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When describing muscle, what does "striated" mean?
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Harry was pondering an exam question that said, "What muscle type has elongated cells and is found in the walls of the urinary bladder?" What should he have responded
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A&P Chap 9
Muscles
| Question | Answer |
|---|---|
| When describing muscle, what does "striated" mean? | Striated means "with stripes" |
| Harry was pondering an exam question that said, "What muscle type has elongated cells and is found in the walls of the urinary bladder?" What should he have responded | Smooth Muscle |
| How does the term epimysium relate to the role and position of this connective tissue sheath? | Epimysium translates to the outside of the muscle, and the connective tissue sheath is te outermost muscle sheath which encloses the entire muscle |
| Which myofilaments have binding sites for calcium? What specific molecule binds calcium? | The thin myofilaments have binding sites for calcium on the troponin molecules forming part of those filaments |
| Which structure-T tubule, mitochondrion, or SR- contains the highest conecentration of calcium ions in resting muscle fiber? Which structure provides the ATP needed for muscle activity? | In resting muscle fiber the SR would have the highest concentration of calcium ions. The mitochondrion provides the ATP needed for muscle activity. |
| What are the three structural components of a neuromuscular junction? | axon terminal, synaptic cleft, and junctional folds of the sarcolemma |
| What is the final trigger for contraction? What is the initial trigger? | A certain concentration of calcium ions in the cytosol is the final trigger. The initial trigger is depolarization of the sarcolemma. |
| What prevents filaments from sliding back to their original position each time a myosin cross bridge attaches from actin? | There are always some myosin cross bridges bound to the actin myofilament during the contraction phase. Thus, backward sliding of the actin filaments is prevented. |
| What would happen if a muscle fiber suddenly ran out of ATP when sarcomers had only partially contracted? | Without ATP, rigor would occur because the myosin heads could not detach. |
| What is a motor unit | A motor unit is an axon of a motor neuron and all the muscle fibers it innervates. |
| What is happening in the muscle during the latent period of a twitch contraction | During the latent period, events of excitation-contraction coupling are occuring |
| Jay is competing in a chin up competition. What type of muscle contractions are occuring in his bicesps muscles imediately after he grabs the bar? As his body beings to move upward toward the bar? When his body begins to approach the mat? | After grabbing the bar his bicep muscles are contracting isometrically. As he moves up toward the bar they contract isotonically and concentrically. As he lowers the biceps are contracting isotonically and eccentrically |
| When Eric returned from joggind he was breathing heavily, sweating profusely, and complained that his legs ached and felt weak. On the basis of what you learned about muscle energy metabolism answer the following Why is Eric breathing heavily? | He is breathing heavy because it takes some time for his heart rate and overall metabolism to return to the resting stacge after exercise. |
| List two factors that influence contractile force and two that influence velocity of contraction | Foce is influenced by muscle fiber size, number of muscle fibers stimulated, frequency of stimulation, degree of muscle stretch. Velocity is influnced by muscle fiber type, load, and the number of motor units contacting. |
| Jim called several friends to help him move. Would he prefer to have those with more slow oxidative muscle firbers or those with more fast glycolytic fibers as his helpers? Why? | Fast glycolytic fibers would provide for short periods of intenese strength needed to lift and move furniture. |
| Relative to their effect on muscle size and function, how do aerobic and anaerobic exercise differ? | To increase muscle size and strength anaerobic exercise is best. Muscle endurance is enhanced by aerobic exercise |
| Compare the structure of skeletal muscle fibers to that of smooth muscle fibers | Skeletal and smooth muscle fibers are elongated cells, but unlike smooth muscle cells, which are spindle shaped, uninucleate, and nonstriated skeletal muscle cells are very large cigar shaped, multinucleate striated cells |
| Calcium is the trigger for contraction of all muscle types. How doees its binding site differ in skeletal and smooth muscle fibers | Calcium binds to troponin on the actin filaments in skeletal muscle cells. In smooth muscle cells, it bind to a cytoplasmic protein called calmodulin. |
| How does the stress-relaxation response suit the role of smooth muscle in hollow organs | Hollow orangs that have smooth muscle cells helping to form their walls often must temporarily store the organs contents, an ability ensured by the stress-relaxation response |
| How is the multinucleate condition achieved during development of skeltal muscle fibers | During development of skeletal muscle fibers, the myoblast cells join together forming multinucleate myotubes |
| What does it mean when we say "muscles get stringier with age?" | the connective tissue in muscle increases with age, causing muscles to get stringier |
| How can we defer(or reverse) some of the effects of age on skeletal muscles? | Regular exercise and strenth training help to defer the loss in strength and muscle wasting that tends to occur with age, and improve meuromuscular function. |
| The connective tissue covering that encloses the sarcolemma of an individual muscle fiber is called | endomysium |
| a fascalise is | bundle of muscle fibers enclosed by a connective tissue sheath |
| The function of the T tubules in muscle contraction is to | transmit the action potential deep into the muscle cells |
| The sites where motor nerve impluse is transmitted from the never endings to the skeletal muscle cell membranes are the | neuromuscular junctions |
| Contraction eliceited by a single brief stimulus is called | a twitch |
| a smooth sustained contraction resulting from very rapid stimulation of muscle in which no evidence of relaxation is seen is called | fused tetanus |
| the neurotransmitter released by somatic motor neurons is | acetylcholine |
| the ions that enter the skeletal muscle cell during the action potential generation are | sodium ions |
| Myoglobin has a special function in muscle tissue. It | holds a reserve supply of oxygen in the muscle |
| The smooth muscle type found in the walls of digestive and urinary system organs and that exhibits gap junctions and pacemaker cells is | single unit |
| At the neuromuscular junction, calcium ions act to release synaptic vesicles from ______ | axon terminal |
| What type of ion channel opens in response to an action potential arriving at the axon terminal? | voltage gated calcium |
| What is the name of the enzyme that degrades ACh? | Acetylcholenesterase |
| the elaborate network of membranes in skeletal muscle cells that function in calcium storage is? | SR |
| Which ion links excitation to contraction in skeletal muscle fiber? | calcium |
| As AP travel down a T tubule a voltage sensitive protein changes shape and _____________ | opens a calcium channel |
| What is the functional unit of a skeletal muscle fiber? | sarcomere |
| Interactions betwen think and thin myofilaments of the sarcomere are responsible for | muscle contraction |
| Which is the only muscle subject to conscious control? | Skeletal |
| Which muscle are striated? | cardiac and skeletal |
| Skeletal muscle is attached to the skeleton, striated, and can be controlled____________ | voluntarily |
| ____________ muslce forms in the heart, is striated , and controlled involuntarily | cardiac |
| Smooth muscle, located chiefly in the walls of _____________, is controlled involuntarily its fibers are not strialted | hollow organs |
| What are special functional characteristis of muscle? | Excitability, contractility, extensibility, and elasticity |
| What are functions of muscles? | move internal and external body parts, maintain posture, stabilize joints, generate heat, protect visceral organs |
| _____________ muscle fibers are long, striatedm, and multinucleate | Skeletal |
| Acetylcholine(ACh) | Chemical transmitter substance released by some nerve endings |
| Acetylcholinesterase(AchE) | Enzyme present at the neuromuscular junction and synapses that degrades acetylcholine and terminates its action. |
| Which muscle type is both voluntary and striated cardiac or skeletal? | Skeletal muscle |
| True or False Muscle cells initiate nerve impulses. | False |
| What is a special adaptation present in muscle cells, but absent in most other cells | Muscle cells have myoglobin; most other cells do not |
| The final "go" signal for skeletal muscle contraction is: | an increase in intracellular calcium ion levels. |
| The ___________ serve as a communication network that coordinates the contraction of each myofibril that makes up the muscle fiber. | T-tubules |
| Thin myofilaments are composed chiefly of: | actin. |
| What does acetylcholinesterase do? | breaks down acetylcholine. |
| Myofibrils are composed of repeating contractile elements called: | sarcomeres |
| True or False During contraction, thin filaments slide past thick filaments so that actin and myosin filaments do not overlap. | false |
| true or false During contraction, the distance between Z disks of a sarcomere decreases. | true |
| When an action potential arrives at the neuromuscular junction, the most immediate result is: | the release of acetylcholine. |
| If a muscle is applied to a load that exceeds the muscle's maximum tension: | the muscle length will not change during contraction. |
| The variation of stimulation needed in skeletal muscle contraction in order to have controlled movement is called a: | graded muscle response. |
| The most efficient means of producing ATP is: | aerobic respiration. |
| What would occur if a muscle became totally depleted of ATP? | The muscle would remain in a contracted state due to an inability to break actin-myosin cross bridges. |
| How does a Slow oxidative muscle fiber fatigue | Fatigue resistant |
| How does a Fast oxidative muscle fiber fatigue | Moderately fatigue resistant |
| How does a Fast glycolytic muscle fiber fatigue | Fatigues quickly |
| True or false Once damaged, smooth muscle is unable to regenerate. | false |
| True or False Contraction of smooth muscle is regulated by the autonomic nervous system. | True |
| true or false Smooth muscle depends on the calcium-calmodulin system to regulate contraction while skeletal muscle relies on the calcium-troponin system to regulate contraction. | True |
| True or False Duchenne muscular dystrophy is more common in females than in males. | False |
| Actin | A contractile protein of muscle |
| Action Potential | A large transient depolarization event, including polarity reversal, that is conducted along the membrane of a muscle cell or a nerve fiber |
| Aerobic | Oxygen-requiring |
| Aerobic Endurance | The length of time a muscle can continue to contract using aerobic pathways |
| Aerobic Respiration | Respiration in which oxygen is consumed and glucose is broke down entirely; water, carbon dioxide, and large amounts of ATP are the final products |
| Anerobic | Not requiring oxygen |
| Anaerobic Glycolysis | Energy-yielding conversion of glucose to lactic acid in various tissues, notably muscle, when sufficient oxygen is not avaliable |
| Anaerobic Threshold | The point at which muscle metabolism cnoverts to anaerobic glycolysis |
| Aponeurosis | Fibrous or membranous sheet connecting a muscle and the part it moves |
| Atrophy | Reduction in size or wasting away of an organ or cell resulting from disease or lack of use |
| Cardiac Muscle | Specialized muscle of the heart |
| Contractility | Muscle cell's ability to move by shortening |
| Contraction | To shorten or develop tension, an ability highly developed in muscle cells |
| Creatin Kinase | Enzyme that catalyzes the transfer of phosphate from creatine phosphate to ADP, forming creating and ATP; important in muscle contraction |
| Creatin Phosphate (CP) | Compound that serves as an alternative energy source for muscle tissue |
| Depolarization | Loss of a state of polarity; loss or reduction of negative membrane potential |
| Endomysium | Thin connective tissue surrounding each muscle cell |
| Epimysium | Sheath of fibrous connective tissue surrounding a muscle |
| Excitability (Irritability) | Ablility to respond to stimuli |
| Excitation-Contraction (E-C)Coupling | Sequences of events by which transmission of an action potential along the sarcolemma leads to the sliding of myofilaments |
| Fascia | Layers of fibrous tissue covering and seperating muscle |
| Fascicle | Bundle of nerve or muscle fibers bound together by connective tissue |
| Glycolysis | Breakdown of glucose to pyruvic acidian anerobic process |
| Graded Muscle Responses | Variations in the degree of muscle contraction by changing either the frequency or strength of the stimulus |
| Insertion | Movable attachment of a muscle |
| Isometric Contraction | Contraction in which the muscle does not shorten (the load is too heavy) but its internal tension increases |
| Isotonic Contraction | Contraction in which muscle tension remains constant at a given joint angle and load, and the muscle shortens |
| Lactic Acid | Product of anerobic metabolism, espically in muscle |
| Latent Period | Period of time between stimulation and the onset of muscle contraction |
| Motor Unit | A motor neuron and all the muscle cells it stimulates |
| Muscle Tension | The force exerted by a contracting muscle on some object |
| Muscle Tone | Low levels of contractile activity in relaxed muscle; keeps the muscle healty and ready to act |
| Muscle Twitch | The response of a muscle to a single brief threshold stimulus |
| Myoblasts | Embryonic mesoderm cells from which all mucle fibers develop |
| Myofibril | Rodlike bundle of contractile filaments (myofilaments) found in muscle fibers (cells) |
| Myofilament | Filament that constitutes myofibrils. One of two types; actin and myosin |
| Myoglobin | Oxygen binding pigment in muscle |
| Myogram | A graphic recording of mechanical contractile activity produced by an apparatus that measures muscle contraction |
| Myosin | One of the prinicipal contractile proteins found in muscle |
| Neuromuscular Junction | Region where a motor neuron comes into close contact with a skeletal muscle cell |
| Origin | Attachment of a muscle that remains relatively fixed during muscular contraction |
| Oxygen Deficit | The volume of oxygen required after exercise to replenish stores of O2, ATP, creatine phosphate, and glycogen and oxidize the lactic acid formed during exercise |
| Perimysium | Connective tissue enveloping bundles of muscle fibers |
| Peristalsis | Progressive, wavelike contractions that move foodstuffs through the alimentary tube organs(or that move other substances through other hollow body organs) |
| Repolarization | Movement of the membrane potential to the initial resting (polarized) state |
| Resistance Exercise | High intensity exercise in which the muscles are pitted against high resistance or immovable forces and, as a result, muscle cells increase in size |
| Sarcolemma | The plasma membrane surface of a muscle fiber |
| Sarcomere | The smallest contractile unit of muscle; extends from one Z disc to the next |
| Sarcoplasm | The nonfiber cytoplasm of a muscle fiber |
| Sarcoplasmic Reticulum (SR) | Specialized endoplasmic reticulum of muscle cells |
| Skeletal Muscle | Muscle composed of cylindrical multinucleate cells with obvious striations: the muscle(s) attached to the body's skeleton; voluntary muscle |
| Smooth Muscle | Spindle-shaped cels with one centrally located nucleus and no externally visible striations (bands). Found mainly in the walls of hollow organs |
| Summation | Accumulation of effects, espically those of muscular, sensory, or mental stimuli |
| T Tubule (Transverse Tubule) | Extension of the muscle cell plasma membrane (sarcolemma) that protrudes deeply into the muscle cell |
| Tendon | Cord of dense fibrous tissue attaching muscle to bone |
| Tetanus | A smooth sustained muscle contraction resulting from high frequency stimulation. |
| Threshold Stimulus | Weakest stimulus capable of producing a response in an irritable tissue |
| An entire skeletal muscle is surrounded by: | epimysium |
| As an axon enters a muscle, it branches into a number of axonal terminals, each of which forms a neuromuscular junction with a single muscle fiber. A motor neuron and all the muscle fibers it supplies is called a: | motor unit. |
| Does Hemoglobin concentration in muscle fibers increase during muscle contraction | no |
| Do The I bands shorten and H zones disappear during muscle contraction | yes |
| What is the ion released from the terminal cisternae that combines with troponin and removes the blocking action of tropomyosin, resulting in the formation of cross bridges? | Ca2+ |
| Each skeletal muscle fiber is controlled by a neuron at a single: | neuromuscular junction. |
| How can you best describes the composition of the structure known as a triad in a skeletal muscle fiber? | Terminal cisterna, transverse tubule, and terminal cistern |
| In the sliding filament model of muscle contraction, the myofilaments slide over each other, resulting in the overlapping of actin and _________. | myosin |
| The dense layer of collagen fibers that surround an entire skeletal muscle is the: | epimysium. |
| The functional unit of a skeletal muscle fiber is the: | sarcomere. |
| The space between the neuron and the muscle is the: | synaptic cleft. |
| The term that means a continued mild or partial contraction of an entire muscle is muscle: | tone |
| The type of muscle contraction in which the muscle fibers produce increased tension, but the muscle neither shortens nor lengthens, is called: | isometric. |
| In smooth muscle tissues are Fibers small and spindle shaped. | yes |
| In smooth muscle tissues are Contractions rapid and forceful. | no |
| Are Skeletal muscles are responsible for the pumping action of the heart. | no |
| Do The contractions of skeletal muscles pull on tendons and move elements of the skeleton. | yes |
| Does Lactic Acid increase in quantity during repetitive muscle contraction | yes |
| What do ATP, CP, glucose, and oxygen all do during muscle contraction. | decrease |
| The sequence of electrical changes that occurs along the sarcolemma when a muscle fiber is stimulated is known as the: | action potential |
| An action potential is the result of a predictable sequence of electrical changes that occurs along the length of the _______ | sarcolemma |
| ________________ maintain the organization of the A band and provide for elastic recoil when muscle contraction ends | Elastic filaments |
| What binds calcium ions in a smooth muscle, causing contraction | Calmodulin |
| ____________ causes smooth muscle contractions | Calmodulin |
| _________ is the ability to receive and respond to a stimulus | Irritability |
| Elasticity refers to the ability of a muscle fiber to: | recoil and resume its resting length after being stretched. |
| ______________ is the ability of a muscle to shorten forcibly when adequately stimulated. | Contractility |
| The muscle of the stomach is ________ muscle and is involuntary muscle. | smooth |
| Skeletal muscle contracts ______________. | rapidly |
| A sarcomere is part of a | myofibril |
| The _____________ are part of the sarcomere and are of two types, thick and thin | myofilaments |
| "Cross bridges" that link between the thick and thin filaments are formed by the | globular head of thick filaments |
| The globular head of thick filaments (myosin) are responsible for the formation of _____________ between the thick and thin filaments | cross bridges |
| The refractory period in which the muscle will not contract if stimulated occurs during __________ of the muscle cell | repolarization |
| does Hyperpolarization occur in muscle cells? | no |
| What is the cause of rigor mortis | Calcium influx into the cell after death |
| Calcium influx into the cell after death promotes the formation of _______ and stiffening of muscles after death, which is known as rigor mortis. | myosin cross bridges |
| Where does 95% of the energy needed for contraction come from during moderate exercise? | ATP |
| The alternating contraction and relaxation of opposing layers of smooth muscle is referred to as | peristalsis |
| Isometric contraction is only seen in _________ muscle | skeletal |
| Only ________ muscle is non-striated | smooth |
| The thick filament is composed of what molecule? | Myosin |
| The head of the myosin molecule binds to what molecule to form the cross bridge? | Actin |
| What regulatory molecule on the thin filament covers the myosin head binding site on actin? | Tropomyosin |
| Which molecule on the thin filament has a binding site for calcium? | Troponin |
| The binding of what to the myosin head puts the cross bridge in its high-energy conformation? | ATP |
| What must bind to the cross bridge for it to disconnect from the actin molecule? | ATP |
| Which molecule is responsible for moving the calcium back into the terminal cisternae (sarcoplasmic reticulum)? | ATP |
| What causes the sliding of the thin filament toward the middle of the sarcomere? | Flexing of the cross bridge (power stroke) |
| What is the cause of rigor mortis? | Depletion of ATP |
| Which type of muscle cell has visible striations and many nuclei and is under voluntary control? | Skeletal |
| What attaches muscle to bone? | Tendons |
| Whole muscle is composed of bundles of muscle cells called: | fascicles. |
| The connective tissue covering of the whole muscle is called: | epimysium. |
| The plasma membrane of a muscle cell is called the: | sarcolemma. |
| The part of the sarcoplasmic reticulum where calcium ions are stored is called the: | terminal cisternae. |
| The organelle that is a bundle of contractile elements is called a: | myofibril. |
| The arrangement of the thick and thin myofilaments forms light and dark bands along the myofibril. The length of the thick filament corresponds with which band? | The A band |
| The length of which band decreases as the muscle contracts? | The I band |
| The functional unit of muscle contraction is called the | sarcomere |
| Skeletal muscle cells are electrically insulated from each other by: | endomysium. |
| What neurotransmitter is located in the synaptic vesicles of the motor neuron? | Acetylcholine (ACh) |
| When an action potential arrives at the axon terminal of a motor neuron, what type of ion channel is opened? | Voltage-gated (voltage-regulated) calcium channels |
| What means of membrane transport is used to release the neurotransmitter into the synaptic cleft? | Exocytosis |
| Binding of the neurotransmitter to receptors on the motor endplate opens channels that let which ion enter the cell and cause depolarization? | Sodium ions |
| How is acetylcholine removed from the synaptic cleft? | Acetylcholinesterase, an enzyme, digests the acetylcholine. |
| Depolarization of the motor endplate causes an action potential to travel down the muscle cell membrane and enter the muscle cell through what passageway? | T tubule |
| The action potential causes the release of calcium ions from what structure in the muscle cell? | Terminal cisternae |
| In order for skeletal muscle cells to contract, they must be stimulated by a/an: | motor neuron. |
| The potential energy stored in ATP is found in the: | terminal bonds of phosphate. |
| The potential energy in ATP is released during a process called: | hydrolysis. |
| What molecule must be removed in order to rebuild ADP into ATP? | A water molecule |
| What is the end product in the anaerobic pathway? | Lactic acid |
| Oxygen is available for aerobic respiration directly from the blood and from stores in: | myoglobin. |
| Which type of muscle fiber has a large quantitiy of myoglobin and mainly uses the Krebs cycle and oxidative phosphorylation to synthesize ATP? | Red slow-twitch fibers |
| A motor neuron and all the muscle cells it innervates is called a: | motor unit. |
| Stimulation of additional motor units will increase the strength of contraction. This process is called: | recruitment. |
| Where is the interneuron located? | In the spinal cord |
| The muscles of the eye need to make precise small motor movements. What size are the motor units in the eye? | Small |
| The muscles of the thigh exhibit gross movements for walking. What size are the motor units in the thigh? | Large |
| Random, asynchronous motor unit contractions provide a low-level tension and resistance to stretch called muscle __________. | tone |
| What will happen to a muscle if the motor neuron is cut? | The muscle will become flaccid. |
| Where is the motor neuron located? | Traveling to the muscle |
| The synapse between a motor neuron and the muscle it innervates is called a: | neuromuscular junction. |
| An increase in the strength of the stimulus will cause an increase in tension development caused by: | recruitment of more motor units. |
| The development of tension in a muscle, in response to a single stimulus above threshold, is called a muscle ___________. | twitch |
| The shortest phase of a muscle twitch, usually lasting less than 5 milliseconds, is called the: | latent period. |
| Sarcomeres lengthen during which phase/period of muscle twitch? | Relaxation phase |
| When a second stimulus is applied before complete relaxation, there is a greater development of tension. What is this called? | Temporal summation |
| When a single stimulus is applied to a muscle, a curve of the tension developed (muscle twitch) can be generated. If the same strength stimulus is applied to the muscle again (after complete relaxation), how will the size of the second curve be altered? | The height of the curve will be equal to that of the first curve. |
| During the initial phase of muscle contraction, each successive stimulus produces a slightly stronger contraction because of increased muscle warming and efficiency of enzymes. This stage is called: | treppe. |
| With rapid, multiple stimulations, the contraction-relaxation cycles are shorter but there still is some degree of relaxation. What is this stage called? | Incomplete tetanus |
| With rapid, multiple stimulations, the contractions fuse into a smooth, continuous contraction. This stage in the multiple stimuli graph is called: | complete tetanus. |
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