BIO 137: Unit 3 Lecture Exam Study Guide - Muscle Tissue & The Muscular System

Comprehensive vocabulary flashcards reviewing muscle histology, contraction mechanisms, fiber types, functional arrangements, and clinical applications for BIO 137 Unit 3.

Extensibility

The muscular tissue property that allows muscle to stretch without sustaining damage.

Epimysium

The outermost layer of connective tissue that encircles an entire skeletal muscle.

Perimysium

The connective tissue layer that surrounds individual muscle fascicles.

Endomysium

The innermost connective tissue layer that wraps individual skeletal muscle fibers.

Terminal cisterns of the sarcoplasmic reticulum

The specific storage regions of the sarcoplasmic reticulum from which calcium ion release begins during skeletal muscle contraction.

Dystrophin

A structural protein that reinforces the sarcolemma and transmits tension generated by muscle fibers to tendons.

M line

The midline of the sarcomere toward which thin filaments are pulled during muscle contraction.

Creatine phosphate

An immediate energy source that, along with stored ATP, supports maximal muscle contraction for approximately $15\,\text{seconds}$.

Anaerobic cellular respiration (glycolysis)

The metabolic ATP source that suffices to power vigorous muscular activity, such as running in place, for approximately $1\,\text{minute}$.

Motor unit

A functional unit of contraction consisting of a single somatic motor neuron and all the muscle fibers it innervates.

Twitch contraction

A brief contraction of all muscle fibers in a motor unit in response to a single action potential.

Intercalated discs

Microscopic structures unique to cardiac muscle containing gap junctions and desmosomes that enable coordinated syncytial contraction and autorhythmicity.

Cross-bridge formation

The attachment event that occurs when an energized myosin head binds to an exposed site on actin.

Slow oxidative fibers

Fatigue-resistant muscle fibers predominantly found in leg muscles that are specialized for maintaining posture and endurance.

Titin

An elastic filament extending from the M line to the Z disc that stabilizes thick filaments and provides recoil.

Myosin

The motor protein present in all muscle types that pulls actin filaments to generate tension.

Motor unit recruitment

The process of increasing the number of active motor units to generate a stronger overall muscle contraction.

Fast glycolytic fibers

Muscle fibers specialized for rapid, explosive power that are present in high percentages in world-class shot-putters.

Smooth muscle tone

A state of continuous, long-term partial contraction maintained by the prolonged presence of calcium ions in the cytosol.

Muscular dystrophy

A genetic muscle disorder characterized by little or no structural proteins (such as dystrophin) supporting the sarcolemma.

Fused (complete) tetanus

A sustained, maximal contraction in which individual twitches cannot be distinguished and all fibers in a muscle contract fully.

Concentric contraction

A type of isotonic muscle contraction in which tension is generated while the muscle shortens (e.g., pulling the body upward during a pull-up).

Eccentric contraction

A type of isotonic muscle contraction in which the muscle lengthens under active tension (e.g., lowering the body during a pull-up).

Isometric contraction

A muscular contraction that develops tension without changing the overall length of the muscle (e.g., holding a position or hanging).

Muscle hypertrophy

An enlargement of skeletal muscle tissue resulting from an increase in the number of myofibrils per cell rather than an increase in cell count.

Muscle cramp

A painful, sustained involuntary contraction caused by prolonged relaxation during fatigue.

Oxygen debt

Heavy post-exercise breathing that serves to convert lactic acid, replace myoglobin-bound $O_2$, and resynthesize creatine phosphate.

Acetylcholinesterase

An enzyme located in the synaptic cleft that rapidly degrades acetylcholine to ensure its effect on the motor end plate is brief.

Origin

The site of tendon attachment of a skeletal muscle to a stationary bone.

Insertion

The site of tendon attachment of a skeletal muscle to the movable bone that is pulled during contraction.

Agonist

The prime mover muscle that produces the majority of the force for a specific action.

Circular fascicle arrangement

A concentric arrangement of muscle fascicles that surrounds and controls the opening and closing of body orifices (e.g., sphincters).

First-class lever

A lever category exemplified by head nodding (flexion and extension of the head at the neck).

Strain

A slight or partial tear occurring within a muscle or its tendon (such as the calcaneal tendon), distinct from a ligamentous sprain.