Deck 10: Muscle Tissue

Question 1

The basal lamina of a muscle fiber is part of which structure?

A) Perimysium
B) Epimysium
C) Fascia
D) Endomysium
E) Sarcoplasmic reticulum

Answer 1

Endomysium

Question 2

With the transmission electron microscope skeletal muscle fibers can be seen to contain structures called triads. What do the two lateral components of a triad represent?

A) Attachment sites for thick myofilaments
B) Sites for calcium sequestration and release
C) Sites for impulse conduction into the fiber
D) Sites for ATP production
E) Sites for synthesis of proteins to be secreted outside the cell

Answer 2

Sites for calcium sequestration and release

Question 3

Which characteristic is unique to cardiac muscle?

A) Contain centrally located nuclei
B) Striated
C) Often branched
D) Multinucleated
E) Lack T-tubules

Answer 3

Often branched

Question 4

A healthy 32-year-old man lifts weights regularly as part of his workout. In one of his biceps muscle fibers at rest, the length of the I band is $1.0 \mu \mathrm{m}$ and the $\mathrm{A}$ band is $1.5 \mu \mathrm{m}$ . Contraction of that muscle fiber results in a $10 \%$ shortening of the length of the sarcomere. What is the length of the A band after the shortening produced by muscle contraction?

A) $1.50 \mu \mathrm{m}$
B) $1.35 \mu \mathrm{m}$
C) $1.00 \mu \mathrm{m}$
D) $1.90 \mu \mathrm{m}$
E) $0.45 \mu \mathrm{m}$

Question 5

Which feature typifies T-tubules?

A) Evaginations of the sarcoplasmic reticulum
B) Sequester calcium during muscle relaxation, releasing it during contraction
C) Carry depolarization to the muscle fiber interior
D) Overlie the A-I junction in cardiac muscle cells
E) Rich supply of acetylcholine receptors

Question 6

Which characteristic is unique to smooth muscle?

A) T-tubules lie across $\mathrm{Z}$ lines
B) Each thick filament is surrounded by six thin filaments
C) Thin filaments attach to dense bodies
D) Cells are multinucleated
E) Cells have centrally located nuclei

Question 7

In one type of muscle, numerous gap junctions, desmosomes, and adherens junctions are specifically localized in which structures?

A) Myofilaments
B) Dense bodies
C) Sarcomeres
D) Neuromuscular spindles
E) Intercalated discs

Question 8

A 66-year-old man who lives alone has a severe myocardial infarction and dies during the night. The medical examiner's office is called the following morning and describes the man's body as being in rigor mortis. This state of rigor mortis is due to which one of the following?

A) Inhibition of $\mathrm{Ca}^{2+}$ leakage from the extracellular fluid and sarcoplasmic reticulum
B) Enhanced retrieval of $\mathrm{Ca}^{2+}$ by the sarcoplasmic reticulum
C) Failure to disengage tropomyosin and troponin from the myosin active sites
D) Absence of ATP preventing detachment of the myosin heads from actin
E) Increased lactic acid production

Question 9

A 5-year-old boy sustains a small tear in his gastrocnemius muscle when he is involved in a bicycle accident. Regeneration of the muscle will occur through which of the following mechanisms?

A) Dedifferentiation of muscle cells into myoblasts
B) Differentiation of muscle satellite cells
C) Fusion of damaged myofibers to form new myotubes
D) Hyperplasia of existing muscle fibers
E) Differentiation of fibroblasts to form myoblasts