Anatomy and Physiology Ch11.smartbook

What are smaller motor units used for?
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What are the folds in the sarcolemma at the neuromuscular junction called?Junctional foldsEach muscle fiber is innervated by which of the following?one motor neuronWhich cells have plasma membranes that undergo voltage changes in response to stimuli?neurons and muscle cellsWhat is the intended region of the sarcolemma that participates in neuromuscular junction called?motor end plateThe voltage measured across the muscle cell at rest is about -90mV and is called the resting membranePotentialThe synaptic knob does not touch the muscle fiber but is separated by which structure?Synaptic cleftWhat is the change in membrane potential with the entry of sodium ions called?DepolarizationThe neurotransmitter used in a neuromuscular junction isAcetylcholineDuring an action potential, the loss of potassium ions from the cell results in which of the following?repolarizationThe junctional folds of the neuromuscular junction are the site of ______ receptors.AcetylcholineWhat do neuron and muscle cells have in common?Their membranes undergo voltage changes when stimulatedWhat is an action potential?A rapid fluctuation in the membrane potential following stimulationWhat is the difference in electrical charge from one point to another called?Electrical PotentialRegarding muscle contraction, what is excitation?The process by which action potentials in a nerve fiber lead to action potentials in a muscle fiberDuring depolarization of a muscle cell or nerve cell, Ion channels in the plasma membrane open allowing which ions to enter the cell?sodiumduring repolarization, _____ ions diffuse out of the cell, changing the membrane potential back to negative valuepotassiumThe quick up-and-down voltage shift from negative to positive, created by the movement of Na+ and K+ across the cell membrane, is called a(n) _____ potentialActionWhen acetylcholine binds to its receptors on the motor end plate, an ion channel opens and ______ ions diffuse quickly into the muscle cell.SodiumTrue or false: Excitation involves the generation of action potentials, and occurs in both neurons and muscle fibers.TrueIn contrast to the action potential, the ______ potential causes the opening of ion channels, which results in the initial movement of sodium and potassium across the plasma membrane at the neuromuscular junction. If continued, this in turn can trigger an action potential at the neighboring sarcolemma.end-plateWhat is excitation-contraction coupling?The events that link the action potential of the sarcolemma to the activation of the myofilament contractionWhat is the function of a T tubule?T tubules carry the action potential through the sarcoplasm.When a nerve signal arrives at a synaptic knob, which voltage-gated channels open in the knob?calciumIn an NMJ, after acetylcholine diffuses across the synaptic cleft, where does it bind to ligand-gated channels?On the sarcolemmaWhere does the end-plate potential occur?motor end plateWhich phase of contraction links the action potential in the sarcolemma to the activation of the myofilament?Excitation-contraction couplingAction potentials spread across the sarcolemma and continue down which structures into the sarcoplasm?t-tubulesHow does an action potential move deep into the muscle cell?Via the T-tubulesWhat occurs when calcium binds to troponin?The troponin-tropomyosin complex changes shape and exposes the myosin binding sites (active sites).At the synaptic knob of the motor neuron, calcium stimulates exocytosis of the synaptic vesicles to release the neurotransmitter ______ into the synapse.acetylcholineWhich occurs during muscle contraction?The overlapping of myofilaments increasesWhat does the sliding filament theory describe?muscle contractionAction potentials cause the opening of voltage-gated sodium ion channels in the______ tubules. This leads to the opening of calcium ion channels in the terminal cisternae of the sarcoplasmic reticulum.T, or TransverseWhat must occur before tropomyosin can shift, revealing the active sites that allow myosin heads to bind to the actin filaments?Calcium must bind to troponin.The step in which the muscle fiber develops tension and may shorten is called ______.contractionThe "cocking" of the myosin head, hydrolysis of ATP and the power stroke occur during which phase of skeletal muscle contraction?ContractionThe prevailing theory regarding muscle contraction is called the ______filament theory.SlidingTrue or false: Myosin ATPase is an enzyme in the myosin head that hydrolyzes ATP to release energy.TrueDuring cross-bridge formation, the cocked head of myosin attaches to what on the thin filament?Active siteDuring contraction, what causes a power stroke?When myosin releases ADP and ratchets to a low energy positionWhat is the hydrolysis of ATP and preparation for reattachment to the thin filament by the myosin head called?The recovery strokeWhich is not a step of skeletal muscle contraction?Breakdown of creatine phosphateWhat is myosin ATPase?an enzyme located in the myosin head that hydrolyzes ATPWhy does a filament stay in place when a single myosin head releases?Because hundreds of other myosin heads are still attachedWhat forms a cross-bridge?A cocked head of myosin bound to actinWhat is a power stroke during muscle contraction?The ratcheting of a myosin headClick and drag on elements in order -the nerve signal ceases -AChe breaks ACh down -calcium releases from troponin -tropomyosin covers the myosin binding sites -Active transport pumps in the sarcoplasmic reticulum begin to pump calcium back into the cisternaecorrect: -the nerve signal ceases -AChe breaks ACh down -Active transport pumps in the sarcoplasmic reticulum begin to pump calcium back into the cisternae -calcium releases from troponin -tropomyosin covers the myosin binding sitesThe cross-bridge created by the binding of a myosin head to an active site on an actin filament is broken by binding ______.ATPThe enzyme that breaks down acetylcholine is calledacetylcholinesterase or AChEWhat happens when a myosin head releases from actin?The filament remains in the same place.When excitation of a muscle fiber stops, the SR ______.reabsorbs calciumDuring which phase of muscle contraction is calcium transported back into the cisternae and tropomyosin moves back to block the actin active sites?RelaxationDuring relaxation, active-transport pumps in the sarcoplasmic reticulum move which ion from the sarcoplasm into the cisternae?CalciumWhat is the role of acetylcholinesterase?It breaks down ACh, ending muscle stimulation.From excitation through contraction, the SR ______.releases and reabsorbs calciumIn which phase does muscle tension decline and sarcoplasmic calcium levels fall?RelaxationWhen an overly shortened or overly stretched muscle fiber is stimulated, what kind of contraction is generated?A weak contractionDuring relaxation, calcium is actively pumped back into theBlank 1: sarcoplasmic or terminal Blank 2: reticulum or cisternaeThe partial contraction of a resting muscle is known as which of the following?Muscle toneWhich can be measured by attaching stimulating electrodes to a nerve-muscle preparation and a recording device?Muscle strengthWhich of the following occur during the relaxation phase of muscle contraction? Select all that apply.Muscle tension declines. Myosin releases the thin filaments. Calcium levels in the sarcoplasm fall.True or false: The tension generated by a muscle fiber depends on how stretched or compressed the fiber is before it is stimulated.TrueThe minimum voltage necessary to generate an action potential is called theThresholdWhat is muscle tone?The partial contraction of resting musclesWhich is a quick cycle of contraction in a whole muscle that occurs when a threshold level stimulus is reached?TwitchA record of the timing and strength of a muscle's contraction is called a(n)MyogramOn a myogram, the time between the stimulus and the twitch is known as the _____ period.latentWhat does the length-tension relationship suggests about the generation of muscle tension?The amount of tension generated during a contraction depends on the degree of stretch or shortening prior to contraction.What is threshold, as applied to muscle physiology?The minimum voltage necessary to generate an action potentialThe movement of an object or load results from the development of what kind of tension?ExternalTrue or false: A twitch is a sustained contraction in a whole muscle that occurs when a threshold level stimulus is reached.FalseAs the myosin head releases the thin filament, muscle tension declines during what is referred to as the ______ phase of a muscle twitch.relaxationWhat does the latent period on a myogram indicate?The time period between the stimulus and the twitchTrue or false: Cool muscles contract more strongly than warm ones.FalseAt a constant stimulus voltage, how can one increase the twitch strength?Use a higher frequency of stimulationA muscle fiber shortens and generates force during the ______ period of a muscle twitch.contractionTrue or false: Recruitment occurs when more nerve fibers excite more motor units.TrueOn a myogram, how does the relaxation phase compare to the contraction phase?The relaxation phase is longer.Which would result in the strongest twitch?Warmer temperaturesTemporal summation leads to a state of fluttering contraction known as what?Incomplete tetanusHow would high frequency stimuli at a constant voltage affect twitch strength?It would increase.Complete (fused)_______ is the continuous forceful contraction in a muscle with no relaxation between stimuli.TetanusIn recruitment, which motor units are activated first?Smaller, less powerful motor unitsWhat type of contraction involves the development of tension but no change in length?IsometricThe type of muscle contraction in which there is a change in length, but no change in tension is called a(n) ______ contraction.IsotonicWhat produces incomplete tetanus?temporal summationAerobic respiration produces ______ ATP than glycolysis.moreIn which condition are stimuli are so frequent that the muscle cannot relax, and the muscle twitches fuse into a smooth prolonged contraction?TetanusWhich type of contraction maintains joint stability and posture?IsometricA muscle shortens as it maintains tension in a what type of contraction?ConcentricWhat are anaerobic fermentation and aerobic respiration?Pathways to generate ATPIn muscle, what does the source of ATP depend upon?The duration of exerciseAerobic respiration utilizes what two molecules as fuel to generate ATP?Fatty acids GlucoseThe total supply of ATP and creatine phosphate in a muscle is enough to power contraction for about ______.1 minuteThe glycogen-lactic acid system relies on which form of metabolism?AnaerobicWhat are the two most important pathways by which ATP is generated in muscle cells?Anaerobic fermentation and aerobic respirationTrue or false: Aerobic respiration is important for producing energy for long term energy needs.trueTrue or false: The duration of exercise determines which muscle mechanism supplies ATP.TrueIn high-intensity short-duration exercise, what does muscle fatigue result from?Increased potassiumThe energy needed for short bursts of intense activity is provided by which of the following?Creatine phosphate ATPThe glycogen-lactic acid system utilizes what molecule(s) as fuel to generate ATP?GlucoseWhich three situations lead to fatigue in long-duration exercise?Fuel depletion Electrolyte loss Central fatigueDuring exercise, at which point does the rate of oxygen consumption plateau?The maximum oxygen uptake rateWhich provides long term energy for a cell?aerobic respirationWhy does increased oxygen consumption continue after exercise?To replace the oxygen bound to myoglobin and hemoglobinThe progressive weakness and loss of contractility that results from prolonged use of the muscles is known as muscleFatigueWhich statements about lactic acid in muscle fibers is true?Lactic acid does not build up in muscle fibers so it does not cause muscle fatigue.What is the maximum oxygen uptake?Rate of uptake where increasing workload does not increase oxygen uptakeFibers that are well adapted to aerobic respiration are called ______ -twitch fibers.slowWhat function does increased oxygen consumption after exercise serve?To allow the conversion of lactic acid to pyruvate and glucose by the liverIn high-intensity short-duration exercise, what does muscle fatigue result from?Increased potassiumWhich fibers are adapted for a quick response?fast glycolyticWith long-duration exercise, when does fatigue occur?When glycogen and glucose are depletedWhich describes slow-twitch fibers?They have a rich blood supply.What are muscles that contain mainly slow oxidative fibers called?RedResistance exercise causes muscle growth by stimulating which of the following?An increase in myofibril sizeFast-twitch fibers are also known as ______ fibers.whiteCardiac and smooth muscle are both considered which of the following?involuntaryWhich muscle type is striated, uninucleate, and branched?CardiacCardiac muscle cells are considered because they contract rhythmically and independently.AutorhythmicSkeletal muscles contain which of the following?Both slow oxidative and fast glycolytic fibersWhich muscle tissue is rich in myoglobin, mitochondria, glycogen and uses aerobic respiration almost exclusively for its energy needs?CardiacFatigue resistance is improved by ______ exercise which enhances the delivery and use of oxygen.endurancediscs are the thickened notched ends of cardiac muscle cells which contain gap junctions.IntercalatedThe varicosities of the autonomic neurons that innervate smooth muscle release what when stimulated?NeurotransmittersWhat does it mean that cardiac cells are autorhythmic?They contract rhythmically and independent of nervous stimulation.Which statement explains why cardiac muscle is resistant to fatigue?Cardiac muscle uses little anaerobic fermentation.Which describes smooth muscle?It is slow to contract and slow to relax.What are the swellings along the length of a nerve fiber that innervates smooth muscle called?VaricositiesWhich tissue makes up the piloerector muscle of a hair follicle?Smooth muscleWhich describe smooth muscle?Smooth muscle has no T-tubules. Smooth muscle is uninucleate. Smooth muscle has little SR.What type of smooth muscle is found in the digestive tract, respiratory tract, and urinary tract?Single-unitThe autonomic nervous system is important in the control of which two types of muscle tissue?Smooth CardiacIn which situation would mechanically-regulated calcium gates in smooth muscle cells open?The tissue is stretchedWhat are the functions of smooth muscle?To move material through the digestive tract To constrict or dilate blood vessels to control blood pressure To regulate pupil diameter______ muscle cells have a fusiform shape and taper to a point at the ends.SmoothWhere is single-unit smooth muscle found?- wall of bladder - wall of stomach - wall of uterusHow can the stretching of smooth muscle lead to smooth muscle contraction?Stretching causes the opening of mechanically gated calcium ion channels in the sarcolemma.How do smooth muscle myocytes differ from cardiomyocytes?Smooth muscle myocytes have no T tubules while cardiac muscles do.