Muscular system

myofibril

long, cylindrical organelle that runs parallel within the muscle fiber and contains sarcomeres.

sarcolemma

plasma membrane of a skeletal muscle fiber

fascicle

bundle of skeletal muscle fibers surrounded by perimysium

mitochondrion

location of cellular respiration, makes ATP for muscle contractions

Sarcomere

Region from one z disc to the next z disc, is the smallest functional unit of a skeletal muscle fiber

A band

composed of thick filaments containing myosin

I band

Contain thin actin filaments

Sarcoplasmic reticulum

Specialized smooth endoplasmic reticulum, which stores, releases, and retrieves Ca++

Thick Filament

Thick myosin strands and their multiple heads projecting from the center of the sarcomere toward, but not all the way to the z disc

What is the sliding filament theory

When a sarcomere shortens, the z disk moves closer together, and the i band becomes smaller. The A band stays the same width. At full contraction, the thin and thick filaments have the most amount of overlap

Perimysium

Later is connective tissue surrounding the fascicle of a muscle

Epimysium

coarse, irregular connective tissue that surrounds the whole muscle

Endomysium

delicate connective tissue that surrounds the sarcolemma of a muscle cell

Muscle fiber

a single long cylindrical muscle cell that acts as the building block of a muscular tissue

Sliding filament theory what happens first to last

signal travels down the motor neuron, calcium released from sarcoplasm, actin changes shape, cross bridges form, ATP creates a power stroke, shortening actin filament