Muscle Structure Practice Questions
20 free Muscle Structure practice questions for the NCERT Biology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
Which of the following muscle types is primarily involved in locomotory actions and changes of body postures?
- A Smooth muscles
- B Visceral muscles
- C Cardiac muscles
- D Skeletal muscles
Correct answer: Skeletal muscles
Skeletal muscles are closely associated with the skeletal components of the body. They have a striped appearance under the microscope and are under the voluntary control of the nervous system, making them responsible for locomotion.
Visceral muscles are also known as non-striated muscles because:
- A They lack actin and myosin filaments entirely
- B They show no cross-striations under the microscope
- C They are found exclusively in the walls of the heart
- D They are under the voluntary control of the nervous system
Correct answer: They show no cross-striations under the microscope
Visceral muscles, located in the inner walls of hollow visceral organs, do not have the banded or striated appearance seen in skeletal muscles. Consequently, they are called smooth or non-striated muscles.
The characteristic property of cardiac muscles that distinguishes them from skeletal muscles is that they are:
- A Voluntary and branched
- B Involuntary and unbranched
- C Involuntary and branched
- D Striated and voluntary
Correct answer: Involuntary and branched
Cardiac muscles are the muscles of the heart. While they are striated like skeletal muscles, they are involuntary in nature and possess a branched cellular structure with intercalated discs.
In a skeletal muscle fiber, the plasma membrane is called the ________ and the cytoplasm is called the ________.
- A Sarcolemma; Sarcoplasm
- B Sarcoplasm; Sarcolemma
- C Sarcoplasmic reticulum; Sarcosome
- D Fascicle; Perimysium
Correct answer: Sarcolemma; Sarcoplasm
Each skeletal muscle fiber is lined by a plasma membrane called the sarcolemma. The cytoplasm contained within the fiber is known as the sarcoplasm.
Skeletal muscle fibers are described as 'syncytium' because:
- A They contain many mitochondria
- B The sarcoplasm contains many nuclei
- C They lack a nucleus
- D They are made of several cells fused together linearly
Correct answer: The sarcoplasm contains many nuclei
Skeletal muscle fibers are multinucleated because the sarcoplasm contains many nuclei. This multinucleated state is referred to as a syncytium, which results from the fusion of many embryonic myoblasts.
The storehouse of calcium ions in a muscle fiber is the:
- A Sarcosome (muscle mitochondria)
- B Sarcoplasmic reticulum
- C Golgi complex in the fiber
- D Nucleus of the cell
Correct answer: Sarcoplasmic reticulum
The sarcoplasmic reticulum is an endoplasmic reticulum specialized for muscle cells. It functions as the primary reservoir for calcium ions, which are released into the sarcoplasm to trigger muscle contraction.
The light bands of a myofibril contain which protein and are also known by what name?
- A Myosin; A-band
- B Actin; I-band
- C Myosin; I-band
- D Actin; A-band
Correct answer: Actin; I-band
The light bands, or Isotropic bands (I-bands), contain the protein actin. These bands appear lighter under a microscope compared to the dark Anisotropic bands (A-bands).
The functional unit of contraction in a muscle fiber, located between two successive Z-lines, is called a:
- A Sarcosome
- B Sarcomere
- C Myofibril
- D Fascicle
Correct answer: Sarcomere
A sarcomere is the segment of a myofibril between two consecutive Z-lines. It is considered the basic functional and structural unit of muscle contraction.
The 'H-zone' in the skeletal muscle fiber is defined as:
- A The central region of the I-band near the Z-line
- B The mid-region of the A-band not covered by thin filaments
- C The line that bisects and anchors the I-band
- D The zone spanning the entire length of the thick filament
Correct answer: The mid-region of the A-band not covered by thin filaments
In the resting state, the central part of the thick filament (A-band) is not overlapped by the thin filaments (actin). This central gap is known as the H-zone.
Which of the following is a complex protein that masks the active binding sites for myosin on the actin filaments in a resting state?
- A Troponin complex
- B Tropomyosin
- C Meromyosin
- D Alpha-actinin
Correct answer: Troponin complex
Troponin is a complex protein distributed at regular intervals on the tropomyosin. In the resting state, a subunit of troponin masks the active binding sites for myosin on the actin filaments.
Each myosin (thick) filament is a polymerized protein made of monomeric units called:
- A Actins
- B Troponins
- C Meromyosins
- D Tropomyosins
Correct answer: Meromyosins
Myosin filaments are composed of many monomeric proteins called meromyosins. Each meromyosin has two important parts: a globular head with a short arm (Heavy Meromyosin) and a tail (Light Meromyosin).
The globular head of meromyosin possesses binding sites for:
- A ATP and Actin both
- B Calcium ions and Troponin
- C ATP and Tropomyosin
- D Actin and Troponin
Correct answer: ATP and Actin both
The globular head of meromyosin is an active ATPase enzyme. it has specific binding sites for ATP and also active sites to bind with the protein actin during cross-bridge formation.
Which of the following muscle types would be found in the wall of the alimentary canal?
- A Skeletal muscles
- B Striated muscles
- C Smooth involuntary muscles
- D Cardiac muscles
Correct answer: Smooth involuntary muscles
Smooth (visceral) muscles are found in the inner walls of hollow visceral organs like the alimentary canal and reproductive tract. They assist in the transportation of food or gametes through these ducts.
Which protein is composed of two 'F' (filamentous) helically wound to each other?
- A Myosin
- B Actin (thin filament)
- C Troponin
- D Meromyosin
Correct answer: Actin (thin filament)
Each actin (thin) filament is made of two 'F' actins helically wound together. Each 'F' actin is a polymer of monomeric 'G' (globular) actins.
The 'M-line' is a thin fibrous membrane that holds together:
- A Actin filaments in the middle of the I-band, anchoring thin filaments
- B Myosin filaments in the middle of the A-band
- C The sarcolemma and the underlying sarcoplasm together
- D Troponin and Tropomyosin
Correct answer: Myosin filaments in the middle of the A-band
The thick filaments in the A-band are held together in the middle of this band by a thin fibrous membrane called the M-line. This helps maintain the structural integrity of the sarcomere.
Red muscle fibers are rich in which oxygen-storing pigment?
- A Globin
- B Hemocyanin
- C Myoglobin
- D Phycoerythrin
Correct answer: Myoglobin
Some muscles contain a high content of a red-colored oxygen-storing pigment called myoglobin. These are called red fibers and contain plenty of mitochondria for aerobic respiration.
White muscle fibers differ from red muscle fibers in having:
- A High myoglobin and high mitochondria
- B Low myoglobin and high sarcoplasmic reticulum
- C High myoglobin and low mitochondria
- D Low myoglobin and low sarcoplasmic reticulum content
Correct answer: Low myoglobin and high sarcoplasmic reticulum
White fibers have very little myoglobin and fewer mitochondria. However, they possess a high amount of sarcoplasmic reticulum and depend primarily on anaerobic processes for energy.
Skeletal muscles are bundled together in a parallel fashion by a common collagenous connective tissue layer called:
- A Sarcolemma
- B Deep fascia
- C Sarcoplasm
- D Endomysial sheath
Correct answer: Deep fascia
In a skeletal muscle, several muscle bundles (fascicles) are held together by a common collagenous connective tissue layer called fascia. This organizes the muscle into a cohesive organ.
The 'Z-line' is an elastic fiber that bisects each:
- A A-band
- B H-zone
- C I-band
- D M-line
Correct answer: I-band
Each I-band has at its center an elastic fiber called the Z-line which bisects it. The thin filaments are firmly attached to the Z-line, marking the boundaries of the sarcomere.
Which muscle type is characterized by having 'intercalated discs'?
- A Skeletal muscle
- B Cardiac muscle
- C Smooth muscle
- D Voluntary muscle
Correct answer: Cardiac muscle
Cardiac muscle cells are joined by intercalated discs, which are specialized communication junctions. These allow the heart to contract as a synchronized unit by facilitating rapid electrical impulse transmission.