Week 1 (Myofibers & Muscle Fiber Types)

Myofiber

A muscle cell that functions to produce force and heat.

What Factors affect Myofiber diameter

Age, genetics, nutrition, diseases, and training.

What is the relationship between myofiber diameter and force production?

A bigger diameter results in a bigger force.

Factors affecting Myofiber length

Age, genetics, and the specific skeletal muscle.

What affects maximal speed of shortening in muscle fibers?

The length of the muscle fiber.

Effects of higher absolute length in muscles

Higher possibility of length change, higher velocity/speed, and greater concentric/contraction force produced.

Key proteins in muscle contraction

Myosin is heavily important for the force or movement of muscle fibers.

Type I muscle fibers

Slow contraction fibers with high mitochondria, myoglobin, capillary density; and low glycolytic enzymes.

Myosin heavy chain type I

MHC is a motor protein that uses the energy from ATP hydrolysis to power muscle contraction. This one specifically is associated with Type I muscle fibers that perform slowly.

Type IIa muscle fibers

Moderate contraction fibers with high mitochondria, myoglobin, and capillary density; and high glycolytic enzymes.

What distinguishes Type IIx muscle fibers?

They are the fastest type of muscle fibers with low mitochondria and myoglobin.

Myoglobin function in muscle fibers

It helps store oxygen for muscle metabolism.

What type of enzymes are involved in glycolysis?

Glycolytic enzymes are responsible for breaking down glucose for energy.

Role of capillaries in muscle fiber function

They supply oxygen and nutrients to muscle fibers and remove waste.

What is the sarcomere?

The sarcomere is the basic contractile unit of muscle fiber.

What proteins compose the sarcomere?

Each sarcomere is composed of two main protein filaments—actin and myosin.

What is the function of actin and myosin in muscle fibers?

Actin and myosin are the active structures responsible for muscular contraction.