The Role of Muscles in Movement Muscles can t push, they can only pull as they contract, so most often body movements are the result of the activity of pairs or teams of muscles acting together or against each other. Reciprocal Inhibition, is the process where muscles on one side of a joint relax to accommodate contraction on the other side of the joint. Joints are controlled by two opposing sets of muscles, extensors and flexors, which must work in synchrony for smooth movement. Muscles are arranged on the skeleton in such a way that whatever one muscle (or group of muscles) can do, another group of muscles can reverse. Because of this, muscles are able to bring about an immense variety of movements. A muscle can be termed one of the following depending on its role within a particular movement: 1. Prime Mover (PM) (Agonist) MUSCLES PULL THEY DON T PUSH. the primary muscle effecting a desired joint movement This is an important When several muscles are contracting at the same time, the muscle that concept when learning has the major responsibility for causing a particular movement is called about muscular action the prime mover (this physiologic term has been borrowed by the business world to label a person who gets things done). 2. Antagonist the muscle which opposes a certain movement Muscles that oppose or reverse a movement are antagonists. When a prime mover is active, its antagonist is stretched and relaxed. 3. Fixator a muscle that stabilises a joint during movement Fixators are specialized synergists. They act to hold a bone still or to stabilize the origin of a prime mover so all the tension can be used to move the insertion bone. The postural muscles stabilising the vertebral column are fixators, as are the muscles anchoring the scapula to the thorax. 4. Synergist Antagonists can be prime movers in their own right. For example, the biceps of the arm (prime mover of elbow flexion) is antagonized by the triceps (a prime mover of the elbow extension). a muscle which assists in performing the desired joint movement Synergists are muscles that help prime movers by producing the same movement, or by reducing undesirable or unnecessary movement. When a muscle crosses two or more joints, its contraction will cause movement in all joints crossed unless synergists are there to stabilize them. For example, the finger flexor muscles cross both the wrist and the finger joints. You can make a fist without bending your wrist because synergist muscle stabilize the wrist joints and allow the prime mover to act on the finger joint. Muscles of the Face and Hand Page 1
Muscles of the Face & Hand This supplement to the Human Biology Module: Musculoskeletal Anatomy includes some key muscles of the body that the massage therapist should have an understanding of. Muscles of the Face Frontalis Temporalis Masseter Frontalis The muscles of facial expression are generally thin, flat bands arising from a facial bone or cartilage and inserting into the dermis of the skin or fibrous tissue. One of the superficial muscles of the cranium or head involved in facial expression is the frontalis which covers the forehead and dome of the skull. The Frontalis muscle has no bony attachments inserting into the facia or galea aponeurotica of the skull. Frontalis Galea Aponeurotica Skin of the eyebrows and root of nose Facial Expression Raises eyebrows, wrinkles forehead Muscles of the Face and Hand Page 2
Temporalis The facial muscles involved in mastication or chewing of food are primarily the temporalis and masseter muscles. Both muscles are responsible for elevation, depression, protraction retraction and lateral movements of the temporomandibular joint. The temporalis is a large scallop or fan shaped muscle covering the side of the temporal, parietal and frontal bones of the head in front of, superior to and behind the ear. Temporalis Temporal fossa Coronoid process of mandible via tendon beneath zygomatic arch Jaw/Mandible: Elevation Retraction Maintains position of mandible at rest Masseter Masseter The Masseter is the most prominent chewing muscle of the jaw. A powerful muscle, the masseter covers the lateral aspect of the mandibular ramus and is primarily responsible for jaw closure. Zygomatic arch Mandible (angle and ramus) Jaw: Elevation (PM) Muscles of the Face and Hand Page 3
Muscles of the Hand & Forearm Flexor carpi radialus Flexor carpi ulnaris Palmar longus Pronator teres Extensor carpi radialis Supinator Forearm Flexors A group of muscles on the anterior forearm, including Flexor carpi radialis, Flexor carpi ulnaris, and Palmaris longus. Also included in this group is Pronator teres a two headed muscle on the anterior forearm between brachioradialis and flexor carpi radialis. Its origin is the medial epicondyle of the humerus and the coronoid process of the ulnar. As its name suggests its function is to pronate the forearm and assist with wrist flexion. Medial epicondyle of humerus Carpals, metacarpals and phalanges - anterior aspect Wrist: Flexion PM Fingers: Flexion PM Flexor carpi radialis Flexor carpi ulnaris Palmaris longus Muscles of the Face and Hand Page 4
Forearm Flexors Muscles of the Face and Hand Page 5
Forearm Extensors A group of muscles on the posterior forearm including amongst others the Extensor carpi radialis longus and brevis, Extensor carpi ulnaris and Extensor digitorum. Also included in this area of the body is the Supinator Muscle, deep to the extensor carpi radialis this muscle assists the biceps brachii to supinate the forearm and is an antagonist to pronator teres. Lateral epicondyle of humerus Carpals, metacarpals and phalanges - posterior aspect Wrist: Extension PM Fingers: Extension PM Posterior view Supinator Extensor carpi radialis Extensor carpi ulnaris Extensor digitorum Muscles of the Face and Hand Page 6