Human Skeletal System MCQ Quiz in বাংলা - Objective Question with Answer for Human Skeletal System - বিনামূল্যে ডাউনলোড করুন [PDF]

The correct answer is It marks the boundary of a sarcomere, anchoring actin filaments.

Explanation:

The Z-line (or Z-disc) is a crucial structural component of the sarcomere, the basic contractile unit of muscle fibers. It has the following functional significance:

• The Z-line marks the boundaries of a sarcomere, the repeating unit that runs between two Z-lines.
• It serves as an anchor point for the thin actin filaments (thin myofilaments), which are attached to it. This helps in organizing the actin filaments and maintaining the alignment of the sarcomeres during contraction.
• During muscle contraction, the Z-lines move closer together as the actin filaments slide over the myosin filaments, shortening the sarcomere.

Other options are incorrect:

• a) It serves as a connection between actin and myosin filaments: This is incorrect because the Z-line primarily anchors the actin filaments, while the myosin filaments are anchored at the M-line.
• b) It attaches to the M-line to stabilize the sarcomere: This is not entirely correct. The Z-line defines the boundaries of a sarcomere, while the M-line is where the myosin filaments are anchored. The Z-line does not directly attach to the M-line.
• d) It is where the calcium ions are stored for muscle contraction: Calcium ions are stored in the sarcoplasmic reticulum, not at the Z-line. The Z-line's role is related to structural support for actin filaments.

The correct answer is A-II, B - III, C - IV, D - I

Explanation:

A. Joint between humerus and pectoral girdle: Ball and Socket joint

• A ball and socket joint is a type of synovial joint that allows for multi-directional movement and rotation.
• This joint features a spherical "ball" at the end of one bone fitting into a cup-like "socket" of another bone, enabling the bones to move and rotate in several directions.

B. Knee joint: Hinge joint

• Hinge joints allow movement primarily in one axis, permitting flexion (bending) and extension (straightening).
• The range of motion is similar to the movement of a door hinge, predominantly in one plane (sagittal plane).
• Examples: The elbow and the knee are classic examples of hinge joints.

C. Joint between atlas and axis: Pivot joint

• A pivot joint, also known as a rotary joint or trochoid joint, allows for rotational movement around a single axis.
• Atlas (C1): The first cervical vertebra that supports the skull. It has a ring-like shape.
• Axis (C2): The second cervical vertebra, characterized by the presence of the odontoid process (or dens), a peg-like projection that extends upwards.
• The atlantoaxial joint enables the head to turn from side to side. This rotational movement is essential for a wide range of head and neck mobility.

D. Joint between carpals: Gliding joint

• Gliding joints, also known as plane joints, are a type of synovial joint where the articular surfaces are nearly flat or slightly curved, allowing bones to slide past one another.
• These joints are characterized by limited movement, primarily in the form of gliding actions.
• They are crucial for providing stability and enabling small adjustments in the positions of bones, which is essential for various functional movements. 

The correct answer is option 3 i.e It involves release of  from sarcoplasmic reticulum (SR) and pumping  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  ions from the sarcoplasmic reticulum.
• These  ions initiate contraction, which is sustained by ATP.
• As long as  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  ion pumped back to the SR. Hence, correct answer is option 3.

The correct answer is option 3.

Concept: 

• There are two types of muscle fiber in birds and mammals, which are red and white muscle fiber.
• Red muscle fibers are rich in myoglobin and mitochondria.
• White muscle fibers are longer and thicker in size. These are less vascularized and light-colored, so lack myoglobin and do not store oxygen.
• Each muscle fiber is composed of myofibrils.
• Muscle fiber has a functional unit called the sarcomere.

​

Explanation:

Fast muscle fibers-lactic acid:

• It is known that the fast muscle fibers (white muscle fibers) carry less amount of myoglobin and mitochondria, therefore, they depend upon anaerobic oxidation, which produces lactic acid. 
• It is to be noted that they also exhibit a fast rate of contraction.

Slow muscle fibres-Myoglobin

• Red Muscles are also called slow twitch fibers.
• This type of muscle fiber is rich in myoglobin and mitochondria.
• They appear red in color due to the presence of myoglobin.
• They are called slow twitch fibers as they exhibit a slow rate of contraction.

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Actin filament- I band

• Muscle fiber comprises myofibrils.
• They exhibit alternate dark and light bands.
• The dark bands are made up of mainly myosin protein and the light bands comprise actin protein.
• Actin filaments form the isotropic part of the sarcomere.

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Sarcomere- Contractile unit

• The functional unit of muscle fiber is called the sarcomere.
• The sarcomeres have a large number of parallelly arranged filaments known as myofibrils.
• These myofibrils consist of light and dark bands
• The light bands are made up of actin filaments, known as an I-band or Isotropic band, whereas dark bands are composed of myosin filaments, known as Anisotropic or A-band.
•  
  The sarcomere is the fundamental contractile unit of the myofibril.
• In the center of each I-band, a Z-line is present and an M-line is present in the A-band, the A & I-bands are arranged alternately throughout the myofibrils.
• The portion between 2 successive Z-line is called Sarcomere.
• Therefore, the correct answer is option 3. A - ii, B - i, C - iv, D - iii.

The correct answer is option 3 i.e It involves release of  from sarcoplasmic reticulum (SR) and pumping  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  ions from the sarcoplasmic reticulum.
• These  ions initiate contraction, which is sustained by ATP.
• As long as  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  ion pumped back to the SR. Hence, correct answer is option 3.

The correct answer is option 3 i.e It involves release of  from sarcoplasmic reticulum (SR) and pumping  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  ions from the sarcoplasmic reticulum.
• These  ions initiate contraction, which is sustained by ATP.
• As long as  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  ion pumped back to the SR. Hence, correct answer is option 3.

The correct answer is option 2.

Concept: 

• Muscles are contractile tissues present in the human and animal bodies and function in a group to coordinate the efficient functioning of human and animal organs.
• The muscle tissue cells are made up of protein filaments of actin and myosin.
• The protein filaments are arranged one upon the other to help in muscle movement and provide flexibility to the muscles.

Explanation: ​

Option 1:

• Smooth muscles are 'involuntary' and non-striated muscles as they cannot be controlled directly like skeletal muscles which are voluntary, controlled, and possess striations.
• The inner walls of the alimentary canal are non-striated and involuntary muscles. 
• Therefore, this is an incorrect answer.

​​Option 2:

• The heart muscles are made of cylindrical, branched striated cells that are involuntary.
• They are the cardiac muscles.
• Therefore, this is the correct answer.

​Option 3:

• The muscles of the hands and legs are voluntary and are made of cylindrical and striated cells.
• They are the skeletal muscles.
• Therefore, this is an incorrect answer.

​​​Option 4:

The correct answer is option 3.

Concept: 

• Muscles are contractile tissues present in the human and animal bodies and function in a group to coordinate the efficient functioning of human and animal organs.
• The muscle tissue cells are made up of protein filaments of actin and myosin.
• The protein filaments are arranged one upon the other to help in muscle movement and provide flexibility to the muscles.

Explanation: ​

Option 1:

• The heart muscles are made of cylindrical, branched striated cells that are involuntary.
• They are the cardiac muscles.
• Therefore, this is the correct statement and hence the incorrect answer.

​Option 2:

• The muscles of the hands and legs are voluntary and are made of cylindrical and striated cells.
• They are the skeletal muscles.
• Therefore, this is the correct statement and hence the incorrect answer.

​​Option 3: