Sarcomere Structure and Muscle Regions — NEET Biology

Correct answer: B — S3 only

Let's evaluate each statement: S1: Skeletal muscles possess a striped appearance under the microscope and are under the voluntary control of the nervous system. This statement is correct. NCERT states, 'They have a striped appearance under the microscope and hence are called striated muscles. As their activities are under the voluntary control of the nervous system, they are known as voluntary muscles too.' S2: Visceral muscles are characterized by a smooth appearance, lacking striations, and function involuntarily in hollow internal organs. This statement is correct. NCERT states, 'They do not exhibit any striation and are smooth in appearance... Their activities are not under the voluntary control... and are therefore known as involuntary muscles.' S3: Cardiac muscle cells are typically unbranched, but like skeletal muscles, their activities are directly controlled by the central nervous system. This statement is incorrect. NCERT states, 'Many cardiac muscle cells assemble in a branching pattern to form a cardiac muscle.' (implying branched) and 'They are involuntary in nature as the nervous system does not control their activities directly.' (implying not directly controlled by CNS). So, cardiac muscles are branched and involuntary. S4: Each muscle fibre of skeletal muscle is described as a syncytium due to the presence of multiple nuclei within its sarcoplasm. This statement is correct. NCERT mentions, 'Muscle fibre is a syncitium as the sarcoplasm contains many nuclei.' S5: Cardiac muscles exhibit striations and a branching pattern, yet they are involuntary in nature. This statement is correct. NCERT states, 'Based on appearance, cardiac muscles are striated.' and 'Many cardiac muscle cells assemble in a branching pattern...' and 'They are involuntary in nature'. Therefore, only statement S3 is NOT correct.