LABORATORIO DE DE SIMULACIÓN (Physioex (Physioex 9.0). Ejercicio Nº 2: FISIOLOGÍA DEL MÚSCULO ESQUELÉTICO-ACTIVIDADES ESQUELÉTICO-ACTIVIDADES DEL 1 AL 7.
ALUMNO: ANTHONY HUAMÁN ALAYO COD: 20120353 CURSO: FISIOLOGÍA DE ANIMALES DE GRANJA-LABORATORIO GRUPO: A CICLO: 2015-I
Exercise 2: Skeletal Muscle Physiology: Activity 1: The Muscle Twitch and the Latent Period Lab Report Pre-lab Quiz Results You scored 100% by answering 5 out of 5 questions correctly. 1. Skeletal muscles are connected connected to bones by You correctly answered: b. tendons. 2. Skeletal muscles are are composed of hundreds to thousands of individual cells called You correctly answered: c. fibers. 3. The term term motor unit refers refers to You correctly answered: c. one motor neuron and all of the skeletal muscle fibers it innervates. 4. The motor neuron and muscle fiber intersect at what is called You correctly answered: d. the neuromuscular junction. 5. A twitch is You correctly answered: a. one contractile response to a single action potential.
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Experiment Results Predict Question: Predict Question: Will changes to the stimulus voltage alter the duration of the latent latent period? Your answer : b. No, changing the stimulus voltage will not change the latent period duration. Stop & Think Questions: What is the period of time that elapses between the generation of an action potential and the start of muscle tension development in a muscle fiber? You correctly answered: c. the latent period What occurs during the latent period of these isometric contractions? You correctly answered: b. All the steps of excitation-contraction coupling occur. Experiment Data: Voltage 0.0 3.0 4.0 6.0 8.0 10.0
Length 75 75 75 75 75 75
Active Force 0.00 1.04 1.32 1.65 1.81 1.82
Passive Force 0.00 0.00 0.00 0.00 0.00 0.00
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Total Force 0.00 1.04 1.32 1.65 1.81 1.82
Latent Period ----0.40 ----------
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Post-lab Quiz Results You scored 100% by answering 7 out of 7 questions correctly. 1. An action potential in a motor neuron triggers the release of which neurotransmitter? You correctly answered: b. acetylcholine 2. The term skeletal muscle fiber refers to You correctly answered: a. an individual skeletal muscle cell. 3. The graded depolarization in the skeletal muscle fiber that is elicited in response to one action potential from the motor neuron is called You correctly answered: c. an EPP (end-plate potential). 4. Which of the following is not a phase of a skeletal muscle twitch? You correctly answered: b. hyperpolarization phase 5. A skeletal muscle twitch is You correctly answered: a. one contractile response to a single action potential. 6. Which of the following correctly matches the twitch phase with its definition? You correctly answered: d. the contraction phase: the time between the end of the latent period and peak muscle tension 7. A sufficiently strong electrical stimulus applied to an isolated, mounted skeletal muscle induces the development of muscle force, or muscle tension. Which of the following statements concerning this observation is true ? You correctly answered: c. The electrical stimulus mimics acetylcholine release at a neuromuscular junction
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Review Sheet Results 1. Define the terms skeletal muscle fiber, motor unit, skeletal muscle twitch, electrical stimulus, and latent period. Your answer: Definiciones: -Fibra muscular esquelética: Son células musculares estriadas; tienen muchos núcleos dispuestos periféricamente pudiendo considerarse un sincitio, cuyo origen es la fusión de mioblastos, su regulación puede ser voluntaria y está controlada por el sistema nervioso somático. -Unidad motora: Es la que emite el impulso que en último término hace que la fibra muscular se contraiga lo que quiere decir que conduce los impulsos del cerebro y la médula espinal hacia los efectores (músculos). -Contracción del musculo esquelético: Es la fase que comienza al final del período de latencia y termina cuando el músculo alcanza la máxima tensión. -Estimulo eléctrico: Es la aplicación de electricidad en muy poco o reducidos voltaje, en partes del cuerpo, nervios, músculos, con el fin de conseguir una respuesta de movimiento. -Periodo de latencia: Es el tiempo que transcurre entre la generación de un potencial de acción en la célula muscular y el comienzo de la contracción del músculo. Aunque no se genera ninguna fuerza durante el período de latencia, intracelularmente se producen cambios químicos (incluyendo la liberación de calcio desde el retículo sarcoplásmico) que conducen a la contracción.
2. What is the role of acetylcholine in a skeletal muscle contraction? Your answer: La acetilcolina es un neurotransmisor, cuando se libera en la unión neuromuscular produce una despolarización del músculo. En el músculo esquelético esta despolarización permite la entrada de calcio, y en el músculo liso activa un mensajero secundario que se une a receptores en el retículo endoplasmático y así éste libera el calcio necesario para la contracción muscular.
3. Describe the process of excitation-contraction coupling in skeletal muscle fibers. Your answer: Acoplamiento entre excitación y contracción: La llegada de un potencial de acción a los terminales de los axones motores causan la liberación de acetilcolina en la moto-neurona. La acetilcolina se una a la proteína receptora postsinaptica, abriendo los canales iónicos de la fibra muscular. El potencial de acción que se inicia en la placa motora, se propaga en ambas direcciones, excitando así toda la membrana de la fibra muscular y poniendo en marcha la secuencia de acontecimientos que conducen a la contracción. En la placa motora, un solo potencial de acción (PA) de la motoneurona, puede generar un PA en la fibra muscular postsinaptica, lo que hace a esta sinapsis cuantitativamente distinta de muchas sinapsis entre neuronas, siempre que se propaga un PA en una fibra muscular, inicia una contracción breve, denominada contracción fasica, transcurren varios milisegundos entre el instante en que se inicia el PA y el comienzo de la contracción. Durante este periodo de latencia se produce el acoplamiento excitación-contracción. El efecto neto de este acoplamiento es la vinculación de la concentración de calcio libre en el citosol, con un PA de la membrana plasmática de la fibra muscular.
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4. Describe the three phases of a skeletal muscle twitch. Your answer: son 3 fases: 1. Período de latencia Es el tiempo que transcurre entre la generación de un potencial de acción en la célula muscular y el comienzo de la contracción del músculo. Aunque no se genera ninguna fuerza durante el período de latencia, intracelularmente se producen cambios químicos (incluyendo la liberación de calcio desde el retículo sarcoplásmico) que conducen a la contracción. 2. fase de contracción Comienza al final del período de latencia y termina cuando el músculo alcanza la máxima tensión . 3. La fase de relajación Es el período de tiempo desde la tensión máxima hasta el final de la contracción del músculo. 5. Does the duration of the latent period change with different stimulus voltages? How well did the results compare with your prediction? Your answer: el periodo de latencia no cambia con un incremento de voltaje porque; porque el estimulo ya llego al umbral que se nesecitaba para abrir los canales ionicos. 6. At the threshold stimulus, do sodium ions start to move into or out of the cell to bring about the membrane depolarization? Your answer: la sustitución de algunos de sodio por potasio en el liquido extracelular que baña una celula excitable, desplazará el potencial de membrana hacia la despolarizacion.
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Exercise 2: Skeletal Muscle Physiology: Activity 2: The Effect of Stimulus Voltage on Skeletal Muscle Contraction Lab Report Pre-lab Quiz Results You scored 100% by answering 4 out of 4 questions correctly. 1. Skeletal muscle fibers are innervated (stimulated) by You correctly answered: c. motor neurons. 2. A single action potential propagating down a motor axon results in You correctly answered: d. a single action potential and a single contractile event in the muscle fibers it innervates. 3. In resting skeletal muscle, calcium is stored in You correctly answered: c. the sarcoplasmic reticulum. 4. During the latent period for an isometric contraction You correctly answered: c. the cellular events involved in excitation-contraction coupling occur.
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Experiment Results Predict Question: Predict Question: As the stimulus voltage is increased from 1.0 volt up to 10 volts, what will happen to the amount of active force generated with each stimulus? Your answer : c. The active force will first increase and then plateau at some maximal value as the stimulus voltage increases. Stop & Think Questions: What do you see in the active force display when the stimulus voltage is set to 0.0, and why does this observation make sense? You correctly answered: a. 0.00 g; there was no activation of skeletal muscle fibers by this stimulus. What is the lowest stimulus voltage that induces active force in the skeletal muscle? You correctly answered: b. threshold voltage 6. Enter the threshold voltage for this experiment in the field below and then click Submit to record your answer in the lab report You answered: 0.8 volts 12. Enter the maximal voltage for this experiment in the field below and then click Submit to record your answer in the lab report. You answered: 10 volts Experiment Data: Voltage 0.0 0.2 0.8 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0
Length 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75
Active Force 0.00 0.00 0.02 0.15 0.43 0.66 0.87 1.04 1.19 1.32 1.42 1.51 1.59 1.65 1.70 1.74 1.78 1.81 1.82 1.82 1.82 1.82
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Passive Force 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
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Total Force 0.00 0.00 0.02 0.15 0.43 0.66 0.87 1.04 1.19 1.32 1.42 1.51 1.59 1.65 1.70 1.74 1.78 1.81 1.82 1.82 1.82 1.82
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Post-lab Quiz Results You scored 100% by answering 5 out of 5 questions correctly. 1. Motor unit recruitment refers to You correctly answered: a. an increase in the number of active muscle fibers to increase the force developed in a muscle. 2. Active tension (or force) in a skeletal muscle fiber results from You correctly answered: a. activation of cross bridge cycling via increased intracellular calcium levels. 3. The ________ is the minimal stimulus needed to cause a depolarization of the muscle plasma membrane (sarcolemma). You correctly answered: d. threshold voltage 4. By definition, the ________ is the amount of stimulus required to successfully recruit developing active force. You correctly answered: c. maximal voltage
all the
muscle fibers into
5. Why was a maximal voltage observed in this experiment? You correctly answered: b. At the maximal voltage, all the muscle fibers contained in this muscle are depolarized and they all develop active force (that is, they were all successfully recruited).
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Review Sheet Results 1. Describe the effect of increasing stimulus voltage on isolated skeletal muscle. Specifically, what happened to the muscle force generated with stronger electrical stimulations and why did this change occur? How well did the results compare with your prediction? Your answer: Si se incrementa el voltaje del estímulo por encima del umbral, también aumenta la cantidad de fuerza producida por el músculo entero. Este resultado se produce porque, cuanto mayor es el estímulo que recibe un músculo, más fibras musculares se activan y por tanto mayor será la fuerza producida por el músculo. La máxima fuerza en el músculo entero se produce cuando todas sus fibras musculares han sido activadas por un estímulo suficientemente grande (denominado voltaje máximo). La estimulación con voltajes superiores al voltaje máximo no aumentarán la fuerza de contracción ya que todas las fibras musculares han sido activadas.
2. How is this change in whole-muscle force achieved in vivo ? Your answer: en el experimento se logra aumentando el estimulo de voltaje desde 0.8 hasta 8.5, de ahi en adelante, se aumento el voltaje hasta 10.0 pero la fuerza generada ya no aumento debido a que todas las fibras musculares ya estaban activadas. 3. What happened in the isolated skeletal muscle when the maximal voltage was applied? Your answer: cuando se aplico la tension maxima 8.5, todas las fibras musculares se activaron generando una fuerza de 1.82, a partir de ahi, los estimulos que se dan a pesar de ser más fuertes no logran resultado debido a que ya no hay más fibras celulares que activar.
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Exercise 2: Skeletal Muscle Physiology: Activity 3: The Effect of Stimulus Frequency on Skeletal Muscle Contraction Lab Report Pre-lab Quiz Results You scored 100% by answering 4 out of 4 questions correctly. 1. During a single twitch of a skeletal muscle You correctly answered: b. maximal force is never achieved. 2. When a skeletal muscle is repetitively stimulated, twitches can overlap each other and result in a stronger muscle contraction than a stand-alone twitch. This phenomenon is known as You correctly answered: c. wave summation. 3. Wave summation is achieved by You correctly answered: a. increasing the stimulus frequency (the rate of stimulus delivery to the muscle). 4. Wave summation increases the force produced in the muscle. Another way to increase the force produced by a muscle is to You correctly answered: d. increase the number of activated motor units.
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Experiment Results Predict Question: Predict Question 1: As the stimulus frequency increases, what will happen to the muscle force generated with each successive stimulus? Will there be a limit to this response? Your answer : d. As the stimulus frequency increases, the muscle force generated by each successive stimulus will first increase and then decrease as the stimulus frequency becomes very high. Predict Question 2: In order to produce sustained muscle contractions with an active force value of 5.2 grams, do you think you will need to increase the stimulus voltage? Your answer : a. yes Stop & Think Questions: Was there any change in the force generated by the muscle during the second stimulated twitch? You correctly answered: c. Yes, the second twitch generated more muscle force. Is the total muscle force generated by the higher frequency stimulation greater than the force generated in previous stimulations? You correctly answered: a. Yes, it is greater than the previous stimulations. Does the force generated by the muscle change with each additional stimulus? You correctly answered: b. As the stimulus frequency increased, the muscle tension generated by each successive stimulus also increased, and a limiting maximum value was observed. Experiment Data: Voltage 8.5 8.5 8.5 8.5 10 8.5
Length 75 75 75 75 75 75
Stimulus Single Multiple Multiple Multiple Multiple Multiple
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Active Force 1.83 1.83 1.83 4.45 4.64 5.72
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Passive Force 0.00 0.00 0.00 0.00 0.00 0.00
Total Force 1.83 1.83 1.83 4.45 4.64 5.72
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Post-lab Quiz Results You scored 100% by answering 4 out of 4 questions correctly. 1. Which of the following is not one of the ways that the body can increase the force produced by a skeletal muscle? You correctly answered: d. application of higher voltages to the whole muscle 2. When a muscle receives a stimulus frequency that causes non-overlapping twitches to follow each other closely in time such that the peak tension of each twitch rises in a stepwise fashion up to a plateau value, the result is known as You correctly answered: c. treppe. 3. In this experiment the isolated skeletal muscle was repetitively stimulated such that individual twitches overlapped with each other and resulted in a stronger muscle contraction than a standalone twitch. This phenomenon is known as You correctly answered: c. wave summation. 4. Wave summation is achieved by You correctly answered: a. increasing the rate of stimulus delivery (frequency) to the muscle.
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Review Sheet Results 1. What is the difference between stimulus intensity and stimulus frequency? Your answer: la intensidad de estimulo es la accion que se ejerce sobre el musculo (puede ser quimico o electrico) para hacer que este se contraiga por un periodo determinado, mientras que la frecuencia de estimulo es aplicar la misma accion( puede ser mayor o menor a la inicial) pero en un perido de tiempo establecido, por eso hablamos de frecuencia de estimulo. 2. In this experiment you observed the effect of stimulating the isolated skeletal muscle multiple times in a short period with complete relaxation between the stimuli. Describe the force of contraction with each subsequent stimulus. Are these results called treppe or wave summation? Your answer: incrementando la frtecuencia de estimulos, es decir en periodos más cortos se obetenia una mayor fuerza generada por parte del musculo, aun cuando en diferentes experimentos el voltaje era el mismo, los resultados variaban porque la frecuencia de estimulos habia variado. 3. How did the frequency of stimulation affect the amount of force generated by the isolated skeletal muscle when the frequency of stimulation was increased such that the muscle twitches did not fully relax between subsequent stimuli? Are these results called treppe or wave summation? How well did the results compare with your prediction? Your answer: al incrementar la frecuencia de estimulos sedio lo que conocemos como "efecto escalera"es decir , cada contracción produce una fuerza ligeramente mayor que la anterior siempre y cuando el músculo se pueda relajar completamente entre estímulos relativamente próximos.Cuando un músculo esquelético es estimulado repetidaente,de tal manera que los estímulos lleguen uno tras otro separados por un período de tiempo corto, las contracciones pueden superponerse entre sí y dar lugar a una contracción muscular más fuerte. Este fenómeno se conoce como sumación.
4. To achieve an active force of 5.2 g, did you have to increase the stimulus voltage above 8.5 volts? If not, how did you achieve an active force of 5.2 g? How well did the results compare with your prediction? Your answer: sí, se logro aumentar la fuerza del musculo, elevando la frecuencia de las estimulaciones pero usando el voltaje maximo de 8.5 5. Compare and contrast frequency-dependent wave summation with motor unit recruitment (previously observed by increasing the stimulus voltage). How are they similar? How was each achieved in the experiment? Explain how each is achieved in vivo . Your answer: la frecuencia depende de la la sumacion de impulsos que se pueda dar, estos generaran una fuerza segun sea la frecuanecia, pero otra variable a tener en cuenta es la intensidad del voltaje para el efecto escalera, por ejemplo al aumentar el voltaje a 10, este voltaje no dia oportunidad para que el musculo se relaje y continue eficientemente el efecto, en cambio con un voltaje de 8.5 (voltaje maximo) si dio oportunidad para que el musculo se reñlaje y siga con el efecto.
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Exercise 2: Skeletal Muscle Physiology: Activity 4: Tetanus in Isolated Skeletal Muscle Lab Report Pre-lab Quiz Results You scored 100% by answering 3 out of 3 questions correctly. 1. Stimulus frequency refers to You correctly answered: b. the rate that stimulating voltage pulses are applied to an isolated whole skeletal muscle. 2. Which of the following distinguishes a state of unfused tetanus from a state of complete (fused) tetanus? You correctly answered: d. Muscle tension increases and decreases during a state of unfused tetanus. 3. When the stimulus frequency reaches a value beyond which no further increases in force are generated by the muscle, the muscle has reached its You correctly answered: a. maximal tetanic tension.
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Experiment Results Predict Question: Predict Question: As the stimulus frequency increases further, what will happen to the muscle tension and twitch appearance with each successive stimulus? Will there be a limit to this response? Your answer : b. As the stimulus frequency increases, the muscle tension generated by each successive stimulus will increase. There will be a limit to this increase. Stop & Think Questions: What begins to happen at around 80 msec? You correctly answered: c. unfused tetanus develops How does the trace at 130 stimuli/sec compare with the trace at 50 stimuli/sec? You correctly answered: b. Fused tetanus develops at this greater stimulus frequency. How do the traces with 146–150 stimuli per second compare with the trace at 130 stimuli per second? You correctly answered: d. Maximal tetanic tension develops with these very high stimulation frequencies. Experiment Data: Voltage 8.5 8.5 8.5 8.5 8.5 8.5 8.5 8.5
Length 75 75 75 75 75 75 75 75
Stimuli/sec 50 130 140 142 144 146 148 150
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Active Force 5.12 5.88 5.91 5.94 5.94 5.95 5.95 5.95
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Passive Force 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Total Force 5.12 5.88 5.91 5.94 5.94 5.95 5.95 5.95
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Post-lab Quiz Results You scored 100% by answering 3 out of 3 questions correctly. 1. The term tetanus refers to You correctly answered: b. sustained muscle tension due to very frequent stimuli. 2. Which of the following distinguishes a state of unfused tetanus from a state of complete (fused) tetanus? You correctly answered: d. Muscle tension increases and decreases between different values for an unfused tetanus. 3. When the stimulus frequency reaches a value beyond which no further increases in force are generated by the muscle, the muscle has reached its You correctly answered: a. maximal tetanic tension.
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Review Sheet Results 1. Describe how increasing the stimulus frequency affected the force developed by the isolated whole skeletal muscle in this activity. How well did the results compare with your prediction? Your answer: Si se aplican estímulos incluso a mayor frecuencia, las contracciones comenzarán a unirse de tal manera que los picos y valles de cada contracción no se distinguirán unos de otros, este estado es conocido como tétanos completos (tétanos fusionados). Cuando la frecuencia de estimulación alcanza un valor más allá del cual no aumenta la fuerza generada por el músculo, decimos que el músculo ha alcanzado su máxima tensión tetánica. 2. Indicate what type of force was developed by the isolated skeletal muscle in this activity at the following stimulus frequencies: at 50 stimuli/sec, at 140 stimuli/sec, and above 146 stimuli/sec. Your answer: indicar qué tipo de fuerza fue desarrollado por el músculo esquelético aislado en esta actividad en las siguientes frecuencias de estímulo : a 50 estímulos / seg, a 140 estímulos / seg, y por encima de 146 estímulos / seg a un estimulo de 50 la fuersa generada fue de 5.12; a 140 fue de 5.91 y 146 genro una fuerza de 5.95; podemos observar que conforme aumenta el estimulo por segundo aumenta la fuerza generada, pero hasta un tope ya que se da el estado de tetanos completos. 3. Beyond what stimulus frequency is there no further increase in the peak force? What is the muscle tension called at this frequency? Your answer: Cuando la frecuencia de estimulación alcanza un valor más allá del cual no aumenta la fuerza generada por el músculo, decimos que el músculo ha alcanzado su máxima tensión tetánica.
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Exercise 2: Skeletal Muscle Physiology: Activity 5: Fatigue in Isolated Skeletal Muscle Lab Report Pre-lab Quiz Results You scored 100% by answering 4 out of 4 questions correctly. 1. When skeletal muscle twitches fuse so that the peaks and valleys of each twitch become indistinguishable from each other, the muscle is in a state known as You correctly answered: d. complete (fused) tetanus. 2. When the stimulus frequency reaches a value beyond which no further increase of skeletal muscle force can occur, the muscle has reached its You correctly answered: c. maximal tetanic tension. 3. A decline in a muscle's ability to maintain a constant level of force, or tension, after prolonged, repetitive stimulation is called You correctly answered: c. fatigue. 4. Which of the following is not thought to be a contributing factor to the development of fatigue? You correctly answered: a. buildup of Ca2+ in the muscle fibers
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Experiment Results Predict Question: Predict Question: If the stimulator is briefly turned off for defined periods of time, what will happen to the length of time that the muscle is able to sustain maximal developed tension when the stimulator is turned on again? Your answer : b. The length of the rest period will proportionately increase the length of time for sustained muscle tension. Stop & Think Questions: Why does the stimulated muscle force begin to decrease over time despite the maintained stimuli? (Note that a decrease in maximal force indicates muscle fatigue is developing.) You correctly answered: d. More than one of these answers could be correct. Why did the length of the intervening rest period affect the length of time the skeletal muscle can maintain maximum tension once the stimulator is turned on again? You correctly answered: c. Intracellular concentrations of ADP and Pi declined during the rest period. Experiment Data: Voltage
Stimuli/sec
Rest Period (sec)
Active Force (g)
8.5 8.5 8.5 8.5
120 120 120 120
0 0 8 21
5.86 5.86 5.86 5.86
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Sustained Maximal Force (sec) 10 10 0.20 5.40
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Post-lab Quiz Results You scored 100% by answering 5 out of 5 questions correctly. 1. During cross bridge cycling in skeletal muscle, force is created by the You correctly answered: c. power stroke of the myosin heads. 2. The term tetanus refers to You correctly answered: b. sustained muscle tension due to repetitive stimuli. 3. A decline in a muscle's ability to maintain a constant level of force, or tension, after prolonged, repetitive stimulation is called You correctly answered: c. fatigue. 4. During fatigue You correctly answered: c. the number of active cross bridges begins to decline although the rate of stimulus delivery (frequency) remains constant. 5. If an intervening rest period is imposed on active skeletal muscle You correctly answered: c. the development of fatigue will be delayed.
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Review Sheet Results 1. When a skeletal muscle fatigues, what happens to the contractile force over time? Your answer: Una disminución en la capacidad del músculo para mantener una fuerza de contracción constante tras una estimulación repetida y prolongada. 2. What are some proposed causes of skeletal muscle fatigue? Your answer: Una de las causas de la fatiga en los ejercicios de alta intensidad, es la acumulación de ácido láctico, ADP y Pj en los músculos. 3. Turning the stimulator off allows a small measure of muscle recovery. Thus, the muscle will produce more force for a longer time period if the stimulator is briefly turned off than if the stimuli were allowed to continue without interruption. Explain why this might occur. How well did the results compare with your prediction? Your answer: cuando el periodo de descanso se acorta, el musculo al ser estimulado no logra mantener la energia que genera como en el primer periodo.
4. List a few ways that humans could delay the onset of fatigue when they are vigorously using their skeletal muscles. Your answer: -Dandole un periodo adecuado de descanso a los musculos. -Trabajando la respiración, para poder llevar oxigeno a la sangre. -adecuarse a entrenamientos si el ejercicio es para periodos cortos o largos.
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Exercise 2: Skeletal Muscle Physiology: Activity 6: The Skeletal Muscle Length-Tension Relationship Lab Report Pre-lab Quiz Results You scored 100% by answering 5 out of 5 questions correctly. 1. During an isometric contraction You correctly answered: d. the skeletal muscle is generating force, but it remains at a fixed length. 2. The force that results from muscles being stretched is You correctly answered: a. passive force. 3. Active force You correctly answered: b. is determined by the amount of myosin bound to actin. 4. When you generate the isometric length-tension curve, which of the following forces screen? You correctly answered: c. tetanic force 5. Passive force in skeletal muscle is largely caused by You correctly answered: c. the protein titin.
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will not be
indicated on your
Experiment Results Predict Question: Predict Question: As the resting length of the muscle is changed, what will happen to the amount of total force the muscle generates during the stimulated twitch? Your answer : c. Total force can increase or decrease depending upon the starting resting length. Stop & Think Questions: Note the dip in total force at a muscle length of 90 mm. Why does this occur? You correctly answered: d. At this muscle length, active force has decreased in value and passive force has not yet increased to a significant value. Experiment Data: Voltage 8.5 8.5 8.5 8.5 8.5 8.5 8.5 8.5 8.5
Length 75 70 65 60 55 50 80 90 100
Active Force 1.82 1.75 1.55 1.21 0.73 0.11 1.75 1.21 0.11
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Passive Force 0.00 0.00 0.00 0.00 0.00 0.00 0.02 0.25 1.75
Total Force 1.82 1.75 1.55 1.21 0.73 0.11 1.77 1.46 1.86
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Post-lab Quiz Results You scored 100% by answering 5 out of 5 questions correctly. 1. When a skeletal muscle is stimulated and generates force but remains at a fixed length You correctly answered: d. the muscle is contracting isometrically. 2. Which protein is mostly responsible for the development of passive force in a muscle? You correctly answered: d. titin 3. In skeletal muscle, active force stimulated through a range of muscle lengths You correctly answered: b. will utilize ATP hydrolysis to drive the cross bridge cycle. 4. Which if the following is not depicted in a typical skeletal muscle isometric length-tension curve? You correctly answered: a. time 5. Maximal active tension will be produced in a skeletal muscle fiber when You correctly answered: a. the fiber is at its resting length.
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Review Sheet Results 1. What happens to the amount of total force the muscle generates during the stimulated twitch? How well did the results compare with your prediction? Your answer: a un mismo estimulo (voltaje), la fuerza total que se da, es en base a la longitud del musculo; recordemos que la fuerza total es la suma de la fuerza pasiva y la fuerza activa. 2. What is the key variable in an isometric contraction of a skeletal muscle? Your answer: la clave para que se de una concentracion isometrica es que el músculo intente soportar una carga que es igual a la fuerza que él genera, el músculo se contrae isométricamente. Durante la contracción isométrica elmúsculo se mantiene con una longitud fija (isométrico significa “misma longitud”.
3. Based on the unique arrangement of myosin and actin in skeletal muscle sarcomeres, explain why active force varies with changes in the muscle's resting length. Your answer: Como podemos observar en los experimentos, a medida que aumenta la longitus del musculo la fuerza activa que genera va aumentando complementandose con la fuerza pasiva. 4. What skeletal muscle lengths generated passive force? (Provide a range.) Your answer: longitudes mayor o igual a 80. 5. If you were curling a 7-kg dumbbell, when would your bicep muscles be contracting isometrically? Your answer: en base a los experimentos la fuerza generada sera de 1.86 por cada gramo, osea se generara 13020 unidades de fuerza.
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Exercise 2: Skeletal Muscle Physiology: Activity 7: Isotonic Contractions and the Load-Velocity Relationship Lab Report Pre-lab Quiz Results You scored 100% by answering 5 out of 5 questions correctly. 1. During an isotonic concentric contraction, the You correctly answered: b. force generated by the muscle is greater than the weight of the attached load. 2. During an isotonic concentric contraction You correctly answered: b. the latent period increases with heavier loads. 3. During the latent period for an isotonic concentric contraction You correctly answered: c. cross bridges cycle and, when muscle tension exceeds the load, muscle shortening occurs. 4. Muscle shortening velocity You correctly answered: a. decreases with heavier loads. 5. An isotonic contraction of a muscle is one in which You correctly answered: a. the length of the muscle changes.
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Experiment Results Predict Question: Predict Question: As the load on the muscle increases , what will happen to the latent period, the shortening velocity, the distance that the weight moves, and the contraction duration? Your answer : b. The latent period will increase, the shortening velocity will decrease, the distance will decrease, and the contraction duration will decrease. Stop & Think Questions: What kind of contraction did you observe when you attached the 2.0 gram weight to the skeletal muscle and stimulated a contraction? You correctly answered: c. isometric Experiment Data: Voltage
Length
Weight
8.5 8.5 8.5 8.5
75 75 75 75
0.5 1.0 1.5 2.0
Velocity (mm/msec) 0.100 0.057 0.022 0.000
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Twitch Duration (msec) 78.00 49.00 30.00 0.00
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Distance Lifted (mm) 4.0 2.0 0.5 0.0
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Post-lab Quiz Results You scored 100% by answering 6 out of 6 questions correctly. 1. Which of the weights allowed the fastest muscle shortening velocity? You correctly answered: a. 0.5-g weight 2. Which of the weights induced the longest latent period of the muscle contraction? You correctly answered: c. 1.5-g weight 3. Which weight did the muscle contraction move the greatest distance? You correctly answered: a. 0.5-g weight 4. Which of the weights allowed the longest duration of muscle contraction? You correctly answered: a. 0.5-g weight 5. An isotonic contraction of a muscle is one in which You correctly answered: a. the length of the muscle changes. 6. When lifting a heavy load You correctly answered: d. the muscle shortening velocity is decreased in comparison with lighter loads.
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