Chapter 9

Skeletal Muscle

Attached to bones/skin, voluntary, striated, and powerful.

Smooth Muscle

Found in walls of most hollow organs (except heart), no striations, single nucleus.

Cardiac Muscle

Muscle of the heart, striated, involuntary, and regulated by pacemaker cells.

Functions of Muscles

Stabilize joints, movement of bones/fluids, maintaining posture, and heat generation.

Epimysium

Dense regular connective tissue surrounding the entire muscle.

Perimysium

Fibrous connective tissue surrounding fascicles (groups of muscle fibers).

Endomysium

Fine areolar connective tissue surrounding each muscle fiber.

Sarcolemma

Plasma membrane of a muscle fiber.

Sarcoplasm

Cytoplasm of a muscle fiber.

Myofibrils

Contractile elements in muscle fibers; chains of sarcomeres.

Neuromuscular Junction

The synapse between a somatic motor neuron and a skeletal muscle fiber.

Acetylcholine (ACh)

A neurotransmitter released at the neuromuscular junction to stimulate muscle contraction.

Role of Calcium (Ca2+) in Muscle Contraction

Calcium binds to troponin, moving tropomyosin away from active sites and allowing cross-bridge cycling.

Sarcomere Anatomy

Contains thick (myosin) and thin (actin) filaments, Z-discs, A bands, and H zones.

Thick Filaments

Composed of myosin; myosin heads form cross-bridges with actin.

Thin Filaments

Composed of actin, tropomyosin, and troponin; contains myosin binding sites.

Excitation-Contraction Coupling

The process that converts an electrical stimulus into a mechanical response in muscle fibers.

Aerobic Exercise

Requires oxygen, increases muscle capillaries and mitochondria, produces 36 ATP per glucose.

Anaerobic Exercise

Does not require oxygen, increases muscle glycogen stores, produces 2 ATP per glucose.

Factors Influencing Force of Contraction

Number of muscle fibers stimulated, size of fibers, frequency of stimulation, and length-tension relationship.