In the resting state of skeletal muscle, which molecule lies on top of the active sites of the actin strands, preventing contraction?
Explanation
This question tests the knowledge of the regulatory proteins in the thin filament, specifically the role of tropomyosin in inhibiting contraction in a relaxed muscle.
Other questions
What is the typical diameter range for the numerous fibers that compose skeletal muscles?
Each myofibril is composed of approximately how many adjacent myosin and actin filaments?
What are the light bands in myofibrils that contain only actin filaments called, and why?
What is the portion of the myofibril that lies between two successive Z disks called?
What is the approximate length of a sarcomere when the muscle fiber is contracted and capable of generating its greatest force?
What is the primary function of the filamentous protein titin in the sarcomere?
What is the molecular weight of a single titin molecule, making it one of the largest protein molecules in the body?
Which neurotransmitter is secreted by a motor nerve at its endings on muscle fibers to initiate contraction?
What is the primary mechanism by which muscle contraction occurs, as demonstrated in Figure 6-5?
A myosin molecule is composed of how many polypeptide chains in total?
What is the approximate molecular weight of a single myosin molecule?
What essential enzymatic function does the myosin head perform, which is critical for muscle contraction?
Which subunit of the troponin complex has a strong affinity for calcium ions, initiating the contraction process?
What is the phenomenon called where the amount of ATP cleaved during muscle contraction is proportional to the amount of work performed?
In the walk-along theory of contraction, what is the tilting of the myosin head that drags the actin filament called?
What event directly causes the detachment of the myosin head from the actin filament after a power stroke?
At what sarcomere length does a contracting muscle fiber begin to lose tension because the ends of the two actin filaments start to overlap each other?
What is the first source of energy used to reconstitute ATP in a muscle fiber after it has been used for contraction?
For how long can the combined energy of stored ATP and phosphocreatine in a muscle fiber sustain maximal muscle contraction?
The rate of ATP formation by glycolysis is approximately how many times as rapid as ATP formation from oxidative metabolism?
More than 95 percent of all energy used by muscles for sustained, long-term contraction is derived from which source?
Under the best conditions, what is the maximum efficiency of muscle contraction, meaning the percentage of input energy converted into work?
When is maximum efficiency of muscle contraction realized in terms of contraction velocity?
What is the term for a muscle contraction where the muscle does not shorten, but its tension increases?
The duration of an isometric contraction of an ocular muscle is less than what fraction of a second?
Which characteristic is typical of slow fibers (Type I, red muscle)?
What gives slow fibers (Type I muscle) their characteristic reddish appearance?
Which characteristic is typical of fast fibers (Type II, white muscle)?
What constitutes a 'motor unit' in skeletal muscle?
What is the term for increasing the intensity of muscle contraction by increasing the number of motor units contracting simultaneously?
According to the size principle, when the central nervous system sends a weak signal to contract a muscle, which motor units are stimulated first?
What is the process called when successive muscle contractions fuse together due to increasing stimulation frequency, resulting in a smooth, continuous contraction?
What is the average maximum strength of tetanic contraction for a muscle with a normal length?
What is the staircase effect, or treppe?
What is believed to be the primary cause of the staircase effect (treppe)?
Studies in athletes have shown that muscle fatigue increases in almost direct proportion to the rate of depletion of what substance?
What is the term for the increase in the total mass of a muscle?
Virtually all muscle hypertrophy results from which of the following changes at the cellular level?
What is the process called when the number of muscle fibers increases, which can occur under rare conditions of extreme muscle force generation?
How does stretching a muscle to a greater than normal length lead to hypertrophy?
What happens to a muscle that loses its nerve supply (denervation)?
What is the cause of rigor mortis, the state of muscle contracture after death?
In Duchenne muscular dystrophy (DMD), a mutation in the gene that encodes which protein is the cause of the disease?
What is the primary function of the sarcolemma in a skeletal muscle fiber?
According to the general mechanism of muscle contraction, what is the direct result of acetylcholine opening cation channels on the muscle fiber membrane?
What is the approximate molecular weight of a G-actin molecule, the monomer that polymerizes to form F-actin?
What is believed to be the function of the ADP molecules attached to each G-actin molecule?
In a whole muscle, about what percentage of the cardiac output does it normally receive, which is sufficient to maintain contraction for only a short period?
What is the term for the process where a muscle remains unused for many weeks, and the rate of degradation of contractile proteins is more rapid than the rate of replacement?