Muscle Physiology

Question 1

The striated appearance of skeletal muscle is due to:

Answer 1

Regular orderly arrangement of the thick and thin filaments into A and I bands

Question 2

Thick filaments in skeletal muscle are composed of:

Answer 2

Myosin

Question 3

Sarcomeres are arranged end to end as:

Answer 3

Myofibrils

Question 4

Which of the following statements concerning cross bridges is not correct?
Cross bridges _________

A) Bind to actin during muscle contraction
B) Are formed by the globular heads of the myosin molecules
C) Consist of troponin and tropomyosin protruding from the actin helix
D) Bend during muscle contraction

Answer 4

C) Consist of troponin and tropomyosin protruding from the actin helix

Question 5

Troponin:

Answer 5

Binds with calcium to allow Sarcomeres shortening

Question 6

A function of tropomyosin is:

Answer 6

Prevent myosin cross bridges from attaching to the thin filaments

Question 7

According to the sliding filament mechanism of muscle contraction, the _________

Answer 7

Thin filaments slide inward toward the centre of the A band

Question 8

During contraction, asynchronous cycling of crossbridges:

Answer 8

Prevents thin filaments from slipping backwards

Question 9

The sarcoplasmic reticulum stores _______ when a muscle is relaxed and releases it for binding to _______ during contraction.

A) Calcium/troponin
B) Calcium/tropomyosin
C) Sodium/tropomyosin
D) Sodium/troponin

Answer 9

A) Calcium/Troponin

Question 10

IF you wanted to pick up something heavier than your pencil, you would:

Answer 10

Stimulate more motor units

Question 11

Myoglobin:

Two Answers

Answer 11

• Can store small amounts of O2

- Increases the rate of O2 transfer from the blood into muscle fibres

Question 12

Muscular fatigue is caused by:

Answer 12

• Lactic acid accumulation
• Depletion of ATP
• Depletion of ACh

Question 13

Select the correct statement about the summation of simple twitches:

A) They can occur from the long duration of the action potential in a muscle fibre
B) They reduce the tension in a muscle
C) They result from the slow summation of a muscle fibre
D) The effect is unrelated to the refractory periods of action potentials
E) The twitches from action potentials add together

Answer 13

E) The twitches from action potentials add together

Question 14

If the load on a muscle is increased, eventually a load will be reached at which the velocity of shortening becomes zero.
At this point, the muscle contraction is referred to as:

Answer 14

Isometric

Question 15

Select the correct statement regarding smooth muscle:

A) It composes the wall of the hear
B) It is absent in the walls of hollow organs
C) It's cells are multi uncleared 
D) It's cells are spindle shaped
E) It's cells lack actin and myosin

Answer 15

D) It’s cells are spindle shaped

Question 16

What is the characteristic of cardiac muscle tissue?

Answer 16

Presence of gap junctions