Muscle and Skeletal System MCQ Quiz in मल्याळम - Objective Question with Answer for Muscle and Skeletal System - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

The correct answer is Actin and myosin filaments do not shorten they only pass each other.

Concept:

• The sliding filament theory is a widely accepted explanation for how muscles contract to produce force. It was first proposed by scientists Huxley and Hanson in the 1950s.
• According to this theory, muscle contraction occurs when the thin actin filaments slide past the thick myosin filaments, causing the sarcomere (the functional unit of a muscle fiber) to shorten.
• During contraction, the myosin heads bind to actin, forming cross-bridges, and then pull the actin filaments toward the center of the sarcomere through a series of power strokes.
• This sliding of filaments does not involve any shortening of the filaments themselves; instead, it is the relative movement of the actin and myosin filaments that leads to muscle contraction.

Explanation:

Actin and myosin filaments do not shorten; they only pass each other.

• This is the correct answer. The sliding filament theory describes that during muscle contraction, the actin and myosin filaments slide past one another without changing their length, leading to the shortening of the sarcomere and thus the muscle itself.

Other Options:

• Actin and myosin filaments shorten and slide past each other.
  • This is incorrect because the actin and myosin filaments do not shorten during muscle contraction. They remain the same length but slide past each other to create the shortening of the muscle.
• When myofilaments slide past each other, shortening of actin filaments occur.
  • This is incorrect because actin filaments do not shorten. The sliding filament theory specifies that it is the sliding of the filaments, not their shortening, that leads to muscle contraction.
• When myofilaments slide past each other, shortening of myosin filaments occur.
  • This is incorrect because myosin filaments do not shorten. Similar to actin, the myosin filaments remain the same length and it is their sliding action relative to the actin filaments that causes contraction.

The correct answer is option 2.

Concept: 

• The pectoral girdle consists of a clavicle and a scapula.
•  The scapula is a large triangular flat bone situated in the dorsal part of the thorax between the second and the seventh ribs.
• The dorsal, flat, triangular body of the scapula has a slightly elevated ridge called the spine, which projects as a flat, expanded process called the acromion.
• The clavicle articulates with this.

Explanation: ​

• The head of the humerus bone articulates with the glenoid cavity of the pectoral girdle.
• This articulation results in the formation of ball and socket joints, e.g., ball and socket joints present in the shoulder.
• The humerus bone is the longest and largest bone of the upper limb.
• It articulates proximally with the scapula and distally at the elbow with both the ulna and radius.
• Humerus articulate with the glenoid cavity of the pectoral girdle.
• The rest of the statements are incorrect.
• Therefore, the correct answer is option 2.

The correct answer is option 4.

Concept: 

• A joint is defined as the point of contact between two or more bones, or between a bone and cartilage.
• Joints are important because they facilitate the movement of the body parts.
• Adjacent bones and cartilage articulate with one another to form a joint.
• The joint acts as a pivot and the muscles create the necessary force needed for movement.

​Explanation: 

Option 1:​

• Saddle joints exhibit biaxial rotation, i.e., show rotation around two planes.
• The saddle joint can be seen between the carpal (bones of the wrist) and metacarpal (bones of the palm) of the thumb.
• Therefore, this is the incorrect answer.

Option 2:

• The ball and socket joint is a freely movable joint.
• In this type of joint, the ball-like structure of one bone fits into the socket-like structure of another bone.
• Shoulder and hip joints are examples of ball and socket joints.
• Therefore, this is the incorrect answer.

Option 3:

• The movement only occurs in one direction in the case of the pivot joint.
• The pivot joint can be observed between the atlas (1st vertebral bone) and the axis bone (2nd vertebral bone).
• Therefore, this is the incorrect answer.

​Option 4:

The correct answer is option 1.

Concept: 

• A joint is defined as the point of contact between two or more bones, or between a bone and cartilage.
• Joints are important because they facilitate the movement of the body parts.
• Adjacent bones and cartilage articulate with one another to form a joint.
• The joint acts as a pivot and the muscles create the necessary force needed for movement.

Explanation: 

Option 1:

• The movement only occurs in one direction in the case of the pivot joint.
• The pivot joint can be observed between the atlas (1st vertebral bone) and the axis bone (2nd vertebral bone).
• Therefore, this is the correct answer.
• 

Option 2:

• Saddle joints exhibit biaxial rotation, i.e., show rotation around two planes.

• The saddle joint can be seen between the carpal (bones of the wrist) and metacarpal (bones of the palm) of the thumb.
• Therefore, this is the incorrect answer.

Option 3:

• The hinge joint is a joint which creates a hinge between the movement of two bones.
• This joint also allows movement only in one direction.
• One example of a hinge joint is an interphalangeal joint is a type of hinge joint present between phalanges (bones of the fingers).

The correct answer is option 2.

Concept:

• The skeletal system in the human body is a framework of bone and cartilage.
• It is divided into an axial skeleton (present along the main axis of the body) and an appendicular skeleton (bones with limbs and their girdles).

Explanation:

• The axial skeleton consists of 80 bones out of the 206 bones found in the human body.
• The appendicular skeleton consists of limbs and their associated girdles. It has 126 bones.
• Let us see some of the bones in the skeletal system and their location

• Sl. No.	Part of the skeletal system	Description
  1	Floating ribs	There are 12 pairs of ribs.  The first seven ribs are attached dorsally to the thoracic vertebrae and ventrally to the sternum. They are called true ribs. The 8th, 9th, and 10th pair of ribs join the seventh pair of ribs through cartilage and are then attached to the sternum. They are called vertebrochondral ribs. The 11th and 12th pair of ribs are not attached ventrally to the sternum and are called the floating ribs.
  2	Scapula	Each half of the pectoral girdle (part of the appendicular skeleton) consists of a scapula and a clavicle. The scapula is the large triangular bone present in the dorsal part of the thorax. It is positioned between the second and seventh rib in the thoracic region.
  3	Acromion	Acromion is the outer edge of the bony tip of the scapula (shoulder blade).  The clavicle articulates with the acromion.
  4	Glenoid cavity	It is present below the acromion. It is present as depression. It articulates with the head of the humerus to form the shoulder joint.

   

Floating ribs

Pectoral girdle

So, the correct answer is option 2.

Correct Answer: 1)

Solution:

Concept:

• Skeletal muscles in our body are made up of muscle fibers.
• Each muscle fiber has a large number of parallelly arranged myofibrils.
• Each myofibril has a light band made of actin and a dark band consisting of myosin. 

Explanation:

• Muscle contraction starts with the impulse which travels along the axon and gets to the neuromuscular junction (motor endplate).
• Acetylcholine is secreted into the synaptic cleft, as a result, and on the sarcolemma, an action potential is generated.
• This action potential formation releases calcium ions within the sarcoplasm from the sarcoplasmic reticulum.
• An increase of calcium ions (inside sarcoplasm) causes the activation of actin sites.
• Calcium ions further stick to the troponin on actin filaments and elimination of the troponin wrapped all over actin filaments will take place.
• Hence, uncovered active action sites enable myosin heads to link to this site.
• After the muscle contraction, the myosin heads free ADP along with inorganic phosphate and pull the actin filament.
• The cross-bridge is damaged as the ATP molecules bind and separate myosin.
• These calcium ions remove the masking of the active sites by binding to the protein complex.
• As a result, active binding sites acting for myosin are exposed.

Option 1: binds to troponin to remove the masking of active sites on actin for myosin. – CORRECT

• Calcium ion binds to troponin for the removal of the masking of active sites on actin for myosin.
• Hence, this statement is correct.

Option 2: activates the myosin ATPase by binding to it. – INCORRECT

• In the presence of high-salt and divalent cation chelators, the ATPase activities of some myosin are activated.
• Hence, this statement is incorrect.

Option 3: prevents the formation of bonds between the myosin cross bridges and the actin filament. – INCORRECT

• Calcium ions do not prevent the formation of bonds between the myosin cross bridges and the actin filament but lead to the formation of this bridge.
• Hence, this statement is incorrect.

Option 4: detaches the myosin head from the actin filament. – INCORRECT 

• Calcium ions help in the unmasking of the actin filament active site which leads to the attachment of the myosin head with the actin filament.
• Hence, this statement is incorrect.

So, the correct answer is option 1).

The correct answer is Binding of ATP molecules to the myosin head

Concept:

• At the neuromuscular junction, the release of acetylcholine (ACh) is crucial for initiating muscle contraction.
• Acetylcholine binds to receptors on the muscle cell membrane, leading to a series of events that result in muscle contraction.
• These events include the generation of an action potential, the release of calcium ions (Ca²⁺), and the exposure of myosin binding sites on actin filaments.
• However, the binding of ATP to the myosin head is a separate event that occurs during the cross-bridge cycle and is not directly triggered by acetylcholine release.

Explanation:

• Generation of an action potential in the muscles: When acetylcholine is released into the synapse at the neuromuscular junction, it binds to receptors on the muscle cell membrane, causing depolarization and triggering an action potential. This action potential spreads along the muscle fiber, initiating contraction. This is directly triggered by acetylcholine release.
• Release of Ca²⁺ from the sarcoplasmic reticulum: The action potential generated in the muscle cell travels along the sarcolemma and down the T-tubules, leading to the release of Ca²⁺ from the sarcoplasmic reticulum. The increase in intracellular Ca²⁺ concentration is essential for muscle contraction. This is also a direct consequence of acetylcholine release and subsequent action potential propagation.
• Binding of ATP molecules to the myosin head: This is a part of the cross-bridge cycle, where ATP binds to the myosin head, causing it to detach from the actin filament. This event is not directly triggered by acetylcholine release but is essential for muscle contraction and relaxation cycle. Hence, this option is the correct answer as it is NOT triggered by acetylcholine.
• Shifting of tropomyosin to expose the myosin binding sites on actin filaments: The release of Ca²⁺ from the sarcoplasmic reticulum leads to the binding of Ca²⁺ to troponin, which causes a conformational change that shifts tropomyosin away from the myosin binding sites on actin filaments. This allows myosin heads to attach to actin and initiate contraction. This process is indirectly triggered by acetylcholine through the cascade of events it initiates.

The correct answer is A- Troponin B- Tropomyosin

Explanation:

• Each actin (thin) filament is made of two ‘F’ (filamentous) actions helically wound to each other.
• Each ‘F’ actin is a polymer of monomeric ‘G’ (Globular) actins.
• Two filaments of another protein, tropomyosin also run close to the ‘F’ actins throughout its length.
• A complex protein Troponin is 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

​

The correct answer is The arrangement of thick and thin myofilaments (actin and myosin)

Explanation:

The striated appearance of myofibrils in muscle fibers is due to the regular arrangement of thick (myosin) and thin (actin) myofilaments within the sarcomere, which is the basic contractile unit of muscle fibers. The alternating light and dark bands created by the overlapping of these filaments under a microscope give the muscle fiber its characteristic striated appearance.

• The A bands (dark bands) contain the thick myosin filaments and overlapping thin actin filaments.
• The I bands (light bands) contain only the thin actin filaments.
• The Z line marks the boundary between adjacent sarcomeres.
• The H zone is the region where only thick myosin filaments are present (without overlap with actin).

• The M line is the center of the sarcomere, where myosin filaments are anchored.

Why other options are incorrect:

• b) The arrangement of the sarcoplasmic reticulum: The sarcoplasmic reticulum is involved in the storage and release of calcium ions for muscle contraction, but it does not contribute to the striated appearance of the myofibrils.
• c) The arrangement of mitochondria: Mitochondria provide energy for muscle contraction but do not cause the striated appearance of myofibrils.
• d) The presence of nuclei: While muscle fibers are multinucleated, the presence of nuclei does not contribute to the striated appearance of the myofibrils. The striations are due to the arrangement of the myofilaments.

The correct answer is A, B & E only

Explanation:

A. Myasthenia gravis: Auto immune disorder affecting neuromuscular junction leading to fatigue, weakening and paralysis of skeletal muscle.

B. Rheumatoid arthritis: Rheumatoid arthritis (RA) is an autoimmune condition in which the immune system mistakenly attacks the joints. This causes inflammation, pain, and swelling, leading to joint damage and deformities over time.

C. Gout: Inflammation of joints due to accumulation of uric acid crystals.

D. Muscular dystrophy: Progressive degeneration of skeletal muscle mostly due to genetic disorder.

E. Systemic Lupus Erythematosus (SLE): SLE is a chronic autoimmune disease where the immune system attacks its own tissues, causing widespread inflammation and tissue damage in the affected organs. It can affect the skin, joints, kidneys, brain, and other organs.

Therefore, Myasthenia gravis, Rheumatoid arthritis, Systemic Lupus Erythematosus (SLE) are examples of autoimmune disorders.