Muscle Tissue Physiology and Pathophysiology Review

A complete vocabulary set covering muscle tissue types, fiber classifications, connective tissue coverings, pathological conditions, structural properties, and sarcomere components from the lecture transcript.

Slow Oxidative Muscle Fibers

Muscle fibers that facilitate long-duration, low-intensity postural activities such as standing during a ten-hour shift.

Fast Oxidative Muscle Fibers

Muscle fibers used for moderate-duration, aerobic activities such as hiking or running a mile.

Fast Glycolytic Muscle Fibers

Muscle fibers adapted for short-burst, high-intensity movements such as jumping and sprinting.

Muscular Dystrophy

A group of inherited diseases characterized by muscle fibers being replaced by fat and connective tissue, causing a progressive loss of contractile ability.

Duchenne Muscular Dystrophy

The most common type of muscular dystrophy; an X-linked progressive disease caused by a lack of the functional protein dystrophin.

Dystrophin

A protein that links the sarcolemma to the extracellular matrix of muscle; its absence disrupts calcium release mechanisms and compromises muscle contraction.

Fibromyalgia

A musculoskeletal disorder characterized by widespread pain and extreme tenderness at specific body points, often accompanied by fatigue, sleep disturbances, headaches, and chronic pain linked to mental health factors.

Fibromyalgia Diagnostic Criterion

A clinical finding where a patient experiences pain upon palpation in at least $11$ out of $18$ designated tender points on the body.

Sarcolemma

The plasma membrane surrounding a muscle fiber cell.

Four Core Properties of Muscle

The fundamental characteristics of muscle tissue summarized as $E^3C$: Excitability, Extensibility, Elasticity, and Contractility.

Contractility

The muscle property that allows myofilaments to slide past each other to generate physical force and shorten the tissue.

Excitability

The ability of muscle tissue to receive a neural signal and propagate electrical impulses along its sarcolemma.

Extensibility

The muscle property that permits tissue to stretch or extend without damage when an opposing muscle contracts.

Elasticity

The muscle property that allows tissue to change shape during movement and rebound to its original resting length.

Internal Sphincters

Passageway valves made of smooth muscle that operate under involuntary autonomic control.

External Sphincters

Passageway valves composed of skeletal muscle that are managed under voluntary conscious control.

Skeletal Muscle Tissue

Voluntary, striated muscle tissue attached to bones that makes up approximately 40\text{\null} of total body weight and contains peripheral nuclei in mature fibers.

Cardiac Muscle Tissue

Involuntary, striated muscle tissue found in the heart containing unique intercalated discs that spread nerve impulses evenly across cells.

Intercalated Discs

Specialized junctional structures unique to cardiac muscle that facilitate the uniform transmission of electrical impulses across heart cells.

Smooth Muscle Tissue

Involuntary, non-striated muscle tissue found in the walls of hollow internal organs, blood vessels, respiratory airways, and the digestive tract.

Mesodermal Cells

Embryonic stem cells that differentiate to form developing muscle fibers.

Young Muscle Fibers

Immature muscle fibers characterized by a lack of striations and centrally located nuclei arranged in a straight row.

Mature Muscle Fibers

Fully developed muscle fibers displaying distinct striations, a fully formed sarcolemma, and nuclei located at the periphery of the cell.

Epimysium

The outermost layer of areolar connective tissue surrounding an entire individual muscle.

Perimysium

The connective tissue sheath that surrounds bundles of muscle fibers known as fascicles.

Endomysium

The delicate connective tissue layer that surrounds each individual muscle fiber within a fascicle.

Myofilaments

Protein filaments inside myofibrils consisting of thick myosin fibers and thin actin fibers.

Contractile Proteins

Actin and myosin, the main structural proteins that physically slide past one another to shorten the sarcomere during muscle contraction.

Regulatory Proteins

Troponin and tropomyosin, which regulate muscle contraction by masking or unmasking myosin-binding sites on actin in response to calcium.

Sarcomere

The functional contractile unit of a myofibril, defined as the region bounded between two adjacent Z-lines (Z-discs).

A Band

The dark central region of a sarcomere spanning the full length of thick myosin filaments along with regions of overlapping thin actin filaments, maintaining a constant length during contraction.

H Zone

The central portion of the A band consisting strictly of thick myosin filaments, which disappears as thin filaments slide inward during muscle contraction.

I Band

The light region of a sarcomere composed exclusively of thin actin filaments, which narrows or gets smaller during contraction.

M Line

A central structural line in the middle of the H zone consisting of tiny protein rods that anchor thick myosin filaments in place.

Sarcoplasmic Reticulum

A specialized smooth endoplasmic reticulum wrapped around myofibrils that stores and releases calcium ions required for contraction.

Transverse Tubule (T-tubule)

Deep invaginations of the sarcolemma that conduct electrical energy into the muscle cell interior to stimulate calcium release.

Terminal Cisterns

Expanded end-sacs of the sarcoplasmic reticulum located directly adjacent to transverse tubules.

Triad

A structural grouping formed by one central T-tubule flanked on both sides by terminal cisterns of the sarcoplasmic reticulum.