Once a motor neuron has fired, all the muscle fibers in a muscle contract.
The thin filaments (actin) contain a polypeptide subunit G actin that bear active sites for myosin attachment.
The force of muscle contraction is controlled by multiple motor unit summation or recruitment.
Eccentric contractions are more forceful than concentric contractions.
A motor neuron and all the muscle cells that it stimulates are referred to as a motor end plate
Peristalsis is characteristic of smooth muscle.
A contraction in which the muscle does not shorten but its tension increases is called isometric.
During isotonic contraction, the heavier the load, the faster the velocity of contraction.
During isometric contraction, the energy used appears as movement.
One of the important functions of skeletal muscle contraction is production of heat.
Oxygen debt refers to the oxygen required to make creatine phosphate.
Muscle contraction will always promote movement of body parts regardless of how they are attached.
Although there are no sarcomeres, smooth muscle still possesses thick and thin filaments.
Whereas skeletal muscle cells are electrically coupled, smooth muscle cells appear to be chemically coupled by gap junctions.
Single-unit smooth muscle is found in the intestines.
A resting potential is caused by a difference in the concentration of certain ions inside and outside the cell.
The effect of a neurotransmitter on the muscle cell membrane is to modify its ion permeability properties temporarily.
When a muscle fiber contracts, the I bands diminish in size, the H zones disappear, and the A bands move closer together but do not diminish in length.
The more slowly a skeletal muscle is stimulated, the greater its exerted force becomes.
Contractures are a result of a total lack of ATP.
Smooth muscles relax when intracellular Ca2+ levels drop but may not cease contractions.
Recruitment is an option in a single-unit smooth muscle cell.
muscle fibers degenerate and atrophy
With muscular dystrophy ________.
Which muscle cells have the greatest ability to regenerate?
a mixture of fiber types
Most muscles contain ________.
intense exercise of short duration
Fatigued muscle cells that recover rapidly are the products of ________.
increasing the stimulation up to the maximal stimulus
The strongest muscle contractions are normally achieved by ________.
motor units with larger, less excitable neurons
Which of the following would be recruited later in muscle stimulation when contractile strength increases?
increase in the number of muscle cells
Which of the following is not a usual result of resistance exercise?
remove the blocking action of tropomyosin
In skeletal muscle contraction, calcium apparently acts to ________.
Calcium ions bind to the ________ molecule in skeletal muscle cells.
stores oxygen in muscle cells
An elaborate network of membranes in skeletal muscle cells that functions in calcium storage is the ________.
the area between two Z discs
A sarcomere is ________.
Immediately following the arrival of the stimulus at a skeletal muscle cell there is a short period called the ________ period during which the events of excitation-contraction coupling occur.
storing energy that will be transferred to ADP to resynthesize ATP
Creatine phosphate functions in the muscle cell by ________.
level in the cytoplasm drops
After nervous stimulation of the muscle cell has ceased, the calcium ________.
regulate intracellular calcium concentration
The major function of the sarcoplasmic reticulum in muscle contraction is to ________.
the arrangement of myofilaments
The striations of a skeletal muscle cell are produced, for the most part, by ________.
Which of the following are composed of myosin?
During muscle contraction, myosin cross bridges attach to which active sites?
Which of the following surrounds the individual muscle cell?
Smooth muscles that act like skeletal muscles but are controlled by autonomic nerves and hormones are ________.
no ATP is available to release attached actin and myosin molecules
Rigor mortis occurs because ________.
a change of temperature
Which of the following does not act as a stimulus to initiate a muscle contraction?
a sheetlike indirect attachment to a skeletal element
The term aponeurosis refers to ________.
The oxygen-binding protein found in muscle cells is ________.
The contractile units of skeletal muscles are ________.
The site of calcium regulation in the smooth muscle cell is ________.
One functional unit of a skeletal muscle is ________.
enhance cellular communication during muscle contraction
The functional role of the T tubules is to ________.
bind to regulatory sites on troponin, changing the configuration
The role of calcium ions in muscle contraction is to ________.
The warm-up period required of athletes in order to bring their muscles to peak performance is called ________.
enhance the availability of calcium and the efficiency of enzyme systems
The main effect of the warm-up period of athletes, as the muscle contractions increase in strength, is to ________.
During vigorous excercise, there may be insufficient oxygen available to completely break down pyruvic acid for energy. As a result, the pyruvic acid is converted to ________.
When a muscle is unable to respond to stimuli temporarily, it is in which of the following periods?
changes in length and moves the "load"
In an isotonic contraction, the muscle ________.
The muscle cell membrane is called the ________.
Smooth muscle contracts in a twisting way.
Smooth muscle is significantly different from striated muscle in several ways. Which of the following is true?
the site of calcium regulation differs
The mechanism of contraction in smooth muscle is different from skeletal muscle in that ________.
exhibit spontaneous action potentials
The cells of single-unit visceral muscle ________.
There is no biological basis for the difference in strength between women and men.
Which of the following statements is not true concerning developmental aspects of muscle?
Certain smooth muscle cells can actually divide to increase their numbers.
Which of the following is true about smooth muscle contraction?
there are more thick filaments than thin filaments
Smooth muscle is characterized by all of the following except ________.
Muscle tissue has all of the following properties except ________.
The giant protein titin maintains the organization of the ________ assisting in muscle stretching.
Striated muscle cells are long and cylindrical with many nuclei.
Which of the following statements is true?
An anaerobic metabolic pathway that results in the production of two net ATPs per glucose plus two pyruvic acid molecules is ________.
a state of sustained partial contraction
Muscle tone is ________.
actin and myosin sliding past each other and partially overlap
The sliding filament model of contraction involves ________.
acetylcholinesterase destroying the ACh
After nervous stimulation stops, ACh in the synaptic cleft is prevented from continuing stimulation of contraction by ________.
Muscle tension remains relatively constant during isotonic contraction.
Which of the following is most accurate?
the ability to transform chemical energy into mechanical energy
The most distinguishing characteristic of muscle tissue is ________.
a long, relaxing swim
Three discrete types of muscle fibers are identified on the basis of their size, speed, and endurance. Which of the following athletic endeavors best represents the use of red fibers?
multiunit smooth muscle
Of the following muscle types, which has only one nucleus, no sarcomeres, and rare gap junctions?
no muscle tension could be generated
Hypothetically, if a muscle were stretched to the point where thick and thin filaments no longer overlapped ________.
no contraction at all by nervous mechanisms, but contraction if stimulated by an external electrode
An individual has just ingested a chemical that binds irreversibly to the ACh receptors in the sarcolemma. By itself it does not alter membrane potential, yet prevents normal neurotransmitter binding. Ignoring the effects on any other system, the consequence to skeletal muscle would be ________.