ch 9 - Human Anatomy & Physiology, 7e (Marieb)...

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Unformatted text preview: Human Anatomy & Physiology, 7e (Marieb) Chapter 9 Muscles and Muscle Tissue MATCHING QUESTIONS Figure 9.1 Using Figure 9.1, match the following: 1) Endomysium. Answer: B Diff: 1 Page Ref: 283; Fig. 9.2 2) Fascicle. Answer: D Diff: 1 Page Ref: 283; Fig. 9.2 3) The tissue that binds muscles into functional groups. Answer: A Diff: 2 Page Ref: 283; Fig. 9.2 4) Perimysium. Answer: E Diff: 1 Page Ref: 283; Fig. 9.2 5) Muscle fiber. Answer: C Diff: 1 Page Ref: 283; Fig. 9.2 Figure 9.2 Using Figure 9.2, match the following: 6) I band. Answer: C Diff: 1 Page Ref: 284; Fig. 9.3 7) H zone. Answer: B Diff: 1 Page Ref: 284; Fig. 9.3 8) A band. Answer: D Diff: 2 Page Ref: 284; Fig. 9.3 9) Z disc. Answer: A Diff: 1 Page Ref: 284; Fig. 9.3 10) M line Answer: E Diff: 1 Page Ref: 284; Fig. 9.3 Match the following: 11) Depends on oxygen delivery and aerobic mechanisms. Answer: B Diff: 1 Page Ref: 305-307 12) Have very fast-acting myosin ATPases and depend upon anaerobic metabolism during contraction. Answer: A Diff: 1 Page Ref: 305-307 13) Red fibers, the smallest of the fiber types. Answer: B Diff: 2 Page Ref: 305-307 14) Contain abundant amounts of glycogen. Answer: A Diff: 2 Page Ref: 305-307 15) Abundant in muscles used to maintain posture. Answer: B Diff: 2 Page Ref: 305-307 16) A relatively high percentage are found in successful marathon runners. Answer: B Diff: 2 Page Ref: 305-307 A) Fast (oxidative or glycolytic), fatigable fibers B) Slow (oxidative), fatigue-resistant fibers Match the following: 17) The stimulus above which no stronger contraction can be elicited, because all motor units are firing in the muscle. A) Wave summation B) Multiple motor unit summation Answer: E Diff: 1 Page Ref: 298 18) The phenomenon in which the contraction strength of a muscle increases, due to increased Ca2+ availability and enzyme efficiency during the warm-up. C) Treppe D) Tetanus E) Maximal stimulus Answer: C Diff: 1 Page Ref: 299 19) Continued sustained smooth contraction due to rapid stimulation. Answer: D Diff: 1 Page Ref: 298 20) The situation in which contractions become stronger due to stimulation before complete relaxation occurs. Answer: A Diff: 1 Page Ref: 297 21) How a smooth increase in muscle force is produced. Answer: B Diff: 2 Page Ref: 298 Match the following: 22) A sarcomere is the distance between two ________. Answer: A Diff: 1 A) Z discs B) A band Page Ref: 284 C) I band 23) The ________ contains only the actin filaments. Answer: C Diff: 1 Page Ref: 284 24) The thicker filaments are the ________ filaments. Answer: D Diff: 1 Page Ref: 286 25) Both actin and myosin are found in the ________. Answer: B Diff: 1 Page Ref: 284, 286 26) The myosin filaments are located in the ________. Answer: B Diff: 2 Page Ref: 284, 286 D) Myosin Match the following: 27) Serves as the actual "trigger" for muscle contraction by removing the inhibition of the troponin molecules. A) Calcium ions B) Acetylcholine Answer: A Diff: 1 Page Ref: 293 28) A neurotransmitter released at motor end plates by the axon terminals. Answer: B Diff: 1 Page Ref: 289 Page Ref: 302 30) Normally stored in the terminal cisternae of the sarcoplasmic reticulum. Answer: A Diff: 1 Page Ref: 287 31) Used to convert ADP to ATP by transfer of a high-energy phosphate group. A reserve high-energy compound. Answer: E Diff: 2 Page Ref: 301-302 32) Destroys ACh. Answer: D Diff: 2 D) Acetylcholinesterase E) Creatine phosphate 29) A metabolic pathway that provides for a large amount of ATP per glucose because oxygen is used. Products are water and carbon dioxide and ATP. Answer: C Diff: 1 C) Aerobic respiration Page Ref: 289 TRUE/FALSE QUESTIONS 1) Once a motor neuron has fired, all the muscle fibers in a muscle contract. Answer: True False Diff: 2 Page Ref: 296 2) The thin filaments (actin) contain a polypeptide subunit G actin that bear active sites for myosin attachment. True False Answer: Diff: 1 Page Ref: 286 3) The force of muscle contraction is controlled by multiple motor unit summation or recruitment. True False Answer: Diff: 1 Page Ref: 297-298 4) Eccentric contractions are more forceful than concentric contractions. True False Answer: Diff: 1 Page Ref: 300 5) A motor neuron and all the muscle cells that it stimulates are referred to as a motor end plate. Answer: True False Diff: 1 Page Ref: 296 6) Peristalsis is characteristic of smooth muscle. Answer: True False Diff: 1 Page Ref: 309-310 7) A contraction in which the muscle does not shorten but its tension increases is called isometric. Answer: True False Diff: 1 Page Ref: 300 8) During isotonic contraction, the heavier the load, the faster the velocity of contraction. False Answer: True Diff: 1 Page Ref: 300 9) During isometric contraction, the energy used appears as movement. Answer: True False Diff: 1 Page Ref: 300 10) One of the important functions of skeletal muscle contraction is production of heat. Answer: True False Diff: 1 Page Ref: 281 11) Oxygen debt refers to the oxygen required to make creatine phosphate. False Answer: True Diff: 1 Page Ref: 304 12) Muscle contraction will always promote movement of body parts regardless of how they are attached. Answer: True False Diff: 1 Page Ref: 281 13) Although there are no sarcomeres, smooth muscle still possesses thick and thin filaments. Answer: True False Diff: 1 Page Ref: 310 14) Whereas skeletal muscle cells are electrically coupled, smooth muscle cells appear to be chemically coupled by gap junctions. False Answer: True Diff: 1 Page Ref: 312 15) Single-unit smooth muscle is found in the intestines. True False Answer: Diff: 1 Page Ref: 316 16) A resting potential is caused by a difference in the concentration of certain ions inside and outside the cell. Answer: True False Diff: 2 Page Ref: 290 17) The effect of a neurotransmitter on the muscle cell membrane is to modify its ion permeability properties temporarily. Answer: True False Diff: 2 Page Ref: 290 18) When a muscle fiber contracts, the I bands diminish in size, the H zones disappear, and the A bands move closer together but do not diminish in length. Answer: True False Diff: 2 Page Ref: 284 19) The more slowly a skeletal muscle is stimulated, the greater its exerted force becomes. Answer: True False Diff: 2 Page Ref: 297 20) Contractures are a result of a total lack of ATP. True False Answer: Diff: 1 21) Page Ref: 303 Smooth muscles relax when intracellular True False Answer: Diff: 1 levels drop but may not cease contractions. Page Ref: 312 22) Recruitment is an option in a single-unit smooth muscle cell. False Answer: True Diff: 1 Page Ref: 316 MULTIPLE-CHOICE QUESTIONS 1) With muscular dystrophy ________. A) muscles decrease in size due to loss of fat and connective tissue B) muscle fibers degenerate and atrophy C) most forms do not appear to be inherited D) most cases appear in young females Answer: B Diff: 1 Page Ref: 317 2) Which muscle cells have the greatest ability to regenerate? A) skeletal B) cardiac C) smooth D) no muscle can regenerate Answer: C Diff: 1 Page Ref: 317 3) Most muscles contain ________. A) muscle fibers of the same type B) a mixture of fiber types C) a predominance of slow oxidative fibers D) a predominance of fast oxidative fibers Answer: B Diff: 1 Page Ref: 307 4) Fatigued muscle cells that recover rapidly are the products of ________. A) intense exercise of long duration B) intense exercise of short duration C) slow exercise of long duration D) slow exercise of short duration Answer: B Diff: 2 Page Ref: 303 5) The strongest muscle contractions are normally achieved by ________. A) increasing stimulus above the threshold B) increasing stimulus above the treppe stimulus C) increasing the stimulation up to the maximal stimulus D) recruiting small and medium muscle fibers Answer: C Diff: 1 Page Ref: 298 6) Which of the following would be recruited later in muscle stimulation when contractile strength increases? A) motor units with the longest muscle fibers B) many small motor units with the ability to stimulate other motor units C) large motor units with small, highly excitable neurons D) motor units with larger, less excitable neurons Answer: D Diff: 2 Page Ref: 298 7) Which of the following is not a usual result of resistance exercise? A) increase in the efficiency of the respiratory system B) increase in the efficiency of the circulatory system C) increase in the number of muscle cells D) increase in the number of myofibrils within the muscle cells Answer: C Diff: 1 Page Ref: 307 8) In skeletal muscle contraction, calcium apparently acts to ________. A) increase the action potential transmitted along the sarcolemma B) release the inhibition on Z discs C) remove the blocking action of tropomyosin D) cause ATP to bind to actin Answer: C Diff: 1 Page Ref: 293 9) Calcium ions bind to the ________ molecule in skeletal muscle cells. A) actin B) tropomyosin C) troponin D) myosin Answer: C Diff: 1 Page Ref: 293 10) Myoglobin ________. A) breaks down glycogen B) is a protein involved in the direct phosphorylation of ADP C) stores oxygen in muscle cells D) produces the end plate potential Answer: C Diff: 2 Page Ref: 284, 306 11) An elaborate network of membranes in skeletal muscle cells that functions in calcium storage is the ________. A) sarcoplasmic reticulum B) mitochondria C) intermediate filament network D) myofibrillar network Answer: A Diff: 1 Page Ref: 287 12) A sarcomere is ________. A) the nonfunctional unit of skeletal muscle B) the area between two Z discs C) the area between two intercalated discs D) the wavy lines on the cell seen in the microscope Answer: B Diff: 1 Page Ref: 284 13) Immediately following the arrival of the stimulus at a skeletal muscle cell there is a short period called the ________ period during which the events of excitation-contraction coupling occur. A) contraction B) relaxation C) latent D) refractory Answer: C Diff: 1 Page Ref: 297 14) Creatine phosphate functions in the muscle cell by ________. A) forming a temporary chemical compound with myosin B) forming a chemical compound with actin C) inducing a conformational change in the myofilaments D) storing energy that will be transferred to ADP to resynthesize ATP Answer: D Diff: 1 Page Ref: 301-302 15) After nervous stimulation of the muscle cell has ceased, the calcium ________. A) is destroyed by cholinesterase B) is chemically bound to the filaments C) level in the cytoplasm drops D) is actively pumped into the extracellular fluid for storage until the next contraction Answer: C Diff: 1 Page Ref: 290-291 16) The major function of the sarcoplasmic reticulum in muscle contraction is to ________. A) make and store phosphocreatine B) synthesize actin and myosin myofilaments C) provide a source of myosin for the contraction process D) regulate intracellular calcium concentration Answer: D Diff: 1 Page Ref: 287 17) The striations of a skeletal muscle cell are produced, for the most part, by ________. A) a difference in the thickness of the sarcolemma B) the arrangement of myofilaments C) the sarcoplasmic reticulum D) the T tubules Answer: B Diff: 1 Page Ref: 284 18) Which of the following are composed of myosin? A) thick filaments B) thin filaments C) all myofilaments D) Z discs Answer: A Diff: 1 Page Ref: 286 19) During muscle contraction, myosin cross bridges attach to which active sites? A) myosin filaments B) actin filaments C) Z discs D) thick filaments Answer: B Diff: 1 Page Ref: 288 20) Which of the following surrounds the individual muscle cell? A) perimysium B) endomysium C) epimysium D) fascicle Answer: B Diff: 1 Page Ref: 283 21) Smooth muscles that act like skeletal muscles but are controlled by autonomic nerves and hormones are ________. A) single-unit muscles B) multiunit muscles C) red muscles D) white muscles Answer: B Diff: 1 Page Ref: 316 22) Rigor mortis occurs because ________. A) the cells are dead B) sodium ions leak out of the muscle C) no ATP is available to release attached actin and myosin molecules D) proteins are beginning to break down, thus preventing a flow of calcium ions Answer: C Diff: 1 Page Ref: 294 23) Which of the following does not act as a stimulus to initiate a muscle contraction? A) hormonal activity B) neurotransmitters C) a change in the pH of a muscle D) a change of temperature Answer: D Diff: 1 Page Ref: 280 24) The term aponeurosis refers to ________. A) the bands of myofibrils B) a sheetlike indirect attachment to a skeletal element C) the rough endoplasmic reticulum D) the tropomyosin-troponin complex Answer: B Diff: 1 Page Ref: 284 25) The oxygen-binding protein found in muscle cells is ________. A) hemoglobin B) ATP C) myoglobin D) immunoglobin Answer: C Diff: 1 Page Ref: 284 26) The contractile units of skeletal muscles are ________. A) microtubules B) mitochondria C) T tubules D) myofibrils Answer: D Diff: 1 Page Ref: 284 27) The site of calcium regulation in the smooth muscle cell is ________. A) actin B) troponin C) myosin D) calmodulin Answer: D Diff: 1 Page Ref: 312 28) One functional unit of a skeletal muscle is ________. A) a sarcomere B) a myofilament C) a myofibril D) the sarcoplasmic reticulum Answer: A Diff: 1 Page Ref: 284 29) The functional role of the T tubules is to ________. A) stabilize the G and F actin B) enhance cellular communication during muscle contraction C) hold cross bridges in place in a resting muscle D) synthesize ATP to provide energy for muscle contraction Answer: B Diff: 1 Page Ref: 287 30) The role of calcium ions in muscle contraction is to ________. A) act as a third messenger B) reestablish glycogen stores C) bind to regulatory sites on troponin, changing the configuration D) initiate the conversion of carbon dioxide to oxygen for storage Answer: C Diff: 1 Page Ref: 293 31) The warm-up period required of athletes in order to bring their muscles to peak performance is called ________. A) twitch B) wave summation C) treppe D) incomplete tetanus Answer: C Diff: 1 Page Ref: 299 32) The main effect of the warm-up period of athletes, as the muscle contractions increase in strength, is to ________. A) increase the myoglobin content B) convert glycogen to glucose C) tone the muscles and stabilize the joints for the workout D) enhance the availability of calcium and the efficiency of enzyme systems Answer: D Diff: 1 Page Ref: 299 33) During vigorous excercise, there may be insufficient oxygen available to completely break down pyruvic acid for energy. As a result, the pyruvic acid is converted to ________. A) a strong base B) stearic acid C) hydrochloric acid D) lactic acid Answer: D Diff: 1 Page Ref: 304 34) When a muscle is unable to respond to stimuli temporarily, it is in which of the following periods? A) relaxation period B) refractory period C) latent period D) fatigue period Answer: B Diff: 1 Page Ref: 291 35) In an isotonic contraction, the muscle ________. A) changes in length and moves the "load" B) does not change in length but increases tension C) never converts pyruvate to lactate D) rapidly resynthesizes creatine phosphate and ATP Answer: A Diff: 1 Page Ref: 300 36) The muscle cell membrane is called the ________. A) endomysium B) sarcolemma C) perimysium D) epimysium Answer: B Diff: 1 Page Ref: 283 37) Smooth muscle is significantly different from striated muscle in several ways. Which of the following is true? A) Smooth muscle has transverse tubules. B) Smooth muscle is larger and more powerful than striated muscle. C) The fibers of smooth muscle are arranged quadrangularly. D) Smooth muscle contracts in a twisting way. Answer: D Diff: 1 Page Ref: 310, 312, 316 38) The mechanism of contraction in smooth muscle is different from skeletal muscle in that ________. A) actin and myosin interact by the sliding filament mechanism B) the trigger for contraction is a rise in intracellular calcium C) the site of calcium regulation differs D) ATP energizes the sliding process Answer: C Diff: 1 Page Ref: 311-312 39) The cells of single-unit visceral muscle ________. A) contract all at once B) are chemically coupled to one another by gap junctions C) exhibit spontaneous action potentials D) consist of muscle fibers that are structurally independent of each other Answer: C Diff: 1 Page Ref: 316 40) Which of the following statements is not true concerning developmental aspects of muscle? A) There is no biological basis for the difference in strength between women and men. B) Skeletal muscle is derived from mesoderm. C) Skeletal muscle develops from somites. D) Most muscle tissues develop from myoblasts. Answer: A Diff: 2 Page Ref: 316-317 41) Which of the following is true about smooth muscle contraction? A) Certain smooth muscle cells can actually divide to increase their numbers. B) Smooth muscle, in contrast to skeletal muscle, cannot synthesize or secrete any connective tissue elements. C) Smooth muscle cannot stretch as much as skeletal muscle. D) Smooth muscle has well-developed T tubules at the site of invagination. Answer: A Diff: 2 Page Ref: 316 42) Smooth muscle is characterized by all of the following except ________. A) it appears to lack troponin B) there are more thick filaments than thin filaments C) there are no sarcomeres D) there are noncontractile intermediate filaments that attach to dense bodies within the cell Answer: B Diff: 2 Page Ref: 309-311 43) Muscle tissue has all of the following properties except ________. A) secretion B) contractility C) extensibility D) excitability Answer: A Diff: 1 Page Ref: 280 44) The giant protein titin maintains the organization of the ________ assisting in muscle stretching. A) A band B) I band C) Z disc D) M line Answer: A Diff: 2 Page Ref: 287 45) Which of the following statements is true? A) Cardiac muscle cells have many nuclei. B) Smooth muscle cells have T tubules. C) Striated muscle cells are long and cylindrical with many nuclei. D) Cardiac muscle cells are found in the heart and large blood vessels. Answer: C Diff: 2 Page Ref: 280 46) An anaerobic metabolic pathway that results in the production of two net ATPs per glucose plus two pyruvic acid molecules is ________. A) the citric acid cycle B) glycolysis C) hydrolysis D) the electron transport chain Answer: B Diff: 2 Page Ref: 302 47) Muscle tone is ________. A) the ability of a muscle to efficiently cause skeletal movements B) the feeling of well-being following exercise C) a state of sustained partial contraction D) the condition of athletes after intensive training Answer: C Diff: 2 Page Ref: 300 48) The sliding filament model of contraction involves ________. A) actin and myosin sliding past each other and partially overlap B) the shortening of thick filaments so that thin filaments slide past C) actin and myosin shortening but not sliding past each other D) the Z discs sliding over the myofilaments Answer: A Diff: 2 Page Ref: 287-288 49) After nervous stimulation stops, ACh in the synaptic cleft is prevented from continuing stimulation of contraction by ________. A) calcium ions returning to the terminal cisternae B) the tropomyosin blocking the myosin once full contraction is achieved C) acetylcholinesterase destroying the ACh D) the action potential stopped going down the overloaded T tubules Answer: C Diff: 2 Page Ref: 289 50) Which of the following is most accurate? A) Muscle tension remains relatively constant during isotonic contraction. B) T-tubles may be sliding during isotonic contraction. C) The I band lenghtens during isotonic contraction. D) Myofilaments slide during isometric contractions. Answer: A Diff: 2 Page Ref: 300 51) The most distinguishing characteristic of muscle tissue is ________. A) the design of the fibers B) the sarcoplasmic reticulum C) the diversity of activity of muscle tissue D) the ability to transform chemical energy into mechanical energy Answer: D Diff: 2 Page Ref: 280 52) Three discrete types of muscle fibers are identified on the basis of their size, speed, and endurance. Which of the following athletic endeavors best represents the use of red fibers? A) a sprint by an Olympic runner B) a long, relaxing swim C) playing baseball or basketball D) mountain climbing Answer: B Diff: 2 Page Ref: 305; Tbl. 9.2 53) Of the following muscle types, which has only one nucleus, no sarcomeres, and rare gap junctions? A) visceral smooth muscle B) multiunit smooth muscle C) cardiac muscle D) skeletal muscle Answer: B Diff: 2 Page Ref: 316 54) Hypothetically, if a muscle were stretched to the point where thick and thin filaments no longer overlappe d ________. A) cross bridge attachment would be optimum because of all the free binding sites on actin B) no muscle tension could be generated C) maximum force production would result since the muscle has a maximum range of travel D) ATP consumption would increase since the sarcomere is "trying" to contract Answer: B Diff: 3 Page Ref: 305 55) An individual has just ingested a chemical that binds irreversibly to the ACh receptors in the sarcolemma. By itself it does not alter membrane potential, yet prevents normal neurotransmitter binding. Ignoring the effects on any other system, the consequence to skeletal muscle would be ________. A) irreversible contraction as soon as the first nervous stimulation reached the sarcolemma B) no contraction at all by nervous mechanisms C) contraction if stimulated by an external electrode D) no contraction at all by nervous mechanisms, but contraction if stimulated by an external electrode Answer: D Diff: 3 Page Ref: 289 FILL-IN-THE-BLANK/SHORT ANSWER QUESTIONS 1) Only ________ muscle cells are alwyas multinucleated. Answer: skeletal Diff: 1 Page Ref: 284 2) Claudication might more simply be called ________. Answer: limping Diff: 3 Page Ref: 320 3) The end of the muscle that typically moves when a muscle contracts is called the ________. Answer: insertion Diff: 1 Page Ref: 283-384 4) In the synaptic cleft of a neuromuscular junction, an enzyme called ________ is always present. Answer: acetylcholinesterase Diff: 1 Page Ref: 289 5) The time in which cross bridges are active is called the period of ________. Answer: contraction Diff: 1 Page Ref: 297 6) ________ (color) fibers are slow (oxidative) fibers. Answer: Red Diff: 1 Page Ref: 306 7) Only ________ muscle cells commonly branch. Answer: cardiac Diff: 1 Page Ref: 314; Tbl. 9.3 8) A smooth, sustained contraction is called ________. Answer: tetanus Diff: 1 Page Ref: 298 9) Define physiologic muscle fatigue. Answer: Fatigue occurs when ATP production fails to keep pace with ATP use even though the muscle still receives stimuli. Diff: 1 Page Ref: 303 10) Compare red and white muscles relative to their speed of action and endurance. Answer: Red muscles tend to have a slow (oxidative) rate and fatigue resistance, whereas white muscle cells have a fast (oxidative) rate and fatigue easily. Diff: 2 Page Ref: 306; Tbl. 9.2 11) Briefly, what causes rigor mortis? Answer: Following the death of an individual, ATP is rapidly consumed and cannot be replaced. Because cross bridge detachment and calcium active transport is ATP driven, calcium leakage from the sarcoplasmic reticulum causes attachment of cross bridges, and lack of ATP prevents detachments. Diff: 3 Page Ref: 294 12) What ultimately stops muscle stimulation when the motor neuron ceases firing? Answer: The ultimate switch is the enzyme acetylcholinesterase. When the neuron stops releasing ACh, the muscle would not stop contracting if the acetylcholinesterase did not split the ACh into its two components, acetyl and choline, making them release their binding sites. Diff: 3 Page Ref: 289 13) A long-distance runner is about to enter a 5-mile race. Beforehand, he spends several minutes warming up. During the warm-up period, the phenomenon of treppe is occurring in body muscles being used. What is treppe and why does it occur? Answer: Treppe is the staircase phenomenon in which muscles increase their strength of contraction due to increased availability of calcium. Additionally, the increased warmth due to activity causes an increase in the efficiency of muscle enzyme systems. Diff: 3 Page Ref: 299 14) What are the two special inclusions of skeletal muscle cells and how would they be useful to the cell? Answer: Skeletal muscle cells require a lot of rapidly available fuel to burn in order to function properly. They also require a lot of oxygen to burn this fuel efficiently. Glycosomes store glycogen which can be quickly converted to glucose, which in turn can be burned to produce ATP. Myoglobin is a chemical much like hemoglobin in blood cells which can store large quantities of oxygen. Diff: 2 Page Ref: 284 15) What is the relationship that occurs in the triad of a skeletal muscle cell? Answer: The sarcoplasmic reticulum is a reservoir for calcium ions in the cell's normal resting state. The T tubule is a fold in the cell membrane between the sarcoplasmic reticuli. When an impulse is activated by a motor neuron, the voltage-regulated change causes SR foot proteins to open Ca2+ channels. The calcium ions are flushed out where they interact with the troponin complex to initiate a contraction. Once the axon stops firing, the membrane polarity is quickly restored and the calcium ions are pulled off the troponin and attracted back into the sarcoplasmic reticulum. Diff: 2 Page Ref: 287, 293 16) Briefly explain where the energy comes from in a one-minute sustained muscle contraction. Answer: 1. The first 4-6 seconds of energy come from stored ATP in the muscle cell. 2. 6-15 seconds of energy come from the transfer of creatine phosphate and ADP (which come from the first few seconds of burn) to form additional ATP. 3. 15-60 seconds of energy come from glycolysis which by now has begun full production of ATP from glucose. Diff: 2 Page Ref: 300-303 17) What are caveoli? Answer: Folds on the surface of smooth muscle cells that correspond to T tubules in skeletal muscle cells. Diff: 2 Page Ref: 310 18) How is it that norepinephrine (NE) can inhibit smooth muscle action in airways, yet stimulate contractions in smooth muscles everywhere else in the body? Answer: Airway passages have smooth muscle cells that are unique in that they have two receptor sites on their outer membrane. One receptor site accepts ACh as the neurotransmitter. When excited it causes the smooth muscle to contract. The second site accepts NE and the inhibitory effect is that the ACh dilates the airway. Diff: 2 Page Ref: 312 19) How do the three muscle types respond to being stretched? Answer: All three muscle types initially respond by contracting more forcefully. However, in smooth muscle cells the increased tension persists only briefly, and the muscle adapts to its new length and relaxes. Diff: 2 Page Ref: 313 20) What is agrin? Answer: Agrin is a growth factor of developing muscles. Agrin stimulates ACh receptors to cluster around a newly forming motor end plate. Diff: 2 Page Ref: 316-317 CLINICAL QUESTIONS 1) Gary was injured in an automobile accident that severed the motor neurons innervating his quadriceps. Even though he has had extensive physical therapy, he is still suffering muscle atrophy. Why is the therapy not working? Answer: In denervation atrophy, fibrous connective tissue replaces the muscle tissue that was lost. When atrophy is complete, fibrous tissue cannot be reversed to muscle tissue. Diff: 3 Page Ref: 309 2) Aaron arrived at the hospital with the following symptoms: drooping eyelids; fatigue and weakness of his muscles; and difficulty talking, breathing, and swallowing. What was his diagnosis? Answer: Aaron probably has myasthenia gravis (an autoimmune disease), which involves a shortage of ACh receptors at the neuromuscular junction. Diff: 3 Page Ref: 289 3) Lynn has been waking up each night with intense pain in her calves. She does not feel that it is serious enough to seek medical attention but would like to know what is causing the pain. What would you tell her concerning this problem? She has been playing tennis all summer for several hours each day. Could this have anything to do with the night pain? Answer: This is due to sustained spasm, or tetanic contraction, of the gastrocnemius muscle. The causes could be low blood sugar, electrolyte depletion (particularly sodium and calcium), dehydration, or irritability of the spinal cord neurons. The fact that Lynn has been playing tennis for several hours each day may have caused an electrolyte depletion. She should increase her intake of calcium. Diff: 3 Page Ref: 298 4) After removal of an elbow cast, Lauren noticed her arm was immovable. What happened to her arm? Answer: Two things have occurred to Lauren while she was convalescing from her injury. First, the immobilization of the arm caused some muscle mass to atrophy. Second, the loss of muscle was replaced with tough connective tissue that locked her arm in place. With therapy the tissue can be stretched or torn enough to return the full range of motion. Diff: 3 Page Ref: 309 5) When a geriatric client is admitted to the rehabilitation unit, an important nursing measure is to prevent the loss of muscle mass. What is the term used for loss of muscle mass and how can the patient prevent it? Answer: Disuse atrophy is degeneration and loss of muscle mass. The size, shape, tone, and strength of muscles (including the heart) are maintained with mild exercise and increased with strenuous exercise. Promoting exercise to maintain a patient's muscle tone, joint mobility, and cardiovascular function is an important nursing function. Diff: 3 Page Ref: 309 6) A patient has no peristalsis in the gastrointestinal tract. Explain a possible complication of this condition. Answer: Peristalsis is wavelike movement produced by the circular and longitudinal muscle fibers of the intestinal walls that propels the intestinal contents forward. Without peristalsis, the patient would be unable to expel their stool, leading to intestinal obstruction. Diff: 3 Page Ref: 309-310 7) The nurse encourages the patient to do his own activities of daily living such as bathing, feeding, dressing, and toileting activities. How do these activities promote physical conditioning? Answer: These activities are isotonic exercises in which muscle tension is constant and then shortens to produce muscle contraction and movement. Because the muscles contract, the shape, size, and strength of the muscles are maintained as well as joint mobility. Diff: 3 Page Ref: 300 8) A patient is admitted for electroconvulsive treatment (ECT). The physician orders the neuromuscular blocking agent metocurine iodide (metubine) to reduce trauma by relaxing skeletal muscles. Explain the process of muscle contraction and how a neuromuscular blocking agent such as metubine would interfere with muscle contraction. Answer: Muscle contraction begins with a stimulus to the nerve. When the impulse reaches the neuromuscular junction, depolarization occurs, resulting in an influx of calcium ions from the extracellular fluid into the terminals, which then release a neurotransmitter, acetylcholine (Ach), into the cleft. The Ach combines with receptor sites on the post-junctional muscle cell membrane, depolarizing it and facilitating the entry of sodium. Neuromuscular blocking agents act at the motor end plate by competing with the Ach for the receptor sites, or by blocking depolarization. Diff: 3 Page Ref: 290-291 ...
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