Answer and Explanation:
In rest, attraction strengths between myosin and actin filaments are inhibited by the tropomyosin. When the muscle fiber membrane depolarizes, the action potential caused by this depolarization enters the t-tubules depolarizing the inner portion of the muscle fiber. This activates calcium channels in the T tubules membrane and releases calcium into the sarcolemma. At this point, tropomyosin is obstructing binding sites for myosin on the thin filament. When calcium binds to the troponin C, the troponin T alters the tropomyosin by moving it and then unblocks the binding sites. Myosin heads bind to the uncovered actin-binding sites forming cross-bridges, and while doing it ATP is transformed into ADP and inorganic phosphate which is released. Myofilaments slide impulsed by chemical energy collected in myosin heads, producing a power stroke. The power stroke initiates when the myosin cross-bridge binds to actin. As they slide, ADP molecules are released. A new ATP links to myosin heads and breaks the bindings to the actin filament. Then ATP splits into ADP and phosphate, and the energy produced is accumulated in the myosin heads, which starts a new binding cycle to actin. Z-bands are then pulled toward each other, thus shortening the sarcomere and the I-band, and producing muscle fiber contraction.
Answer:
Answer:
First let's add the missing piece of information
1. Protection
2. Electrolyte balance
3. Movement
4. Support
The answers
A. 3
B. 4
C. 1
D. 2
Explanation:
A. Muscles exert force against bones -3. Movement
Muscles puts a force on bones during contraction to cause body movement and lifting of objects.
B. The body's mass is suspended from bones and rest upon bones -4. Support
This provides support.
C. The lungs are surrounded by the ribs -1. Protection
The lungs are protected by the rib cage (12 sets of ribs) connected to the spine and around the lungs for protection.
D. Calcium is released from bones to restore the calcium levels in body fluids -2. Electrolyte balance
The bones is rich in calcium. It is deposited at high blood levels and released at low blood levels as it is controlled by PTH, vitamin D, and calcitonin.
Because of their resemblance and relationship to prehistoric reptiles and many people think that birds descended from dinosaurs
Eye strain - hope this helped
