Skeletal Muscle Function and Physiology

Flashcards covering key functions, structures, and concepts related to skeletal muscle physiology.

Functions of Skeletal Muscle

Movement of bones, maintain posture, support soft tissues, guard body openings, maintain temperature (heat from contractions), store nutrients (glycogen).

Skeletal Muscles

Attached to bones, voluntary muscles.

Cardiac Muscle

Found in the heart, involuntary.

Smooth Muscle

Found in walls of hollow organs (stomach, bladder, intestines), involuntary.

Excitability

Ability of muscle fibers to respond to signals.

Contractility

Ability of muscle fibers to shorten and create movement.

Extensibility

Ability of muscle fibers to stretch without damage.

Elasticity

Ability of muscle fibers to return to original shape after stretching.

Myofibrils

Thread-like structures with a contractile function in muscle fibers.

Sarcoplasmic Reticulum

Membranous sacs that encircle myofibrils and store calcium ions.

Tendon

Connective tissue formed by merging epimysium, perimysium, and endomysium, connects muscle to bone.

Myoblast

Immature muscle cells that fuse to form muscle fibers, found during embryonic development.

Sarcolemma

Membrane of a muscle cell.

Sarcoplasm

Cytoplasm of a muscle cell.

Transverse Tubules (T Tubules)

Carry electrical signals inside muscle fibers.

A Band

Region of muscle fiber that contains thick filaments (myosin).

I Band

Region of muscle fiber with thin filaments (actin).

Z Line

Boundary between sarcomeres in a muscle fiber.

Striations

Stripes seen under a microscope due to the arrangement of filaments in muscles.

Myosin

Thick filament in muscle contraction; consists of protein molecules with heads and tails.

Actin

Thin filament in muscle contraction that has active sites for myosin binding.

Troponin

Small protein that moves tropomyosin away from actin binding sites when calcium binds.

Tropomyosin

Protein that covers myosin-binding sites on actin in relaxed muscles.

Muscle Contraction

Occurs when myosin heads attach to actin, forming cross-bridges, leading to the shortening of the muscle fiber.

Calcium in Muscle Contraction

Triggers muscle contraction by binding to troponin, causing tropomyosin to shift and expose binding sites on actin.

Neuromuscular Junction (NMJ)

The connection between a motor neuron and a muscle fiber.

Acetylcholine (ACh)

Neurotransmitter that transmits the signal from the neuron to the muscle at the NMJ.

Motor Unit

A motor neuron and all the muscle fibers it controls.

Recruitment

Activating more motor units to increase the strength of a muscle contraction.

Aerobic Metabolism

Uses oxygen to produce ATP in the mitochondria; best for endurance.

Anaerobic Glycolysis

Breaks down glucose without oxygen to produce ATP; leads to lactic acid buildup.

Creatine Phosphate

Acts like a backup energy source for ATP production.

Cori Cycle

The recycling of lactic acid from muscles back into glucose in the liver.

Hypertrophy

Growth or enlargement of muscle fibers due to frequent and intense use.

Atrophy

Shrinking or wasting away of muscles due to lack of use or nerve supply.

Muscular Dystrophy

Genetic disease causing progressive muscle weakness due to muscle fiber breakdown.

Myasthenia Gravis

An autoimmune disorder where ACh receptors are attacked, leading to muscle weakness.

Amyotrophic Lateral Sclerosis (ALS)

A nerve disease that leads to muscle weakness and atrophy due to motor neuron death.

Tetanus

Bacterial toxin-induced continuous muscle contractions, potentially life-threatening.

Botulism

A toxin that blocks ACh release at the NMJ, preventing muscle contraction.