Muscle Performance, Physiology, and Development Flashcards

Vocabulary practice flashcards covering muscle performance, exercise adaptations, cardiac muscle structures, smooth muscle physiology, and muscle development and regeneration.

Hypertrophy

The process in which structural proteins are added to muscle fibers, increasing cell diameter and total muscle mass.

Atrophy

The loss of structural proteins from muscle fibers, resulting in decreased muscle mass and cell diameter.

Sarcopenia

Irreversible age-related muscle atrophy where dying muscle fibers are replaced by non-contractile connective tissue and adipose tissue.

Myoglobin

An oxygen-storing protein found in the sarcoplasm that supplies oxygen to mitochondria for aerobic respiration.

Angiogenesis

The formation of more extensive capillary networks around muscle fibers in response to endurance exercise to deliver oxygen and remove wastes.

Anabolic Steroids

Synthetic forms of testosterone that stimulate muscle formation, leading to increased muscle mass and power output.

Erythropoietin (EPO)

A hormone produced by the kidneys that triggers red blood cell production to increase oxygen availability for aerobic respiration.

Human Growth Hormone (hGH)

A supplement that promotes the healing of muscle and other tissues after strenuous exercise, reducing recovery time.

Creatine Phosphate

A high-energy molecule that provides quick bursts of ATP to muscle cells in the initial stages of contraction to enhance explosive power output.

Intercalated Disc

A specialized part of the cardiac muscle sarcolemma containing gap junctions and desmosomes that joins adjacent cardiac fibers at their ends.

Gap Junction (Cardiac)

Protein channels within intercalated discs that allow depolarizing ionic currents to pass directly between cardiac cells for electric coupling.

Desmosome

A cellular structure in intercalated discs that anchors the ends of cardiac muscle fibers together to prevent detachment during contraction.

Functional Syncytium

A continuous network of electrically connected cardiac muscle cells that contract in a synchronized, coordinated wave.

Pacemaker Cells

Specialized cardiac muscle cells that generate independent electrical impulses to directly control heart rate.

Autorhythmicity

The inherent ability of cardiac pacemaker cells to spontaneously depolarize to threshold and fire action potentials at regular intervals.

Depolarization Plateau

A sustained period of depolarization in cardiac action potentials caused by extracellular $\text{Ca}^{++}$ entry through voltage-gated calcium channels.

Dense Body

A structure in smooth muscle fibers, analogous to Z-discs, that anchors actin thin filaments to the sarcolemma and sarcoplasmic network.

Calmodulin

A regulatory protein in smooth muscle that binds calcium ions to trigger cross-bridge formation in the absence of troponin.

Myosin Light Chain Kinase

An enzyme activated by the $\text{Ca}^{++}$-calmodulin complex that phosphorylates myosin heads so they can bind to actin in smooth muscle.

Latch-Bridges

Subset of actin-myosin cross-bridges in smooth muscle that remain linked without ATP consumption to maintain sustained muscle tone.

Varicosity

A neurotransmitter-filled enlargement along an autonomic neuron axon that releases neurotransmitters into synaptic clefts across smooth muscle.

Pacesetter Cell

A specialized cell in visceral smooth muscle that spontaneously initiates action potentials to trigger rhythmic contractions.

Single-Unit Smooth Muscle

Visceral smooth muscle tissue with fibers interconnected by gap junctions, enabling the entire sheet to contract as a unified structure.

Multiunit Smooth Muscle

Smooth muscle tissue lacking gap junctions where contractions are limited to individually stimulated cells, found in the iris and large arteries.

Stress-Relaxation Response

A mechanical response in visceral smooth muscle where stretching triggers contraction followed immediately by relaxation to allow expansion.

Hyperplasia

The division and production of new muscle cells, a process unique to smooth muscle tissue among muscle types.

Somites

Blocks of paraxial mesodermal cells flanking the neural tube during embryonic development that give rise to myoblasts.

Myoblast

An embryonic muscle-forming stem cell that migrates and fuses with other myoblasts to create a multinucleate myotube.

Myotube

A multinucleate syncytium formed by the developmental fusion of multiple myoblasts.

Satellite Cell

A stem cell positioned outside the sarcolemma of skeletal muscle fibers that facilitates repair and protein synthesis following injury or stress.

Fibrosis

The replacement of damaged or dead muscle fibers by non-contractile scar tissue, resulting in loss of power and function.

Pericyte

A specialized stem cell located along small blood vessels that allows smooth muscle tissue to regenerate and repair efficiently.