Muscle Physiology Quiz

Skeletal and Cardiac Muscles

• Skeletal muscles have light and dark stripes.
• Cardiac muscles have light and dark stripes.

Sliding Filament Model

• The sliding filament model of contraction involves actin and myosin sliding past each other but not shortening.

Proteins

• Tropomyosin is a long, fibrous protein that winds around the actin polymer, blocking all the myosin-binding sites.
• Myoglobin is a protein that holds a reserve supply of oxygen in muscle cells.
• Troponin is a regulatory protein that moves tropomyosin aside and exposes myosin binding sites when Ca+ is released during muscle contraction.

Muscle Structure

• The sarcoplasmic reticulum is an elaborate network of membranes in skeletal muscle cells that functions in calcium storage.
• Sarcoplasm is the cytoplasm of a striated muscle fiber.
• The neuromuscular junction is the point of contact between a motor neuron and a skeletal muscle cell.
• A fascicle is a bundle of skeletal muscle cells.
• Muscle fibers are grouped into fascicles, which form skeletal muscles.

Muscle Characteristics

• Glycogen is a complex carbohydrate consisting of stored glucose molecules in skeletal muscles; breaks down to release glucose when it is needed for energy.
• Muscle types can be classified as:
  • Cardiac: forms most of the heart, exhibits autorhythmicity, and has a striped appearance.
  • Skeletal: has a striped appearance, voluntary, and forms the walls of hollow internal structures.
  • Smooth: involuntary, forms the walls of hollow internal structures.

Muscle Contraction

• The contractile unit of muscle is the sarcomere.
• The ability of an electrical impulse to stimulate a muscle cell to contract is called excitability.
• The ability of muscle cells to shorten and generate a pulling force is called contractility.
• The ability of muscle cells to recoil after being stretched is called elasticity.
• The ability of muscle cells to be stretched back to its original length by contraction of an opposing muscle is called extensibility.
• Cross bridges are the connections of a myosin head group to an actin filament during muscle contraction.

Muscle Function

• The function of the sarcoplasmic reticulum is to store calcium.
• The function of skeletal muscle is to move bones.
• Acetylcholine (ACh) is the neurotransmitter for muscle contraction.
• Stored ATP is the energy needed for muscle contraction.