Locomotion and Movement – Skeletal Muscle and Its Contraction: NEET MCQs with Answers

15 free questions on Locomotion and Movement – Skeletal Muscle and Its Contraction for NEET (UG), starting with previous-year NEET and AIPMT questions. Try each one, then tap Show answer for the answer and a short explanation.

Syllabus covered: Skeletal Muscle and Its Contraction: - contractile proteins and muscle contraction

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Question 1

Previous-year question
Choose the correct statements about the mechanism of muscle contraction. [Re-NEET 2024]
A. It is initiated by a signal sent by the CNS via a sensory neuron.
B. The neurotransmitter generates an action potential in the sarcolemma.
C. Increased Ca⁺⁺ level leads to binding of calcium with troponin on actin filaments.
D. Masking of the active site for actin is activated.
E. Energy from ATP hydrolysis is utilised to form cross bridges.
  1. B, C and E only
  2. C, D and E only
  3. A and D only
  4. B, D and E only
Show answer
Answer: (A) B, C and E only
Explanation: B, C and E are correct: the neurotransmitter generates an action potential in the sarcolemma, increased Ca²⁺ binds troponin on actin filaments, and energy from ATP hydrolysis is used to form cross bridges. A is wrong because the signal from the CNS travels via a motor neuron, and D is wrong because the masking of active sites is removed, not activated.

Question 2

Previous-year question
Assertion: After death, the body muscles become stiff, remaining in a state of partial contraction. [NEET 2024]
Reason: Myosin heads can partially attach to the unexposed sites on actin.
  1. Both Assertion and Reason are true but the Reason is not a correct explanation of the Assertion.
  2. Assertion is true but the Reason is false.
  3. Assertion is false but the Reason is true.
  4. Both Assertion and Reason are true and the Reason is a correct explanation of the Assertion.
Show answer
Answer: (B) Assertion is true but the Reason is false.
Explanation: The Assertion is true: after death muscles become stiff (rigor mortis) in a state of partial contraction, because without ATP the myosin heads cannot detach from actin. The Reason is false as stated: myosin heads bind only to exposed (unmasked) active sites on actin, not to unexposed sites.

Question 3

Previous-year question
Which of the statements given below about skeletal muscle are correct? [NEET 2023]
A. Muscle bundles are held together by a collagenous connective tissue layer called fascicle.
B. The sarcoplasmic reticulum of a muscle fibre is a store house of calcium ions.
C. The striated appearance of a skeletal muscle fibre is due to the distribution pattern of actin and myosin proteins.
D. The M line is considered the functional unit of contraction, called the sarcomere.
  1. B and C only
  2. A, C and D only
  3. C and D only
  4. A, B and C only
Show answer
Answer: (A) B and C only
Explanation: B is correct: the sarcoplasmic reticulum stores Ca²⁺. C is correct: the striated appearance is due to the distribution pattern of actin and myosin. A is wrong because a fascicle is a muscle bundle (held together by fascia, the collagenous connective tissue layer), and D is wrong because the sarcomere is the part between two Z-lines, not the M-line.

Question 4

Previous-year question
Which statement is in accordance with the sliding filament theory? [Re-NEET 2022]
  1. Actin and myosin filaments slide over each other to increase the length of the sarcomere.
  2. Length of A–band does not change.
  3. I–band increases in length
  4. The actin filaments slide away from A–band resulting in shortening of sarcomere.
Show answer
Answer: (B) Length of A–band does not change.
Explanation: In the sliding filament theory, the thin filaments slide towards the centre of the A-band, so the sarcomere and I-band shorten while the A-band retains its length. The other options describe lengthening or movement in the wrong direction.

Question 5

Previous-year question
Which of the following statements is correct? [NEET 2022 (Overseas)]
  1. Z-lines anchor myosin (thick) filament to the ends of the sarcomere.
  2. Sarcoplasmic reticulum stores acetylcholine.
  3. Myosin cross bridges contain calcium binding sites.
  4. Actin and regulatory proteins are located in thin filament.
Show answer
Answer: (D) Actin and regulatory proteins are located in thin filament.
Explanation: The thin filament consists of F-actin along with the regulatory proteins tropomyosin and troponin. Z-lines anchor the thin (actin) filaments, the sarcoplasmic reticulum stores Ca²⁺ (not acetylcholine), and the calcium-binding sites are on troponin, not on myosin.

Question 6

Previous-year question
Which ion is essential for muscle contraction? [AIPMT 1994]
  1. Na
  2. K
  3. Ca
  4. Cl
Show answer
Answer: (C) Ca
Explanation: Calcium is an essential element for the contraction of muscles. The release of calcium ions from the sarcoplasmic reticulum triggers the contraction process, in which calcium ions, ATP, actin and myosin interact to form actomyosin.

Question 7

Previous-year question
When a muscle bends one part upon the other, it is called [AIPMT 1996]
  1. abductor
  2. regulator
  3. extremor
  4. flexor
Show answer
Answer: (D) flexor
Explanation: A flexor muscle bends one part upon the other — for example, the biceps, which brings the forearm towards the upper arm.
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Question 8

Previous-year question
Which of the following is a contractile protein of a muscle? [AIPMT 1998]
  1. Myosin
  2. Tropomyosin
  3. Actin
  4. Tubulin
Show answer
Answer: (A) Myosin
Explanation: Myosin-II, a two-headed tailed variety of myosin, is the protein involved in muscle contraction. (Tropomyosin and troponin are regulatory rather than contractile proteins, and tubulin is a microtubule protein.)

Question 9

Previous-year question
The functional unit of the contractile system in striated muscle is the [AIPMT 1998]
  1. myofibril
  2. sarcomere
  3. Z-lines
  4. cross-bridges
Show answer
Answer: (B) sarcomere
Explanation: Skeletal muscle is also called striated muscle because the regular arrangement of the myofilaments creates a repeating pattern of light and dark bands. Each repeating unit is a sarcomere, the basic functional unit of the striated muscle.

Question 10

Previous-year question
What is a sarcomere? [AIPMT 2001]
  1. Part between two H-lines
  2. Part between two A-lines
  3. Part between two I-bands
  4. Part between two Z-lines
Show answer
Answer: (D) Part between two Z-lines
Explanation: The part of the myofibril between two successive Z-lines functions as the contractile unit and is called the sarcomere. Sarcomeres facilitate both the relaxation and the contraction movements of the muscles with which our overall movement occurs.

Question 11

Previous-year question
Which statement is correct for muscle contraction? [AIPMT 2001]
  1. Length of the H-zone decreases
  2. Length of the A-band remains constant
  3. Length of the I-band increases
  4. Length of two Z-lines increases
Show answer
Answer: (B) Length of the A-band remains constant
Explanation: During muscle contraction the Z-lines come closer together and the sarcomere shortens. The length of the A-band remains constant throughout, while the I-bands shorten and the H-zone narrows.

Question 12

Previous-year question
The ATPase enzyme needed for muscle contraction is located in [AIPMT 2004]
  1. actinin
  2. troponin
  3. myosin
  4. actin
Show answer
Answer: (C) myosin
Explanation: Myosin is not only an actin-binding protein; it is also an ATPase enzyme, activated by Ca²⁺ and Mg²⁺ ions. The ATPase enzyme is therefore located in myosin.

Question 13

Previous-year question
The contractile protein of skeletal muscle involving ATPase activity is [AIPMT 2006]
  1. myosin
  2. α-actinin
  3. troponin
  4. tropomyosin
Show answer
Answer: (A) myosin
Explanation: Each myosin monomer (meromyosin) has a globular head that acts as an active ATPase enzyme and has binding sites for ATP and actin. Hydrolysis of ATP by the myosin head provides energy for cross-bridge formation and sliding of actin filaments.

Question 14

Previous-year question
Which one of the following is the correct pairing of a body part and the kind of muscle tissue that moves it? [AIPMT 2009]
  1. Heart wall — Involuntary unstriated muscle
  2. Biceps of upper arm — Smooth muscle fibres
  3. Abdominal wall — Smooth muscle
  4. Iris — Involuntary smooth muscle
Show answer
Answer: (D) Iris — Involuntary smooth muscle
Explanation: The iris is moved by involuntary smooth muscle, so this pair is correct. The heart wall is made of cardiac muscle, which is involuntary but striated; the biceps of the upper arm and the abdominal wall are both made of skeletal muscle, not smooth muscle.

Question 15

Previous-year question
The H-zone in the skeletal muscle fibre is due to [NEET 2013]
  1. the absence of myofibrils in the central portion of the A-band
  2. the central gap between myosin filaments in the A-band
  3. the central gap between actin filaments extending through myosin filaments in the A-band
  4. extension of myosin filaments in the central portion of the A-band
Show answer
Answer: (C) the central gap between actin filaments extending through myosin filaments in the A-band
Explanation: The H-zone arises from the central gap between actin filaments extending through the myosin filaments in the A-band. The alternate arrangement of dark and light bands gives skeletal muscle its striated appearance, and at the centre of the A-band lies the comparatively less dark H-zone, within which the M-line is formed by threads connecting the myofilaments.

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