. In a test of biology a figure of smooth muscle labeled as A, B, C and D for different parts of the muscles. Four students P, Q, R and S in a way to attempt the question named the four parts as given below. But only one student could name all the four parts correctly. Which of the following option is the answer written by that student? *
Answers
Answer:
Each muscle fibre is long and cylindrical cells, that contain many nuclei, i.e., are multinucleated. Here, labelling E is the nucleus.
The cell membrane is called as sarcolemma. Here, labelling D is sarcolemma.
When skeletal muscle is viewed in longitudinal section, it exhibits a distinctive pattern of alternating light and dark bands. The dark-staining bands are called as A-band, sometimes contain a pale region in the middle called as H-zone.
The light staining bands, I bands are bisected by a thin Z-line. This striated pattern in due to the presence of myofibrils in the sarcoplasm. Here, labelling A and labelling F are light and dark bands respectively, while labelling C is myofibril.
The segment of a myofibril from Z-line to Z-line is referred to as sarcomere.
So, the correct answer is 'A- Light band, B- Sarcoplasm, C- Myofibril, D- Sarcolemma, E- Nucleus, F- Dark band'
"It seems this is what you are looking for"
Which of the following options is the answer written by that student?
(a) A – Intercalated disc; B – Sarcoplasm; C – Branched fibres; D – Nucleus
(b) A – Intercalated disc; B – Branched fibres; C – Sarcoplasm; D – Nucleus
(c) A – Branched fibres; B – Intercalated disc; C – Sarcoplasm; D – Nucleus
(d) A – Branched fibres; B – Sarcoplasm; C – Intercalated disc; D – Nucleus
Answer:
A is Intercalated disc, B is Branched fibres, C is Sarcoplasm and D is Nucleus.
Therefore, option (b) is correct.
Explanation:
- Intercalated discs connect adjacent cardiac muscle cells and are complex structures. Three kinds of cell junction make an intercalated disc are fascia adherens junctions, desmosomes and adherens junctions.
- The smooth muscle fibers are grouped up in form of branching bundles is called branched fibres . These fibres consist in a complex system and do not run exactly parallel.
- The cytoplasm of a smooth muscle fibre is called Sarcoplasm . It is a water solution carrying phosphagens, ATP, enzymes, intermediate and product molecules which are involved in many metabolic reactions. Potassium is the most abundant metal in Sarcoplasm.
- Smooth muscle consists a single central nucleus. The cells are connected by cell junctions. The nucleus is located in the center and during contraction, changes a cigar-like shape.
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