Ch 9A

The region between which two points corresponds to the entire A (dark) band?

2 and 6 The A band, also know as the dark band, is occupied by the entire length of thick myofilaments.

Both actin and myosin are found in the __________

A band

The myosin filaments are located in the __________

A band

The ______ contains only the actin filaments

I band

The thicker filaments are the _________ filaments

Myosin

Which of the following statements is true?

Skeletal muscle cells are long and cylindrical with many nuclei

Which organelle can chemically regulate the shortening of the muscle?

The sarcoplasmic reticulum

What is the role of tropomyosin in skeletal muscles?

Tropomyosin serves as a contraction inhibitor by blocking the myosin binding sites on the actin molecules

In the muscles of the limbs, the origin is usually the immobile muscle attachment.

True In the muscles of the limbs the insertion is pulled toward the immobile origin

A sarcomere is the distance between two z discs________

Z discs

What is the functional unit of a skeletal muscle called?

a sarcomere

Which description is most appropriate for a myofibril?

a single long, thin organelle containing many proteins A fibril is a very small, fiber-like structure. Since muscle cells are called muscle fibers, the myofibrils are the smaller, fiber-like organelles within a muscle fiber.

The sliding filament model of contraction involves ________.

actin and myosin sliding past each other and partially overlapping

During muscle contraction, myosin cross bridges attach to which active sites?

actin filaments

A muscle fiber represents which organizational level of anatomy?

cellular level Muscle fibers are simply muscle cells. But muscle cells are unique in many ways, and they are often very long, which is why they are described as fibers.

Myofilaments represent which organizational level of anatomy?

chemical level The chemical level of anatomy refers to the atoms and molecules that make up the parts of the body. Myofilaments are protein structures. Proteins are large molecules.

The sliding filament model of contraction states that __________.

during contraction, the thin myofilaments slide past the thick myofilaments so that the actin and myosin myofilaments overlap to a greater degree The sliding filament model of contraction states that during contraction, the thin myofilaments slide past the thick myofilaments so that actin and myosin myofilaments overlap to a greater degree. In a relaxed muscle fiber, the thick and thin myofilaments overlap only at the ends of the A band.

Although all the anatomical parts of muscle work together to give it its characteristics, which of the following proteins listed below would be most associated with the characteristics of extensibility?

elastic (titin) filaments

Which of the following surrounds the individual muscle cell?

endomysium

What is the functional role of the T tubules?

enhance cellular communication during muscle contraction

Which membrane surrounds the others?

epimysium Epi means "over," "above," or "outer." Epimysium, therefore, is the outermost membrane

Muscle tissue can be stimulated by the nervous system. Cells with the ability to change their membrane potential have what property?

excitability Excitability, also termed responsiveness, is the ability to receive and respond to a stimulus. For example, skeletal muscle contracts in response to receiving chemical stimulation from the central nervous system

What level of structural organization do voltage-gate sodium channels in muscle in muscle sarcolemma represent?

molecule

During development embryonic cells will fuse to form muscle fibers. This will result in ________.

multinucleated muscle fibers that can extend as long as 30 centimeters

Which term best identifies a muscle cell?

muscle fiber Skeletal muscle cells fuse during development to form the mature, multinucleated muscle fibers.

The contractile units of skeletal muscles are ________.

myofibrils

Approximately 80% of a muscle fiber's volume are the myofibrils. This characteristic reflects muscles ability to ________.

produced movement through contractile force

What is the function of the filaments found in ranges 1-2 and 6-7 but no other ranges?

protection from overstretching Elastic (titin) filaments help to protect the muscle from overstretching and also aid in returning it to normal length.

The __________ shorten(s) during muscle contraction

sarcomere As actin slides over myosin, the z lines are pulled closer together, shortening the sarcomere.

What structure in skeletal muscle cells functions in calcium storage?

sarcoplasmic reticulum

Which of the following is NOT a normal function of muscle tissue?

secreting hormones Secreting hormones is a function of the endocrine system.

Muscle tissue has all of the following properties except ________.

secretion

Which type of muscle requires voluntary nervous stimulation for activation?

skeletal In order to contract, skeletal muscle fibers must be voluntarily stimulated by the nervous system. The site of muscle stimulation, where the nerve fiber communicates with the muscle fiber, is called the neuromuscular junction.

Of the following items listed below, which is the best description for why skeletal muscle stores glycogen.

skeletal muscle is a heavy consumer of energy

Which of the following are correctly paired?

skeletal muscle; voluntary control Skeletal muscle is under voluntary control

Myoglobin_____________.

stores oxygen in muscle cells

What is the most distinguishing characteristic of muscle tissue?

the ability to transform chemical energy into mechanical energy to move the body

Based on what you know of the relationship between the thick and the thin filaments, what would happen if a disorder existed that caused a person to produce no tropomyosin?

the muscle tissues would never be able to relax The tropomyosin covers the myosin binding site on actin. Without tropomyosin, the myosin would constantly have access to those binding sites.

Which of the following regions best identifies where myosin would have maximum cross-bridge access to actin?

the region between 2 ad 3 Actin and myosin are components of thin and thick filaments, respectively. The region between points 2 and 3 includes the area of overlap between thin and thick filaments.

The contractile, or functional, unit of a muscle fiber is __________.

the sarcomere The sarcomere is the contractile unit of a muscle fiber and the smallest functional unit of muscle. A sarcomere is the region of a myofibril between two successive Z discs; it primarily consists of thin and thick myofilaments.

An increase in the calcium ion level in the sarcoplasm starts the sliding of the thin filaments. When the level of calcium ions declines, sliding stops.

true

One of the important functions of skeletal muscle contraction is production of heat.

true

When a muscle fiber contracts, the I bands diminish in size, the H zones disappear, and the A bands move closer together but do not diminish in length

true