The Muscular System

Smooth muscle – is located in the walls of hollow internal organs, and its involuntary contraction moves materials through and organ.

Cardiac muscle – forms the heart wall. Its fibers are uninucleated, striated, and branched, which allows the fibers to interlock at intercalated disks.

Skeletal muscle – fibers are tubular, multinuclearted, and striated. They make up the skeletal muscles attached to the skeleton.

Connective Tissue Coverings

Is essential to the to the organization of the fibers within a muscle.

Functions of Skeletal Muscles

~ Skeletal muscles the body

~ Skeletal muscles make bones and other body parts move.

~ Skeletal muscles help maintain a constant body temperature.

~ Skeletal muscles contraction assists movement in cardiovascular.

~ Skeletal muscles help protect internal organs and stabilize joints.

Muscle Fiber- a muscle fiber contains the usual cellular compotents, but special names have been assigned to some of these components.

Myofibrils and Sacromeres

Myofilamants

Muscle fibers are innervated-that is, they are stimulated to contract by motor neurons whose axons are found in nerves. Contraction continues until nerve impulses cease and calcium ions are returned to their storage sites.

Creatine Phosphate is a high energy compound built up when a muscle is resting.

Oxygen Deficit is when a muscle uses fermentation to supply its energy needed.

All-or-none law explains how muscle fibers either contract maximally or not at all, and that neurons either conduct a nerve impulse completely or not at all.

Motor unit is a nerve fiber together with all of the muscle fibers it innervates.

Recruitment result in stronger and stronger muscle contractions.

Atrophy can occur when a limb is placed in a cast or when the nerve serving muscle is damaged.

Hypertrophy occurs only if the muscle contracts to at least 75% of its maximum tension.

Skeletal Muscles of the Body

Basic Principles

When a muscle contracts, one bone remains fairly stationary, and the other one moves. The origin of a muscle is on the stationary bone and the insertion of a muscle is on the bone that moves.

Naming Muscles

1. size

2. shape

3. direction of fibers

4. location

5. attachment

6. number of attachments

7. action

Muscles of the Head

Muscle of Facial Expression

The muscles of facial expressions are located on the scalp and face.

Frontalis lies over the frontal bone, raises eye brows and wrinkles the brow.

Orbicularis oculi is a ringlike band of muscle that encircles the eye, causing it to close and blink.

Orbicularis oris ebcircles the mouth and is used to pucker the lips.

Buccinator muscles are located in the cheek areas, causing you to whistle or blow out air.

Zygomaticus extends from each zygomatic arch to the corners of the mouth, raising the corners of the mouth when a person smiles.

Muscles of Mastication

The masseter is a muscle of mastication because it is a prime mover for elevating the mandible.

Each temporalis is a fan-shaped muscle that overlies the temporal bone, prime mover for elevating the mandible.

Muscles That Move the Head

Sternocleidomastoid muscles ascend obliquely from their origin on the sternum and clavicle to their insertion on the mastoid process of the temporal bone. Each trapezius muscle is triangular, but together, they take on a diamond or trapezoid shape, the base of the skull.

Muscles of the Hip and Lower Limbs

Moving the Thigh

Iliopsoas originates at the ilium and the bodies of the lumbar vertebrae, and inserts on the femur anteriorly.

Gluteus maximus is the largest muscle in the body and covers a large part of the buttock.

Gluteus medius lies partly behind the gluteus maximus, functions to abduct the thigh.

Adductor group muscles are located on the medial thigh, they lower the thigh sideways from a horizontal position.

Muscles That Move the Leg

Quadriceps femoris group is found on the anterior and medial thigh, primarly extensors of the leg, as when you kick a ball. Sartorius is a long straplike muscle that has its origin on the iliac spine and then goes across the anterior thigh to insert on the medial side of the knee. Hamstring group is located on the posterior thigh, they flez and rotate the leg medially, but they also extend the thigh.

Muscles That Move the Ankle and Foot

Gastrocnemius is a muscle of the posterior leg, where it form a large parts of the calf. Tibialis anterior is a long, spindle-shaped muscle of the anterior leg.

Troubleshooting

Spasms are sudden and involuntary muscular contractions most often accompanied by pain. A strain is the overstretching of a muscle near a joint. Myalgia refers to inflammation of muscle tissue. Tendinitis is inflammation of a tendon due to the strain of repeated athletic activity.

Warning!

Muscular dystrophy is a broad term applied to a group of disorders characterized by progressive degeneration and weakening of muscle.

Myasthenia gravis is an autoimmune disease characterized by weakness that especially affects the muscle of the eyelids, face, neck, and extremities.