SELF EVALUATION - CHAPTER 8
CLASSIFICATION
1. Muscle fibers that contract more slowly and fatigue less readily are:
a. red fibers.
b. white fibers.
2. Cardiac-muscle cells have separations between adjacent cells known as intercalated disks.
Their function is to:a. regenerate new cells.
b. provide a location for neuromuscular junctions.
c. provide for low electrical resistance and thus facilitate depolarization from one cell to the next.
d. release Ca2+ for initiation of muscle contraction.
3. The autonomic nervous system regulates the activity of:
a. cardiac muscle only.
b. skeletal muscle only.
c. smooth muscle only.
d. both cardiac and smooth muscle.
ARRANGEMENT
4. A pelvic delivery of an unusually large calf has caused a cow to be down and unable to bring her hind legs together. Obturator nerve paralysis is suspected and the affected muscles are classified as:
a. abductors.
b. adductors.
c. extensors.
d. flexors.
5. Muscles that pull a limb toward the median plane are:
a. abductors.
b. adductors.
c. flexors.
d. extensors.
SKELETAL-MUSCLE HARNESSING
6. The skeletal-muscle harness component most intimately associated with the sarcolemma is the:
a. endomysium.
b. perimysium.
c. epimysium.
7. The part of the skeletal-muscle harness that is continuous with a tendon or an aponeurosis is the:
a. perimysium.
b. epimysium.
c. endomysium.
d. tug.
MICROSTRUCTURE OF SKELETAL MUSCLE
8. In skeletal-muscle fibers, the sarcomeres of a myofibril are in alignment with the sarcomeres of all of the other myofibrils.
a. True
b. False
9. Which one of the following is the smallest component of a skeletal muscle?
a. Sarcomere
b. Myosin
c. Myofibril
d. Muscle fiber
0. The sarcotubular system:
a. is located within muscle fibers but outside of the myofibrils.
b. is a system within each of the.myofibrils.
c. has no direct communication (openings) with extracellular fluid.
d. consists of a nerve fiber and the muscle fibers that it innervates.
11. Conduction of depolarization from the surface of a muscle fiber to its inner aspects is accomplished by the:
a. neuromuscular junction.
b. actin filaments.
c. endomysium.
d. sarcotubular system.
.2. The myofilament of skeletal muscle that is attached to the Z line is:
a. actin.
b. myosin.
c. troponin.
d. tropomyosin.
.3. For skeletal muscle, the neuromuscular junction:
a. is located on the surface at the midpoint of the muscle fiber (one for each muscle fiber).
b. releases acetylcholine when the nerve is stimulated.
c. release of chemical is facilitated by extracellular Ca2+.
d. all of the above.
SKELETAL-MUSCLE CONTRACTION
.4. Which tubule set of the sarcotubular system releases Ca2+ when depolarized, for their diffusion to the myofibrils?
a. Transverse tubules
b. Sarcoplasmic reticulum
15. What chemical substance is released from vesicles at the neuromuscular junction on the arrival of a nerve impulse?
a. Succinylcholine
b. Epinephrine
c. Acetylcholine
d. Curare
.6. Rigor mortis most probably occurs when:
a. actin and myosin are detached.
b. Ca2+ is depleted.
c. insufficient ATP is available for relaxation.
d. contraction frequency is rapid and sustained.
L7. The function of Ca2+ at the level of myofilaments is to:
a. uncover active sites on actin so that the “cocked” projections of myosin may make an attachment.
b. depolarize the muscle-fiber.membrane.
c. initiate acetylcholine release.
d. block pores to prevent Na+ inrush.
8. What chemical begins the depolarization of skeletal-muscle fibers after a nerve impulse initiates its release?
a. Ca2+
b. Acetylcholine
c. Succinylcholine
d.
Acetylcholinesterase.9. After depolarization of the sarcoplasmic reticulum, what chemical is released that initiates the contraction process?
a. ATP
b. Tropomyosin
c. Ca2+
d. ACh
:0. Increased muscle strength associated with tetany is an example of:
a. wave summation.
b. motor-unit summation.
c. Clostridium tetani neurotoxin activity.
»1. Myosin cross-bridge heads detach from actin active sites when the cross-bridge heads bind:
a. Ca2+.
b. ATP.
c. creatine phosphate.
d. ADP + Pi.
:2. Rigor mortis is an example of_______, which results from a depletion of______ and a failure
of cross-bridge heads to______ to/from actin. (Select choice below that has respective words
for the blanks above.)
a. Contraction; Ca2+; attach
b. Relaxation; Ca2+; attach
c. Contracture; ATP; detach
d. Contraction; ATP; detach
:3. The Ca2+ released from the sarcoplasmic reticulum begins the contraction process by:
a. “cocking” the myosin filament cross-bridge heads.
b. rephosphorylating ADP.
c. exposing actin filament cross-bridge binding sites.
d. facilitating ACH release from the neuromuscular junction.
COMPARISON OF CONTRACTION AMONG MUSCLE TYPES
•4. Dense bodies (corresponding to Z lines) and intermediate filament bundles are associated with shortening of the longitudinal axis of:
a. smooth-muscle cells.
b. skeletal-muscle cells.
c. cardiac-muscle cells.
:5. The slower attachment-detachment of cross-bridge heads that extend from myosin to actin is advantageous for:
a. smooth muscle.
b. cardiac muscle.
c. skeletal muscle.
CHANGES IN MUSCLE SIZE
:6. Muscles showing an increase in the size of their individual muscle fibers are said to have undergone:
a. atrophy.
b. treppe.
c. hypertrophy.
d. gangrene.
>7. An increase in the number of muscle fibers is called:
a. atrophy.
b. hypertrophy.
c. hyperplasia.