Lecture 4: Skeletal Muscle Contraction

Question 1

Which of the following terms refers to a chain of sarcomeres?

A. Muscle
B. Myofiber
C. Myofibril
D. Myofilament

Answer 1

C. Myofibril

Question 2

Which of the following sarcomeric bands does not undergo a change in length during the contraction of a skeletal muscle?

A. A band
B. H band
C. I band
D. J band

Answer 2

A. A band

Question 3

Which of the following sarcomeric bands is composed entirely of actin filaments?

A. A band
B. H band
C. I band
D. J band

Answer 3

C. I band

Question 4

Dihydropyridine (DHP) channels are part of which of the following structures?

A. Sarcoplasmic Reticulum
B. Plasmalemma
C. T-tubules
D. Z disks

Answer 4

C. T-tubules

Question 5

Ryanodine-sensitive calcium ion release channels are part of which of the following structures?

A. Sarcoplasmic reticulum
B. Plasmalemma
C. T-tubules
D. Z disks

Answer 5

A. Sarcoplasmic reticulum

Question 6

Which of the following events occurs first during the transmission of a signal from an alpha motor neuron to a skeletal muscle fiber?

A. End-plate depolarization (EPP)
B. Calcium Ion Influx into Axon Terminal
C. Exocytosis of Synaptic Vesicles
D. Sarcolemma Action Potential

Answer 6

B. Calcium Ion Influx into Axon Terminal

Question 7

Which of the following represents the facto by which the concentration of calcium ions increases in the cytosol after release from the sarcoplasmic reticulum?

A. 10
B. 50
C. 100
D. 1000

Answer 7

C. 100

Question 8

Which of the following maintains an optimum calcium concentration gradient to facilitate return of calcium to SR?

A. Calsequestrin
B. SERCA
C. DHP
D. Ryanodine

Answer 8

A. Calsequestrin

Question 9

Fast twitch fibers have which of the following characteristics?

A. They are reddish in color compared to slow twitch fibers
B. They have more mitochondria than slow twitch fibers
C. They have more myoglobin than slow twitch fibers
D. They are more fatigable than slow twitch fibers

Answer 9

D. They are more fatigable than slow twitch fibers

Question 10

Which of the following represents an example of an eccentric contraction?

A. The triceps muscle during the throwing of a ball
B. The triceps muscle while raising the body from the floor during a push-up
C. The triceps muscle while lowering the body to the floor during a push-up
D. The biceps muscle while raising the body during a pull-up

Answer 10

C. The triceps muscle while lowering the body to the floor during a push-up

Question 11

Isometric contraction

Answer 11

Increase in tension, but not length

Question 12

Isotonic contraction

Answer 12

muscle length changes

Question 13

Eccentric contraction

Answer 13

Isotonic contraction where the muscle LENGTHENS

Question 14

Concentric contraction

Answer 14

Isontonic contraction where the muscle SHORTENS

Question 15

Fast Fibers

Answer 15

AKA White fibers; contract rapidly, but less endurance; fewer mitochondria, anaerobic respiration, little myoglobin, large concentration of ATPase

Question 16

Slow Fibers

Answer 16

AKA Red fibers; contract more slowly, but have more endurance; more mitochondria, aerobic respiration, more myoglobin, smaller concentration of ATPase