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