Structure and Function of Exercising Muscle

Vocabulary flashcards covering muscle anatomy, sliding filament theory, motor unit recruitment, muscle fiber types, and force generation relationships from exercise physiology lecture notes.

Anatomy

The basic body structure of an organism.

Physiology

The normal operational functions of the body and its parts.

Homeostasis

The body's ability to maintain stable internal conditions.

Exercise Physiology

The study of how the body's functions change when exposed to physical activity.

Sport Physiology

A subset of exercise physiology focused on enhancing sport performance.

Exercise Genomics

Research on the role of specific genes and single-nucleotide polymorphisms (SNPs) and how they affect exercise training from one person to another.

Single-Nucleotide Polymorphism (SNP)

A genetic variation at a single nucleotide position in DNA that contributes to individual differences in response to exercise training.

Exercise Proteomics

The study of how protein content in a tissue (such as muscle) changes with exercise.

Epigenetics

The study of changes in gene expression (turning genes on/off or changing intensity) without altering the underlying DNA code.

Smooth Muscle

Involuntary muscle tissue found in blood vessels and internal organs.

Cardiac Muscle

Involuntary muscle tissue that makes up the heart.

Skeletal Muscle

Muscle tissue attached to bones or the skeleton that is under volitional (voluntary) control.

Types of Muscle

The three muscle classifications in the body: smooth, cardiac, and skeletal muscle.

Epimysium

An outer connective tissue sheath surrounding an entire muscle.

Perimysium

A connective tissue sheath that surrounds a muscle fascicle (bundle of muscle fibers).

Endomysium

A connective tissue sheath located within a fascicle that surrounds each individual muscle fiber.

Plasmalemma

A plasma membrane that surrounds each individual muscle fiber.

Motor End Plate

The specialized communication point between a motor neuron of the nervous system and a muscle fiber.

Sarcoplasmic Reticulum (SR)

A network of tubules surrounding myofibrils that stores calcium needed for muscle contraction.

Transverse Tubules (T-tubules)

Tubular structures that carry nerve impulses from the motor end plate deep into the muscle fiber to each individual myofibril.

Myofibril

A cylindrical subunit within a muscle fiber made up of repeating contractual units called sarcomeres.

Sarcomere

The basic contractile unit of a myofibril, bounded by Z-disks and comprised primarily of actin and myosin filaments.

Actin

The protein that forms thin filaments inside a sarcomere.

Myosin

The protein that forms thick filaments inside a sarcomere.

Titin

A protein filament in the sarcomere that stabilizes sarcomeres, provides increased force when muscle is stretched, and prevents overstretching.

Alpha Motor Neuron

A nerve cell body originating in the central nervous system that innervates multiple muscle fibers.

Motor Unit

A single alpha motor neuron and all of the muscle fibers it innervates.

Acetylcholine (ACh)

The neurotransmitter released at the axon terminal that depolarizes the motor end plate to generate an action potential in a muscle fiber.

Sliding Filament Theory

The concept that muscle contraction occurs when thin actin filaments are pulled past thick myosin filaments toward the sarcomere center, shortening the sarcomere and myofibril.

Type I Muscle Fibers

Slow-twitch muscle fibers that primarily use aerobic pathways to produce ATP from carbohydrates and fats, resistant to fatigue and optimal for endurance activities.

Type II Muscle Fibers

Fast-twitch muscle fibers that primarily rely on anaerobic pathways to rapidly generate higher force, but fatigue quickly.

Type IIa Muscle Fibers

Fast oxidative glycolytic (FOG) muscle fibers utilizing a combination of aerobic and anaerobic energy, best suited for short, high-intensity activities like a 400 m swim or mile run.

Type IIx Muscle Fibers

Fast glycolytic (FG) muscle fibers relying almost entirely on anaerobic energy, recruited last for short, highly explosive events like a 100 m dash.

Size Principle

The principle stating that motor units are recruited in order of motor neuron size: smaller motor neurons (Type I) are recruited first, followed by larger motor neurons (Type IIa, then Type IIx).

Concentric Contraction

A dynamic muscle contraction where the muscle generates force while shortening, resulting in joint movement.

Eccentric Contraction

A dynamic muscle contraction where the muscle generates force while lengthening or stretching, resulting in joint movement.

Dynamic Contractions

Muscle contractions that result in joint movement, including concentric and eccentric contractions.

Isometric Contraction

A muscle contraction where force is generated without a change in muscle length and without joint movement.

Length-Tension Relation

The principle that every muscle has an ideal length for producing maximal force, where excessive shortening or lengthening reduces force production.

Force-Velocity Relation

The principle stating that during concentric contractions maximal force decreases as contraction velocity increases, whereas during eccentric contractions maximal force increases as speed decreases.