Biology · General Awareness

Muscle Biology

836 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

Which of the following statements does not characterise skeletal muscles in humans?

  1. It has the similar structure as that of cardiac muscle.

  2. Skeletal muscle cells contain myosin filaments.

  3. Skeletal muscle has a system of T-tubules.

  4. The myofibrils of skeletal muscle are enveloped by sarcoplasmic reticulum.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Skeletal muscle cells do not contain myosin filaments. Smooth muscle cells have no repeating sarcomeres, but a loose array of actin and myosin filaments.

Multiple choice

Which of the following does not characterise skeletal muscle contractions in humans?

  1. The alpha motor neuron generates action potential.

  2. The neurotransmitter noradrenaline diffuses across the synapse and binds to nicotinic acetylcholine receptors on the myocyte.

  3. The end-plate potential spreads evenly across the myocyte's sarcolemma.

  4. The T-tubule system accomodates voltage-dependent calcium plexus.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This statement is incorrect. The neurotransmitter acetylcholine diffuses across the synapse and binds to nicotinic acetylcholine receptors on the myocyte, opening them. An influx of Na+ and an efflux of K+ results, depolarising the cell and generating an end-plate potential.

Multiple choice

In cardiac muscle, the excitation contraction coupling method is dependent on an anomaly famed as calcium-induced calcium release. Which of the following statements is true regarding excitation contraction coupling in cardiac muscles?

  1. Intracellular Ca+2 is drawn by endoplasmic reticulum ATPase pump.

  2. The cytoplasmic calcium binds to troponin T.

  3. The ryanodine receptors find out the increase in intracellular calcium ions.

  4. The action potential propogates across the T-tubules.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This statement is incorrect as cytoplasmic calcium binds to troponin C instead of troponin T making the troponin complex to move off the actin binding site allowing the myosin head to bind to the actin filament.

Multiple choice

Which of the following statements concerning the role of Ca2+ in contraction of skeletal muscles is true?

  1. The SER acts as a reserve of Ca2+ for the contractile process.

  2. Ca2+ entry across the plasma membrane is significant in maintaing the contraction of skeletal muscle in the body.

  3. A rise in intracellular Ca2+ permits actin to interact with myosin.

  4. The tension of a skeletal muscle fibre is totally governed by G proteins.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The calcium for skeletal muscle contraction is derived from sarcoplasmic reticulum. The increase in intracellular calcium permits the interaction between actin and myosin head groups.

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

All the following muscles are grouped together as muscle of mastication except

  1. buccinators

  2. masseter

  3. temporalis

  4. pterygoids
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The infratemporal fossa contains two of the four principle muscles of mastication, medial and lateral pterygoid. The tendon of a third muscle, temporalis, is also found in this region. The remaining muscle, masseter, lies on the lateral surface of the ramus, but is considered here with the muscles of mastication. The masticatory muscles are most immediately concerned with movements to the mandible at the temporomandibular joints.

Multiple choice

Muscle supplied by facial and mandibular nerves is

  1. masseter

  2. digastric muscle

  3. medial pterygoid

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

Digastric muscle has two bellies and lies below the mandible, extending from the mastoid process to the chin. The posterior belly, which is longer than the anterior, is attached in the mastoid notch of the temporal bone and passes downwards and forwards. The anterior belly is attached to the digastric fossa on the base of the mandible near the midline and it slopes downwards and backwards. The two bellies meet in an intermediate tendon, which runs in a fibrous sling attached to the greater cornu of the hyoid bone and is sometimes lined by a synovial sheath. The tendon perforates the stylohyoid.

Multiple choice

All the following muscles are attached to the oblique line of thyroid cartilage except

  1. sternothyroid

  2. cricothyroid

  3. superior constrictor

  4. inferior constrictor
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Superior constrictor is inserted into the median raphe, being also prolonged by means of an aponeurosis to the pharyngeal spine on the basilar part of the occipital bone.Sternothyroid arises from the posterior surface of the manubrium sterni inferior to the origin of sternohyoid and from the posterior edge of the cartilage of the first rib. It is attached above to the ablique line on the thyroid cartilage, where it delineates the upward extent of the thyroid gland. 

Multiple choice

Which of the following muscles is/are the composite muscle(s)?

  1. Pectineus

  2. Biceps femoris

  3. Adductor magnus

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Definition: Composite muscles are those, whose functions are regarded the same in terms of skeletal structure and muscle arrangement condition, as a single muscle model, e.g. vastus intermedius, lateralis and medialis working with rectus femoris on the knee joint for its extension.

Multiple choice

The muscle responsible for bringing about protrusion of mandible is

  1. lateral pterygoid

  2. medial pterygoid

  3. masseter

  4. temporalis

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

When a jaw muscle contracts in the absence of a restraint, the mandible is pulled in the direction of the shortening muscle. The lateral pterygoids are each capable of exerting about 160 N force, a total of 320 N, and yet less than 5% of this is used to protrude or open the jaw.

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.