Muscle Cell Structure and Contraction

Practice flashcards covering muscle fiber specializations, organelle functions, sarcomere organization, and the sliding filament mechanism based on the lecture.

What is the primary function of T-tubules in a muscle fiber?

They carry electrical signals deep into the cell to trigger the release of calcium from the sarcoplasmic reticulum.

What structure stores and releases calcium into the sarcoplasm to facilitate muscle contraction?

The sarcoplasmic reticulum.

How does calcium trigger filament interaction during muscle contraction?

Calcium binds to proteins on the myofilaments, changing their conformation so that one filament can bind to the other and pull it toward the middle.

What are two alternative names for muscle cells?

Muscle fibers and myofibers.

Why do muscle cells contain multiple nuclei throughout the cell?

To provide the genetic code needed for protein synthesis anywhere in the cell.

What two main ingredients are required by mitochondria in muscle cells to produce ATP?

Glucose and oxygen.

What is the role of glycosomes within muscle fibers?

They store enzymes responsible for breaking down glycogen into readily accessible glucose molecules.

What is the function of myoglobin in muscle cells?

It stores oxygen inside the muscle cells.

According to the lecture, what wraps around the muscle fiber directly above the sarcolemma?

Endomycin.

What are myofibrils, and what are the two main myofilaments that compose them?

Myofibrils are protein bundles inside muscle fibers, composed primarily of actin and myosin filaments.

What is the contractile unit of a muscle, defined as the distance between two Z discs?

The sarcomere.

How does the Z disc appear when viewed on a histology slide of muscle tissue?

It appears as the darkest line or feature on the slide.

Which region of the sarcomere appears as the lightest area on a histology slide and contains only actin?

The I band.

What is the M line?

The line located at the very center of a sarcomere toward which actin filaments are pulled.

What is the H zone, and what happens to it during a full muscle contraction?

It is the region on either side of the M line containing only myosin with no actin overlap; it narrows and completely disappears during full contraction.

Which band represents the entire span of myosin and never changes its length during contraction?

The A band.

What is the function of disconnectin (also known as elastic filament or titin)?

It anchors and helps hold the myosin filament to the Z disc.