Answer:
When a muscle cell contracts, the myosin heads each produce a single power stroke.
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, <em>tropomyosin is obstructing binding sites for myosin on the thin filament</em>. 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 liberated. Myofilaments slide impulsed by chemical energy collected in myosin heads, <u>producing a power stroke</u>. 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:
B) sympathetic and parasympathetic
Explanation:
e autonomic nervous system also called the vegetative nervous system is part of the peripheral nervous system which inervates smooth muscle and glands. Thus, it directly affects the function of internal organs and regulates functions such as the heart rate, digestion, respiratory rate, urination etc. This nervous system control is unconscious.
The autonomic nervous system is divided into: the sympathetic nervous system, the parasympathetic nervous system and the enteric nervous system.
Parasympathetic nervous system works when organism is at rest so it is known as system responsible for "rest and digest functions". On the other hand, sympathetic nervous system works at active and stressful situations and it is known as "fight and flight" system.
The variables are defined as the factors in an experiment, which are liable to change. The variable can be dependent or independent. The Independent variable is a variable, which is unaffected by the changes in the other variables.
In this case, the brand of the food Shara feeds to the rats is independent factor, but it is changes in the system, so, it is an independent variable.
The effect on the weight of the rat is dependent on the brand of food they are consuming. So, the weight of rats is dependent variable.
