actually occurs in the forearm?

supination

type of movement that allows you to carry a bowl of soup

supination