Chapter 11 Muscular System I Lever systems bonemuscle

Chapter 11 Muscular System

I. Lever systems: bone-muscle relationships The joints act as a fulcrum (a fixed point at which a lever moves) the bones act as levers (rigid bars) and the muscle contraction provides the effort (force in opposing direction to the load). What ever weight or object the muscle is trying to move is the load. A. The distance of the load and effort from the fulcrum determines if there is mechanical advantage (not much effort is needed) or mechanical disadvantage (much effort is needed). B. See page 257 on the types of levers.

Effort is farther from the joint and load= mechanical advantage. Average speed and mobility. Effort (muscle insertions) is further from the joint than is the load. Slow, stable, and can bear a lot of weight. Effort lies between the joint and the load. Fast and moveable but less force. Most common body lever system.

• II. Arrangement of fascicles in muscles – Fascicles can be seen with the naked eye, these arranged in different patterns, this pattern influences the muscles function. • A. Parallel-fascicle axis is parallel to muscle, belly is flanked by tendons. The muscle may be strap like (sternocleidomatoid) or fusiform (biceps) • B. Convergent-broad muscle origin with fan shaped fascicles that converge at one tendon and resemble a triangle (Pectoralis major) • C. Pennate- fasciles are arranged along the length of a tendon, structure resembles a feather. 1. unipennate- fascicles are on one side of the tendon only(flexor pollicis longus) 2. bipennate-fascicles are on both sides and the tendon runs down the middle (bicep femoris), also one of the strongest types of muscles. 3. multipennate- multiplebipennates arranged side by side and end up connecting to one tendon. Is considered one of the strongest types of muscles. • D. Circular- fascicles are arranged in concentric rings, these are found at the opening of an organ, may be called sphincter or orbicularis

• IV. Naming the skeletal muscles. A. Location- names relates to region of the body in which the muscle is located. B. Shape- some muscle are named after geometric figures they resemble C. Relative size of the muscle- muscle length or relative size may make up the name such as maximus, minimus, longus, breves. D. Diretion of the fascicles and muscle fibers- the name may refer to the direction of the fibers in relationship to the body midline (rectus- parallel, obliqueat a right angle) E. Location of attachment- name may incorporate the origin and insertion (sternohyoid) F. Number of origins- a name that has a numerical prefix refers to the number of origins, such as the biceps, triceps, quadriceps, ect. G. Action- name may reveal the action the muscle takes at that joint such as flexor, extensor.

III. Interactions of skeletal muscles in the body Muscles work in opposing groups and are arranges in opposite sides around a joint. The action they perform determines their functional types. A. Agonist (prime mover)produces the movement (example: joint flexor-bicep). B. Antagonist- performs that opposite action as the agonist but remains relaxed or stretched while agonist is contracting (example: joint extensor-tricep) C. Synergest- a muscle that works with an agonist to stabilize a joint or reduce unnecessary action at a particular joint. Fixators hold a bone in place to provide a stable base for an agonist.

• V. A development-based organization of muscles • All muscles develop from the mesoderm germ layer which folds into sections called myotomes and somitomeres. There are four major groups: • 1. visceral organ musculature- this includes the development of smooth and cardiac muscle. Most often smooth muscle is called visceral muscle because it is found in abdominal viscera. However cardiac muscle also makes up an organ and thus is visceral muscle. • 2. pharyngeal arch muscles- these developed around the embryonic pharynx and include muscles of facial expression, chewing, swallowing, and some head neck muscles. • 3. axial muscles- these developed from some somitomeres and myotomes they include all throrax and abdominpelvic muscles as well as back, neck, and eye muscles. • 4. limb muscles-developed from myotomes near the budding limbs, includes all muscles of superior and inferior limbs.

• MUSCLE FIGURES • • • HEAD FACE NECK ANTERIOR THORAX POSTERIOR THORAX

Web link on muscle drawings: www. gpc. edu/~jal iff/anahumus. htm

Anterior View of Facial Muscles

Muscles that move the eye Chapter 16 picture- pg 486

Muscles used for mastication and jaw movement

Muscles that move the tongue for ingestion and speech

Muscles involved in swallowing

Anterior View of Neck Muscles

Cadaver picture showing neck muscles

Lateral view of neck muscles

The largest and most superficial back muscles are the trapezius and latissimus dorsi. The Rhomboids are superficial to the erector spinae muscles.

Anterior Thorax: Chest

Serratus Anterior and Intercostal muscles Subscapular Fossa Serratus Anterior

Top view of the pelvic floor and other muscles inside the pelvic bone

SHOULDER, ARM, AND FOREARM • Muscles that move the scapula (shoulder movement) – Pectoralis minor, Serratus anterior, – Trapezius, Levator scapulae, Rhomboid major and minor, • Muscle that move the humerus (arm movement) – Subscapularis, pectoralis major, deltoid, coracobrachialis, – Latissimus dorsi, Teres major & minor, Supraspinatus, Infraspinatus • Muscles that move the ulna & radius(forearm movement) – Biceps Brachii, Brachialis, Brachioradialis, pronator teres, pronator quadratus – Triceps Brachii, anconeus, supinator, • Muscles that move the carpals, metacarpals, & phalanges (hand movement) – Flexor carpi radialis, plamaris longus, flexor carpi ulnaris, flexor digitorum superficialis and profundus, flexor pollicis longus – Extensor Carpi radialis longus and breves, Extensor digitorum, Extensor carpi ulnaris, abductor pollicis, extensor pollicis longus flexor pollicis, and brevis, Extensor indicis