Human Functional Anatomy - Muscle and Tendon Basics

Comprehensive vocabulary flashcards covering human functional anatomy, muscle sliding filament theory, muscle architecture, and tendon biomechanics based on lecture notes.

Human functional anatomy

The study of the functional role of musculoskeletal and neurological structures in isolation and movement to better understand injury risk and physical performance.

Hierarchical structures

The classification of muscles organized like a Russian doll: Muscle, Fascicles, Muscle fibres (cells), Myofibrils, and Thick and thin filaments.

Sarcomere

The fundamental unit of muscle, measured from Z-disc to Z-disc.

Cross bridge

The attachment formed when myosin filaments attach to actin filaments.

ATP

A molecule that releases energy for myosin to pull actin inwards and binds to the myosin head to break the cross bridge.

A-band

A region in the sarcomere classified as anisotropic, meaning it is muddled and not consistent.

I-band

A region in the sarcomere classified as isotropic, meaning it is consistent and looks the same.

Actin

The thin filament in the sarcomere that is anchored to Z-lines.

Myosin

The thick filament in the sarcomere consisting of a heavy chain (head, neck, and tail) and light chains.

Cross bridge cycling

The process where myosin heads rotate, detach, recover, and then reattach to actin.

Force-velocity relation

The relationship stating that when muscles shorten faster, the maximum force that can be produced decreases.

Optimum length

The sarcomere length where the most cross bridges are bound because myosin and actin are perfectly within reach.

Ascending limb

The state of a short muscle with too much overlap, preventing the generation of high force.

Descending limb

The state of a long muscle where there is not enough overlap between actin and myosin to generate force.

Parallel elastic component (PEC)

Membranes surrounding fibres, fascicles, and whole muscles that provide passive force to stop a muscle from stretching too far.

Series elastic component (SEC)

Components including the tendon, myofilaments, and cross bridges that stretch as fibres shorten during contraction.

Concentric contraction

A muscle contraction where the force moves towards the midline.

Eccentric contraction

A muscle contraction where the force moves away from the midline and the muscle lengthens under load.

Pennate

The term used to describe the angles of fascicles in muscles, categorized as uni (one), bi (two), or multi (multiple).

Work (W)

$$W = F \times d$$

Physiological cross sectional area (PCSA)

The cross-sectional area perpendicular to the fibres; a greater angle of pennation allows for a larger PCSA for a given anatomical cross section.

Tendon hierarchy

The structural levels of a tendon: Molecule, Fibril, Fascicle, and Tendon.

Collagen

The fundamental component of a tendon, characterized by a natural wavy or crimped pattern.

Toe region

The initial part of a tendon stress-strain curve where the tendon stretches easily as collagen crimps straighten.

Linear region

The part of the stress-strain curve where collagen fibres are already straight and begin to stretch themselves, making the tendon stiffer.

Failure region

The final part of the stress-strain curve where collagen fibres break and the tendon sustains permanent structural damage.

Stress

Force change divided by cross sectional area ($N/mm^2$).

Strain

Length change divided by initial length (%).

Young's Modulus

The ratio of stress change to strain change.

Hysteresis

The energy lost during the loading and unloading cycle of a tissue, represented by the area between the curves.

Viscoelasticity

A property of tissues describing both viscous (flow-related) and elastic (self-reorganizing) behaviors, which are rate and time dependent.

Creep

Increased strain under constant stress.

Stress relaxation

Decreased stress at constant strain.