Muscle Movements, Types, and Names

Muscle Movements, Types, and Names

A. Gross Skeletal Muscle Activity

1. With a few exceptions, all muscles cross at least one joint

2. Typically, the bulk of the muscle lies proximal to the joint it crossed 3. All muscles have at least two attachments: the origin and insertion 4. Muscles can only pull; they never push

5. During contraction, the muscle insertion moves toward the origin

B. Types of Body Movements

1. Body movement occurs when muscles contract across joints

a. The type of movement depends on the mobility of the joint and on where the muscle is located in relation the joint.

b. Origin: point where the muscle attaches to the immovable or less movable bone

c. Insertion: point where the muscle attaches to the movable bone

i. When the muscle contracts, the insertion moves toward the origin d. Some muscles have interchangeable origins and insertions

Example: rectus femoris (which crosses hip and knee joint)

2. Flexion: movement that decreases the angle of the joint and brings two bones closer together a. Generally, occurs in the sagittal plane

Example: bending elbow

3. Extension: movement that increases the angle of the joint and the distance between tow bones or parts of the body

Example: straightening the knee or elbow a. Hyperextension: extension greater than 1800

Example: tipping your head posteriorly so your chin points to the ceiling 4. Rotation: movement of a bone around its longitudinal axis

Example: shaking your head “no”

5. Abduction: moving a limb away from the midline or medial plane of the body Example: raising arm to the side; spreading fingers apart

6. Adduction: movement of a limb toward the midline of the body Example: lowering an arm to your side

7. Circumduction: moving the distal end of a bone in a circle while the proximal end stays fixed

a. Combines flexion, extension, abduction, and adduction Example: ball-and-socket joint movement (shoulder) 8. Special Movements

a. Dorsiflexion: lifting the foot at the ankle so the superior surface gets closer to the shin

Example: standing on your heels

b. Plantar Flexion: depressing the foot at the ankle

Example: pointing your toes

c. Inversion: invert the foot; turn the sole of the foot medially

d. Eversion: evert the foot; turn the sole of the foot laterally

e. Supination: forearm rotates laterally so the palm faces anteriorly

i. The radius and ulna are parallel

f. Pronation: forearm rotates medially so the palm faces posteriorly

i. The radius is brought across the ulna so the bones form an X g. Opposition: bringing the thumb to the fingertips

ii. Gives human hand its grasping and manipulating ability

C. Interactions of Skeletal Muscles in the Body

a. Body movements are the result of two or more muscles acting together or against one another

b. Whatever one muscle group can do, another muscle group can reverse

2. Prime Mover: muscle that has the major responsibility for causing a particular movement 3. Antagonists: muscles that oppose or reverse a movement

a. When a prime mover is active, its antagonist is stretched and relaxed

4. Synergist: muscles that help prime movers by producing the same movement or by reducing undesirable movements

a. When a muscle the crosses multiple joints contracts, all joints will move unless a synergist stabilizes the joint

Example: Making a fist without bending your wrist

5. Fixator: muscles that hold a bone still or stabilize the origin of a prime mover so all the tension can be used to move the insertion bone

a. They are specialized synergists

Example: muscles that stabilize the vertebrae for posture

D. Naming Skeletal Muscles

a. Named in reference to an imaginary line (usually the midline of the longitudinal axis) b. Example:

i. Rectus means “Straight”

2. Relative Size of the Muscle a. Maximus = largest b. Minimus = smallest c. Longus = long 3. Location of the Muscle

a. Named for the bone with which they are associated

Example: Temporalis overlies the temporal bone of the skull 4. Number of Origins

a. Biceps = two origins b. Triceps = three origins c. Quadriceps = four origins

5. Location of the Muscle’s Origin and Insertion a. Named for their attachment sites b. Example: Sternocleidomastoid

i. Origin on sternum (Sterno—) and Clavicle (—cleido—) ii. Insertion on mastoid process of temporal bone (—mastoid) 6. Shape of the Muscle

a. Some muscles have a distinctive shape b. Example: Deltoid means “triangular” 7. Action of the Muscle

a. Named for actions such as flexor, extensor, and adductor

E. Arrangement of Fascicles

2. Circular: fascicles are arranged in concentric rings a. General term is “Sphincters”

b. Surround external body openings

Examples: orbicularis muscles of the mouth

3. Convergent: fascicles converge toward a single insertion tendon. a. Muscle is triangular or fan shaped

Example: pectoralis major muscle of the chest

4. Parallel: fascicles run parallel the length of the long axis of the muscle a. Muscles are strap-like

b. Fusiform: spindle-shaped muscle with an expanded belly

Example: Biceps brachii muscle of the arm 5. Pennate: short fascicles attach obliquely to a central tendon

a. Unipennate: fascicles insert into only one side of the tendon

Example: Extensor Digitorum Longus

b. Bipennate: the fascicles insert into opposite sides of the tendon

Example: Rectus Femoris

c. Multipennate: the fascicles insert from several different sides of the tendon

Example: Deltoid

6. A muscle’s fascicle arrangement determines its range of motion and power a. Longer and more nearly parallel fascicles:

i. Muscle can shorten more ii. Not usually very powerful

i. Packs in the most fibers ii. Muscle shortens little iii. Very Powerful