The Muscular System Questions and Answers (57-99)

12) An aponeurosis is a ropelike piece of muscle fascia that forms indirect connections to muscles of the leg. Answer : FALSE Diff: 1 Page Ref: 185 13) A muscle twitch results when the muscle is stimulated so rapidly that no evidence of relaxation is seen. Answer : FALSE Diff: 2 Page Ref: 194 14) The effect of the neurotransmitter on the muscle cell membrane is to temporarily modify its permeability of ions such as Na+ and K+. Answer : TRUE Diff: 2 Page Ref: 189-190 15) 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 Diff: 2 Page Ref: 192 16) The insertion of the biceps brachii muscle is on the radius. Answer : FALSE Diff: 2 Page Ref: 211 39 17) A prime mover of the arm that acts in adduction is the deltoid. Answer : FALSE Diff: 1 Page Ref: 210 18) The deepest muscle of the abdominal wall is the transversus abdominis. Answer : TRUE Diff: 2 Page Ref: 209 19) Dorsiflexion and plantar flexion are synergistic actions. Answer : FALSE Diff: 1 Page Ref: 202 20) Plantar flexion at the ankle joint is accomplished by the tibialis anterior muscle. Answer : FALSE Diff: 2 Page Ref: 214 21) The bicpes brachii muscle is named for the two heads that orginiate from the shoulder girdle. Answer : TRUE Diff: 2 Page Ref: 211 22) There are 206 skeletal muscles in the human body. 40 FALSE Diff: 1 Page Ref: 198 23) Supination and pronation refer to up and down movements of the foot at the ankle. Answer : FALSE Diff: 2 Page Ref: 202 Matching Match the following: 1) The distance between two Z discs A) I band Diff: 2 Page Ref: 187-188 B) myosin filaments 2) Otherwise known as thick filaments C) actin filaments Diff: 2 Page Ref: 189 D) Z discs 3) Contains only the actin filaments E) sarcomere Diff: 2 Page Ref: 187-188 41 F) H zone 4) Both actin and myosin are found in this band G) A band Diff: 1 Page Ref: 187-188 5) The type of filament that is studded with myosin heads Diff: 1 Page Ref: 189 6) Tiny contractile unit that shortens during muscle contraction Diff: 2 Page Ref: 187; 192 7) Actin filaments are anchored to these disclike membranes Diff: 1 Page Ref: 189 8) Lighter central portion of the A band Diff: 2 Page Ref: 187 1) E 2) B 3) A 4) G 42 5) B 6) E 7) D 8) F 43 Match the following: 9) Serves as the actual "go" signal for muscle contraction A) creatine phosphate Diff: 2 Page Ref: 193 B) acetylcholine 10) Neurotransmitter substance released at motor end plates by the motor neuron C) enzymes D) potassium ions Diff: 2 Page Ref: 189 E) calcium ions 11) Normally stored in the sarcoplasmic reticulum F) aerobic respiration Diff: 2 Page Ref: 189 G) anaerobic respiration 12) A metabolic pathway that produces water, carbon dioxide, and ATP, and provides for a large amount of ATP per glucose because oxygen is used H) sodium ions Diff: 3 44 Page Ref: 195 13) A reserve, high-energy compound used to convert ADP to ATP by the transfer of a highenergy phosphate group Diff: 2 Page Ref: 195 14) Destroys acetylcholine (ACh) Diff: 2 Page Ref: 190 9) E 10) B 11) E 12) F 13) A 14) C 45 Match the following: 15) Type of movement that decreases the angle of the joint A) supination B) extension Diff: 2 Page Ref: 199 C) pronation 16) Type of movement that results when the forearm rotates laterally so that the palm faces anteriorly D) rotation E) adduction Diff: 2 Page Ref: 202 F) flexion 17) The movement of a limb toward the body midline G) abduction Diff: 2 Page Ref: 199 18) Type of movement that increases the angle of the joint Diff: 2 Page Ref: 199 19) The movement of a bone around its longitudinal axis 46 Diff: 2 Page Ref: 199 20) The movement of a limb away from the body midline Diff: 2 Page Ref: 199 21) Type of movement that results when the forearm rotates medially so the palm faces posteriorly Diff: 2 Page Ref: 202 22) Primary action of the deltoid Diff: 2 Page Ref: 210 23) Primary action of the adductor muscles Diff: 2 Page Ref: 214 24) Primary action of the erector spinae Diff: 2 Page Ref: 210 25) Primary action of the rectus abdominis Diff: 2 Page Ref: 209 15) F 16) A 17) E 47 18) B 19) D 20) G 21) C 22) G 23) E 24) B 25) F Essay 1) Compare skeletal, smooth, and cardiac muscles as to their body location, microscopic anatomy, regulation of contraction, speed of contraction, and rhythmicity. Answer : Body location—skeletal muscle is attached to bones or to skin (some facial muscles); cardiac muscle is located in the walls of the heart; smooth muscle is found in the walls of hollow visceral organs (other than the heart). Microscopic anatomy—skeletal muscle consists of very long, cylindrical, multinucleated cells with very obvious striations; cardiac muscle consists of branching chains of cells that are uninucleated and possess striations; smooth muscle consists of single fusiform uninucleated cells that lack striations. Regulation of contraction—skeletal muscle is voluntary via nervous system controls, but this normal voluntary control can be overridden by involuntary reflex arcs (as explained in later chapters); cardiac muscle is involuntary via the heart pacemaker, nervous system controls, and hormones; smooth muscle is involuntary via nervous system controls, hormones, other chemicals, and stretching. Speed of contraction—skeletal muscle is slow to fast; cardiac muscle is slow; smooth muscle is the slowest. Rhythmicity—skeletal muscle is arrhythmic; cardiac muscle is rhythmic; smooth muscle is sometimes rhythmic. Diff: 3 48 2) Describe the events that occur from the time that a motor neuron releases acetylcholine at the neuromuscular junction until muscle cell contraction occurs. Answer : Acetylcholine is released, which diffuses through the synaptic cleft and attaches to receptors on the sarcolemma. The sarcolemma permeability to sodium ions increases briefly, causing sodium ions to rush into the muscle cell, which changes the electrical conditions of the resting sarcolemma. An action potential is initiated and sweeps over the entire sarcolemma. Calcium ions are released from storage areas inside the sarcoplasmic reticulum of the muscle cell. They attach to the myofilaments, which triggers the sliding of the myofilaments and causes a muscle cell contraction. Diff: 3 Page Ref: 189-192 3) List the seven criteria that are used in naming muscles and give an example of each. Answer : 1. Direction of the muscle fibers (e.g., external oblique) 2. Relative size of the muscle (e.g., maximus, minimus, longus) 3. Location of the muscle (e.g., temporalis, frontalis) 4. Number of origins (e.g., biceps, triceps, quadriceps) 5. Location of the muscle's origin and insertion (e.g., the sternocleidomastoid muscle has its origin on the sternum [sterno] and clavicle [cleido] and inserts on the mastoid process of the temporal bone) 6. Shape of the muscle (e.g., the deltoid muscle is roughly triangular—deltoid means "triangular") 7. Action of the muscle (e.g., the adductor muscles of the thigh all bring about its adduction, and the extensor muscles of the wrist all extend the wrist) Diff: 3 Page Ref: 202; 204 4) What is the effect of aging on skeletal muscles? Answer : With aging, the amount of connective tissue in muscle increases and the amount of skeletal muscle tissue decreases, thus the muscles become stringier (more sinewy). Since skeletal muscle represents a larger portion of body weight, it begins to decline in elderly persons as this normal loss of muscle mass occurs. Another result of the loss in muscle mass is a decrease in muscle strength—strength decreases by about 50% by the age of 80. Regular exercise can help offset the effects of aging on the muscular system, and frail elders who begin to "pump iron" can rebuild muscle mass and significantly increase their functional strength. Diff: 3 Page Ref: 221 49 5) Explain the steps in the sliding filament theory of muscle contraction, following the spreading of an action potential along the sarcolemma. Answer : An action potential triggers the sarcoplasmic reticulum to release calcium ions into the sarcoplasm of the muscle cell. The calcium ions bind to regulatory proteins on the actin filaments, changing both their shape and their position on the actin filaments. This action allows myosin receptor sites on the thin actin filaments to become exposed. The myosin heads attach to the myosin binding sites on the actin filaments. Energized by ATP, the myosin heads swivel toward the center of the sarcomere, attaching and detaching several times. In the process the thin actin filaments are pulled toward the center of the sarcomere. As this event occurs simultaneously in sarcomeres throughout the cell, the muscle cell shortens. When the action potential ends, the calcium ions are reabsorbed back into the sarcoplasmic reticulum storage areas, causing the regulatory proteins to resume their original shape and position. Since the myosin heads now have nothing to attach to, the muscle cell relaxes and returns to its original length. Diff: 3 Page Ref: 192-193 6) Fascicle arrangements produce skeletal muscles with different structures and functional properties, and determine their individual range of motion and power. List the seven different fascicle arrangements of human skeletal muscles and give a specific example of each: Answer : 1. 2. 3. 4. 5. 6. 7. Circular—orbicularis oris, orbicularis oculi Convergent—pectoralis major Parallel—sartorius Unipennate—extensor digitorum longus Multipennate—deltoid Fusiform—biceps brachii Bipennate—rectus femoris Diff: 3 Page Ref: 204-206 7) List the "five golden rules" of gross skeletal muscle activity. Answer : 1. 2. 3. 4. 5. With few exceptions, all muscles cross at least one joint. Typically, the bulk of the muscle lies proximal to the joint crossed. All muscles have at least two attachments: the origin and the insertion. Muscles can only pull: they never push. During contraction, the muscle insertion moves toward the origin. Diff: 3 Page Ref: 198 50 8) Explain how isometric and isotonic contractions differ, using examples of each. Answer : 1. Isometric contractions are contractions in which the muscles do not shorten. An example of an isometric contraction is pushing against a wall with bent elbows. The muscles cannot shorten since the wall doesn't move. 2. Isotonic contractions occur when muscles shorten and movement occurs due to the sliding of the myofilaments. Flexion and extension of the arm are just two examples of isotonic contractions. Diff: 2 Page Ref: 197 9) Explain the difference between a motor unit and a neuromuscular junction. Answer : 1. The motor unit is the one neuron and all of the skeletal muscle cells it stimulates. 2. The neuromuscular junction occurs between the axon terminals of one neuron and the sarcolemma of a skeletal muscle cell. Diff: 2 Page Ref: 189 10) Explain how muscle movements mature in a baby, using examples of each. Answer : 1. Muscle development proceeds in a cephalic/caudal direction. For instance, babies can raise their heads before they can walk. 2. Muscle control proceeds in a proximal/distal direction. For instance, babies can perform gross movements like wave "bye-bye" before they can use the pincher grasp to pick up a pin. Diff: 2 Page Ref: 221