أسئلة المحاضرة 11 فسيولوجي - دمياط

Skeletal muscles convert chemical energy to mechanical energy (work) and heat, making up about 40% of body weight.

The structural unit of skeletal muscle, an elongated, multinucleated cell (10-100 micrometers in diameter) containing sarcoplasmic reticulum, Golgi apparatus, ribosomes, mitochondria, glycogen, and T-tubules.

The part of muscle fiber with alternating light (I) and dark (A) bands, due to myofilament arrangement, giving skeletal muscle striations.

The functional unit of a muscle, located between two Z-lines, containing an A-band and half of each I-band on either side.

The light band in a myofibril, containing only thin filaments.

The dark band in a myofibril, containing both thick and thin filaments.

The dark line in the center of the I-band.

Tubular extensions of the muscle cell membrane that extend deep into the muscle fiber.

Contractile filaments found in skeletal muscle

Myosin protein filaments in the middle of a sarcomere

Actin, tropomyosin, and troponin protein filaments., attached by Z-lines

Projections connecting thick and thin filaments

Protein that makes up thick filaments

Protein forming twisted chains in thin filaments

Electrical signal that triggers muscle contraction

Binds to troponin causing tropomyosin to move, exposing actin binding sites.

The repeated process of myosin cross-bridges attaching to actin, pulling it towards the center of the sarcomere, detaching, and then reattaching to another actin molecule, resulting in muscle contraction.

During muscle contraction, the sarcomere shortens due to the sliding of thin filaments over thick filaments. This causes the Z lines to move closer, the I band to shorten, the H zone to narrow, and the A band to remain constant.

Calcium ions (Ca++) bind to troponin, causing a conformational change that moves tropomyosin away from the myosin-binding sites on actin, allowing cross-bridge cycling to occur. The continued presence of Ca++ ensures muscle contraction.

Muscle relaxation occurs when Ca++ is actively pumped back into the sarcoplasmic reticulum by Ca++ ATPase. This removes Ca++ from troponin, allowing tropomyosin to cover the myosin-binding sites on actin, stopping cross-bridge cycling, and resulting in muscle relaxation.

ATP is required by the Ca++ pump (Ca++ ATPase) to actively transport Ca++ back into the sarcoplasmic reticulum, which is crucial for muscle relaxation.

A specialized tissue that converts chemical energy into mechanical energy (movement) and heat. It's responsible for voluntary movement and makes up about 40% of body weight.

The individual cells that make up skeletal muscle. They are elongated, multinucleated, and contain specialized structures like the sarcoplasmic reticulum and T-tubules.

Long, cylindrical structures within muscle fibers that contain the contractile proteins (actin and myosin) arranged in a specific pattern, creating the striations.

The functional unit of a muscle fiber. It's the segment between two Z-lines and includes an A-band and half of each I-band.

Tubular extensions of the muscle cell membrane that penetrate deep into the muscle fiber, allowing electrical signals to reach every part of the muscle.

The dark A-band contains both thick (myosin) and thin (actin) filaments, while the light I-band contains only thin filaments.

Thin filaments are composed of three proteins: actin, tropomyosin, and troponin.

Thick filaments are composed of the protein myosin. They have projections called myosin heads that bind to actin, leading to muscle contraction.

Thick filaments are composed of myosin protein molecules, each containing a head with binding sites for actin and ATP, a body or arm that forms cross bridges with the head, and a long tail.

Thin filaments are composed of three protein molecules:

1. Actin molecules: form two twisted chains with binding sites for myosin.
2. Tropomyosin: thin filamentous protein covering the actin binding sites during relaxation.
3. Troponin: a regulatory protein.

Cross bridges, projections from the thick filaments, connect thick and thin filaments allowing them to interact during muscle contraction.

Released Ca++ ions bind to troponin on the thin filaments, causing tropomyosin to move away from the actin binding sites, exposing them to the myosin heads.

Muscle contraction occurs when thin filaments slide over thick filaments due to the repeated attachment, pulling, detachment, and reattachment of the myosin cross bridges, shortening the sarcomere.

During muscle contraction, the Z lines move closer together, the I band shortens, the H zone narrows, while the A band remains constant.

Muscle relaxation occurs when Ca++ is actively pumped back into the sarcoplasmic reticulum, causing tropomyosin to cover the actin binding sites, stopping cross-bridge cycling.

The sarcomere shortens due to the sliding of thin filaments over thick filaments, causing the Z lines to move closer, the I band to shorten, the H zone to narrow, and the A band to remain constant.

Calcium ions (Ca++) bind to troponin, causing a conformational change that moves tropomyosin away from the myosin-binding sites on actin, allowing cross-bridge cycling to occur.

A sarcomere contains an A-band (thick and thin filaments), an I-band (thin filaments only), an H zone (thick filaments only), and a Z-line at the ends.

Thin filaments slide over thick filaments, shortening the sarcomere and causing muscle contraction. This is driven by the interaction of myosin cross-bridges with actin.

Calcium binds to troponin, causing tropomyosin to move away from actin binding sites, allowing myosin to bind and initiate contraction.

Contractile filaments within muscle fibers, responsible for muscle contraction.

Myosin molecules are composed of a head with binding sites for actin and ATP, a body or arm forming cross bridges, and a long tail.

Muscle contraction occurs when thin filaments slide over thick filaments, due to the repeated attachment, pulling, detachment, and reattachment of myosin cross bridges.

Calcium ions (Ca++) bind to troponin causing tropomyosin to move, exposing actin binding sites for myosin heads.

Ca++ is actively pumped back into the sarcoplasmic reticulum, tropomyosin covers actin binding sites again, and the muscle relaxes.

During contraction, the sarcomere shortens due to thin filament sliding over thick filaments. Z lines move closer, I band shortens, and H zone narrows.

Calcium ions (Ca++) bind to troponin, causing a conformational change that moves tropomyosin away from the myosin-binding sites on actin, allowing cross-bridge cycling to occur. The continued presence of Ca++ ensures muscle contraction.

Specialized tissues that convert chemical energy into mechanical energy (work) and heat, responsible for voluntary movements.

Thick filaments (myosin) and thin filaments (actin, tropomyosin, troponin)

Calcium ions bind to troponin, causing tropomyosin to move away from actin binding sites, allowing myosin to bind and initiate contraction.

Tubular extensions of the muscle cell membrane that penetrate deep into the muscle fiber, allowing electrical signals to reach every part of the muscle.

Actin is a protein forming two chains that are twisted together in a spiral manner. Each chain has a binding site for myosin.

Tropomyosin is a thin filamentous protein that covers the binding sites on actin during relaxation. It prevents myosin from binding to actin.

Troponin is a regulatory protein that interacts with calcium ions. It aids in moving tropomyosin away from actin binding sites, allowing myosin to bind and initiate contraction.

Calcium ions (Ca++) bind to troponin, causing a conformational change that moves tropomyosin away from the myosin-binding sites on actin, allowing the cross-bridge cycling to occur. The continued presence of Ca++ ensures muscle contraction.