Skeletal Muscle Organisation

Layers of skeletal muscle

Epimysium, perimysium, endomysium

Define epimysium

Surrounds muscle, maintains structural integrity when contracting and separates muscle from other organs and tissue in the area

Define perimysium

Surrounds fascicles, fascicle organisation allows nervous tissue to trigger a specific movement in the muscle, activates a subset of muscle fibres within a fascicle

Define endomysium

Surrounds each muscle fibre, contains ECF and nutrients for muscle fibre

Define satellite cell

Stem cells that allow growth of skeletal muscle, located under epimysium but outside of muscle fibres

Define fascicle

Functional unit where a group of muscle fibres work together

Define muscle fibre

Myoblast cells fused together to for one long, multinucleated cell

Define myofibril

Contractile cells - long and run parallel

Define myofilaments

Thin actin and thick myosin filaments and elastic titin filaments - long tubular structures within myofibrils

Function of muscle fibres

Controls production of proteins and enzymes needed for muscle contraction due to large number of nuclei

Define sarcolemma

Cell membrane around myocyte

Define sarcoplasm

Cytoplasm in muscle cells, surrounds myofibrils and other structure/organelles

Define transverse tubules

Invaginations - where the cell membrane is pushed down into the interior of cell, run along the length of muscle cells, have ecf and ensure action potential gets deep into muscle cell so that myofibril can contract

Define sarcoplasmic reticulum

Highly specialised ER that stores, released and retrieves calcium ions

Define sarcomere

Function unit of skeletal muscle where contraction occurs, highly organised arrangement of actin and myosin, runs from one z line to another z line

Describe myofibril structure

Bundles of myofilaments, organised structure makes it striated, myofilaments anchored to cell membrane of muscle cell - when they contract the whole cell shortens

Sarcomere structure

Actin is attached to the z line, myosin is attached to the m line
Myosin grips onto actin, pulls actin towards the m line on the left and right, causes sarcomere to shorten - contraction