Muscle MCQs

endomysium. perimysium. epimysium. sarcolemma. The fibrous connective tissue sheath which encloses a whole muscle is called the endomysium. perimysium. epimysium. sarcolemma.

sarcomeres sarcolemmas myofibers fascicles 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.

A and I bands H and M bands Z and M lines I and H bands 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

D line. H line. Z line. X line. 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.

isometric contraction. 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.

isometric contraction. isotonic 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.

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

narrow dark line known as the Z line. dark color of the I bands. 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 binding of titin to ATP. 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.

tropomyosin. myosin. troponin. actin. The thin filaments of a muscle fiber consist of all of the following except tropomyosin. myosin. troponin. actin.

synaptic vesicles of the motor neuron. sarcoplasmic reticulum. 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.

binding of acetylcholine to the motor end plate. 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.

be actively transported into the cell. 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.