Be 3142 muscle system

Characteristics of Muscle Tissue

Contractability, extensibility, excitability, elasticity.

Contractability

The ability of muscle tissue to shorten or contract.

Extensibility

The ability of muscle tissue to be extended or stretched within limits.

Excitability

The susceptibility of muscle tissue to react to external stimuli.

Elasticity

The ability of muscle tissue to return to its original state after being stretched.

Skeletal Muscle

Muscle that acts on the skeletal system, striated, voluntary.

Cardiac Muscle

Muscles of the heart, striated, involuntary.

Smooth Muscle

Lines organs, vessels, and gland ducts, not striated, involuntary.

Actin

Found in thin filaments of sarcomeres within myofibrils; includes regulatory proteins tropomyosin and troponin.

Myosin

Found in thick filaments of sarcomeres within myofibrils.

Myofibril

One of the longitudinal fibrils found in skeletal and cardiac muscle fibers.

Myofilament

A protein filament that makes up the myofibrils in skeletal muscle.

Muscle Fiber

Myofiber/muscle cell consists of bundles of myofibrils surrounded by sarcolemma.

Origin of a Muscle

The more stable (less moveable) point attachment to the skeleton.

Insertion of a Muscle

The point of attachment that is more moveable (less fixed).

Fascia

Sheath of dense connective tissue that envelops the body beneath the skin, encloses muscles, and separates their various layers or groups.

Criteria for Naming Muscles

Structure, function, shape, location, and number of heads.

Rectus Abdominis

Example of structure in muscle name.

Depressor Labii Inferioris

Example of function in muscle name.

Deltoid

Example of shape in muscle name.

Tibialis Anterior

Example of location in muscle name.

Quadriceps

Example of number of heads in muscle name.

Circular Muscle

Fascicles arranged concentrically around an opening, acts as a sphincter.

Parallel Muscle

Fascicles are parallel to the long axis of the muscle, body of muscle increases in diameter with contraction.

Convergent Muscle

Triangular muscle with common attachment site, direction of pull can be changed.

Pennate Muscle

Muscle body has one or more tendons, fascicles at oblique angle to tendon.

Unipennate Muscle

All fascicles on the same side of the tendon.

Bipennate Muscle

Fascicles on both sides of the tendon.

Multipennate Muscle

Tendon branches within the muscle.

Ligaments

Attach bone to bone and increase joint stability during action.

Muscle Tendons

Attach muscle to bone.

Aponeurosis

Large sheets of connective tissue that act as ligaments for larger muscles.

Somatic Motor Neuron

A neuron that innervates skeletal muscle fibers, has a long extension called the axon.

Neuromuscular Junction

The junction between the axon and the muscle fiber.

Muscle Fibers

Individual muscle cell that receives signals from the neuron and contracts.

Flexion

Angle between articulating bones decreases.

Extension

Angle between articulating bones increases.

Lateral Flexion

Vertebral column bends in a lateral direction along the coronal plane.

Abduction

Lateral movement of a body part away from the midline.

Adduction

Medial movement of a body part toward the midline.

Circumduction

Continuous movement that combines flexion, abduction, extension, and adduction.

Pronation

Rotation of the forearm where the palm is turned posteriorly.

Supination

Rotation of the forearm in which the palm is turned anteriorly.

Depression

Movement of a body part inferiorly.

Elevation

Movement of a body part superiorly.

Dorsiflexion

Ankle joint movement where the dorsum of the foot is brought closer to the anterior surface of the leg.

Plantar Flexion

Ankle joint movement whereby the sole of the foot is brought toward the posterior surface of the leg.

Inversion

Twisting motion of the foot that turns the sole medially or inward.

Eversion

Twisting motion of the foot that turns the sole laterally or outward.

Protraction

Anterior movement of a body part from anatomic position.

Retraction

Posterior movement of a body part from anatomic position.

Opposition

Special movement of the thumb across the palm toward the fingers to permit grasping.

Muscles Development

Muscles develop from the mesoderm and organize into muscle tissue.

Primordial Muscles

Migrate down the developing limb bud and construct groups around the underlying skeletal structures.

Dense Connective Tissue

Separates individual muscles from one another.

Deep Connective Tissue

Divides compartments of muscle from one another and creates passageways for neurovascular bundles.

Agonists

Muscles whose primary movement elicits a particular action.

Synergists

Muscles in the same compartment that often have the same or similar actions.

Antagonists

Muscle compartments on opposing surfaces of the body that have opposing actions.

Abductors

Laterally placed muscles that move the appendages away from the midline.

Adductors

Medially placed muscles that move the appendages toward the midline.