Experts can i have the answer for the 23 & 24 th question
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23.
The sliding filament theory explains the process of muscle contraction during which the thin filaments slide over the thick filaments, which shortens the myofibril.
Each muscle fibre has an alternate light and dark band, which contains a special contractile protein, called actin and myosin respectively. Actin is a thin contractile protein present in the light band and is known as the I-band, whereas myosin is a thick contractile protein present in the dark band and is known as the A-band. There is an elastic fibre called z line that bisects each I-band. The thin filament is firmly anchored to the z line. The central part of the thick filament that is not overlapped by the thin filament is known as the H-zone.
During muscle contraction, the myosin heads or cross bridges come in close contact with the thin filaments. As a result, the thin filaments are pulled towards the middle of the sarcomere. The Z line attached to the actin filaments is also pulled leading to the shortening of the sarcomere. Hence, the length of the band remains constant as its original length and the I-band shortens and the H-zone disappears.
| Systemic Circulation | Pulmonary Circulation |
| 1.It carries oxygenated blood away from the heart to the whole body. And carries the deoxygenated blood back to the heart. | 1.It carries deoxygenated blood away from the heart to the lungs and also carries the oxygenated blood from the lungs to the heart. |
| 2.Oxygenated blood leaves the heart through left ventricle. | 2.Deoxygenated blood leaves through the right ventricle. |
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