Q&A Hero

Q: A skeletal muscle fiber contains numerous ____________________, which are cylindrical intracellular structures.

Q: A single skeletal muscle cell is known as a(n) ____________________.

Q: Smooth muscle cells are interconnected by gap junctions found in intercalated discs that join cells together. a. True b. False

Q: ATP splitting is much slower in smooth muscle, so cross-bridge activity and filament sliding occur about ten times more slowly in smooth muscle than in skeletal muscle. a. True b. False

Q: A smooth muscle cell has many T tubules and well developed sarcoplasmic reticulum. a. True b. False

Q: Unlike skeletal muscle cells, a single smooth muscle cell extends the full length of a muscle. a. True b. False

Q: The crossed extensor reflex is a postural reflex that ensures that the opposite limb is in a position to bear the weight of the body as the injured limb is withdrawn from the stimulus. a. True b. False

Q: A connection involving stimulation of the nerve supply to one muscle and simultaneous inhibition of the nerves to its antagonistic muscle is known as reciprocal innervation. a. True b. False

Q: In contrast to muscle spindles, which lie in the tendons of muscle, Golgi tendon organs are in the belly of muscle. a. True b. False

Q: Loss of excitatory input from higher centers brings about flaccid paralysis. a. True b. False

Q: Disuse atrophy occurs when a muscle is not used for a long period of time due to reduced or absent nerve supply. a. True b. False

Q: Slow and fast fibers are interconvertible. a. True b. False

Q: During the recovery period, fresh supplies of ATP are formed by oxidative phosphorylation using the newly acquired oxygen, which is provided by the sustained increase in breathing after exercise has stopped. a. True b. False

Q: Central fatigue occurs when the central nervous system no longer adequately activates the motor neurons supplying the working muscles. a. True b. False

Q: At the outer limits of a muscle's length, it still can achieve about 80% of its maximal contraction strength. a. True b. False

Q: Twitch summation results primarily from a sustained elevation in cytosolic Ca2+. a. True b. False

Q: Muscles that produce precise, delicate movements have fewer muscle fibers in their motor units compared to muscles made for powerful movements. a. True b. False

Q: In an isokinetic contraction, the load remains constant as the muscle changes length. a. True b. False

Q: The action potential is over before the contractile apparatus even becomes operational. a. True b. False

Q: Ca2+ binding to tropomyosin causes myosin to change shape, physically moving it away from its blocking position. a. True b. False

Q: On binding to actin, the myosin head tilts 45 degrees inward. a. True b. False

Q: Both the thin and thick filaments change length during muscle fiber shortening. a. True b. False

Q: Tropomyosin and troponin are often called stimulation proteins because of their role in covering or exposing the binding sites for cross-bridge interaction between actin and myosin. a. True b. False

Q: Tropomyosin molecules are threadlike proteins that lie end to end alongside the groove of the actin spiral. a. True b. False

Q: Myofibrils are made from thick and round filaments. a. True b. False

Q: Viewed with an electron microscope, a myofibril displays alternating dark bands (the A bands) and light bands (the I bands). a. True b. False

Q: Muscles are categorized as striated (skeletal and cardiac muscle) or unstriated (smooth muscle). a. True b. False

Q: What phenomenon enables smooth muscle to maintain tension with comparatively less ATP consumption, as compared to skeletal muscle? a. stretch phenomenon b. jump phenomenon c. piggy back phenomenon d. click phenomenon e. latch phenomenon

Q: What does smooth muscle contain that enables it to stretch much more than skeletal muscle? a. calcium b. glucosamine c. sarcomeres d. connective tissue e. microfilaments

Q: What are the two major types of spontaneous depolarizations displayed by self-excitable cells? a. fast-wave and slow-wave potentials b. membrane potentials and slow-wave potentials c. pacemaker potentials and slow-wave potentials d. smooth potentials and fast-wave potentials e. cardiac potentials and fast-wave potentials

Q: Contractile activity in both skeletal muscle and multiunit smooth muscle is ____. a. myogenic b. phasic c. tonic d. clonic e. neurogenic

Q: What kind of smooth muscle contracts in bursts? a. phasic b. tonic c. clonic d. cardiac e. vascular

Q: How many filament types do smooth muscle cells have? a. 2 b. 3 c. 4 d. 5 e. 6

Q: How developed is the sarcoplasmic reticulum in cardiac muscle? a. non-existent b. poorly developed c. moderately developed d. well developed e. heavily developed

Q: For effective control of motor output, what two types of muscle proprioceptors are needed by the CNS? a. muscle spindles and Golgi tendon organs b. muscle spindles and stretch receptors c. sarcoplasmic reticulum and Golgi tendon organs d. sarcomeres and Golgi tendon organs e. sarcomeres and stretch receptors

Q: Damage to the cerebellum or basal nuclei results in ____. a. spastic paralysis b. flaccid paralysis c. tetanus d. clumsy movement e. cerebral palsy

Q: Loss of descending inhibitory inputs on motor neurons may result in ____. a. spastic paralysis b. flaccid paralysis c. tetanus d. clumsy movement e. cerebral palsy

Q: What do the basal nuclei coordinate? a. slow twitch muscle fibers b. spinal reflexes c. slow, sustained movement d. fast movement e. fast twitch muscle fibers

Q: What plays a key role in mediating performance of fine, discrete, voluntary movements of the hands and fingers? a. premotor area b. supplementary motor area c. multineuronal system d. corticospinal system e. the pons

Q: What level of neural input (to motor neurons) involves pyramidal cells? a. input from the brain stem b. input from the efferent neurons c. input from afferent neurons d. input from the sensory cortex e. input from the primary motor cortex

Q: What is the least complex type of purposeful motor movement? a. somatic reflex responses b. voluntary movements c. rhythmic activities d. tetanus contraction e. fine motor movements

Q: What are the two types of fast-twitch muscle fibers? a. oxidative and phosphoric b. oxidative and glycolytic c. pyruvic and glycolytic d. acetic and glycolytic e. fast and slow

Q: What hormone, elevated during exercise, increases oxygen consumption? a. dopamine b. serotonin c. acetylcholine d. norepinephrine e. epinephrine

Q: What are the two main types of fatigue? a. skeletal and cardiac b. skeletal and smooth c. muscle and cerebral d. muscle and psychological e. muscle and central

Q: What is the first source for supplying additional ATP when exercise begins? a. oxidative phosphorylation b. glycolysis c. lactate d. creatine phosphate e. chondroitin

Q: How many additional pathways supply ATP as needed during muscle contraction? a. 1 b. 2 c. 3 d. 4 e. 5

Q: How many steps in the muscle excitation, contraction, and relaxation processes require ATP? a. 3 b. 4 c. 5 d. 6 e. 7

Q: Because of skeletal constraints, what is the maximum percentage that muscles can stretch or shorten relative to their length? a. 30% b. 35% c. 40% d. 45% e. 50%

Q: What happens when two or more overlapping action potentials are "added" together within a muscle? a. twitch fatigue b. twitch summation c. contraction addition d. contraction paralysis e. sarcoplasmic reduction

Q: One motor neuron, plus all the muscle fibers it innervates, is known as a(n): a. nerve bundle b. motor unit c. activated component d. cross bridge e. functional unit

Q: The portion of a lever between the fulcrum and the point where a force is applied by the muscle is called the ____. a. fulcrum angle b. velocity c. power arm d. load arm e. interactive unit

Q: What happens to a muscle during an isometric contraction? a. It produces more calcium. b. It lengthens. c. It shortens. d. It is prevented from shortening. e. Sarcomeres are destroyed.

Q: Muscle tension is produced internally within the ____. a. myosin molecules b. actin molecules c. T tubules d. sarcoplasmic reticulum e. sarcomeres

Q: How many skeletal muscles are there in the body? a. about 400 b. 442 c. about 500 d. 535 e. about 600

Q: How long does a single action potential in a skeletal muscle fiber last? a. 1 to 2 seconds b. 0.5 seconds c. 5 milliseconds d. 1 to 2 milliseconds e. 0.5 milliseconds

Q: Which molecule binds ATP in order for muscle contraction to occur? a. sarcolemma b. actin c. myosin d. calcium e. phosphate

Q: What are the two membranous structures within the muscle fiber that play important roles in linking excitation to contraction? a. horizontal tubules and sarcoplasmic reticulum b. transverse tubules and sarcoplasmic reticulum c. transverse tubules and endoplasmic reticulum d. horizontal tubules and endoplasmic reticulum e. sarcolemma and plasma end plates

Q: How many thin filaments are on each end of a sarcomere? a. 6 b. 5 c. 4 d. 3 e. 2

Q: How many "heads" does each myosin molecule have? a. 5 b. 4 c. 3 d. 2 e. 1

Q: During muscle contraction, what becomes smaller? a. H zone b. thin filaments c. the width of the A band d. thick filaments e. myosin molecules

Q: What two molecules participate in cross-bridge interactions? a. tropomyosin and myosin b. troponin and myosin c. troponin and tropomyosin d. actin and myoblasts e. actin and myosin

Q: What shape are actin molecules? a. elongated b. spherical c. bicuspid d. rectangular e. triangular

Q: What molecules form the thick filaments within muscle? a. microfilaments b. myosin c. actin d. myoblasts e. troponin

Q: During the embryonic developmental stage, skeletal muscle fibers are derived from: a. fibroblasts b. lymphoblasts c. connective tissue d. myoblasts e. microfilaments

Q: What types of muscles are involuntary in terms of movement? a. cardiac and smooth b. skeletal and cardiac c. arterial and venous d. rough and smooth e. skeletal and contractile

Q: What are the three main muscle types? a. skeletal, rough, and smooth b. flexion, extension, and rotation c. skeletal, cardiac, and smooth d. thick, thin, and flat e. skeletal, arterial, and venous

Q: Approximately what percentage of body weight does muscle comprise? a. 20% b. 35% c. 50% d. 70% e. 85%

Q: Describe the three types of filaments in smooth muscle.

Q: Describe the symptoms of muscular dystrophy.

Q: Outline the three primary types of muscle contraction.

Q: What is rigor mortis?

Q: What functions does the controlled contraction of muscles allow?

Q: Figure 8-12Which number in the accompanying figure represents the state of rigor complex in the cross-bridge cycle?a. 1b. 2c. 3d. 4e. 5f. 6

Q: Figure 8-12Which number in the accompanying figure represents the resting state of the cross-bridge cycle?a. 1b. 2c. 3d. 4e. 5f. 6

Q: Figure 8-12Which number in the accompanying figure represents the detachment stage of the cross-bridge cycle?a. 1b. 2c. 3d. 4e. 5f. 6

Q: Figure 8-12Which number in the accompanying figure represents the energized state of the cross-bridge cycle?a. 1b. 2c. 3d. 4e. 5f. 6

Q: Figure 8-12Which number in the accompanying figure represents the bending stage of the cross-bridge cycle?a. 1b. 2c. 3d. 4e. 5f. 6

Q: A group of interconnected muscle cells that function electrically and mechanically as a unit is known as a functional ____________________.

Q: ____________________ smooth muscle is usually partially contracted at all times; that is, it exhibits smooth muscle tone.

Q: Smooth muscle myosin can interact with actin only when the light chain is ____________________.