Muscle Tissue PPT 2 – Vocabulary on Force Regulation

Eighteen vocabulary flashcards summarizing key terms and definitions on how muscles vary their force.

Hypertrophy

Growth of existing muscle fibers by adding more thin and thick filaments, making each cell—and the whole muscle—larger and stronger.

Thin Filament

Actin-based filament in a sarcomere that is pulled by myosin heads to generate muscle force.

Thick Filament

Myosin-based filament in a sarcomere whose heads form cross-bridges with actin to create tension.

Sarcomere

The repeating contractile unit within a myofibril; its length and degree of overlap determine force output.

Spatial Summation

Increase in muscle force by activating more motor neurons, thereby turning on more muscle fibers at once.

Motor Unit

One motor neuron and all the muscle fibers it innervates; its size dictates how much force is produced when it fires.

Recruitment

The process of activating additional motor units to raise overall muscle tension and generate greater force.

Muscle Tone

Low-level, continuous contraction of muscles caused by partial activation of motor units; rises as you prepare to move and falls during deep sleep.

Temporal Summation

Increase in muscle force by delivering nerve impulses more rapidly so that twitches add together.

Incomplete Tetanus

‘Stairstep’ rise in tension when stimuli arrive quickly but allow slight relaxation between twitches; force progressively increases.

Tetanus (Physiological)

Maximum, sustained plateau of force achieved when stimuli are so rapid that the muscle cannot relax between them.

Muscle Fatigue

Decline in a muscle’s ability to generate force despite continued stimulation, due to depleted ATP, oxygen, glucose, and ion imbalances.

Length–Tension Relationship

Principle that the amount of force a muscle can produce depends on its starting sarcomere length.

Optimal Sarcomere Length

80–120 % of resting length, where thin and thick filaments overlap ideally, allowing maximal cross-bridge formation and force.

Isotonic Contraction

Type of contraction where muscle tension exceeds the load, the muscle shortens, and movement occurs—yet ATP is still consumed.

Isometric Contraction

Type of contraction where muscle tension is generated but the load is not moved; cross-bridges cycle and ATP is used without external shortening.

Neuromuscular Junction (NMJ)

Synapse between a motor neuron and a muscle fiber where neural signals trigger muscle contraction.

ATP Replenishment

Post-exercise recovery step involving rest, oxygen intake, hydration, and nutrient replacement to rebuild ATP stores and restore muscle function.