Muscle MCQs

• The fibrous connective tissue sheath which encloses a whole muscle is called the

• endomysium.

• perimysium.

• epimysium.

• sarcolemma.

• Within a muscle the fibers are divided into larger bundles called ____, each surrounded by its own

connective tissue sheath.

• sarcomeres

• sarcolemmas

• myofibers

• fascicles

• The term ____ is synonymous with muscle cell.

• myofiber

• sarcomere

• myofibril

• fascicle

• Skeletal muscle cells are unusual in that they

• lack smooth endoplasmic reticulum.

• have no mitochondria.

• have multiple nuclei.

• depend entirely on anaerobic respiration.

• Skeletal muscle cells are striated that is, they have alternating dark and light bands called ____,

respectively.

• A and I bands

• H and M bands

• Z and M lines

• I and H bands

• The I bands of skeletal muscle fibers each have a dark line in the middle called a

• D line.

• H line.

• Z line.

• X line.

• A muscle is stimulated and exhibits a contraction (twitch). Before this twitch is over, it is stimulated again, and a second twitch occurs

"piggyback" on the first one and causes a higher contraction strength. This phenomenon is called

• tetanus.

• graded contraction.

• summation. • isometric contraction.

• If enough muscle fibers contract to make the muscle as a whole shorten in length, the muscle is said to

exhibit

• complete tetanus.

• graded contraction.

• isometric contraction.

• isotonic contraction.

• A motor unit is

• the motor end plate where a nerve fiber synapses with a muscle fiber.

• one motor neuron and all muscle fibers to which it leads.

• a spinal reflex arc.

• a sarcomere.

• The contraction strength of a whole muscle varies in accordance with the

• number of motor units activated.

• innervation ratio.

• amount of calcium released from the sarcoplasmic reticulum.

• amplitude of the arriving action potentials.

• Contraction in a muscle occurs because the

• thin filaments get shorter.

• thick filaments get shorter.

• thin filaments slide between the thick filaments.

• titin proteins pull on opposite ends of the sarcomere.

• The region of the resting sarcomere where the thin and thick filaments are overlapping is seen in the

• narrow dark line known as the Z line.

• dark color of the I bands.

• lighter region of the I bands.

• dark color of the A bands.

• The thick filaments of muscle are composed of

• tropomyosin.

• actin.

• troponin.

• myosin.

• The basic unit of muscle contraction is the sarcomere, which is

• one A band and the adjacent I band.

• the distance from one Z line to the next.

• equivalent to a fascicle of muscle fibers.

• equivalent to one of the myofibrils within a muscle fiber.

• During contraction the

• actin filaments bind to the myosin filaments.

• I bands shorten.

• sarcomeres do not change in length.

• size of the H zone increases.

• The ability of myosin to interact with actin is regulated by the binding of

• Ca2+ to troponin.

• ATP to actin.

• Ca2+ to tropomyosin.

• the binding of titin to ATP.

• The thin filaments of a muscle fiber consist of all of the following except

• tropomyosin.

• myosin.

• troponin.

• actin.

• The calcium that binds to troponin to activate muscle contraction comes from storage sites located in the

• T tubules.

• extracellular fluid.

• synaptic vesicles of the motor neuron.

• sarcoplasmic reticulum.

• Excitation-contraction coupling refers especially to the

• events at the neuromuscular junction where a motor fiber excites a muscle cell.

• propagation of action potentials from the neuromuscular junction to the T tubules.

• calcium release and binding to troponin molecules.

• attachment of myosin cross bridges to the thin filaments.

• ATP is required by two different processes that are necessary to the contraction and relaxation of a muscle: the interaction between

the thick and thin filaments of the sarcomeres, and the

• binding of acetylcholine to the motor end plate.

• release of calcium from the sarcoplasmic reticulum.

• movement of the troponin-tropomyosin complex.

• reuptake of calcium by the sarcoplasmic reticulum.

• In skeletal muscle contraction Ca2+ must bind to troponin for contraction to occur and in order for the

muscle to relax the Ca2+ must

• diffuse out of the cell.

• be actively transported into the cell.

• be actively transported into the sarcoplasmic reticulum.

• be bound to tropomyosin until the next contraction.