Biology · General Awareness

Muscle Biology

798 Questions

Muscle biology covers the structures, functions, and contraction mechanisms of skeletal, cardiac, and smooth muscles. Test questions target filaments, stimuli, and specific muscle roles. A clear understanding helps secure marks in biology sections.

Skeletal muscle controlCardiac muscle propertiesMuscle contraction mechanismActin and myosin filamentsMuscle functions

Muscle Biology Questions

Multiple choice

In cardiac muscles, which of the following events takes place?

  1. The force of contraction is enhanced by propogating epinephrine.

  2. Cardiac muscle contracts in reaction to action potentials generated in the autonomic nerve fibers.

  3. The action potential of cardiac muscle has the similar duration as that of skeletal muscle in the body.

  4. All of Ca2+ needed for contraction of cardiac muscles comes in a myocyte during the plateau phase of the action potential.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Epinephrine is a catecholamine hormone secreted by adrenal medulla. It is a potent stimulator of the sympathetic nervous system stimulating the heart muscle, accelerating the heart rate and increasing cardiac output. In a cardiac muscle, the force of contraction is enhanced by propogating epinephrine.

Multiple choice

Which of the following statements regarding smooth muscle fibres is correct?

  1. These are innervated by autonomic nerves similar to the neuromuscular junction of skeletal muscle.

  2. All smooth muscles of the body act as a single motor unit.

  3. Some smooth muscles also get contracted in absence of an action potential.

  4. They never form the part of circulatory system.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Smooth muscle fibers have a fusiform shape and, like striated muscle, can tense and relax. Some smooth muscles have the ability to contract spontaneously, i.e., it contracts without any external stimulation.

Multiple choice

The maximum power originated in a skeletal muscle fibre

  1. is independent of initial length of the muscle

  2. occurs with an isometric contraction

  3. confides in the load moved by the muscle

  4. is independent of the load moved by the muscle
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

As power = force x velocity, the maximum power depends on the load moved by the muscle. Too high a load and the muscle cannot shorten effectively; too light a load requires little power to move it.

Multiple choice

Profuse sweating takes place during heavy muscular exercise. The reason is _________.

  1. to excrete excessive amount of sodium chloride

  2. to eliminate excessive lactic acid produced due to anaerobic metabolism

  3. to regulate the temperature of the body

  4. all of these

  5. none of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

All the above reasons are correct. Profuse sweating takes place during heavy muscular exercise, to excrete excessive amount of sodium chloride, to eliminate excessive lactic acid produced due to anaerobic metabolism and to regulate the temperature of the body.

Multiple choice

The action potential in contractile muscle fibers of the heart is similar to that in skeletal muscles of the body. Among the following statements, select the incorrect statement regarding the action potential of human heart?

  1. Within the cell, Ca 2+ binds to troponin.

  2. Rapid depolarization occurs when fast‐opening Na + channels in the sarcolemma open.

  3. A plateau phase occurs during which K+ enters the cytosol of the muscle cell.

  4. Repolarization occurs as K + channels open and K + diffuses out of the cell.

  5. The refractory period of cardiac muscle is dramatically longer than that of the skeletal muscle.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A plateau phase occurs, during which Ca2+ enters the cytosol of the muscle cell. Ca2+ enters from the sarcoplasmic reticulum within the cell and also from outside the cell through slow‐opening Ca2+ channels in the sarcolemma. 

Multiple choice

Why does heavy exercise cause muscle cramps?

  1. Due to the formation of ethanol

  2. Due to the formation of lactic acid

  3. Due to the evolution of CO2

  4. Due to the absence of oxygen
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

During heavy exercise, when there is a lack of oxygen in our muscle cells, pyruvate is converted into lactic acid. 

Multiple choice

The intrinsic laryngeal muscles are responsible for maintaining sound production in humans. The movement of which of the following muscles causes abducted vocal folds?

  1. Posterior cricoarytenoid

  2. Lateral cricoarytenoid

  3. Transverse arytenoid

  4. Oblique arytenoid

  5. Cricothyroid
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Posterior cricoarytenoid is the ligament that passes downward from the posterior border of the arytenoid cartilage to the lamina of the cricoid cartilage. Posterior cricoarytenoid muscles abduct and externally rotate the arytenoid cartilages resulting in abducted vocal folds.

Multiple choice

Muscle fatigue is caused by the accumulation of

  1. pyruvic acid

  2. lactic acid

  3. oxalacetic acid

  4. uric acid
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Muscle fatigue during intense exercise is caused by the accumulation of lactic acid in muscle tissues. When oxygen supply is insufficient for aerobic respiration, muscles switch to anaerobic glycolysis, producing lactic acid as a byproduct. This buildup interferes with muscle contraction and causes the sensation of fatigue.

Multiple choice

In which of the following autoimmune disorders, muscles of the limbs become weak?

  1. Lambert-Eaton myasthenic syndrome

  2. Cutaneous small-vessel vasculitis

  3. Lichen planus

  4. Lichen sclerosus

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Lambert-Eaton myasthenic syndrome is a rare autoimmune disorder that is characterised by muscle weakness of the limbs. It is the result of an autoimmune reaction, where antibodies are formed against voltage-gated calcium channels in the neuromuscular junction .

Multiple choice

The substance found in tendons and ligaments is

  1. collagenous fibres

  2. elastic fibres

  3. fibrous connective tissue

  4. reticular fibres

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Another type of connective tissue is  Fibrous Connective Tissue,. It is composed of large amounts of closely packed collagenous fibres.