Deck 3: Muscle Structure and Function

Question 1

A decrease in the torque of a muscle when full range of motion (ROM)is attempted over all joints in a multijoint muscle is referred to as ____________________.

A) passive insufficiency
B) active insufficiency
C) passive tension
D) active tension

Answer 1

B

Question 2

Which of the following statements is true regarding cross-bridges?

A) A cross-bridge is the basic unit of active muscle tension.
B) A cross-bridge is formed when head groups on the actin myofilament bind with tropomyosin on the myosin filament.
C) Cross-bridges do not occur in lengthening contractions.
D) A release of sodium is necessary to reveal the binding site on the actin.

Answer 2

A

Question 3

You are passively stretching the hip flexors of a patient in the position of prone hip extension and knee flexion.You later note that the patient demonstrates greater hip extension passive range of motion (PROM)when you allow the knee to be straight during the stretching procedure.The reason for the improved hip extension PROM may best be explained by ____________________.

A) elimination of active insufficiency that occurred during the original position
B) elimination of passive insufficiency that occurred during the original position
C) elimination of both active and passive insufficiency that occurred during the original position
D) activation of passive insufficiency that occurred in the second position

Answer 3

B

Question 4

Name four components of a motor unit.In what ways can these components vary among motor units?

Question 5

The soleus muscle exhibits which type of fiber arrangement?

A) Fusiform
B) Unipennate
C) Bipennate
D) Multipennate

Question 6

When the body segments act in a closed kinematic chain,are muscles most commonly acting in normal or reverse action?

Question 7

The function of a Sharpey fiber is to:

A) Attach the periosteum to the bone
B) Attach ligaments to capsules
C) Attach muscle to tendon
D) Attach tendon to bone

Question 8

The elbow flexors will exert the greatest amount of torque/tension for which type of muscle contraction?

A) Isometric
B) Eccentric
C) Concentric
D) Synergistic

Question 9

How do pennate muscles compare to fusiform or strap muscles with respect to ability to generate tension? What causes whatever differences to exist?

Question 10

What must happen before a motor unit will fire (discharge)? What occurs immediately after discharge of the motor unit?

Question 11

Describe what happens to the angular velocity of a limb during a constant concentric muscle contraction when the load (resistance)is increased.Describe this in terms of net torque.

Question 12

The human body selectively recruits one size motor unit before another.Which size is recruited first,and why is this efficient?

Question 13

Your patient attempts to strengthen his triceps by positioning his shoulder at the end of range of shoulder and elbow extension.He reports weakness and inability to extend his shoulder more in this position.His report may best be explained by which of the following?

A) Active insufficiency of the biceps
B) Active insufficiency of the triceps
C) Passive insufficiency of the biceps
D) Passive insufficiency of the triceps

Question 14

Which of the following would result in increased active muscle tension if the task required the muscle to produce greater torque/tension?

A) Increased firing rate of the activated motor units
B) Decreased number of motor units activated
C) Increased amount of perimysium and endomysium
D) Decreased number of cross-bridges formed

Question 15

Which of the following statements best describes the length-tension relationship of a muscle?

A) The total amount of tension a muscle can develop is related only to the muscle's active tension.
B) During active concentric contraction,maximal tension is developed in the muscle's midrange.
C) During active shortening,no tension is present after all cross-bridges have formed and the myofilaments are overlapping.
D) All of the above answers are correct.

Question 16

Aging will cause the following normal connective tissue change:

A) Decreased connective tissue stiffness
B) Increase in the amount of connective tissue in the extracellular matrix
C) Increase in the number of motor units
D) Decrease of sarcopenia

Question 17

Which of the following statements is true regarding connective tissue and muscle?

A) Parallel elastic components only move after the muscle has completed a contraction.
B) Epimysium is an example of a series elastic component.
C) Parallel elastic components help to "uncrimp" the tendon.
D) A tendon is an example of a series elastic component.

Question 18

Maintaining a posture for a prolonged period of time requires muscles that are slow to fatigue and able to make small adjustments in muscle tension.Therefore,muscles with a high percentage of ________________muscle fibers would be very active during a maintained posture.

A) Type I
B) Type IIB
C) Type IIA

Question 19

The complete sarcomere unit lies within the boundaries of the ____________________.

A) Z disks
B) A bands
C) H zone
D) M band

Question 20

Your patient holds a weight in his right hand.Consider only the muscle activity of the elbow flexors.What type of muscle contraction would occur if T_M = 400 N,and T_L = 500 N,and motion is in the direction of elbow extension? (T_M = torque of muscle; T_L = torque of load)

A) Isometric
B) Concentric
C) Eccentric
D) Synergistic

Question 21

What is tenodesis? Give an example.

Question 22

In order to produce maximum torque for an isokinetic concentric contraction,should the speed of the motion be fast or slow? For an isokinetic eccentric contraction?

Question 23

Contrast active and passive insufficiency.Give examples of each using the same muscle.

Question 24

What protects the muscle from overcontraction or overstretch? What "monitors" length of a muscle?