Muscle and Skeletal System MCQ Quiz - Objective Question with Answer for Muscle and Skeletal System - Download Free PDF

The correct answer is Both 1 & 2

Concept:

• Fibrous joints do not allow any movement. This type of joint is shown by the flat skull bones which fuse end-to-end with the help of dense fibrous connective tissues in the form of sutures, to form the cranium.
• In cartilaginous joints, the bones involved are joined together with the help of cartilages. The joint between the adjacent vertebrae in the vertebral column is of this pattern and it permits limited movements.
• Synovial joints are characterised by the presence of a fluid filled synovial cavity between the articulating surfaces of the two bones. Such an arrangement allows considerable movement. These joints help in locomotion and many other movements. Examples:-
  • Ball and socket joint (between humerus and pectoral girdle),
  • Hinge joint (knee joint),
  • Pivot joint (between atlas and axis),
  • Gliding joint (between the carpals)
  • Saddle joint (between carpal and metacarpal of thumb).

Explanation:

• Ball and Socket Joint: This type of synovial joint allows for rotational movement in almost any direction. Examples include the shoulder and hip joints. 
• Hinge Joint: These joints allow for movement in one plane, much like the hinge of a door. Examples include the elbow and knee joints. They permit flexion and extension movements, making them crucial for activities such as walking and lifting objects.

Other options:

• Fibrous Joint: These joints are connected by dense connective tissue and have no joint cavity. They are typically immovable or only slightly movable. Examples include sutures in the skull.

The correct answer is The second and seventh ribs

Explanation:

• 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 scapula has a slightly elevated ridge called the spine which projects as a flat, expanded process called the acromion.
• The clavicle articulates with this.
• Below the acromion is a depression called the glenoid cavity which articulates with the head of the humerus to form the shoulder joint.

Fig: Right pectoral girdle and upper arm

Explanation:

• Pelvic girdle consists of two coxal bones
• Each coxal bone is formed by the fusion of three bones – ilium, ischium and pubis.
• At the point of fusion of the above bones is a cavity called acetabulum to which the thigh bone articulates.
• The two halves of the pelvic girdle meet ventrally to form the pubic symphysis containing fibrous cartilage.

Fig: Right pelvoc girdle and lower limb 

The correct answer is Actin filaments

Explanation:

• Muscle contraction is regulated by the presence of calcium ions and the proteins troponin and tropomyosin.
• In a resting state, troponin and tropomyosin work together to block the active binding sites on actin filaments, preventing muscle contraction.
• When calcium ions bind to troponin, it causes a conformational change that moves tropomyosin away from the binding sites on actin filaments, allowing myosin heads to bind to actin and initiate muscle contraction.
  • Actin filaments: In the resting state, the troponin-tropomyosin complex covers the active binding sites on actin filaments, preventing myosin from attaching to actin and thus preventing muscle contraction.
  • Meromyosin filament: This is not involved in the regulation of muscle contraction by troponin. Meromyosin is part of the myosin molecule, which interacts with actin but is not regulated by troponin.
  • M-line: The M-line is a structural component within the sarcomere that holds the myosin filaments in place. It does not play a role in the blocking of active sites on actin by troponin.
  • H-zone: The H-zone is the region within the sarcomere where only myosin filaments are present. It does not involve the interaction with actin filaments or the regulation by troponin.

The correct answer is Option 1: 8, 14, 1, and 6

Concept:

• The human skull is a complex structure composed of multiple bones that protect the brain and support the structures of the face.
• The cranium is the part of the skull that encloses the brain. The face consists of several bones that form the structure of the face.
• The hyoid bone is a unique bone located in the neck that supports the tongue and is not directly connected to other bones.
• The middle ear contains three small bones known as ossicles, which are involved in the process of hearing.

Explanation:

• Cranium: The cranium consists of 8 bones. These bones include the frontal, parietal (2), temporal (2), occipital, sphenoid, and ethmoid bones.
• Face: The face is made up of 14 bones. These bones include the nasal (2), maxilla (2), zygomatic (2), palatine (2), lacrimal (2), inferior nasal concha (2), vomer, and mandible.
• Hyoid Bone: There is only 1 hyoid bone in the human body present at the base of the buccal cavity.
• Middle Ear: The middle ear contains 6 bones in total, with 3 small bones (ossicles) in each ear: malleus, incus, and stapes.

The correct answer is the Pivotal joint.

The joint where our neck joins the head is a pivotal joint. It allows us to bend our head forward and backwards and turn the head to our right or left. In a pivotal joint, a cylindrical bone rotates in a ring.
Additional Information

•  The ball and socket joint provides swinging and rotating movements.
  • The articulating bone is received into the cavity of another bone, allowing the distal bone to move around three main axes with a common centre.
  • The joint has to stabilize ligaments that limit the directions and extent to which the bones can be moved
• Hinge joints are those that allow movement along one plane.
  • They facilitate bending and straightening actions, such as flexing a finger.
  • In a hinge joint, protective cartilage covers the bones, and a thick gel called synovial fluid lubricates them, allowing them to move without rubbing against one another.

Option 2 is correct, i.e. Collar's bone.

Key Points

• In human anatomy, the clavicle or collarbone is a long bone that serves as a strut between the scapula (shoulder blade) and the sternum (breastbone).
• The mandible forms the lower jaw and holds the lower teeth in place.

Additional Information

The human skeleton is made up of 206 bones, including bones of the:

• Skull:  including the jaw bone
• Spine: cervical, thoracic and lumbar vertebrae, sacrum and tailbone (coccyx)
• Chest: ribs and breastbone (sternum)
• Arms: the shoulder blade (scapula), collar bone (clavicle), humerus, radius and ulna
• Hands: wrist bones (carpals), metacarpals and phalanges
• Pelvis: hip bones
• Legs: the thigh bone (femur), the kneecap (patella), the shin bone (tibia) and the fibula
• Feet: tarsals, metatarsals, and phalanges.

The correct answer is option 3 i.e It involves release of \(Ca^{++}\) from sarcoplasmic reticulum (SR) and pumping \(Ca^{++}\) back in SR

Explanation:

• Muscle contraction is the activation of tension- generating sites within muscle fibres.
• The sequence of events in the contraction of muscle fibre is as follows: -
• It begins with a signal- the neurotransmitter, Ach - from the motor neuron innervating that fibre.
• The local membrane of the fibre will depolarize as positively charged Na+ ions enter, triggering an action potential that spreads to the rest of the membrane will depolarize, including the T-tubules.
• This triggers the release of \(Ca^{++}\) ions from the sarcoplasmic reticulum.
• These \(Ca^{++}\) ions initiate contraction, which is sustained by ATP.
• As long as \(Ca^{++}\) ions remain in the sarcoplasm to bind to troponin, which keeps the actin-binding sites unshielded and as long as ATP is available to drive the cross bridge cycling and pulling of actin strands by myosin.
• Muscle contraction usually ends when signalling from the neuron ends and after this \(Ca^{++}\) ion pumped back to the SR. Hence, correct answer is option 3.

Key Points

• Sarcomere is the functional unit of striated muscles.
• Also the elementary unit of contraction in the muscles. 
• Sarcomeres are composed of long, fibrous proteins that slide past each other when a muscle contract or relaxes.
• It is the repeating unit between two Z lines and consists of one A-band and one I-band.

• During the sarcomere contraction, the length of the A-bands remains the same.
• But the length of the I-bands and the H-zone reduce in size.
• The mechanism of muscle contraction is best explained by the sliding filament theory.
• It postulates that the thin actin filaments are displaced with respect to the thick myosin filaments during each cycle of contraction and relaxation.
• The actin filaments slide over myosin filaments thus decreasing the length of the sarcomere and contracting the muscle fibers.
• The myosin head binds to the exposed active sites on actin to form a cross bridge by consuming energy from ATP hydrolysis.
• As a result, the connected actin filaments are drawn toward the center of the A band.
• Moreover, the Z line connected to these actin filaments is dragged inward, shortening the sarcomere and generating contraction.
• Thus, the size of the A bands remains the same, the size of the H zone becomes smaller and the size of the I bands decreases during muscle contraction.

Hence, the correct answer is option (1).

Key Points

• Hyaline cartilage is a type of connective tissue that is found in many parts of the body, including the nose, trachea, and the ends of bones in joints.
• It is a transparent tissue because it has a glassy appearance when viewed under a microscope.
• Hyaline cartilage is also smooth and firm, which makes it an excellent shock absorber.

Additional Information

• Fibrous Cartilage: Fibrous cartilage is a tough, dense connective tissue that is found in areas of the body that need to withstand pressure and tension. It is found in the intervertebral discs, pubic symphysis, and in some tendons and ligaments.
• Tendon: Tendons are tough, fibrous connective tissues that attach muscles to bones. They are not transparent but are rather white, shiny, and reflective.
• Ligament: Ligaments are fibrous connective tissues that connect bones to other bones. Like tendons, they are not transparent but are rather white, shiny, and reflective.

The correct answer is A: Troponin, B: F - actin,  C: 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

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Concept:

• The ability of the human body to fight against the different pathogenic organisms or the toxins that they release that damage the tissues and organs are called immunity.
• When the immune system undergoes overdrive and starts attacking the body's own cells. This condition is referred to as an autoimmune disorder.
• In autoimmune disorders, due to some trigger, the immune system starts producing antibodies.
• These antibodies instead of fighting pathogens start attacking the body's own cells.
• Treatment involves reducing immune system activity.
• E.g.: Rheumatoid arthritis, Multiple sclerosis, Guillain-Barre syndrome, Grave's disease, Myasthenia gravis, etc.

Explanation:​​ 

Myasthenia gravis - 

• It is an autoimmune disease.
• It is a chronic disease that affects the muscles.
• In this disorder, antibodies bind to the nerve making it unable to stimulate the muscles. As a result, skeletal muscles are weakened.
• It affects the voluntary muscles of the body such as those of the eyes, mouth and limbs.
• Symptoms:
  • Weakness in eye muscles
  • Blurred vision
  • Change in facial expression
  • Shortness of breath and trouble swallowing
  • Weakening muscles
  • Trouble in walking
  • Fatigue

Additional InformationOsteoporosis - 

• ​Osteoporosis is a disease that makes bones weak and brittle.
• Causes:
  • Diet with low calcium 
  • Severe restrictions on food intake
  • Lack of exercise
  • Low levels of estrogen in women after menopause is known to cause osteoporosis in women.
  • Medical conditions such as intestinal problems, kidney diseases and parathyroid & thyroid problems.
  • Smoking and alcohol abuse.
• Symptoms include back pain, loss of height over the time, stooped posture and fragile bones.

Arthritis - 

• Arthritis refers to a disease associated with swelling  or pain in joints.
• There are several types of arthritis. Some of these are osteoarthritis, rheumatoid arthritis, gout, etc.
• Common arthritis causes are ​age, wear and tear of a joint, injuries, obesity, autoimmune disorders as in the case of rheumatoid arthritis, and muscle weakness.
• ​Symptoms include pain, swelling in joints, stiffness and loss in range of motion.

Muscular dystrophy - 

• Muscular dystrophy refers to diseases that affect muscle mass.
• It causes progressive weakness and loss of muscle mass.
• Causes:
  • Muscular dystrophy occurs due to mutations in genes.
  • The abnormal genes do not produce proteins that are needed for the formation of healthy muscles.
  • Deletion in the DMD gene (dystrophin gene) causes Duchenne and Becker muscular dystrophy.
• Symptoms include muscle pain and stiffness, delayed growth, large calf muscles, frequent falls, difficulty in getting up from lying position, trouble in running and jumping, etc.

So the correct answer is option 3 (Myasthenia gravis).

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.

Concept:

• Skeletal muscles are also known as striated or voluntary muscles.
• These muscles are attached to the skeletal structures, hence the name.
• These muscles occur in bundles with each bundle consisting of several fibers.
• Each fiber represents a multinucleated cell that is covered by sarcolemma.
• The cytoplasm encloses several fine fibrils known as myofibrils. These are bundles of actin and myosin filaments.
• Striated muscles are voluntary. It gets its nerve supply from the ventral root of the spinal nerve.

Important Points

Formation of cross-bridge during muscle contraction:

• ​The muscle contraction cycle triggers with binding of calcium ions to troponin a protein complex.
• This in turn exposes the active-binding site on the actin.
• The actin-binding site once exposed attaches to the myosin head.
• The high-energy myosin head thus bridges the gap forming a cross-bridge.
• Once the actin and myosin bind, phosphate is released and myosin undergoes a conformational change.
• Myosin changes to a lower energy state and pulls the actin filament towards the "M" line.
• As a result of the actin being pulled, the sarcomere shortens and the muscle contracts.

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So from the above-given information, the correct answer is option 2 (Actin binds to the exposed myosin head).