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Go to the questions at the end of chapter 9 of Vanders Human Physiology 14th Edition by Widmaier - all the answers are in Chegg under Vander's Human Physiology (14th Edition) Many of the questions are above the level of BIO 225 some are not - see which ones you can do.

430. Which of the following is NOT a primary function of the skeletal system? (A) It provides support for movement. (B) It is essential for cellular metabolism. (C) It is the primary reservoir for calcium and phosphate. (D) It provides for hematopoiesis. (E) It protects the organs.

430. (B) One of the primary functions of the bones is that they serve as a reservoir for calcium and phosphate, which are vital for organ and cellular function. Long bones are also homes for the tissues that produce blood cells. The skeleton also serves to protect the internal organs from trauma and to provide the support necessary for motion produced by muscle contraction.

7. If an adolescent breaks a leg bone close to the ankle joint, after the break heals, that leg may not grow as long as the other one. Why?

7. If the break and healing have damaged the epiphyseal plate, and the primary and secondary areas of ossification fuse, the bone can no longer grow at that end.

Which statement about bone is true? Please choose the correct answer from the following choices, and then select the submit answer button. Calcitonin and thyroxine regulate calcium levels in the bone and extracellular fluid. Insoluble calcium carbonate crystals are in the extracellular matrix of bone. Time spent in zero gravity causes bones to decalcify, while weight-bearing exercise increases bone deposition. Bone remodeling occurs only while a young person is growing. Bone is devoid of collagen fibers.

Correct answer is; Time spent in zero gravity causes bones to decalcify, while weight-bearing exercise increases bone deposition.

19. A motor unit is a. a sarcomere that extends from one Z line to the next Z line. b. a motor neuron and the muscle fibers it innervates. c. the muscle fibers that make up a muscle. d. the antagonistic set of muscles that flex and extend a body part.

6. What prevents a drop in muscle fiber ATP concentration during the first few seconds of intense contraction? a. Because cross-bridges are pre-energized, ATP is not needed until several cross-bridge cycles have been completed. b. ADP is rapidly converted back to ATP by creatine phosphate. c. Glucose is metabolized in glycolysis, producing large quantities of ATP. d. The mitochondria immediately begin oxidative phosphorylation. e. Fatty acids are rapidly converted to ATP by oxidative glycolysis.

b In the first few seconds of exercise, mass action favors transfer of the high-energy phosphate from creatine phosphate to ADP by the enzyme creatine kinase

8. Which is false regarding the structure of smooth muscle? a. The thin filament does not include the regulatory protein troponin. b. The thick and thin filaments are not organized in sarcomeres. c. Thick filaments are anchored to dense bodies instead of Z lines. d. The cells have a single nucleus. e. Single-unit smooth muscles have gap junctions connecting individual cells.

c In smooth muscle cells, dense bodies serve the same functional role as Z lines do in striated muscle cells—they serve as the anchoring point for the thin filaments

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Refer to the figure of sarcomeres. (Click image to enlarge.) When you bend your elbow to touch your cheek, the sarcomeres in your biceps muscle look most like the sarcomere in panel _______.

The correct answer is: B

Which feature characterizes a muscle that is fully stretched? Please choose the correct answer from the following choices, and then select the submit answer button. Little overlap between actin and myosin filaments Myosin bundles pressed up against Z lines Production of maximum force Shortened sarcomeres Maximum number of cross-bridges

The correct answer is: Little overlap between actin and myosin filaments

423. Bone tissue is best associated with the storage of (A) calcium. (B) water. (C) sodium. (D) proteins. (E) potassium.

423. (A) The bones are the primary storage location for both phosphate and calcium.

10. Malignant hyperthermia is a rare but frequently lethal condition stimulated by certain anesthetics. Suddenly the individual's muscles become rigid, heart rate shoots up, and body temperature rises rapidly. Those at risk for malignant hyperthermia have a mutation in the gene that codes for the ryanodine receptor. The mutation results in excessive opening of the Ca2+ channels in the sarcoplasmic reticulum. Knowing this cause of the condition, how can you explain all of its manifestations— temperature, heart rate, and muscle tension?

10. The increased amount and duration of Ca2+ in the sarcoplasm causes increased contraction of the muscles and therefore an increase in muscle tension. The increase in muscle tension requires additional expenditure of ATP, raising metabolism and producing more heat. The increased metabolism causes elevated heart rate. This is in addition to the effect of the increased Ca2+ in the cardiac muscle itself.

Go to the Questions at the end of chapter 44 of Brooker - all the answers are in Chegg under Biology 4th Edition

15. When striated muscle fibers contract, a. the Z lines are pulled closer together. b. the thin filaments become shorter. c. the thick filaments become thicker. d. both a and b occur.

1. The role of Ca2+ in the control of muscle contraction is to a. cause depolarization of the T tubule system. b. change the conformation of troponin, thus exposing myosin-binding sites. c. change the conformation of myosin heads, thus causing microfilaments to slide past each other. d. bind to tropomyosin and break actin- myosin cross-bridges. e. block the ATP-binding site on myosin heads, enabling muscles to relax.

22. Hydrostatic skeletons are used for movement by all of the following animals except a. cnidarians. b. arthropods. c. nematodes. d. annelids.

5. Insects can beat their wings at exceptionally high frequencies because a. their wing muscles have mostly fast-twitch fibers. b. their motor neurons can fire action potentials at a very high frequency. c. their wings have exoskeletal supports. d. their wing muscles have extensive sarcoplasmic reticulum that cycles Ca2+ very fast. e. their wing muscles can generate a rapid oscillation of contraction that is asynchronous with motor neuron firing.

24. Which of the following combinations of animal size and mode of locomotion has the lowest en- ergy cost (calories/kilogram·meter) ? a. small and swimming b. small and running c. large and flying d. large and swimming

4. Which statement about the structure of skeletal muscle is true? a. The light bands of the sarcomere are the regions where actin and myosin filaments overlap. b. When a muscle contracts, the A bands of the sarcomere lengthen. c. The myosin filaments are anchored in the Z lines. d. When a muscle contracts, the H zone of the sarcomere shortens. e. The sarcoplasm of the muscle cell is contained within the sarcoplasmic reticulum.

7. Which correctly characterizes a "fast-oxidative" type of skeletal muscle fiber? a. few mitochondria and high glycogen content b. low myosin ATPase rate and few surrounding capillaries c. low glycolytic enzyme activity and intermediate contraction velocity d. high myoglobin content and intermediate glycolytic enzyme activity e. small fiber diameter and fast onset of fatigue

d Fast-oxidative-glycolytic fibers are an intermediate type that are designed to contract rapidly but to resist fatigue. They utilize both aerobic and anaerobic energy systems; thus, they are red fibers with high myoglobin (which facilitates production of ATP by oxidative phosphorylation), but they also have a moderate ability to generate ATP through glycolytic pathways.

441. Cardiac muscle cells, when grown in the lab in petri plates, begin to beat in a synchronized fashion when they make contact with each other. Why might this be so? (A) The cells start to form nerve connections between themselves. (B) The cells release ATP into the surrounding medium in a synchronized fashion. (C) The cells release calcium ions, which synchronize contractions, into the surrounding medium. (D) The cells connect to each other by gap junctions upon making contact. (E) When one cell starts to contract, any cell in contact with that cell responds to the sudden motion as a physically gated stimulus.

441. (D) When a myofibril contracts, it is responding to a sudden release of calcium ions from the sarcoplasmic reticulum, which then permits the expenditure of ATP to activate the sliding filament mechanism that produces muscle contraction. The ions dumped in one cell rapidly pass to adjacent cells through the connecting gap junctions, producing a synchronized beating.

442. What is the sequence of the repair of a bone following fracture? (A) Callus forms → hematoma forms → osteoclasts remove fragments → osteoblasts replace bone material. (B) Osteoclasts remove debris → osteocytes form haversian canals → hematoma forms → callus forms. (C) Hematoma forms → callus forms → osteocytes form haversian canals → osteoblasts replace bone material. (D) Callus forms → osteoclasts remove debris → hematoma forms → osteoblasts form haversian canals. (E) Hematoma forms → callus forms → osteoclasts remove debris → osteoblasts replace bone material.

442. (E) When a bone fractures, blood flows out of the vessels in the haversian canals and produces a clot, or hematoma, that fills the fractured area. A fibrocartilage superstructure is then formed between the bone ends to immobilize them within the resulting callus. Osteoclasts start dissolving the damaged crystalline structure for recycling. Following behind their hollow trail are osteoblasts that deposit fresh reformed bone.

23. When you pull up your lower arm and "make a muscle" in your biceps, you are a. contracting a flexor. b. relaxing a flexor. c. contracting an extensor. d. contracting a tendon.

Actin and Myosin Filaments Overlap to Form Myofibrils Myosin filaments are bundles of molecules with globular heads and polypeptide tails; the protein titin holds these filaments centered within the sarcomeres. Actin filaments consist of two chains of actin monomers twisted together. They are wrapped by chains of the polypeptide tropomyosin and are studded at intervals with another protein, troponin. An actin filament consists of actin monomers polymerized into long chains that look like two strands of beads twisted together. Twisting around the actin chains is another protein, tropomyosin, and attached to tropomyosin at intervals are molecules of troponin. We'll discuss these two proteins in more detail later in this section. The myosin heads can bind specific sites on actin, to form cross-bridges between the myosin and the actin filaments. Moreover, when a myosin head binds to an actin filament, the head's conformation changes. As the head bends, it exerts a tiny force that causes the actin filament to move 5-10 nanometers relative to the myosin filament. When the myosin heads are bound to actin, they can bind and hydrolyze ATP. The energy released when this happens changes the conformation of the myosin head, causing it to release the actin and return to its extended position, from which it can bind to actin again.

Animation 47.1 Molecular Mechanisms of Muscle Contraction www.life11e.com/a47.1

Go to Activity 48.1 The Structure of a Sarcomere Sarcomeres are the units of contraction in a single myofibril. Life10e.com/ac48.1

Go to Animated Tutorial 48.1 Molecular Mechanisms of Muscle Contraction Life10e.com/at48.1

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Go to the Review Questions at the end of chapter 29 of Hickman - all the answers are in Chegg under Integrated Pinciples of Zoology 14th Edition

Which ratio of load arm to force arm would generate the greatest force over a small distance? Please choose the correct answer from the following choices, and then select the submit answer button. 2:1 3:1 4:1 5:1 6:1

The correct answer is: 2:1

T or F ? In skeletal muscle, a single action potential causes a minimum unit of contraction called a twitch. Fast-twitch fibers facilitate extended, aerobic work. Slow-twitch fibers generate maximum forces for short periods of time. The ratio of slow-twitch to fast-twitch fibers in the muscles of an individual is largely genetically determined. Muscle performance depends on a supply of ATP.

T F Slow-twitch F Fast-twitch T T

Troponin has three subunits T or F ?

T Troponin has three subunits: one binds actin, one binds tropomyosin, and one binds Ca2+.

1. Which is a false statement about skeletal muscle structure? a. A myofibril is composed of multiple muscle fibers. b. Most skeletal muscles attach to bones by connective-tissue tendons. c. Each end of a thick filament is surrounded by six thin filaments. d. A cross-bridge is a portion of the myosin molecule. e. Thin filaments contain actin, tropomyosin, and troponin.

3. When a skeletal muscle fiber undergoes a concentric isotonic contraction, a. M lines remain the same distance apart. b. Z lines move closer to the ends of the A bands. c. A bands become shorter. d. I bands become wider. e. M lines move closer to the end of the A band.

b As filaments slide during a shortening contraction, the I band becomes narrower, so the distance between the Z line and the thick filaments (at the end of the A band) must decrease

18. How does calcium affect muscle contraction? a. It is released from the T tubules in response to an action potential and initiates contraction. b. The binding of acetylcholine opens calcium channels in the plasma membrane, creating an action potential that travels down the T tubules. c. It binds to tropomyosin and helps to stabilize cross-bridge formation. d. Its binding to troponin causes tropomyosin to move away from the myosin-binding sites on the actin filament.

21. Smooth muscle contracts and relaxes relatively slowly because a. the only ATP available is supplied by fermentation. b. its contraction is stimulated by hormones, not motor neurons. c. it does not have a well-developed sarcoplasmic reticulum, and Ca2+ enters the cell through the plasma membrane during an action potential. d. it is composed exclusively of slow-twitch mus- cle fibers.

5. Why is the latent period longer during an isotonic twitch of a skeletal muscle fiber than it is during an isometric twitch? a. Excitation-contraction coupling is slower during an isotonic twitch. b. Action potentials propagate more slowly when the fiber is shortening, so extra time is required to activate the entire fiber. c. In addition to the time for excitation-contraction coupling, it takes extra time for enough cross-bridges to attach to make the tension in the muscle fiber greater than the load. d. Fatigue sets in much more quickly during isotonic contractions, and when muscles are fatigued the cross-bridges move much more slowly. e. The latent period is longer because isotonic twitches only occur in slow (type I) muscle fibers.

c In an isometric twitch, tension begins to rise as soon as excitation- contraction is complete and the first cross-bridges begin to attach. In an isotonic twitch, excitation-contraction coupling takes the same amount of time, but the fiber is delayed from shortening until after enough cross-bridges have attached to move the load

2. Which is correct regarding a skeletal muscle sarcomere? a. M lines are found in the center of the I band. b. The I band is the space between one Z line and the next. c. The H zone is the region where thick and thin filaments overlap. d. Z lines are found in the center of the A band. e. The width of the A band is equal to the length of a thick filament.

e The dark stripe in a striated muscle that constitutes the A band results from the aligned thick filaments within myofibrils, so thick filament length is equal to A-band width.

421. Thin filaments of the muscle cell are composed of all of the following EXCEPT (A) actin. (B) troponin. (C) tropomyosin. (D) myosin binding sites. (E) myosin.

421. (E) Calcium interacts with troponin, which then uncovers myosin binding sites on the tropomyosin strands, which are interwoven along a backbone of actin on the thin filament. This then permits the myosin, which makes up the bulk of the thick filament, to repetitively bind to and detach from the binding sites, producing a walking effect that contracts the sarcomere. All of these components except myosin are thus on the thin filament.

422. If half of the calcium present in a muscle cell leaked out of the cell into the surrounding tissue, what would occur? (A) Muscle strength would increase. (B) Signal strength from the neuron to the muscle would increase. (C) The action potential within the adjacent neuron would be dampened. (D) The force of contraction of the muscle cell would decrease. (E) The muscle cell would contract with its normal strength.

422. (D) If there is a shortfall in calcium release, such as might occur if there is leakage out of the cell, then there can be an insufficient interaction with troponin, resulting in the uncovering of fewer myosin binding sites and resulting in reduced muscle contraction force. This calcium leakage is known to occur in the elderly, who lose muscle strength even when weight training.

424. Which of the following correctly describes smooth muscle? (A) Smooth muscle tissue is localized only along the digestive system. (B) Smooth muscle cells are striated and under involuntary control. (C) Smooth muscle tissues are best associated with bony structures. (D) Smooth muscle tissues provide for long-term slow contractions. (E) Smooth muscle contractions are under voluntary control.

424. (D) Smooth muscle is located throughout the body. Smooth muscle cells are nonstriated (that's why they are called smooth). Skeletal muscles are associated with the bony structures of the skeleton. All smooth muscle tissue is under the involuntary control of the autonomic nervous system.

428. A fibrous joint is best described as (A) immovable. (B) a joint similar to the knee or elbow. (C) slightly movable. (D) a joint similar to that which connects the sternum to the adjacent cartilage. (E) highly movable.

428. (A) A joint is defined as a joining between bones. Articulated joints are held in position by ligaments that restrict their range of motion. There are joints, however, that are not intended to be mobile, such as the sutures of the skull. These nonmobile joints are identified as fibrous joints.

429. The best concept related to a sarcomere is that it (A) is the place where a bone attaches to muscle tissue. (B) is another name for a muscle cell. (C) contains the postsynaptic receptors of a muscle. (D) stores calcium needed for muscle contraction. (E) is the contractile unit of the myofibril.

429. (E) A sarcomere is the basic contractile unit of the muscle cell and is identified under the microscope as the region of bands located between the Z lines.

431. The sarcoplasmic reticulum is (A) protected by the skull. (B) essential for muscle contraction. (C) involved in protein synthesis and transport. (D) a cellular joining structure that provides for muscle fiber integrity and strength. (E) essential in the transport of ATP from the mitochondria to the contractile unit in muscle cells.

431. (B) The sarcoplasmic reticulum serves as a storehouse of calcium ions (Ca2+), a flood of which is necessary to initiate the actin-myosin interactions that produce a muscle contraction.

432. Spongy bone is best associated with (A) bone loss. (B) the structure of the diaphysis. (C) the medullary cavity. (D) the proximal epiphysis. (E) the periosteum.

432. (D) A long bone consists of three broad sections: the two ends, or epiphyses, and the diaphysis in between. The end closest to the head is the proximal epiphysis, and that farthest away is the distal epiphysis. While loss of calcium can lead to osteoporosis, this is an abnormal condition affecting the compact bone and is not related to the normal spongy bone of the epiphyses.

434. Which of the following is used to power muscle cells immediately after the initial supply of ATP is exhausted? (A) Glucose (B) Creatine phosphate (C) Fatty acids (D) Glycogen (E) Protein

434. (B) Muscle contraction requires a huge expense of energy. The initial supply of ATP on hand is consumed within the first 10 seconds of contraction. After that, the ATP is replenished by the donation of the phosphate group on creatine phosphate to recharge ADP to ATP, which lasts about an additional 30 seconds.

435. The _____ is the connective tissue that contains osteoclasts. (A) epiphysis (B) yellow marrow (C) haversian canal (D) compact bone (E) periosteum

435. (E) Intact compact bone holds two types of cells: osteoclasts, which are free-roving, and osteocytes, which are bone cells that are locked into spaces known as lacuna and connected together by canalicula. Osteoclasts become active within compact bone following a fracture, when they are needed to recycle bone debris. These osteoclasts normally reside in the periosteum. Microscopically, bone consists of hard, apparently homogeneous intercellular material, within or upon which can be found four characteristic cell types: osteoblasts, osteocytes, osteoclasts, and undifferentiated bone mesenchymal stem cells. Osteoblasts are responsible for the synthesis and deposition on bone surfaces of the protein matrix of new intercellular material. Osteocytes are osteoblasts that have been trapped within intercellular material, residing in a cavity (lacuna) and communicating with other osteocytes as well as with free bone surfaces by means of extensive filamentous protoplasmic extensions that occupy long, meandering channels (canaliculi) through the bone substance. With the exception of certain higher orders of modern fish, all bone, including primitive vertebrate fossil bone, exhibits an osteocytic structure. Osteoclasts are usually large multinucleated cells that, working from bone surfaces, resorb bone by direct chemical and enzymatic attack. Undifferentiated mesenchymal stem cells of the bone reside in the loose connective tissue between trabeculae, along vascular channels, and in the condensed fibrous tissue covering the outside of the bone (periosteum); they give rise under appropriate stimuli to osteoblasts.

437. During adolescent development, bones elongate by (A) forming bone tissue just under the joint cartilage. (B) deposition of spongy bone within the marrow cavity. (C) forming bone tissue under the cartilage epiphyseal plate. (D) deposition of dense bone along the marrow cavity. (E) deposition of collagenous fibrocartilage at the ends of the marrow cavity.

437. (C) During childhood, spongy bone starts to form at some secondary ossification sites near the ends of the bones. Later, during early adolescence, bone elongation takes place as new cartilage is laid down on the undersurface of the cartilage growth plate, also known as the epiphyseal plate.

438. Which of the following is the best description of a tendon? (A) A connective tissue that encloses synovial fluid (B) A bone-derived tissue that connects bone to bone (C) A highly vasculated tissue that connects bone to muscle (D) A collagenous material that connects bone to bone (E) A connective tissue that connects bone to muscle

438. (E) Joints are held together by collagenous ligaments. This eliminates option D, which does not describe a tendon, although both are composed of collagen, and option B as well. Option C is incorrect because neither of these tissues has an extensive blood supply. Option A describes a synovium sealed within a fibrous joint capsule. It is a tendon that connects bone to muscles.

439. The thin filament of a sarcomere is composed primarily of (A) titin. (B) tropomyosin. (C) actin. (D) troponin. (E) myosin.

439. (E) When an action potential signals the need for muscle contraction, it causes a release of calcium ions from the sarcoplasmic reticulum. This calcium interacts with troponin, opening up the myosin binding sites on the tropomyosin strands that cover the thick filament composed of actin. This allows the myosin heads extending from the thin filament to bind to these sites.

452. What actually happens following a period of oxygen debt? (A) Oxygen levels in the blood rebound to above preexercise levels. (B) Conversion of lactic acid to glucose. (C) ATP conversion of creatine phosphate. (D) Oxygen levels in the muscles rebound to above preexercise levels. (E) Creatine phosphate levels rebound to above preexercise levels.

452. (B) When large amounts of energy are expended producing the muscle exertion during exercise, larger than normal amounts of oxygen must be available to permit a maximum level of ATP production. Commonly, the respiratory and circulatory systems are incapable of providing adequate amounts of oxygen. Thus, cells switch from the much more efficient oxidative phosphorylation to fermentation, with a resulting buildup of lactic acid in the muscles. Once the exertion ceases, oxygenation must remain high in order to allow the conversion of the lactic acid back into glucose and the restoration of creatine phosphate and ATP to normal levels

455. Which of the following is NOT descriptive of red muscle? (A) Rich in mitochondria (B) High capillary density (C) Rich in myoglobin (D) Fast twitch (E) Best for sustained exertion

455. (D) Skeletal muscle is subdivided into two broad categories: fast twitch and slow twitch. Fast-twitch muscle contracts more rapidly and with greater force than slow-twitch muscle, but tires more quickly. Slow-twitch muscle has a higher density of myoglobin and mitochondria and a richer capillary bed, thus making it redder than fast-twitch muscle. Additionally, slow-twitch muscle is capable of more sustained but weaker contraction than fast-twitch.

458. What protein is found at the highest levels in bone tissue? (A) Elastin (B) Fibronectin (C) Keratin (D) Actin (E) Collagen

458. (E) Actin is most closely associated with muscle contraction and the cytoskeleton framework. Keratin is the major structural protein of fully differentiated skin cells, hair, and nails. Fibronectin, best associated with blood and the extracellular matrix, and elastin, best associated with tissues subject to stretching forces, such as arteries and veins, are both major components of connective tissue. However, it is collagen that comprises up to 30 percent of a bone's mass, the remainder being inorganic hydroxyapatite.

ATP is present in muscles in very small amounts. However, muscle fibers also contain a storage compound called creatine phosphate (CP). This molecule stores energy in a phosphate bond, which it can transfer to ________?

ADP

Refer to the figure relating sarcomere length to the force a muscle can generate. (Click image to enlarge.) At the beginning of a pull-up, the sarcomeres in your biceps are best represented by _______. As you get within an inch of the bar, the same sarcomeres are best represented by _______. Please choose the correct answer from the following choices, and then select the submit answer button. A and 1; B and 2 B and 1; A and 3 A and 2; B and 3 B and 3; A and 2 A and 3; B and 1

The correct answer is: A and 3; B and 1

Which statement about muscle contractile proteins is true? Please choose the correct answer from the following choices, and then select the submit answer button. A myosin filament consists of a single myosin molecule with its heads projecting at the ends of the filament. A molecule of myosin consists of two long linear polypeptide chains each with a globular head. The polypeptides that make up actin have globular heads. Tropomyosin twists around the myosin molecule. Three chains of actin monomers twisted together form an actin filament.

The correct answer is: A molecule of myosin consists of two long linear polypeptide chains each with a globular head.

Which event is not associated with the interaction between actin and myosin? Please choose the correct answer from the following choices, and then select the submit answer button. ATP is formed by the interaction. The actin filament moves relative to the myosin filament. A change in the myosin head conformation causes the head to bend. Myosin heads bind specific sites on actin, forming cross-bridges. A change in the myosin head conformation releases actin.

The correct answer is: ATP is formed by the interaction.

Which statement about muscle cells is true? Please choose the correct answer from the following choices, and then select the submit answer button. The plasma membrane of a muscle cell does not conduct action potentials. A motor unit is a motor neuron and one of the muscle fibers with which it synapses. An action potential in a muscle fiber travels into the T tubules of the muscle cell. A neuromuscular junction is the area of contact between the axon terminal of a motor neuron and a T tubule of a skeletal muscle cell. Each skeletal muscle has a single motor unit.

The correct answer is: An action potential in a muscle fiber travels into the T tubules of the muscle cell.

Refer to the figure. (Click image to enlarge.) If the purple structure labeled 2 was not present, what would be the most likely position for the structure labeled 5? Bound to one of the green structures labeled 3 Bound somewhere along the blue structure labeled 1 Bound to the tan structure labeled 4 Released from the tan structure labeled 4 and bound somewhere along the blue structure labeled 1 Released from the structure labeled 4 and bound to one of the structures labeled 3

The correct answer is: Bound somewhere along the blue structure labeled 1

The _______ activates _______, which phosphorylates myosin heads, leading to cycles of binding and releasing of actin in smooth muscle cells. Please choose the correct answer from the following choices, and then select the submit answer button. Ca2+ in the sarcoplasm; myosin kinase enzyme myosin kinase; myosin phosphatase myosin-Ca2+ complex; myosin phosphatase Ca2+-calmodulin complex; myosin kinase Ca2+-calmodulin complex; myosin phosphatase

The correct answer is: Ca2+-calmodulin complex; myosin kinase

Which statement about the development of skeletal muscle fibers is true? Please choose the correct answer from the following choices, and then select the submit answer button. Many muscle filaments bundled together form a muscle. A skeletal muscle cell is a muscle filament. During development, many myoblasts fuse to form a muscle fiber with more than one nucleus. Bundles of myoblasts form myofibrils. Osteoblasts are embryonic muscle cells.

The correct answer is: During development, many myoblasts fuse to form a muscle fiber with more than one nucleus.

Which of the following about tetanus is true? Please choose the correct answer from the following choices, and then select the submit answer button. It is the minimum level of contraction of a muscle fiber. During tetanus there is a continuous presence of high levels of calcium ions in the sarcoplasm. It is sustained by a lack of ATP. Experiencing repeated tetanic contractions puts a person at risk for developing the disease tetanus. It ends when a source of ATP is added to the muscle.

The correct answer is: During tetanus there is a continuous presence of high levels of calcium ions in the sarcoplasm.

Which statement about cardiac muscle cells is true? Please choose the correct answer from the following choices, and then select the submit answer button. There is a physical connection between DHP and ryanodine receptors. The T tubules are smaller than those of skeletal muscle cells. The DHP proteins are in the sarcoplasmic reticulum membrane. Extracellular Ca2+ flows into the cytoplasm through DHP channels and then opens calcium channels in the sarcoplasmic reticulum. Ryanodine receptors are ion-gated Na+ channels.

The correct answer is: Extracellular Ca2+ flows into the cytoplasm through DHP channels and then opens calcium channels in the sarcoplasmic reticulum.

Which bone articulates with the pelvis? Please choose the correct answer from the following choices, and then select the submit answer button. Fibula Femur Clavicle Humerus Ulna

The correct answer is: Femur

Which feature characterizes actin? Please choose the correct answer from the following choices, and then select the submit answer button. Contractile carbohydrate Filaments parallel to myosin filaments Make up the fibers in muscle cells Typically located within a circle of six myosin filaments within a myofibril Thick filaments

The correct answer is: Filaments parallel to myosin filaments

Which feature characterizes titin? Please choose the correct answer from the following choices, and then select the submit answer button. Smallest protein in the body Holds bundles of myosin filaments in a centered position within the sarcomere Stretchable between ends of actin bundles and Z lines Responsible for resistance to stretch in contracted skeletal muscles Is absent from the H zone of a sarcomere

The correct answer is: Holds bundles of myosin filaments in a centered position within the sarcomere

Which structure is part of the appendicular skeleton? Please choose the correct answer from the following choices, and then select the submit answer button. Sternum Vertebral column Humerus Skull Ribs

The correct answer is: Humerus

Which pairing of a sarcomere structure with its corresponding description is correct? Please choose the correct answer from the following choices, and then select the submit answer button. A band: region containing only myosin filaments when the muscle is contracted Z line: where myosin is anchored in the center of the H zone H zone: appears light on an electron micrograph; found where actin and myosin filaments overlap when muscle is relaxed I band: appears light on an electron micrograph; found where actin and myosin filaments do not overlap M band: dark stripe within the H zone whose proteins hold actin in a regular arrangement

The correct answer is: I band: appears light on an electron micrograph; found where actin and myosin filaments do not overlap

Which statement about osteoporosis is true? Please choose the correct answer from the following choices, and then select the submit answer button. It is the loss of bone flexibility with increased bone density. Weight-bearing exercise cannot improve the condition. It is most common in premenstrual women. In young people it can be caused by excessive training and malnutrition. It does not occur in young males.

The correct answer is: In young people it can be caused by excessive training and malnutrition.

Which feature characterizes the glycolytic system for supplying ATP to muscle cells? Please choose the correct answer from the following choices, and then select the submit answer button. The ATP it generates is available to myosin filaments once the level of oxidative metabolism has peaked. It takes place in the mitochondria and involves the electron transport chain. It generates lactic acid. It requires oxygen. It activates after 10 minutes.

The correct answer is: It generates lactic acid.

Which statement characterizes skeletal muscle? Please choose the correct answer from the following choices, and then select the submit answer button. Its cells are uninucleate. It is responsible for involuntary movements. It helps maintain posture. It is responsible for the beating of the heart. Its cells are branched.

The correct answer is: It helps maintain posture.

Which of the following characterizes cardiac muscle? Please choose the correct answer from the following choices, and then select the submit answer button. Its striated appearance results from the regular arrangement of actin and myosin. Its cells have numerous nuclei similar to skeletal muscle. Its individual cells are not connected by specialized junctions. Its cells are larger than those of any skeletal muscle. Its cells are long and unbranched.

The correct answer is: Its striated appearance results from the regular arrangement of actin and myosin.

Which feature characterizes slow-twitch skeletal muscle fibers? Please choose the correct answer from the following choices, and then select the submit answer button. Higher ATPase activity than fast-twitch fibers Ability to develop tension quickly Large amounts of myoglobin Few mitochondria Fewer blood vessels than fast twitch-fibers in the same muscle

The correct answer is: Large amounts of myoglobin

_______ results from the activity of a small number of constantly changing motor units in a given muscle. Please choose the correct answer from the following choices, and then select the submit answer button. Tetanus Summation A twitch Muscle tone High muscle tension

The correct answer is: Muscle tone

What is the correct order of events in the pathway leading up to the release of calcium from the sarcoplasmic reticulum of a skeletal muscle cell? Please choose the correct answer from the following choices, and then select the submit answer button. Plasma membrane of muscle cell; T tubules; DHP receptor; ryanodine receptor T tubules; plasma membrane of muscle cell; DHP receptor; ryanodine receptor Plasma membrane of muscle cell; T tubules; ryanodine receptor; dihydropyridine (DHP) receptor DHP receptor; plasma membrane of muscle cell; T tubules; ryanodine receptor Ryanodine receptor; plasma membrane of muscle cell; T tubules; DHP receptor

The correct answer is: Plasma membrane of muscle cell; T tubules; DHP receptor; ryanodine receptor

Which of the following would likely have the highest proportion of slow-twitch fibers? Please choose the correct answer from the following choices, and then select the submit answer button. Muscles in the fingers Muscles of the shoulder Muscles of the arm Muscle controlling elevation of the eyelid Postural muscles of the neck and spine

The correct answer is: Postural muscles of the neck and spine

Which of the following would likely have the highest proportion of slow-twitch fibers? Please choose the correct answer from the following choices, and then select the submit answer button. Postural muscles of the neck and spine Muscles of the arm Muscle controlling elevation of the eyelid Muscles of the shoulder Muscles in the fingers

The correct answer is: Postural muscles of the neck and spine

Which statement about the process of muscle contraction is true? Please choose the correct answer from the following choices, and then select the submit answer button. Changes in tropomyosin's conformation twist troponin, exposing the actin-myosin binding sites. Removal of calcium from the sarcoplasm indirectly causes tropomyosin's conformation to return to the position of blocking actin-myosin binding sites. When a muscle is relaxed, troponin blocks the sites on the actin filament where myosin can bind. Calcium released into the sarcoplasm binds to tropomyosin, changing the protein's conformation. When calcium increases in the sarcoplasm, the muscle relaxes.

The correct answer is: Removal of calcium from the sarcoplasm indirectly causes tropomyosin's conformation to return to the position of blocking actin-myosin binding sites.

Which statement about smooth muscle cells is true? Please choose the correct answer from the following choices, and then select the submit answer button. They are spindle-shaped and multinucleate. Their plasma membrane is insensitive to stretching. Some occur in sheets and are electrically coupled through gap junctions. Their arrangement of actin and myosin filaments is more regular than that found in skeletal and cardiac muscle cells. They occur more extensively in the walls of veins and capillaries than arteries because of the difficulty associated with returning blood to the heart against gravitational forces.

The correct answer is: Some occur in sheets and are electrically coupled through gap junctions.

Which statement about skeletal muscle is true? Please choose the correct answer from the following choices, and then select the submit answer button. Endurance is the minimum force a muscle can put forth. The major effect of strength training is the production of more muscle fibers. Aerobic physical activity increases strength without increasing endurance. Strength is the maximum force a muscle can put forth. Anaerobic physical activity does not increase strength.

The correct answer is: Strength is the maximum force a muscle can put forth.

Which statement about skeletal muscle is true? Please choose the correct answer from the following choices, and then select the submit answer button. Twitches sum when action potentials arrive well separated in time. The fewer muscle fibers a motor neuron innervates, the larger the forces produced by a muscle. A single action potential stimulates multiple twitches. The number of motor units activated and the frequency with which the motor units fire determine the level of tension in a muscle. Summing of twitches occurs because ATP pumps in the sarcoplasmic reticulum are unable to clear ATP from the sarcoplasm between action potentials.

The correct answer is: The number of motor units activated and the frequency with which the motor units fire determine the level of tension in a muscle.

Which feature is an advantage of endoskeletons over exoskeletons? Please choose the correct answer from the following choices, and then select the submit answer button. Endoskeletons are stiffer than exoskeletons. Muscles can attach more firmly to bones than to the cuticle. Joints are present in endoskeletons but not in exoskeletons. An endoskeleton provides better protection. With an endoskeleton, growth is possible without shedding of the skeleton.

The correct answer is: With an endoskeleton, growth is possible without shedding of the skeleton.

Which feature characterizes skeletal muscle contraction? Please choose the correct answer from the following choices, and then select the submit answer button. Sarcomeres lengthen I band broadens M band moves toward H zone H zone broadens Z lines move toward A band

The correct answer is: Z lines move toward A band

The minimum unit of contraction of a muscle fiber is Please choose the correct answer from the following choices, and then select the submit answer button. a summation. the smallest number of fibers in a motor unit. a tetanus. a sustained contraction. a twitch.

The correct answer is: a twitch.

Cartilage bone, found in the _______, forms first as a _______ "model," which is later replaced by _______. Please choose the correct answer from the following choices, and then select the submit answer button. appendages; bone; cartilage appendages; cartilage; bone roof of the skull; cartilage; bone appendages; cancellous bone; compact bone roof of the skull; cartilage; cancellous bone

The correct answer is: appendages; cartilage; bone

Transverse (T) tubules of skeletal muscle cells Please choose the correct answer from the following choices, and then select the submit answer button. are continuous with the plasma membrane of a muscle cell. project from the cell surface. are continuous with the sarcoplasmic reticulum. are reservoirs for calcium ions. transmit action potentials from the endoplasmic reticulum (ER).

The correct answer is: are continuous with the plasma membrane of a muscle cell.

Troponin binds with Please choose the correct answer from the following choices, and then select the submit answer button. sodium ions, only. calcium ions, only. actin, only. tropomyosin, only. calcium ions, actin, and tropomyosin.

The correct answer is: calcium ions, actin, and tropomyosin.

Bone that retains its strength despite being lightweight and having numerous cavities is called _______ bone. Please choose the correct answer from the following choices, and then select the submit answer button. cartilage Haversian compact osteoporotic cancellous

The correct answer is: cancellous

The most important determinant of the proportions of muscle fiber types a person has is Please choose the correct answer from the following choices, and then select the submit answer button. amount of exercise they engage in. body size. genetic heritage. age. type of exercise they do.

The correct answer is: genetic heritage.

When the circular muscles of a segment in an earthworm contract, that compartment _______, and when the longitudinal muscles of a segment contract, that compartment _______. Please choose the correct answer from the following choices, and then select the submit answer button. shortens and bulges outward; narrows and elongates pulls other segments forward; projects forward lengthens; shortens anchors the earthworm; projects forward narrows and elongates; shortens and bulges outward

The correct answer is: narrows and elongates; shortens and bulges outward

Refer to figure showing the knee joint and the bones and muscles of the human leg. (Click image to enlarge.) Structure 1 is a _______ and attaching ______. Structure 2 is a _______ and attaching _______. tendon; muscle to bone; ligament; bone to bone ligament; muscle to joint; tendon; bone to bone ligament; bone to bone; tendon; joint to joint ligament; muscle to bone; tendon; bone to bone tendon; bone to bone; ligament; muscle to bone

The correct answer is: tendon; muscle to bone; ligament; bone to bone

When ATP binds to myosin, Please choose the correct answer from the following choices, and then select the submit answer button. the myosin head attaches to actin. the myosin head releases actin. troponin changes conformation. tropomyosin exposes actin-myosin binding sites. calcium binds to troponin.

The correct answer is: the myosin head releases actin.

Bisphosphonates are a class of drug used to treat osteoporosis. These drugs kill osteoclasts. One of the effects of long-term use of this drug is Please choose the correct answer from the following choices, and then select the submit answer button. accelerated remodeling of bone matrix. severe osteoporosis. a reduction in bone matrix. unusual fractures due to suppression of bone turnover. bones that are stronger but thinner.

The correct answer is: unusual fractures due to suppression of bone turnover.

16. Venom from the black widow spider (Lactrodectus mactans) causes massive release of acetylcholine from neurons. How would muscles be affected by this venom? a. The muscles would exhibit spastic paralysis; that is, they would be massively contracted and unable to relax. b. The muscles would exhibit flaccid paralysis; that is, they would be floppy and unable to contract. c. The muscles would be unable to utilize ATP. d. The muscles would be unaffected because ace- tylcholine is a neurotransmitter used only for communication between neurons.

20. Which of the following characteristics does not pertain to cardiac muscle? a. scattered arrangement of actin and myosin filaments b. intercalated disks that spread action potentials between cells c. striations d. ability to generate action potentials without nervous input

17 . The role of ATP in muscle contraction is to a. form cross-bridges between thick filaments and thin filaments. b. release the myosin head from actin when it binds and to provide energy when hydrolyzed to form myosin's high-energy form. c. remove the tropomyosin-troponin complex from blocking the binding sites on actin. d. bend the cross-bridge and pull the thick fila- ments toward the center of the sarcomere.

3. Which statement about skeletal muscle contraction is not true? a. A single action potential at the neuromuscular junction is sufficient to cause a muscle to twitch. b. Once maximum muscle tension is achieved, no ATP is required to maintain that level of tension. c. An action potential in the muscle cell activates contraction by releasing Ca2+ into the sarcoplasm. d. Summation of twitches leads to a graded increase in the tension that can be generated by a single muscle fiber. e. The tension generated by a muscle can be varied by controlling how many of its motor units are active.

9. The function of myosin light-chain kinase in smooth muscle is to a. bind to calcium ions to initiate excitation-contraction coupling. b. phosphorylate cross-bridges, thus driving them to bind with the thin filament. c. split ATP to provide the energy for the power stroke of the cross-bridge cycle. d. dephosphorylate myosin light chains of the cross-bridge, thus relaxing the muscle. e. pump Ca2+ from the cytosol back into the sarcoplasmic reticulum.

b When myosin-light-chain kinase transfers a phosphate group from ATP to the myosin light chains of the cross-bridges, binding and cycling of cross-bridges are activated.

2. Fifteen minutes into a 10-kilometer run, what is the major energy source of the leg muscles? a. Preformed ATP b. Glycolysis c. Oxidative metabolism d. Pyruvate and lactate e. High-protein drink consumed right before the race

4. During excitation-contraction coupling in a skeletal muscle fiber, a. the Ca21-ATPase pumps Ca2+ into the T-tubule. b. action potentials propagate along the membrane of the sarcoplasmic reticulum. c. Ca2+ floods the cytosol through the dihydropyridine (DHP) receptors. d. DHP receptors trigger the opening of terminal cisternae ryanodine receptor Ca2+ channels. e. acetylcholine opens the DHP receptor channel.

d DHP receptors act as voltage sensors in the T-tubule membrane and are physically linked to ryanodine receptors in the sarcoplasmic reticulum membrane. When an action potential depolarizes the T-tubule membrane, DHP receptors change conformation and trigger the opening of the ryanodine receptors. This allows Ca2+ to diffuse from the interior of the sarcoplasmic reticulum into the cytosol.

10. Single-unit smooth muscle differs from multiunit smooth muscle because a. single-unit muscle contraction speed is slow, and multiunit is fast. b. single-unit muscle has T-tubules, and multiunit muscle does not. c. single-unit muscles are not innervated by autonomic nerves. d. single-unit muscle contracts when stretched, whereas multiunit muscle does not. e. single-unit muscle does not produce action potentials spontaneously, but multiunit muscle does.

d Stretching a sheet of single-unit smooth muscle cells opens mechanically gated ion channels, which causes a depolarization that propagates through gap junctions, followed by Ca2+ entry and contraction. This does not occur in multiunit smooth muscle

11. Which of the following describes a similarity between cardiac and smooth muscle cells? a. An action potential always precedes contraction. b. The majority of the Ca2+ that activates contraction comes from the extracellular fluid. c. Action potentials are generated by slow waves. d. An extensive system of T-tubules is present. e. Ca2+ release and contraction strengths are graded.

e The amount of Ca2+ released during a typical resting heart beat exposes less than half of the thin filament cross-bridge binding sites. Autonomic neurotransmitters and hormones can increase or decrease the amount of Ca2+ released to the cytosol during EC coupling.

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