Chapter 11: Muscular System Flashcards
describe the relationship between bones and skeletal muscles in producing body movements
Skeletal muscles that produce movements do so by exerting force on tendons which in turn pull on
bones or other structures (such as the skin). Most muscles cross at least 1 joint and are usually
attached to articulating bones that form the joint.
When a skeletal muscle contracts, it moves one of the articulating bones. Usually the bones do not
move equally in response to the contraction. 1 bone remains stationary near its original position
because other muscles stabilize it or because its structure makes it less movable.
define lever and fulcrum and compare the three types of levers based on location of the fulcrum, effort, and load.
Lever systems and leverage (fulcrum, effort, load/resistance)
A. lever – rigid structure that can move around a fixed point called a fulcrum
B. fulcrum – fixed point around which a lever can move.
C. Effort – force which causes movement, exerted by muscular contraction.
Levers are classified into 3 types according to the positions of the fulcrum, effort, and load.
A. first-class levers – The fulcrum is between the effort and the load. Ex. Scissors
and seesaws. The fist-class lever can produce either a mechanical advantage or
disadvantage depending on whether the effort of the load is closer to the fulcrum.
“EFL”
Example: An adult and a child on a see saw. Child = effort, Adult = load. If the effort is farther
from the fulcrum than the load, a heavy load can be moved, but not very far or fast. If the effort
is closer to the fulcrum than the load, only a lighter load can be moved, but it moves far and fast.
In the body, only a few first-class levers. One example: lever formed by head resting on the
vertebral column. When the head is raised, the contraction of the posterior neck muscles
provides the effort. The joint between the atlas and the occipital bone forms the fulcrum.
Weight of the anterior portion of the skull is the load.
B. second-class levers – the load is between the fulcrum and the effort. Operate like a wheelbarrow. Always produce a mechanical advantage because the load is always closer to the fulcrum than the effort. This arrangement sacrifices speed and range of motion for force. This type of lever produces the most force. “ELF”
Uncommon in the human body. An example: standing on your toes. The fulcrum is the ball of
the foot. The load is the weight of the body. The effort is the contraction of the calf muscles
which raise the heel off the ground.
C. third-class levers – the effort is between the fulcrum and the load. Operate like a pair of forceps and are the most common levers in the body. Always produce a mechanical disadvantage because the effort is always closer to the fulcrum than the load. This arrangement favors speed and ROM over force. “FEL”
Examples: The elbow joint, biceps brachii muscle, and the bones of arm and forearm. In flexing
the forearm at the elbow, the elbow joint is the fulcrum, the contraction of the biceps brachii
muscles provides the effort, and the weight of the hand and forearm is the load.
identify the types of fascicle arrangements in a skeletal muscle and relate the arrangements to strength of contraction and range of motion.
Fascicles - muscle bundles (arrangement five patterns with respect to tendon)
1) Parallel
2) Fusiform (narrow ends wide middle)
3) Circular
4) Triangular
5) Pennate (feather)
explain how the prime mover, antagonist, synergist, and fixator in a muscle group work together to produce movement.
A. prime mover or AGONIST – the muscle directly responsible for producing a desired
motion.
B. Antagonist – a muscle that has an action opposite that of the prime mover and yields to
the movement of the prime mover. When the prime mover contracts, the antagonist
stretches and yields to the effects of the prime mover.
The antagonist and prime mover are usually located on opposite sides of the bone or joint.
The role of prime mover and antagonist can switch for different movements, for example:
extension vs flexion. If the contractions of prime mover and antagonist happen simultaneously
with equal strength, there will be no movement.
C. Synergist – a muscle that assists the prime mover by reducing undesired action or
unnecessary movement. Usually located close to the prime mover.
D. Fixator – a muscle that stabilizes the origin of the prime mover so that the prime mover
can act more efficiently. Fixators steady the proximal end of a limb while movements occur
at the distal end.
Example: scapula is a freely movable bone that serves as the origin for several muscles that
move the arm. When the arm muscles contract, the scapula must be held steady.
explain seven features used in naming skeletal muscles.
- Direction : Orientation of muscle fascicles relative to the body’s midline
Rectus: Parallel to midline
Transverse: Perpendicular to midline
Oblique: Diagonal to midline
- Size : Relative size of the muscle
Maximus: Largest
Minimus: Smallest
Longus: Long
Brevis: Short
La9ssimus: Widest
Longissimus: Longest
Magnus: Large
Major: Larger
Minor: Smaller
Vastus: Huge
- Shape: Relative shape of the muscle
Deltoid: Triangular
Trapezius: Trapezoid
Serratus: Saw-toothed
Rhomboid: Diamond shaped
Orbicularis: Circular
Pecinate: Comb-like
Piriformis: Pear-shaped
Platys: Flat
Quadratus: Square, four-sided
Gracillis: Slender
- Number of Origins: Number of tendons of origin
Biceps: Two origins
Triceps: Three origins
Quadriceps: Four origins
- Action: Principal action of the muscle
Flexor: Decreases joint angle
Extensor: Increases joint angle
Abductor: Moves away from the body
Adductor: Moves toward the body
Levator: Raises or elevates
Depressor: Lowers or depresses
Supinator: Turns palm up
Pronator: Turns palm down
Sphincter: Decreases size of an opening
Tensor: Makes body part rigid
Rotator: Rotates bone around am axis
- LOCATION Structure near which a muscle is found
7. ORIGIN AND INSERTION Sites where muscle originates and inserts
describe the origin, insertion, action and innervation of the muscles of facial expression.
SCALP MUSCLES
Occipitofrontalis:
Frontal Belly - raises scalp anteriorly raises eyebrows and wrinkles skin of forehead
Occipital Belly - raises scalp posteriorly
MOUTH MUSCLES
Orbicularis oris - kisses and shapes lips during speech
Zygomatic Major - smiling
Buccinator - whitsling, blowing, sucking, chewing (keeping food b/w teeth)
ORBIT & EYEBROW MUSCLES
Orbiguaris oculi - closes eyes
describe the origin, insertion, action, and innervation of the muscles that move the mandible and assist in mastication and speech.
Closers of jaw - Masseter (STRONGEST), Temporalis, and Medial Pterygoid
Medial and Lateral Pterygoid - move the jaw from side to side to grind food
Lateral Pterygoid protrudes mandible
Teeny Mice Make Petite Little Prints
Temporalis MASSETER Medial Pterygoid Lateral Pterygoid
Masseter
Origin - maxilla and zygomatic arch
Insertion - angle and ramus of mandible
Action - elevates mandible (closes mouth)
Temporalis
Origin Temporal bone
Insertion Coronoid process and ramus of mandible
Action elevates and retracts mandible
describe the origin, insertion, action, and innervation of the muscles that move the head.
Sternocleidomastoid
Origin
Sternal head: Manubrium of sternum; clavicular head; medial third of clavicle
Insertion Mastoid process of temporal bone and lateral half of superior nuchal line of occipital bone
Action Acting together (bilaterally), flex cervical point of vertebral column, extend head at atlanto occipital joints
Acting singularly (unilaterally) laterally flex neck and head to same side and rotate head to side, laterally rotate and flex head
Extension of head
elevate sternum during forced inhalation
describe the origin, insertion, action, and innervation of the muscles that protect the abdominal viscera and move the vertebral column.
Rectus Abdomonis
Origin Pubic crest and pubic symphysis
Insertion cartilage of ribes 5-7 and xiphoid process
Action Flexes vc, esp lumbar and compresses abdomen to aid in poo, pee, exhale, birth
RMA flexis pelvis on vc
External Oblique
Action together - compress ab and flex vc singly - laterally flex vc esp lumbar and rotate vc
Internal Oblique
Action together - compress ab and flex vc singly - laterally flex vc esp lumbar and rotate vc
Transversus Abdominis
Insertion Xiphoid process, linea alba, and pubis
Action Compresses Abs
The aponeuroses (sheathlike tendons) of the external oblique, 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), 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.
describe the origin, insertion, action, and innervation of the muscles of the thorax that assist in breathing.
DIAPHRAGM - most important for breathing
Action - 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.
External Intercostals
Action - 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.
Internal Intercostals
Action Contraction draws adjacent ribs together to further decrease anteroposterior and lateral dimensions of thoracic cavity during forced exhalation.
describe the origin, insertion, action, and innervation of the muscles of the thorax that move the pectoral girdle.
ANTERIOR THORACIC MUSCLES
Pectoralis minor Abducts scapula and rotates it downward. RMA: Elevates ribs 3–5 during forced inhalation when scapula is fixed.
Serratus anterior O Ribs 1–8 or 1–9 I Vertebral border and inferior angle of scapula. A Abducts scapula and rotates it upward. RMA: Elevates ribs when scapula is stabilized. Known as “boxer’s muscle” because it is important in horizontal arm movements such as punching and pushing.
POSTERIOR THORACIC MUSCLES
Trapezius O Superior nuchal line of occipital bone, ligamentum nuchae, and spines of C7–T12 I Clavicle and acromion and spine of scapula. A Superior fibers upward rotate scapula; middle fibers adduct scapula; inferior fibers depress and upward rotate scapula; superior and inferior fibers together rotate scapula upward; stabilizes scapula. RMA: Superior fibers can help extend head.
Levator scapulae O Transverse processes of C1–C4. I Superior vertebral border of scapula. A Elevates scapula and rotates it downward.
Rhomboid major A Elevates and adducts scapula and rotates it downward; stabilizes scapula.
describe the origin, insertion, action, and innervation of the muscles of the thorax that move the humerus.
AXIAL MUSCLES THAT MOVE THE HUMERUS
Pectoralis major O Clavicle (clavicular head), sternum, and costal cartilages of ribs 2–6 and sometimes ribs 1–7 (sternocostal head). I Greater tubercle and lateral lip of intertubercular sulcus of humerus. A As a whole, adducts and medially rotates arm at shoulder joint; clavicular head flexes arm, and sternocostal head extends flexed arm to side of trunk.
Latissimus dorsi A Extends, adducts, and medially rotates arm at shoulder joint; draws arm inferiorly and posteriorly. RMA: Elevates vertebral column and torso.
SCAPULAR MUSCLES THAT MOVE THE HUMERUS
Deltoid O Acromial extremity of clavicle (anterior fibers), acromion of scapula (lateral fibers), and spine of scapula (posterior fibers). I Deltoid tuberosity of humerus. A Lateral fibers abduct arm at shoulder joint; anterior fibers flex and medially rotate arm at shoulder joint; posterior fibers extend and laterally rotate arm at shoulder joint.
Subscapularis A Medially rotates arm at shoulder joint.
Supraspinatus O Supraspinous fossa of scapula. I Greater tubercle of humerus. A Assists deltoid muscle in abducting arm at shoulder joint.
Infraspinatus A Laterally rotates arm at shoulder joint.
Teres Major A Extends arm at shoulder joint and assists in adduction and medial rotation of arm at shoulder joint.
Teres Minor A Laterally rotates and extends arm at shoulder joint.
describe the origin, insertion, action, and innervation of the muscles of the arm that move the radius and ulna.
FOREARM FLEXORS
Biceps brachii O Long head originates from tubercle above glenoid cavity of scapula
(supraglenoid tubercle). I Radial tuberosity of radius and bicipital aponeurosis.* A Flexes forearm at elbow joint, supinates forearm at radioulnar joints, and flexes arm at shoulder joint.
Brachialis A Flexes forearm at elbow joint.
Brachioradialis A Flexes forearm at elbow joint; supinates and pronates forearm at radioulnar joints to neutral position.
FOREARM EXTENSORS
Triceps brachii O Long head originates from infraglenoid tubercle, a projection inferior to glenoid cavity of scapula.
Lateral head originates from lateral and posterior surface of humerus.
Medial head originates from entire posterior surface of humerus inferior to a groove for the radial nerve. I Olecranon of ulna. A Extends forearm at elbow joint and extends arm at shoulder joint.
Anconeus O Lateral epicondyle of humerus. I Olecranon and superior portion of shaft of ulna. A Extends forearm at elbow joint.
FOREARM PRONTTORS
Pronator teres A Pronates forearm at radioulnar joints and weakly flexes forearm at elbow joint.
FOREARM SUPINATOR
Supinator A Supinates forearm at radioulnar joints.
describe the origin, insertion, action, and innervation of the muscles of the forearm that move the wrist, hand, and digits.
SUPERFICIAL ANTERIOR (FLEXOR) COMPARTMENT OF THE FOREARM
Flexor carpi radialis O Flexor digitorum superficialis I Metacarpals II and III. A Flexes and abducts hand
(radial deviation) at wrist joint.
Palmaris longus OIA Weakly flexes hand at wrist joint.
Flexor carpi ulnaris O Medial epicondyle of humerus and superior posterior border of ulna. I Pisiform, hamate, and base of metacarpal V. A Flexes and adducts hand (ulnar deviation) at wrist joint.
Flexor digitorum superficialis O Medial epicondyle of humerus, coronoid process of ulna, and ridge along lateral margin or anterior surface (anterior oblique line) of radius. I Middle phalanx of each finger A Flexes middle phalanx of each finger at proximal interphalangeal joint, proximal phalanx of each finger at metacarpophalangeal joint, and hand at wrist joint.
SUPERFICIAL POSTERIOR (EXTENSOR) COMPARTMENT OF THE FOREARM
Extensor carpi radialis longus Extends and abducts hand at wrist joint (ulnar deviation).
Extensor digitorum O Lateral epicondyle of humerus. I Distal and middle phalanges of each finger A Extends distal and middle phalanges of each finger at interphalangeal joints, proximal phalanx of each finger at metacarpophalangeal joint, and hand at wrist joint.
Extensor carpi ulnaris O Lateral epicondyle of humerus and posterior border of ulna. I Metacarpal V. A Extends and adducts hand at wrist joint (ulnar deviation).
describe the origin, insertion, action, and innervation of the muscles that move the vertebral column.
ERECTOR SPINAE (e-REK-tor SPĪ-nē) Consists of iliocostalis muscles (lateral), longissimus muscles (intermediate), and spinalis muscles (medial).
Acting together, muscles of each region (cervical, thoracic, and lumbar) extend and maintain erect posture of vertebral column of their respective regions; acting singly, laterally flex vertebral column of their respective regions to same side as contracting muscle.
SCALENES
Anterior SCALENES Acting together, right and left anterior scalene and middle scalene muscles elevate first ribs during deep inhalation.
Middle SCALENES RMA: Flex cervical vertebrae; acting singly, laterally flex and slightly rotate cervical vertebrae.
Posterior SCALENES Acting together, right and left posterior scalene elevate second ribs during deep inhalation. RMA: Flex cervical vertebrae; acting singly, laterally flex and slightly rotate cervical vertebrae.
