With muscular dystrophy ________.
A) muscles decrease in size due to loss of fat and connective tissue
B) muscle fibers degenerate and atrophy
C) most forms do not appear to be inherited
D) most cases appear in young females
Which muscle cells have the greatest ability to regenerate?
D) no muscle can regenerate
Most muscles contain ________.
A) muscle fibers of the same type
B) a mixture of fiber types
C) a predominance of slow oxidative fibers
D) a predominance of fast oxidative fibers
Fatigued muscle cells that recover rapidly are the products of
A) intense exercise of long duration
B) intense exercise of short duration
C) slow exercise of long duration
D) slow exercise of short duration
The strongest muscle contractions are normally achieved by ________.
A) increasing stimulus above the threshold
B) increasing stimulus above the treppe stimulus
C) increasing the stimulation up to the maximal stimulus
D) recruiting small and medium muscle fibers
Which of the following would be recruited later in muscle stimulation
when contractile strength increases?
A) motor units with the longest muscle fibers
B) many small motor units with the ability to stimulate other motor units
C) large motor units with small, highly excitable neurons
D) motor units with larger, less excitable neurons
Which of the following is not a usual result of resistance exercise?
A) increase in the efficiency of the respiratory system
B) increase in the efficiency of the circulatory system
C) increase in the number of muscle cells
D) increase in the number of myofibrils within the muscle cells increase in the number of muscle cells
The role of calcium ions in muscle contraction is to ________.
A) increase the action potential transmitted along the sarcolemma
B) release the inhibition on Z discs
C) remove the blocking action of tropomyosin
D) cause ATP to bind to actin
Calcium ions bind to the ________ molecule in skeletal muscle cells.
A) breaks down glycogen
B) is a protein involved in the direct phosphorylation of ADP
C) stores oxygen in muscle cells
D) produces the end plate potential
An elaborate network of membranes in skeletal muscle cells that
functions in calcium storage is the ________.
A) sarcoplasmic reticulum (SR)
C) intermediate filament network
D) myofibrillar network
A sarcomere is ________.
A) the nonfunctional unit of skeletal muscle
B) the area between two Z discs
C) the area between two intercalated discs
D) the wavy lines on the cell seen in the microscope
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.
Creatine phosphate functions in the muscle cell by ________.
A) forming a temporary chemical compound with myosin
B) forming a chemical compound with actin
C) inducing a conformational change in the myofilaments
D) storing energy that will be transferred to ADP to resynthesize ATP
After nervous stimulation of the muscle cell has ceased, the calcium
A) is destroyed by cholinesterase
B) is chemically bound to the filaments
C) level in the cytoplasm drops
D) is actively pumped into the extracellular fluid for storage until the next contraction
The major function of the sarcoplasmic reticulum in muscle
contraction is to ________.
A) make and store phosphocreatine
B) synthesize actin and myosin myofilaments
C) provide a source of myosin for the contraction process
D) regulate intracellular calcium concentration
The striations of a skeletal muscle cell are produced, for the most
part, by ________.
A) a difference in the thickness of the sarcolemma
B) the arrangement of myofilaments
C) the sarcoplasmic reticulum
D) the T tubules
Which of the following are composed of myosin?
A) thick filaments
B) thin filaments
C) all myofilaments
D) Z discs
During muscle contraction, myosin cross bridges attach to which
A) myosin filaments
B) actin filaments
C) Z discs
D) thick filaments
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 ________.
A) single-unit muscles
B) multiunit muscles
C) red muscles
D) white muscles
Rigor mortis occurs because ________.
A) the cells are dead
B) sodium ions leak out of the muscle
C) no ATP is available to release attached actin and myosin molecules
D) proteins are beginning to break down, thus preventing a flow of calcium ions
Which of the following does not act as a stimulus to initiate a
A) hormonal activity
C) a change in the pH of a muscle
D) a change of temperature
The term aponeurosis refers to ________.
A) the bands of myofibrils
B) a sheetlike indirect attachment to a skeletal element
C) the rough endoplasmic reticulum
D) the tropomyosin-troponin complex
The oxygen-binding protein found in muscle cells is ________.
The contractile units of skeletal muscles are ________.
C) T tubules
The site of calcium regulation in the smooth muscle cell is ________.
One functional unit of a skeletal muscle is ________.
A) a sarcomere
B) a myofilament
C) a myofibril
D) the sarcoplasmic reticulum
The functional role of the T tubules is to ________.
A) stabilize the G and F actin
B) enhance cellular communication during muscle contraction
C) hold cross bridges in place in a resting muscle
D) synthesize ATP to provide energy for muscle contraction
The warm-up period required of athletes in order to bring their
muscles to peak performance is called ________.
B) wave summation
D) incomplete tetanus
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 ________.
A) a strong base
B) stearic acid
C) hydrochloric acid
D) lactic acid
When a muscle is unable to respond to stimuli temporarily, it is in
which of the following periods?
A) relaxation period
B) refractory period
C) latent period
D) fatigue period
In an isotonic contraction, the muscle ________.
A) changes in length and moves the "load"
B) does not change in length but increases tension
C) never converts pyruvate to lactate
D) rapidly resynthesizes creatine phosphate and ATP
The muscle cell membrane is called the ________.
Smooth muscle is significantly different from striated muscle in
several ways. Which of the following is true?
A) Smooth muscle has transverse tubules.
B) Smooth muscle is larger and more powerful than striated muscle.
C) The fibers of smooth muscle are arranged quadrangularly.
D) Smooth muscle contracts in a twisting way.
The mechanism of contraction in smooth muscle is different from
skeletal muscle in that ________.
A) actin and myosin interact by the sliding filament mechanism
B) the trigger for contraction is a rise in intracellular calcium
C) the site of calcium regulation differs
D) ATP energizes the sliding process
The cells of single-unit visceral muscle ________.
A) contract all at once
B) are chemically coupled to one another by gap junctions
C) exhibit spontaneous action potentials
D) consist of muscle fibers that are structurally independent of each other
Which of the following statements is not true concerning
developmental aspects of muscle?
A) There is no biological basis for the difference in strength between women and men.
B) Skeletal muscle is derived from mesoderm.
C) Skeletal muscle develops from somites.
D) Most muscle tissues develop from myoblasts
Which of the following is true about smooth muscle contraction?
A) Certain smooth muscle cells can actually divide to increase their numbers.
B) Smooth muscle, in contrast to skeletal muscle, cannot synthesize or secrete any connective tissue elements.
C) Smooth muscle cannot stretch as much as skeletal muscle.
D) Smooth muscle has well-developed T tubules at the site of invagination.
Smooth muscle is characterized by all of the following except
A) it appears to lack troponin
B) there are more thick filaments than thin filaments
C) there are no sarcomeres
D) there are noncontractile intermediate filaments that attach to dense bodies within the cell
Muscle tissue has all of the following properties except ________.
The giant protein titin maintains the organization of the ________
assisting in muscle stretching.
A) A band
B) I band
C) Z disc
D) M line
Which of the following statements is true?
A) cells have many nuclei.
B) Smooth muscle cells have T tubules.
C) Striated muscle cells are long and cylindrical with many nuclei.
D) Cardiac muscle cells are found in the heart and large blood vesselsCardiac muscle
An anaerobic metabolic pathway that results in the production of two
net ATPs per glucose plus two pyruvic acid molecules is ________.
A) the citric acid cycle
D) the electron transport chain
Muscle tone is ________.
A) the ability of a muscle to efficiently cause skeletal movements
B) the feeling of well-being following exercise
C) a state of sustained partial contraction
D) the condition of athletes after intensive training
The sliding filament model of contraction involves ________.
A) actin and myosin sliding past each other and partially overlap
B) the shortening of thick filaments so that thin filaments slide past
C) actin and myosin shortening but not sliding past each other
D) the Z discs sliding over the myofilaments
After nervous stimulation stops, ACh in the synaptic cleft is
prevented from continuing stimulation of contraction by ________.
A) calcium ions returning to the terminal cisternae
B) the tropomyosin blocking the myosin once full contraction is achieved
C) acetylcholinesterase destroying the ACh
D) the action potential stopped going down the overloaded T tubules
Which of the following is most accurate?
A) Muscle tension remains relatively constant during isotonic contraction.
B) T-tubles may be sliding during isotonic contraction.
C) The I band lenghtens during isotonic contraction.
D) Myofilaments slide during isometric contractions.
The most distinguishing characteristic of muscle tissue is ________.
A) the design of the fibers
B) the sarcoplasmic reticulum
C) the diversity of activity of muscle tissue
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?
A) a sprint by an Olympic runner
B) a long, relaxing swim
C) playing baseball or basketball
D) mountain climbing
Of the following muscle types, which has only one nucleus, no
sarcomeres, and rare gap junctions?
A) visceral smooth muscle
B) multiunit smooth muscle
C) cardiac muscle
D) skeletal muscle
if a muscle were stretched to the point where thick and thin
filaments no longer overlapped ________.
A) cross bridge attachment would be optimum because of all the free binding sites on actin
B) no muscle tension could be generated
C) maximum force production would result since the muscle has a maximum range of travel
D) ATP consumption would increase since the sarcomere is "trying" to contract