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