The three sections along the length of a sarcomere are the A band, the I band, and the H zone. The A band is the dark region in the center of the sarcomere that contains both thick and thin filaments, while the I band is the light region at the ends of the sarcomere that contains thin filaments only. The H zone is the region in the center of the sarcomere where only thick filaments are present.
The "M" line.
A sarcomere consists of thin and thick filaments arranged so they can slide over each other. The boundary of the sarcomere are the Z lines. Thin filaments extend from the Z lines and overlap with thick filaments in the middle of the sarcomere. The I band is on each side of the Z line where only thin filaments occur. The A band is the length of the thick filaments and is divided into three parts; the zone of overlap is on each end where thin and thick filaments occur, the H band is in the middle and has only thick filaments, and the M line is the center of the A band.
Flexing of the cross bridge (power stroke)
1. Arrangement of thick and thin filaments: In each sarcomere two sets of actin filaments extend partway toward the center. The myosin filaments are arranged such that they partially overlap the actin filaments. Myosin heads on each side point away from the center of the sarcomere.2. During contraction, the interaction of myosin heads with the actin filaments pulls the thin filaments toward the center of the sarcomere. The actin and myosin filaments slide past each other.3. Cross-bridges = attachement betwn myosin heads and binding sites on actin filaments.4. When a muscle cell is stimulated, myosin heads are energized by ATP. They attach to adjacent actin filaments, and tilt in a short "power stroke" toward the center of the sarcomere. Each power sroke requires an ATP. With many power strokes in rapid succession, the actin filaments are made to slide past the myosin filaments.
Yep, you got it.
The H band is located at the center of the A band in the sarcomere and is where only thick filaments (myosin) are present, with no overlap with thin filaments (actin). It appears lighter under a microscope due to the organization of filaments. This region shortens during muscle contraction as the myosin filaments slide past the actin filaments towards the M line.
A performance center of unusual architecture with a roof made of overlapping shells is the Sydney Opera House in Sydney, Australia. It was designed by Danish architect Jorn Utzon.
A performance center of unusual architecture with a roof made of overlapping shells is the Sydney Opera House in Sydney, Australia. It was designed by Danish architect Jorn Utzon.
The H zone of a sarcomere contains no actin filaments, only myosin filaments. It is located in the center of the A band and gets shorter during muscle contraction.
The interactions between actin and myosin filaments of the sarcomere are responsible for muscle contraction. Myosin heads bind to actin filaments, forming cross-bridges that pull the actin filaments towards the center of the sarcomere. This sliding action shortens the sarcomere, leading to muscle contraction.
During muscle contraction, the thin filaments (actin) are pulled towards the center of the sarcomere, which causes the Z-lines to move closer together. This process is facilitated by the interaction between actin and myosin filaments during the sliding filament mechanism of muscle contraction.