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What is the H zone A band?
Within skeletal muscle there are muscle fibres... and within muscle fibres there are myofibrils... and within a myofibril there is a sarcomere.Within the sarcomere there are 2 types of bands:-Actin (light)-Myosin (dark)There are different striations of these bands, this is what makes up the muscle fibre:The A band is where actin & myosin overlapp- it contains both myosin & actinThe I band only contains actinThe H zone only contains myosinThe Z line is in the centre of each I band, and marks the start of a sarcomere
What are the 3 sections along the length of sarcomere?
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.
What myofibril contains only thick myofilaments?
No, myofibrils contain both thick filaments (myosin) and thin filaments (actin) which when activated overlap each other as part of muscular contraction.
What is the region of the striated muscles banding patterns that contains only the connections between the tails of myosin molecules?
M Line
Striations in striated muscle result from?
Striated muscle appears stripped due to the parallel alignment of many muscle fibers side to side with their sarcomeres lined up. The striations across each cell are caused by the overlap of the contractile proteins actin and myosin. Actin is the main protein of thin filaments and myosin is in the thick filaments. When actin and myosin are overlapped the darkest band appears( A band), when only actin is present a lighter band, is seen (I band).
What type of of muscle is found only in the heart?
Cardiac muscle is found only in the heart. Cardiac muscle contains the proteins actin and myosin. All the other muscles are smooth or skeletal.
Which of the following become connected by myosin cross-bridges during muscle contraction A) thin filaments and thick filaments B) thin filaments and t-tubules C) thick filaments and titin filame?
Interactions between actin and myosin filaments of the sarcomere are responsible for muscle contractions. The I bands contain only thin (actin) filaments, whereas the A bands contain thick (myosin) filaments.
Only type of tissue that can contract?
The only Biological tissue that is able to contract is MUSCLE tissue and this is because of the specialized proteins: actin and myosin that slide across each other.
What is the role of tropomyosin in muscles?
Tropomyosin is the thick filament of a muscle sarcomere. It lines the span of 7 G-actin monomers along the grooves of the F-actin filament. Troponin is a trimer that consists of subunits TN-C, TN-I and TN-T. Troponin is attached to tropomyosin and its function is involved in muscle contraction. In a powerstroke of a muscle contraction you have TN-I blocking the myosin head from attaching to the myosin binding site on the actin filament. This is the resting state. When you contract your muscles, calcium is released and attaches to TN-C. This produces a conformational change that moves TN-I away from the myosin head. In turn the myosin binds to the myosin binding site. On the myosin head there is a myosin ATPase that hydrolyzes an ATP which provides the energy for the head to bend 45 degrees. This is the powerstroke that produces muscle contraction. Another ATP molecule will enter in and release the myosin head and calcium is pumped back into the sarcoplasmic reticulum. The resting state is restored!
What is atrial depolarization?
Atrial depolarization is the first part of the cardiac cycle.Cardiac (and skeletal) muscle is made up of bundled stands of functional units called sarcomeres. Each sarcomere consists of two Z-disks, which mark the ends of each sarcomere, and alternating dark and light bands called A-bands and I-bands respectively. The I-band contains only actin (the main cytoskeletal protein in most cells) filaments whereas the A-band contains overlapping myosin (a "molecular motor" protein) and actin filaments in its periphery and only myosin filaments in the central region called the H-zone. The center of the H-zone is marked by an imaginary line (called the M-line) in which myosin extends in both directions. The sarcomere contracts inward toward the M-line. "Depolarization" occurs when an electrochemical event causes calcium cations to be released from a membranous network (similar to the the endoplasmic reticulum) called the sarcoplasmic reticulum and creates an action potential. The free Ca2+ binds to a specific troponin protein shifting a troponin/tropomyosin protein complex allowing the myosin head groups to bind to the actin filament. ATP hydrolysis causes conformational changes of the myosin filament which in effect "pulls" the actin filament toward the M-line of the sarcomere. The sarcomere can return to its resting potential by allowing potassium (K+) ions to flow out.
What is the role is tropomyosin muscle?
Short answer: Tropomyosin wraps around an actin filament to form a functional actin filament or aka. thin filament. It's purpose is involved in the powerstroke of the myosin head. It does this by kind of like a hook. If you have a hook and you grab a long rope and pull it towards you, the hook is a thick filament (myosin) and the rope is a thin filament (actin). Troppmyosin will block the hook from latching onto the rope in normal resting phase. When it is released (by calcium), you can now freely hook the rope and pull it towards you.Long answer:Tropomyosin wrap around actin like a slinky. It functions to block myosin from attaching to actin. This is done by troponin complex (TN-I, TN-C, TN-T). In the sliding filament model you have the thick (myosin) and thin (actin) filaments sliding past one another. This sliding action is performed by crossbridges formed between the myosin head and myosin-binding site on the actin.Normally in resting phase, when the muscle is relaxed, the troponin complex is blocking the myosin-binding site. This prevents the myosin head from attaching to the myosin-binding site. In addition it is preventing a protein on the myosin head (myosin ATPase) from hydrolizing an ATP for what it will later use in a powerstroke. Whenever the myosin-binding site becomes available, it will always want to attach to the myosin head. This is the high affinity it has. The myosin-binding site reveals itself when calcium enters and makes a conformational change on that troponin complex (first paragraph). Actually it adheres to TN-C specifically (TN-C = troponin calcium). So when calcium attaches to troponin complex it reveals the myosin-binding site. As the myosin-binding site is revealed the head is now free to attach and the myosin ATPase is now free to hydrolyze ATP. It takes that energy to bend the myosin head 45 degrees and it attaches to the myosin-binding site. SUCCESS!However, that's only half the story because now you need detach. Another ATP molecule comes in and it detaches the myosin head from the thin filament (specifically myosin-binding site). It's important to note here that the ATP is not hydrolyzed and it's only used to restore the resting phase. Calcium is taken back by pumps, the troponin complex rears it's ugly face and the myosin head is blocked once again.When a person dies and no longer produces ATP, the muscles that were contracted cannot release because new ATP doesn't exist to restore the resting phase. This is rigor mortis.
What does a muscle cell do that no other cells can do?
Only muscle cell contracts...(filaments contain actin and myosin) that helps them to contract
