Anatomy; Chapter 7

tendon

- Bundle of fibers - attaches muscle to bone

axial muscles

- arise on the axial skeleton - position head and spinal cord and move rib cage

Aponeurosis

- broadsheet of fibers - connects muscles to each other

cardiac muscle

- found only in the heart - The heart has to be able to regulate its contractions. Heart muscle, unlike skeletal muscle, cannot go into tetanus. This is because the heart muscle has to be able to consistently contract and pump blood in a controlled fashion

isotonic contraction

- length of the muscle changes - tension remains constant until relaxation - Force generated exceed the load

Isometric contraction

- muscle length stays the same - The tension produced does not exceed the load - Force generated = load

Name the 5 Main Functions of Muscle

Movement · Bones or fluids Maintain posture and body position · Continuously function to counteract gravity Support soft tissues · Abdominal wall and pelvic floor composed of skeletal muscle Guard entrances and exits · Encircles openings of Digestive and urinary tracts Maintain body temperature · Heat generation upon contraction

Sarcomere

· Contractile units of skeletal muscle · Region between two successive Z discs · Contain microfilaments (thick and thin filaments) · Arrangement of thick and thin filaments produce the banded or striated appearance of the fiber

Myosin

· Each thick filament: 300 myosin and molecules · 2 heavy and 4 light polypeptide chains · Myosin Tails contain to interwoven, heavy polypeptide chains · Myosin Heads: each attached by two smaller, light polypeptide chains § cross-bridges during contraction § binding sites for acting and ATP

Actin

· long Twisted double strand of f actin · F actin consists of G ( Globular) actin subunits § active sites for myosin head attachment

Atrophy

· occurs in a muscle that is not regularly stimulated by a motor neuron - muscle fibers become smaller and weaker - can be observed after a cast comes off of a fracture - reversible if caused by a temporary reduction in use - dying muscle fibers are not replaced

Muscle Tone

- resting tension in skeletal muscle - motor units in muscle always activate although contractions do not produce movement - maintains posture and body position

smooth muscle

- similar in size to cardiac muscle cells - spindle-shaped and have a single nucleus - found in the walls of most organs, in the form of sheets, bundles, or sheets - oriented in different directions to allow for movement of Oregon contents in a specific Direction - Nonstriated, involuntary muscle

Stages of Muscle Contraction

1) Myosin head in low-energy configuration, and bound to by ATP 2) ATP hydrolyzed to ADP and P, switching myosin head to high-energy configuration 3) Myosin head binds to actin 4) ADP and P released, myosin head returns to low-energy configuration, causing thin filament to move toward sarcomere 5) New molecule of ATP binds to myosin head, myosin head detaches from actin, and cycle starts again

Tropomyosin

A protein of muscle that forms a complex with troponin regulating the interaction of actin and myosin in muscular contraction

Troponin

A protein of muscle that together with tropomyosin forms a regulatory protein complex controlling the interaction of actin and myosin and that when combined with calcium ions permits muscular contraction

Describe the Organization of Skeletal Muscle

Epimysium surrounds the Perimysium Perimysium surrounds the Endomysium Endomysium surrounds the Muscle fiber

List and define the 4 characteristics of Muscle Tissue

Excitability - Receive and respond to stimuli Contractility - Shorten when stimulated Extensibility - Stretch Elasticity - Recoiled to resting length

Myofilaments

actin and myosin

appendicular skeleton

stabilize or move the appendicular skeleton