The Muscular System Part Two

1. Body movements are often the result of the activity of two or more muscles acting together or against each other.

2. Muscles are arranged in such a way that whatever one muscle (or group of muscles) can do, other muscles can reverse.

3. The prime mover is the muscle that has the major responsibility for causing a particular movement. Muscles that oppose or reverse this movement are called antagonists. When a prime mover is active, its antagonist is stretched and relaxed.

4. Synergists help prime movers by producing the same movement or reducing undesirable movements. Often, synergists stabilize joints during muscle activity.

5. Fixators are specialized synergists that hold a bone still or stabilize the origin of a prime mover so that all the tension can be used to move the insertion bone.

Naming Skeletal Muscles A.Rectus: straight B.Oblique: slanted C.Maximus: largest D.Longus: long E.Biceps: two origins F.Triceps: three origins G.Quadriceps: four origins

Naming Skeletal Muscles H.Deltoid: triangular I.Flexor: causes flexion J.Extensor: causes extension K.Adductor: causes adduction

7. The two groups of head muscles are facial muscles and chewing muscles.

8. Facial muscles are unique because they are inserted into soft tissues such as other muscles or skin.

Sternocleidomastoid Muscle Shape: two-head muscle found on each side of the neck Origins: the sternum and the clavicle Insertion: mastoid process of the temporal bone Action: together, they contract to flex the neck (bowing the head)

3 Types of Muscles That Make Up the Trunk A.Those that move the vertebral column B.Anterior thorax muscles, which move the ribs, head, and arms C.Abdominal wall muscles

Pectoralis Major  Shape: large, fan-shaped muscle covering the upper chest  Origins: shoulder girdle and first 6 ribs  Insertion: proximal end of the humerus  Action: adduction and flexion of the arm

Muscles of the Abdominal Girdle  The muscles of the abdominal girdle are naturally strong because they resemble the structure of plywood. The fibers of each muscle pair run in a different direction, making the girdle exceptionally strong for its thickness

13. The main function of the rectus abdominus is to flex the vertebral column. Like the rectus abdominus, the external obliques flex the vertebral column, but they also rotate the trunk and bend it laterally.

Muscles of the back MuscleShapeOriginInsertionAction TrapeziusDiamond or kite- shaped Occipital bone Scapular spine and clavicle Extend the head and move the scapula Latissimus Dorsi Large, flat, covering lower back Lower spine and ilium Proximal end of humerus Brings the arm down powerfully DeltoidTriangular shaped and fleshy Spine of scapula and clavicle Proximal humerus Abduction of arm

15. All anterior arm muscles cause elbow flexion.

Anterior Arm Muscles MuscleShapeOriginInsertionAction Biceps Brachii Forms a bulge during elbow flexion Two heads from the shoulder girdle The radial tuberosity Flexion and supin- ation of the forearm Triceps Brachii Fleshing from the posterior humerus Shoulder girdle and proximal humerus Olecranon process of the ulna Prime mover of elbow extension

Muscles of the Buttocks MuscleLocationOriginInsertionAction Gluteus Maximus Superficial forms the flesh of the buttock Sacrum and iliac bones Gluteal tuberosity of the femur Extends the hip Gluteus Medius Long, covered by the gluteus maximus IliumfemurAbducts the hip and steadies the pelvis

The Hamstring Group NameOriginInsertion Biceps femoris Ischial tuberosity Both sides of the proximal tibia Semi- membranosus Ischial tuberosity Both sides of the proximal tibia Semi- tendinosus Ischial tuberosity Both sides of the proximal tibia

The Sartorius Muscle Location: most superficial muscle of the thigh, running obliquely across the quadriceps Origin: anterior iliac crest Insertion: medial side of the tibia Action: weak thigh flexor and synergist of crossing the legs

20. The quadriceps group consists of two groups of muscles, the rectus femoris and three vastus muscles.

Rectus Femoris Location: long fleshy muscle of the upper thigh Origin: pelvis Insertion: tibial tuberosity via the patellar ligament Action: extends the knee and flexes the hip

Vastus Muscle Group Location: long fleshy muscles of the upper thigh Origin: femur Insertion: tibial tuberosity via the patellar ligament Action: extends the knee powerfully

5 Muscles That Move the Foot MuscleLocationOriginInsertionAction Tibialis Anterior Superficial on the anterior leg Upper tibia Tarsal bones Dorsi- flexion and inversion Extensor Digitorum Longus Lateral to the tibialis anterior Lateral tibial condyle and proximal radius Phalanges of toes 2-5 Toe extension and foot dorsi- flexion

5 Muscles That Move the Foot MuscleLocationOriginInsertionAction Fibularis Muscles Lateral part of the lower leg FibulaMetatarsalsPlantar flexion and eversion of the foot Gastroc- nemius Two- bellied muscle on calf Distal femur CalcaneusPlantar flexion of the foot SoleusDeep to the gastroc- nemius TibiaCalcaneusPlantar flexion of the foot

22. The first movements of the fetus, called the quickening, are often felt by the mother in the sixteenth week of pregnancy.

Duchenne Muscular Dystrophy Symptoms: males between ages 2 and 6 become clumsy and fall frequently Causes: diseased muscle fibers lack a protein that helps maintain sarcolemma Results: most victims use wheelchairs by age 12 and generally die before adulthood

Myasthenia Gravis Symptoms: drooping of upper eyelids, difficulty swallowing and talking, generalized muscle weakness and fatigue Causes: shortage of acetylcholine receptors at the neuromuscular junction Results:muscles become progressively weaker; death results from inability of respiratory muscles to function