VMED 5163 - Calcium Regulation of Contraction

Cross bridge binding sites on actin are hidden by tropomyosin

Why can cross bridges not be formed in the absence of calcium?

G proteins

Actin filaments are made of units known as?

300-400 globular protein subunits arranged in a double row and twisted into a helix

How is an actin filament formed and arranged?

A conformational change will cause it to move tropomyosin out of the way of cross bridge binding sites

When a muscle contracts, what is the job of troponin?

Calcium ions

What molecule causes a conformational change in troponin?

Sarcoplasmic reticulum via internal calcium storage

The calcium ions required for skeletal muscle contraction come from where?

Forms a meshwork around each myofibril

Where is sarcoplasmic reticulum located within skeletal muscle cells?

A the junction of the A-band and I-band, in contact with the T tubule

Where are terminal cistern located?

T tubules

The two terminal cisternae surround what structure of the sarcomere?

Small tubular invaginations of the muscle cell membrane; function to spread action potentials from the plasma membrane into the deeper portion of the cells

What are T tubules and what is their function?

A transverse (T) tubule surrounded by two terminal cisternae

Triads within skeletal muscle are formed by which structures?

ATP and calcium ions

The cross bridge cycle required which two molecules to proceed?