Muscle and Body Movements

• movement is attained due to a muscle moving on an attached bone

• muscles are attached to at least two points

  • origin

    • attachment to an immovable bone

  • insertion

    • attachment to a moveable bone

Types of Ordinary Body Movements

• flexion

  • decreases the angle of the joint

  • brings two bones closer together

  • typical of hinge joints like the knee and elbow

• extension

  • opposite of flexion

  • increases the angle between two bones

• rotation

  • movement of a bone around its longitudinal axis

  • common in ball-and-socket joints

  • example is when you move the atlas around the dens of the axis (shake your head “no”)

• abduction

  • movement of a limb away from the midline

• adduction

  • opposite of abduction

  • movement of a limb toward the midline

• circumduction

  • combination of flexion, extension, abduction, and adduction

  • common in ball-and-socket joints

Special Movements

• dorsiflexion

  • lifting the foot so that the superior surface approaches the shin

• plantar flexion

  • depressing the foot (pointing the toes)

• inversion

  • turn the sole of the foot medially

• eversion

  • turn the sole of the foot laterally

• supination

  • forearm rotates laterally so the palm faces anteriorly

• pronation

  • forearm rotates medially so the palm faces posteriorly

• opposition

  • move thumb to touch tips of other fingers on the same hand

Types of Muscles

• prime mover

  • muscle with the major responsibility for a certain movement

• antagonist

  • muscle that opposes or reverses a prime mover

• synergist

  • muscle that aids a prime mover in a movement and helps prevent rotation

• fixator

  • stabilizes the origin of a prime mover

Naming Skeletal Muscles

• by direction of muscle fibers

  • rectus = straight

• by the relative size of the muscle

  • maximus = largest

• by location of the muscle

  • temporalis = temporal bone

• by number of origins

  • triceps = three heads

• by location of the muscle origin and insertion

  • sterno = on the sternum

• by the shape of the muscle

  • deltoid = triangular

• by the action of the muscle

  • flexor and extensor (flexes or extends a bone)

Golden Rules of Skeletal Muscle Activity

• with a few exceptions, all skeletal muscles cross at least one joint

• typically, the bulk of a skeletal muscle lies proximal to the joint crossed

• all skeletal muscles have at least two attachments: the origin and the insertion

• all skeletal muscles can only pull, they never push

• during contraction, a skeletal muscle insertion moves toward the origin

Arrangement of Fascicles

• circular - orbicularis oris

• convergent - pectoralis major

• fusiform - biceps brachii

• parallel - sartorius

• unipennate - extensor digitorum longus

• bipennate - rectus femoris

• multipennate - deltoid

Head and Neck Muscles

• Facial muscles

  • frontalis - raises eyebrows

  • orbicularis oculi - closes eyes, squints, blinks, winks

  • orbicularis oris - closes the mouth and protrudes the lips

  • buccinator - flattens the cheek, chews

  • zygomaticus - raises corners of the mouth

• chewing muscles

  • masseter - closes the jaw and elevates the mandible

  • temporalis - synergist of the masseter, closes the jaw

• neck muscles

  • platysma - pulls the corners of the mouth inferiorly

  • sternocleidomastoid - flexes the neck, rotates the head

Muscles of the Trunk, Shoulder, and Arm

• anterior muscles

  • pectoralis major - adducts and flexes the humerus

  • intercostal muscles

    • external intercostals - raise ribcage during inhalation

    • internal intercostals - depress the rib cage to move air out of the lungs when you exhale forcefully

• Muscles of the Abdominal Girdle

  • rectus abdominis - flexes vertebral column and compress abdominal contracts (defecation, childbirth, forced breathing)

  • external and internal obliques - flex vertebral column; rotate trunk and bend it laterally

  • transversus abdominis - compresses abdominal contents

• Posterior Muscles

  • trapezius -elevates, depresses, adducts, and stabilizes the scapula

  • latissimus dorsi - extends and adducts the humerus

  • erector spinae - back extension

  • quadratus lumborum - flexes the spine laterally

  • deltoid - arm abduction

Muscles of the Upper Limb

• biceps brachii - supinates forearm, flexes elbow

• brachialis - elbow flexion

• brachioradialis - weak muscle

• triceps brachii - elbow extension (antagonist to biceps brachii)

Muscles of the Lower Limb

• gluteus maximus - hip extension

• gluteus medius - hip abduction, steadies pelvis when walking

• iliopsoas - hip flexion, keeps the upper body from falling backward when standing erect

• adductor muscles - adduct the things

• muscles causing movement at the knee joint

  • hamstring group - thing extension and knee flexion

    • biceps femoris

    • semimembranosus

    • semitendinosus

  • sartorius - flexes the thigh

  • quadriceps group - extend the knee

    • rectus femoris

    • vastus muscles (three)

• muscles causing movement at the ankle and foot

  • tibialis anterior - dorsiflexion and foot inversion

  • extensor digitorum longus - toe extension and dorsiflexion of the foot

  • fibularis muscles - plantar flexion, everts the foot

  • soleus - plantar flexion