Question 1

In skeletal muscle,which protein is PRESENT in the I-band but ABSENT from the H-band?&#10;A) Actin&#10;B) Creatine kinase&#10;C) Desmin&#10;D) Myosin&#10;E) Titin

Accepted Answer

Actin is present in the I-band but absent from the H-band in skeletal muscle. Myosin is present in both the I-band and H-band, while desmin and creatine kinase are not specific to any particular band. Titin is present in both I-band and H-band but is not a protein.

Question 2

Cardiac muscle can be distinguished from skeletal muscle because cardiac muscle:&#10;A) Forms muscle fibers with larger diameters than those of skeletal muscle&#10;B) Has 15 to 20 nuclei per muscle fiber (cell)&#10;C) Lacks intercalated disks&#10;D) Lacks striations&#10;E) Possesses a nucleus located in the center of each muscle fiber

Accepted Answer

Cardiac muscle fibers have a single nucleus located centrally within each cell, distinguishing them from skeletal muscle fibers, which typically have multiple nuclei located peripherally.

Question 3

The function of the protein,dystrophin,is to:&#10;A) Anchor actin filaments to the plasma membrane&#10;B) Conduct an action potential to the sarcoplasmic reticulum&#10;C) Form regular arrays of actin filaments within the I-band&#10;D) Regulate the binding of myosin to actin&#10;E) Transport calcium into t-tubules

Accepted Answer

Dystrophin is a cytoskeletal protein that anchors actin filaments to the plasma membrane in muscle cells. This helps to provide structural stability to the muscle fibers during muscle contraction. Mutations in the dystrophin gene can lead to muscular dystrophy, a disease characterized by progressive muscle weakness and wasting.

Question 4

The dense bodies found in smooth muscle cells are functionally and anatomically analogous to which structure found in skeletal muscle cells?&#10;A) A-band&#10;B) Intercalated disks&#10;C) Mitochondria&#10;D) Sarcoplasmic reticulum&#10;E) Z-line

Accepted Answer

The dense bodies found in smooth muscle cells serve as attachment points for actin filaments, similar to how the Z-lines in skeletal muscle cells serve as attachment points for actin filaments. Therefore, the correct answer is E) Z-line.

Question 5

Nervous stimulation of skeletal muscle results in a wave of depolarization along the plasma membrane.This electrical signal is carried into the interior of the muscle cell via the membranes of the:&#10;A) Intercalated disks&#10;B) Nuclear envelope&#10;C) Sarcomere&#10;D) Sarcoplasmic reticulum&#10;E) T-tubules

Accepted Answer

The T-tubules, or transverse tubules, are invaginations of the plasma membrane that penetrate deep into the muscle cell. They allow the depolarization signal to reach the sarcoplasmic reticulum, which then releases calcium ions to initiate muscle contraction. The intercalated disks are found in cardiac muscle, the nuclear envelope surrounds the nucleus and is not directly involved in muscle contraction, and the sarcomere is the basic contractile unit of muscle but does not directly transmit electrical signals.

Question 6

The stem cells of muscle,which multiply and differentiate into muscle fibers to repair damaged muscle,are called:&#10;A) Intercalated cells&#10;B) Myoepithelial cells&#10;C) Pericytes&#10;D) Satellite cells&#10;E) Schwann cells

Accepted Answer

The stem cells of muscle that are responsible for repairing damaged muscles by multiplying and differentiating into muscle fibers are called satellite cells.

Deck 4: Muscle Tissue