Muscular System: Histology & Physiology

Practice vocabulary flashcards covering skeletal muscle anatomy, histological structures, the neuromuscular junction, and muscle physiology based on the lecture notes.

Epimysium

Layer of dense collagen that surrounds skeletal muscle.

Fascicle

A bundle of muscle fibers surrounded by perimysium.

Perimysium

Connective tissue layer around fasiculi.

Endomysium

Connective tissue that surrounds individual muscle fibers, is interwoven with perimysium, and contains blood vessels.

Sarcolemma

The plasma membrane of a muscle cell.

Sarcoplasmic reticulum

Structure surrounding the myofibril that releases calcium; its terminal cisternae store calcium.

Transverse (T) tubule

Tubelike invaginations of the sarcolemma that conduct action potentials.

Sarcomere

The basic contractile unit inside the muscle fiber or cell, extending from Z disk to Z disk.

Myosin

The protein that composes thick filaments in the sarcomere.

Tropomyosin

A protein that blocks the attachment site for the myosin crossbridge in a relaxed muscle, preventing contraction.

Troponin

Protein attached to tropomyosin that binds to $Ca^{2+}$, causing a shape change that removes the blocking action of tropomyosin.

Titin

Elastic chains of amino acids that stretch from the Z disk to the M line, stabilizing contractile filaments and providing elasticity.

Nebulin

A giant protein lying next to thin filaments and attached to the Z disk that helps align actin filaments.

Z disk

A filamentous network of protein that serves as an attachment for actin filaments.

Acetylcholine (ACh)

A neurotransmitter released by a neuron to change the permeability or properties of another cell's plasma membrane.

Acetylcholinesterase (AChE)

An enzyme that breaks down Acetylcholine ($ACh$) into acetic acid and choline.

Excitation-Contraction Coupling

The process of transferring an electrical stimulus into a mechanical response.

Muscle Twitch

A single stimulus-contraction-relaxation cycle in a muscle fiber.

Treppe

A graded response that occurs in muscle rested for a prolonged period.

Motor unit

Comprised of a single motor neuron and all the muscle fibers it controls.

Myoglobin

A protein used for $O_2$ storage inside muscle cells that contains iron and has a higher oxygen affinity than hemoglobin.

Isotonic Contraction

Contraction with the same tension but changing length; includes concentric (shortens) and eccentric (lengthens) movements.

Isometric Contraction

Contraction where the muscle pulls forcefully against a load but stays the same length with no movement.

Slow-twitch fibers

Muscle fibers also known as Type I or red fibers, characterized by a high density of mitochondria and high resistance to fatigue.

Fast-twitch fibers

Muscle fibers also known as Type II-B or white fibers, characterized by large diameter, high tension, and low fatigue resistance.