Muscle Fiber Anatomy
“Epi” - means “over or above” so epimysium refers to the membrane that covers what?
the entire muscle
Name the two types of myofilaments.
actin and myosin
A single myofibril is made up of many sarcomeres connected end-to-end forming what?
They connect end-to-end to form a long chain.
Energy Source of a Type I Fiber uses aerobic metabolism (oxidative phosphorylation) with oxygen, glucose, and fatty acids to create what?
bundles of energy called ATP
Type IIb Fibers are not actually found in humans. In humans this type of muscle fiber is called Type IIx Fibers.
Type IIb Fibers are called Type IIx Fibers in humans.
What does the term "anaerobic" mean?
"anaerobic" means it does NOT use oxygen
What is the name given to a small bundle or tight cluster of fibers (cells)?
a fascicle
Thin filaments are called what?
actin
A Bands are dark regions in a muscle cell that are made up of what?
They made up of only thick filaments called myosin.
Do Type I Fibers contract slowly, moderately fast or fast?
They contract slowly.
What is the appearance of Type IIa Fibers?
Appearance of Type IIa Fibers: Pinkish-red, due to a moderate amount of myoglobin and blood capillaries.
What does the prefix “Myo-” mean?
muscle
What do we call a long rod-like organelle inside muscle cells that cause muscles to contract?
a myofibril
The prefix “sarco-” means what?
“flesh” or “muscle”
What do we call the light colored, low density regions in a muscle cell that contains only actin filaments?
I Bands
What is another name for Type I Muscle Fibers?
Type I Muscle Fibers are also called Slow-Twitch Oxidative Fibers
Name some activities that Type IIa muscle fibers are used for.
1. Middle-Distance running
2. Brisk walking or jogging
3. Moderate swimming or biking that push past a relaxed pace.
What is another name for a muscle cell?
a muscle fiber
The term endomysium refers to the membrane the surrounds what?
the muscle fibers (cells)
What is the specific name of the cytoplasm of the muscle cell, which contains glycosomes (stored glycogen) and myoglobin (oxygen-binding protein)?
sarcoplasm
Z-Discs (Z-Lines) are the boundaries at the ends of each sarcomere where what are anchored?
where thin actin filaments anchor.
What is the function of myoglobin?
Myoglobin stores oxygen inside muscle cells. Myoglobin acts as an oxygen reserve tank in muscles.
Is the contraction speed faster in Type IIa fibers or Type IIx fibers?
The contraction speed in Type IIa fibers is fast, but the contraction speed in Type IIx fibers is even faster. the contraction speed of Type IIx fibers is categorized as rapid and forceful.
What does the term striated mean?
The term striated means that the tissue looks striped under a microscope.
The perimysium is referring to the membrane that surrounds what?
bundles of fibers called fascicles
Transverse Tubules (T-tubules) are deep sheathed tubes of the plasmalemma that carry what deep into the interior of the muscle cell?
they carry instructional electrical impulses
Explain what needs to happen to sarcomeres in order for a muscle to contract.
When thousands of sarcomeres all shorten together, they cause the myofibril to contract, which ultimately makes the whole muscle shorten.
Name some common uses of Type I Muscle Fibers in muscles.
1. Endurance Activities: Powers long-distance running, cycling, and swimming.
2. Posture Control: Helps keep the body upright and stabilizes joints during daily movement.
Is it Type IIa or Type IIx that uses both aerobic and anaerobic glycolysis to produce ATPs.
It's Type IIa that uses both. Type IIx uses only anaerobic gycolysis to produce ATPs.
Name the organization of the Muscular System, starting with the whole muscle.
Hierarchical Organization:
Whole muscle → Fascicles → Muscle fibers (cells) → Myofibrils → Myofilaments.