Muscles Working Together to Create Movement PSK 4

Muscles – Working Together to Create Movement! PSK 4 U Unit 4 Day 5

Muscles Pull! �Muscles pull (by contracting and relaxing) by working in opposing pairs or groups. �Muscles cannot push. �Sometimes muscles attached directly to bone, but more often they are joined to bone by tendons.

How Muscles Attach to Bone �Indirect Attachment – the epimysium (sheath of connective tissue that surrounds the exterior of the muscle fibre) extends past the muscle as a tendon and then attaches to the periosteum of bone. This is most common. �Direct Attachment – the epimysium adheres to and fuses with the periosteum. �Bone markings present where tendons meet bones �Tubercles, trochanters, and crests

Basic Muscular Principles �Skeletal muscles contract only if stimulated to do so �Skeletal muscles produce movements by pulling on bones �Bones serve as levers and joints serve as fulcrums on these levers �Muscles that move a body segment do not usually lie over that part (e. g. bicep flexes elbow but is in upper arm) �Skeletal muscles almost always act in groups rather than individually (prime movers/agonists, antagonists,

Force of Muscle Contraction �The force of contraction is affected by: �The relative size of the muscle �Larger muscles have larger and more muscle fibers �Larger fibers can generate more force than smaller fibers �More muscle fibers can generate more force than fewer fibers �The number of muscle fibers contracting �Greater numbers of motor units generate more force than smaller numbers of motor units �Degree of muscle stretch �Muscles contract strongest when muscle fibers are 80 -

Force of Muscle Contraction Figure 9. 20 (a)

Isometric and Isotonic Contractions �Isometric muscle contraction �Tension (force) does not exceed resistance (load) �important in postural muscle function �Isotonic muscle contraction �Tension exceeds resistance �tension while shortening = concentric �tension while lengthening = eccentric

Agonist and Antagonist Pairs �Agonist– muscle that contracts to produce movement of the body part (prime mover) �Synergists – assist in the action of the agonists but are not primarily responsible for action; known as guiding muscles they assist in refined movements and rule out undesired motions �Antagonist – muscle that opposes or counteracts the agonist (movement). �It lengthens when the agonist contracts shortens.

Examples of opposing muscles and muscle groups AGONIST (Prime Mover) Elbow flexion Shoulder abduction Medial shoulder rotation Knee extension Wrist flexion Dorsi flexion Trunk flexion Hip flexion ANTAGONIST

Examples of opposing muscles and muscle groups AGONIST (Prime Mover) ANTAGONIST Elbow flexion Biceps brachii Triceps brachii Shoulder abduction Deltoid Latissimus Dorsi Medial shoulder rotation Pectoralis major Infraspinatus Knee extension Quadriceps Hamstrings Wrist flexion Flexor carpi radialis Extensor carpi radialis Dorsi flexion Tibialis anterior Gastrocnemius Trunk flexion Rectus abdominis Erector spinae group Hip flexion Iliopsoas Gluteus maximus

Fixators/Stabilizer �Muscles that are active isometrically (muscle does not shorten or lengthen) in order to fixate an area when the agonist contracts �Fixators/ Stabilizers - increase tension to stabilize a joint that is more proximal to allow function at a distal joint �Example: When performing a push-up, the serratus anterior stabilizes the shoulder girdle during the downward stage in order to prevent adduction

Origins and Insertions �Origin – is least moveable part or the part of the muscle that attaches closest to the midline. It is the proximal attachment. �Insertion – is the most moveable part or the part of the muscle that attaches farther from the midline. It is the distal attachment. �The origin usually stays fixed and the insertion moves closer to it

NAMING MUSCLES: Tips �Most skeletal muscles have names that describe some feature of the muscle. �Often several criteria are combined into one name. �Associating the muscle's characteristics with its name will help you learn and remember them. �The following are some terms relating to muscle features that are used in naming muscles.

Size: �vastus (huge) �maximus (large) �longus (long) �minimus (small) �brevis (short)

Shape: � deltoid (triangular) � rhomboid (like a rhombus with equal and parallel sides) � latissimus (wide) � teres (round) � trapezius (like a trapezoid, a four-sided figure with two sides parallel).

Direction of fibers: �rectus (straight) �transverse (across) �oblique (diagonally) �orbicularis (circular)

Location: � pectoralis (chest) � gluteus (buttock) � brachii (arm) � supra- (above) � infra- (below) � sub- (under or beneath) � lateralis (lateral).

Number of origins: �biceps (two heads) �triceps (three heads) �quadriceps (four heads) Triceps Brachii Origin long head: infraglenoid tubercle of scapula lateral head: upper half of the posterior surface of humerus medial head: distal two thirds of the posterior surface of humerus

Origin and insertion: �sternocleidomastoid (origin on the sternum and clavicle, insertion on the mastoid process) � brachioradialis (origin on the brachium or arm, insertion on the distal end of radius at the styloid process)

Action: � abductor (to abduct a structure) � adductor (to adduct a structure) � flexor (to flex a structure) � extensor (to extend a structure) � levator (to lift/elevate a structure)

The name given to a muscle reveals the main kind of functional movement that muscle permits. ADDUCTOR MUSCLES �squeeze limbs in towards the median line of the body �ie. – adductor longus, adductor brevis, adductor magnus �attached along the femur – squeeze thighs together

ABDUCTOR MUSCLES �”push out” from the median line of body. �ie- abductor digiti minimus manus, abductor pollicis longus, abductor pollicis brevis EXTENSOR MUSCLES �extend the limbs and increase the angle between two limbs. �movement is usually directed backwards (with exception of the knee joint) �ie- extensor carpi radialis brevis, extensor carpi radialis longus, extensor carpi ulnaris

FLEXOR MUSCLES �withdraw the limbs and decrease the angle between bones on two sides of a joint. �ie- flexor carpi radialis, flexor carpi ulnaris �from humerus along inside of forearm to metacarpal bones – flex wrist

HOMEWORK �Start working on Muscles Origin/Insertion Chart �Start colouring in muscles in chart on pages 94 -113 in your workbooks! �Wednesday – more memorizing!