Zoology MCQs for NEET — Practice Questions with Answers

The space between two successive Z-bands in a muscle fiber is known as the sarcomere. A sarcomere is the basic unit of striated muscle tissue responsible for muscle contraction. It is composed of repeating units of actin and myosin filaments. Understanding this structural organization helps in studying how muscles contract and generate force.

The Z-band, also known as the Z-line or Z-disc, is sometimes referred to as the Krause membrane. It marks the boundary between adjacent sarcomeres in muscle fibers. The Z-band plays a crucial role in muscle contraction by anchoring the actin filaments and helping maintain the structural integrity of the muscle fiber.

The functional unit of skeletal muscle is called the sarcomere. Sarcomeres are the repeating structural units within myofibrils, bordered by Z-lines. They contain the actin and myosin filaments whose interactions are responsible for muscle contraction. This understanding is fundamental for comprehending how muscles work at a microscopic level.

Actin fibers exist in two main forms: G-actin (globular actin) which are monomers, and F-actin (filamentous actin) which are polymerized chains of G-actin. Hence, options 1 and 3 together (Both 1 & 3) are correct.

Troponin is a complex of three regulatory proteins that are involved in muscle contraction. It is a small, globular protein complex that binds to tropomyosin and helps regulate the interaction of actin and myosin in muscle fibers.

The essential mineral element for muscle contraction is Calcium (Ca⁺⁺). During muscle contraction, calcium ions are released from the sarcoplasmic reticulum into the muscle cell, which then interact with regulatory proteins on the actin filaments, allowing the cross-bridge cycle to occur.

Acetylcholine is essential for the transmission of messages in the nervous system. It is a neurotransmitter that is released at the synaptic cleft and binds to receptors on the post-synaptic membrane, which leads to the propagation of the nerve impulse.

Lactic acid is the chemical evolved during anaerobic respiration of glycogen in muscle. Under anaerobic conditions, pyruvate is converted into lactic acid, which helps regenerate NAD⁺ needed for glycolysis to continue.

Lactic acid is produced during intense exercise when oxygen levels are low, leading to anaerobic respiration in muscles. This accumulation of lactic acid causes a decrease in pH within the muscle cells, leading to the sensation of muscle fatigue.