Unit 4 Review Quiz

Order the steps to skeletal muscle contraction in the correct order. 1. A "Power Stroke" is evoked by the hinge movement of the Myosin 2. The Myosin head is disconnected from the Actin with the aid of ATP 3. Ca+ is released from terminal cisternae into the cytosol and it binds to the troponin which "drags" the tropomyosin off the binding sites of the Actin exposing binding sites 4. Ca+ is removed by ion pumping back into the sarcoplasmic reticulum and Troponin and Tropomyosin return to their original configurations resulting in relaxation of the muscle 5. Depolarization of the motor end plate initiates an action potential which propagates along the sarcolemma in all directions and down the T tubules 6. At the neuromuscular junction, a neurotransmitter (acetylcholine for skeletal muscle) is released into the synaptic cleft and binds to receptor sites of chemically gated ion channels on the motor end plate causing the channels to open allowing Na+ in and K+ out 7. Myosin binds to the Actin forming a "cross bridge" 8. The Actin and Myosin fibers slide past each other a. 6, 5, 3, 7, 1, 8, 2, 4 b. 5, 6, 3, 1, 2, 7, 8, 4 c. 5, 6, 4, 2, 7, 1, 8, 3 d. 6, 5, 3, 7, 8, 1, 2, 4,

a. 6, 5, 3, 7, 1, 8, 2, 4

Which of the following is NOT a property of single-unit smooth muscles? a. Each cell functions independent of its neighbor. b. Their contraction occurs in a coordinated manner. c. Electrical responses travel directly between cells. d. All smooth muscle cells are connected by gap junctions.

a. Each cell functions independent of its neighbor.

Motor units that control skeletal muscles involved with fine motor movements (eye muscles or the hands) have ________ muscle fibers than motor units that control more gross movements (gastrocnemius muscle of the lower leg). a. Fewer b. The same number of c. More

a. Fewer

Which fibers generate more force? a. fast-twitch fibers b. slow-twitch fibers

a. fast-twitch fibers

The functional connection between a neuron and a skeletal muscle fiber is a a. synapse b. fascia c. myoma d. dendrite e. neuroma

a. synapse

The cause of peripheral skeletal muscle fatigue during extended submaximal exercise is primarily a(n): a. Decreased demands of ATP b. Depletion of glycogen stores c. Increased inorganic phosphate concentration d. Depletion of creatine stores

b. Depletion of glycogen stores

The type of muscle growth that results from in increase in the number of actin and myosin contractile proteins that adds strength as well as a small increase in the size of the muscle. a. Sarcoplasmic b. Myofibillar

b. Myofibillar

Myofibrils are composed primarily of a. troponin and tropomyosin. b. actin and myosin. c. ATP and ADP. d. fascia and tendons. e. perimysium and endomysium

b. actin and myosin.

The binding of acetylcholine to its receptor at the neuromuscular junction causes the opening of a a. Na+ channel. b. channel for both Na+ and K+. c. calcium channel. d. ryanodine receptor.

b. channel for both Na+ and K+.

Compared to skeletal muscle, smooth muscle a. contracts more slowly and relaxes more rapidly. b. contracts more slowly and relaxes more slowly. c. contracts more rapidly and relaxes more rapidly. d. contracts more rapidly and relaxes more slowly. e. contracts and relaxes at about the same rate.

b. contracts more slowly and relaxes more slowly.

Rigor mortis affects skeletal muscles a few hours after death, due to a. increased ATP and decreased permeability to calcium. b. decreased ATP and increased permeability to calcium. c. increased ATP. d. nerve impulses that contract the muscles excessively.

b. decreased ATP and increased permeability to calcium.

A highly organized bundles of contractile proteins within a skeletal muscle cell is called a a. muscle fiber b. myofibril c. t-tubules d. fascicle e. sarcolemma

b. myofibril

The muscle cell membrane is the a. t-tubules b. sarcolemma c. muscle fiber d. fascicle e. myofibril

b. sarcolemma

Arrange the following steps for contraction in the correct sequence. 1. The muscle impulse reaches the sarcoplasmic reticulum and calcium is released. 2. Thin filaments are pulled over the thick filaments. 3. Calcium floods the sarcoplasm and binds to troponin molecules leaving active sites. 4. The impulse arrives at the synapse and travels through the transverse tubules. 5. The muscle fiber shortens and contracts. 6. Tropomyosin molecules bind to exposed active sites, linking actin and myosin a. 6, 3, 1, 4, 2, 5 b. 2, 5, 3, 1, 4, 6 c. 4, 1, 3, 6, 2, 5 d. 4, 2, 6, 5, 3, 1 e. 3, 5, 2, 1, 6, 4

c. 4, 1, 3, 6, 2, 5

The speed with which force is developed by skeletal muscles is determined by the: a. Muscle's origin b. Amount of phosphate present c. Muscle fiber type d. Sarcoplasmic calcium concentration e. Speed of the impulse

c. Muscle fiber type

Asynchronous activation of motor units is important because it functions to prevent a. crossbridge formation. b. too much tension being created. c. fatigue d. overstretching of the muscle.

c. fatigue

The thick filament of the myofibril is composed of ________ molecules whereas ________ is a protein that makes up the thin filaments. a. tropomyosin, myosin b. actin, troponin c. myosin, actin d. troponin, tropomyosin

c. myosin, actin

Phosphocreatine a. decomposes ATP. b. decomposes ADP. c. supplies energy for the synthesis of ATP. d. supplies energy for the breakdown of ATP to ADP. e. binds to Ach receptors.

c. supplies energy for the synthesis of ATP.

After death, when metabolism stops, in which step of the contractile cycle must skeletal muscles remain? a. It depends on what part of the contractile cycle they were in at the time of death. b. the power stoke phase c. the rigor state d. a weak binding state

c. the rigor state

In order for high force crossbridges to form in contracting skeletal muscle, calcium must: a. Bind to tropomyosin which moves it b. Bind to tropomyosin, which moves the troponin c. Bind to calmodulin to move myosin d. Bind to troponin, which moves the tropomyosin

d. Bind to troponin, which moves the tropomyosin

A contraction that generates enough force to move a load is known as ________, whereas one that generates force without moving the load is known as ________. a. Isometric, eccentric b. Isotonic, eccentric c. Isometric, isotonic d. Isotonic, isometric e. Isotropic, isometric

d. Isotonic, isometric

Compared to skeletal muscle, contraction of smooth muscle cells is a. only a slower response to a stimulus. b. only sustained without fatigue. c. only controlled by the somatic nervous system. d. a slower response to a stimulus and sustained without fatigue. e. a slower response to a stimulus, sustained without fatigue, and controlled by the somatic nervous system.

d. a slower response to a stimulus and sustained without fatigue.

The first event in muscle fiber contraction is that a. acetylcholine diffuses across a gap at a neuromuscular junction. b. morphine is released from the end of the motor neuron. c. the muscle fiber membrane is stimulated and a muscle impulse travels deep into the fiber through transverse tubules. d. acetylcholine is released from the end of the motor neuron. e. calcium ions diffuse from sarcoplasmic reticulum into the sarcoplasm and bind to troponin molecules.

d. acetylcholine is released from the end of the motor neuron.

The brief period of time between the beginning of the action potential in the muscle and the beginning of contraction is referred to as the a. repolarization period. b. relaxation phase. c. refractory period. d. latent period. e. depolarization period.

d. latent period.

The function of transverse tubules is to a. conduct ATP molecules out of the mitochondria throughout the sarcoplasm. b. ensure a supply of glycogen throughout the muscle sarcoplasm. c. store Ca2+ ions inside the muscle fiber. d. rapidly conduct action potentials to the interior of the muscle fiber.

d. rapidly conduct action potentials to the interior of the muscle fiber.

The striated appearance of skeletal muscle results from the a. distribution of mitochondria. b. sarcoplasmic reticulum network. c. cisternae placement. d. sarcomere organization. e. transverse tubule pattern.

d. sarcomere organization.

A plank position is part of a yoga/Pilates workout. The person supports the body on the floor in a prone position with the arms and feet supporting the body. It is a little like the "up" position of a push-up, held for 30 to 60 seconds. Contraction of the abdominal muscles in a plank is most likely a. eccentric. b. isotopic. c. isotonic. d. plurimetric. e. isometric.

e. isometric.

Neurotransmitters are stored in vesicles in a. myofibrils. b. motor units. c. motor end plates. d. sarcomeres. e. motor neuron axon terminals.

e. motor neuron axon terminals.

Striated muscles are so-called because of a repeating pattern of light and dark bands. One repeating unit of the banding pattern is called a a. crossbridge. b. sarcofibril. c. myofilament. d. myomere. e. sarcomere.

e. sarcomere.

The function of the titin protein is to a. release calcium during contraction. b. cover the myosin binding site on the actin molecule. c. pull Z lines together during contraction. d. interact with actin during contraction. e. stabilize the position of the contractile filaments.

e. stabilize the position of the contractile filaments.

Smooth muscle lacks a. gap junctions. b. myofibrils. c. nuclei and mitochondria. d. actin and myosin. e. transverse tubules and striations.

e. transverse tubules and striations.