Fisiologia Del Musculo Esqueletico Ejercicio 2 Cod 20120353

LABORATORIO DE SIMULACIN (Physioex 9.0). Ejercicio N 2:FISIOLOGA DEL MSCULO ESQUELTICO-ACTIVIDADES DEL 1 AL 7.

ALUMNO: ANTHONY HUAMN ALAYOCOD: 20120353CURSO: FISIOLOGA DE ANIMALES DE GRANJA-LABORATORIOGRUPO: ACICLO: 2015-I

Exercise 2: Skeletal Muscle Physiology: Activity 1: The Muscle Twitch and the Latent Period Lab Report

Pre-lab Quiz ResultsYou scored 100% by answering 5 out of 5 questions correctly.

1. Skeletal muscles are connected to bones byYou correctly answered: b. tendons.

2. Skeletal muscles are composed of hundreds to thousands of individual cells calledYou correctly answered: c. fibers.

3. The term motor unit refers toYou 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 calledYou correctly answered: d. the neuromuscular junction.

5. A twitch isYou correctly answered: a. one contractile response to a single action potential.

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Experiment ResultsPredict Question:Predict Question: Will changes to the stimulus voltage alter the duration of the 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 tensiondevelopment 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 Length Active Force Passive Force Total Force Latent Period0.0 75 0.00 0.00 0.00 ---3.0 75 1.04 0.00 1.04 ---4.0 75 1.32 0.00 1.32 0.406.0 75 1.65 0.00 1.65 ----8.0 75 1.81 0.00 1.81 ----10.0 75 1.82 0.00 1.82 ----

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Post-lab Quiz ResultsYou 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 toYou 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 motorneuron is calledYou 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 isYou 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 ofmuscle 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 Results1. Define the terms skeletal muscle fiber, motor unit, skeletal muscle twitch, electrical stimulus, and latent period.Your answer:Definiciones:

-Fibra muscular esqueltica: Son clulas musculares estriadas; tienen muchos ncleos dispuestos perifricamentepudiendo considerarse un sincitio, cuyo origen es la fusin de mioblastos, su regulacin puede ser voluntaria y estcontrolada por el sistema nervioso somtico.

-Unidad motora: Es la que emite el impulso que en ltimo trmino hace que la fibra muscular se contraiga lo que quieredecir que conduce los impulsos del cerebro y la mdula espinal hacia los efectores (msculos).

-Contraccin del musculo esqueltico: Es la fase que comienza al final del perodo de latencia y termina cuando elmsculo alcanza la mxima tensin.

-Estimulo elctrico: Es la aplicacin de electricidad en muy poco o reducidos voltaje, en partes del cuerpo, nervios,msculos, con el fin de conseguir una respuesta de movimiento.

-Periodo de latencia: Es el tiempo que transcurre entre la generacin de un potencial de accin en la clula muscular y elcomienzo de la contraccin del msculo. Aunque no se genera ninguna fuerza durante el perodo de latencia,intracelularmente se producen cambios qumicos (incluyendo la liberacin de calcio desde el retculo sarcoplsmico) queconducen a la contraccin.

2. What is the role of acetylcholine in a skeletal muscle contraction?Your answer:La acetilcolina es un neurotransmisor, cuando se libera en la unin neuromuscular produce una despolarizacin delmsculo. En el msculo esqueltico esta despolarizacin permite la entrada de calcio, y en el msculo liso activa unmensajero secundario que se une a receptores en el retculo endoplasmtico y as ste libera el calcio necesario para lacontraccin muscular.

3. Describe the process of excitation-contraction coupling in skeletal muscle fibers.Your answer:Acoplamiento entre excitacin y contraccin:

La llegada de un potencial de accin a los terminales de los axones motores causan la liberacin de acetilcolina en lamoto-neurona. La acetilcolina se una a la protena receptora postsinaptica, abriendo los canales inicos de la fibramuscular. El potencial de accin que se inicia en la placa motora, se propaga en ambas direcciones, excitando as toda lamembrana de la fibra muscular y poniendo en marcha la secuencia de acontecimientos que conducen a la contraccin.

En la placa motora, un solo potencial de accin (PA) de la motoneurona, puede generar un PA en la fibra muscularpostsinaptica, lo que hace a esta sinapsis cuantitativamente distinta de muchas sinapsis entre neuronas, siempre que sepropaga un PA en una fibra muscular, inicia una contraccin breve, denominada contraccin fasica, transcurren variosmilisegundos entre el instante en que se inicia el PA y el comienzo de la contraccin. Durante este periodo de latencia seproduce el acoplamiento excitacin-contraccin. El efecto neto de este acoplamiento es la vinculacin de la concentracinde calcio libre en el citosol, con un PA de la membrana plasmtica de la fibra muscular.

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4. Describe the three phases of a skeletal muscle twitch.Your answer:son 3 fases:1. Perodo de latenciaEs el tiempo que transcurre entre la generacin de un potencial de accin en la clula muscular y el comienzo de lacontraccin del msculo.Aunque no se genera ninguna fuerza durante el perodo de latencia, intracelularmente se producen cambios qumicos(incluyendo la liberacin de calcio desde el retculosarcoplsmico) que conducen a la contraccin.

2. fase de contraccin Comienza al final del perodo de latencia y termina cuando el msculo alcanza la mxima tensin.

3. La fase de relajacinEs el perodo de tiempo desde la tensin mxima hasta el final de la contraccin delmsculo.

5. Does the duration of the latent period change with different stimulus voltages? How well did the results compare withyour prediction?Your answer:el periodo de latencia no cambia con un incremento de voltaje porque; porque el estimulo ya llego al umbral que senesecitaba 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 membranedepolarization?Your answer:la sustitucin de algunos de sodio por potasio en el liquido extracelular que baa una celula excitable, desplazar elpotencial de membrana hacia la despolarizacion.

Exercise 2: Skeletal Muscle Physiology: Activity 2: The Effect of Stimulus Voltage on Skeletal Muscle Contraction LabReport


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 inYou 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 inYou correctly answered: c. the sarcoplasmic reticulum.

4. During the latent period for an isometric contractionYou correctly answered: c. the cellular events involved in excitation-contraction coupling occur.

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Experiment ResultsPredict Question:Predict Question: As the stimulus voltage is increased from 1.0 volt up to 10 volts, what will happen to the amount of activeforce generated with each stimulus?Your answer : c. The active force will first increase and then plateau at some maximal value as the stimulus voltageincreases.

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 makesense?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 labreportYou 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 labreport.You answered: 10 volts

Experiment Data:

Voltage Length Active Force Passive Force Total Force0.0 75 0.00 0.00 0.000.2 75 0.00 0.00 0.000.8 75 0.02 0.00 0.021.0 75 0.15 0.00 0.151.5 75 0.43 0.00 0.432.0 75 0.66 0.00 0.662.5 75 0.87 0.00 0.873.0 75 1.04 0.00 1.043.5 75 1.19 0.00 1.194.0 75 1.32 0.00 1.324.5 75 1.42 0.00 1.425.0 75 1.51 0.00 1.515.5 75 1.59 0.00 1.596.0 75 1.65 0.00 1.656.5 75 1.70 0.00 1.707.0 75 1.74 0.00 1.747.5 75 1.78 0.00 1.788.0 75 1.81 0.00 1.818.5 75 1.82 0.00 1.829.0 75 1.82 0.00 1.829.5 75 1.82 0.00 1.8210.0 75 1.82 0.00 1.82

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1. Motor unit recruitment refers toYou 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 fromYou 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 all the muscle fibers intodeveloping active force.You correctly answered: c. maximal voltage

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 theyall develop active force (that is, they were all successfully recruited).

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Review Sheet Results1. Describe the effect of increasing stimulus voltage on isolated skeletal muscle. Specifically, what happened to the muscleforce generated with stronger electrical stimulations and why did this change occur? How well did the results compare withyour prediction?Your answer:Si se incrementa el voltaje del estmulo por encima del umbral, tambin aumenta la cantidad de fuerza producida por elmsculo entero. Este resultado se produce porque, cuanto mayor es el estmulo que recibe un msculo, ms fibrasmusculares se activan y por tanto mayor ser la fuerza producida por el msculo. La mxima fuerzaen el msculo entero se produce cuando todas sus fibras musculares han sido activadas por un estmulo suficientementegrande (denominado voltaje mximo). La estimulacin con voltajes superiores al voltaje mximo no aumentarn lafuerza de contraccin 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 elvoltaje 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 deahi, los estimulos que se dan a pesar de ser ms fuertes no logran resultado debido a que ya no hay ms fibras celularesque activar.

Exercise 2: Skeletal Muscle Physiology: Activity 3: The Effect of Stimulus Frequency on Skeletal Muscle Contraction LabReport


1. During a single twitch of a skeletal muscleYou 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 musclecontraction than a stand-alone twitch. This phenomenon is known asYou correctly answered: c. wave summation.

3. Wave summation is achieved byYou 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 muscleis toYou correctly answered: d. increase the number of activated motor units.

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Experiment ResultsPredict Question:Predict Question 1: As the stimulus frequency increases, what will happen to the muscle force generated with eachsuccessive 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 firstincrease 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 thinkyou 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 previousstimulations?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 stimulusalso increased, and a limiting maximum value was observed.

Experiment Data:

Voltage Length Stimulus Active Force Passive Force Total Force8.5 75 Single 1.83 0.00 1.838.5 75 Multiple 1.83 0.00 1.838.5 75 Multiple 1.83 0.00 1.838.5 75 Multiple 4.45 0.00 4.4510 75 Multiple 4.64 0.00 4.648.5 75 Multiple 5.72 0.00 5.72

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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 timesuch that the peak tension of each twitch rises in a stepwise fashion up to a plateau value, the result is known asYou correctly answered: c. treppe.

3. In this experiment the isolated skeletal muscle was repetitively stimulated such that individual twitches overlapped witheach other and resulted in a stronger muscle contraction than a standalone twitch. This phenomenon is known asYou correctly answered: c. wave summation.

4. Wave summation is achieved byYou correctly answered: a. increasing the rate of stimulus delivery (frequency) to the muscle.

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Review Sheet Results1. 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 estese contraiga por un periodo determinado, mientras que la frecuencia de estimulo es aplicar la misma accion( puede sermayor 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 withcomplete relaxation between the stimuli. Describe the force of contraction with each subsequent stimulus. Are these resultscalled treppe or wave summation?Your answer:incrementando la frtecuencia de estimulos, es decir en periodos ms cortos se obetenia una mayor fuerza generada porparte del musculo, aun cuando en diferentes experimentos el voltaje era el mismo, los resultados variaban porque lafrecuencia de estimulos habia variado.

3. How did the frequency of stimulation affect the amount of force generated by the isolated skeletal muscle when thefrequency of stimulation was increased such that the muscle twitches did not fully relax between subsequent stimuli? Arethese 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 contraccinproduce una fuerza ligeramente mayor que la anterior siempre y cuando el msculo se pueda relajar completamente entreestmulos relativamente prximos.Cuando un msculo esqueltico es estimulado repetidaente,de tal manera que losestmulos lleguen uno tras otro separados por un perodo de tiempo corto, las contracciones pueden superponerse entres y dar lugar a una contraccin muscular ms fuerte. Este fenmeno se conoce como sumacin.

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 youachieve an active force of 5.2 g? How well did the results compare with your prediction?Your answer:s, se logro aumentar la fuerza del musculo, elevando la frecuencia de las estimulaciones pero usando el voltaje maximode 8.5

5. Compare and contrast frequency-dependent wave summation with motor unit recruitment (previously observed byincreasing the stimulus voltage). How are they similar? How was each achieved in the experiment? Explain how each isachieved in vivo.Your answer:la frecuencia depende de la la sumacion de impulsos que se pueda dar, estos generaran una fuerza segun sea lafrecuanecia, pero otra variable a tener en cuenta es la intensidad del voltaje para el efecto escalera, por ejemplo alaumentar 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 relaje y siga con el efecto.

Exercise 2: Skeletal Muscle Physiology: Activity 4: Tetanus in Isolated Skeletal Muscle Lab Report


1. Stimulus frequency refers toYou 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 itsYou correctly answered: a. maximal tetanic tension.

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Experiment ResultsPredict Question:Predict Question: As the stimulus frequency increases further, what will happen to the muscle tension and twitchappearance 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 willincrease. 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 146150 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 Length Stimuli/sec Active Force Passive Force Total Force8.5 75 50 5.12 0.00 5.128.5 75 130 5.88 0.00 5.888.5 75 140 5.91 0.00 5.918.5 75 142 5.94 0.00 5.948.5 75 144 5.94 0.00 5.948.5 75 146 5.95 0.00 5.958.5 75 148 5.95 0.00 5.958.5 75 150 5.95 0.00 5.95

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1. The term tetanus refers toYou 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 itsYou correctly answered: a. maximal tetanic tension.

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Review Sheet Results1. Describe how increasing the stimulus frequency affected the force developed by the isolated whole skeletal muscle inthis activity. How well did the results compare with your prediction?Your answer:Si se aplican estmulos incluso a mayor frecuencia, las contracciones comenzarn a unirse de tal manera que los picos yvalles de cada contraccin no se distinguirn unos de otros, este estado es conocido como ttanos completos (ttanosfusionados). Cuando la frecuencia de estimulacin alcanza un valor ms all del cual no aumenta la fuerza generada por elmsculo, decimos que el msculo ha alcanzado su mxima tensin tetnica.

2. Indicate what type of force was developed by the isolated skeletal muscle in this activity at the following stimulusfrequencies: at 50 stimuli/sec, at 140 stimuli/sec, and above 146 stimuli/sec.Your answer:indicar qu tipo de fuerza fue desarrollado por el msculo esqueltico aislado en esta actividad en las siguientesfrecuencias de estmulo : a 50 estmulos / seg, a 140 estmulos / seg, y por encima de 146 estmulos / seg a un estimulode 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 conformeaumenta el estimulo por segundo aumenta la fuerza generada, pero hasta un tope ya que se da el estado de tetanoscompletos.

3. Beyond what stimulus frequency is there no further increase in the peak force? What is the muscle tension called at thisfrequency?Your answer:Cuando la frecuencia de estimulacin alcanza un valor ms all del cual no aumentala fuerza generada por el msculo, decimos que el msculo ha alcanzado su mxima tensin tetnica.

Exercise 2: Skeletal Muscle Physiology: Activity 5: Fatigue in Isolated Skeletal Muscle Lab Report


1. When skeletal muscle twitches fuse so that the peaks and valleys of each twitch become indistinguishable from eachother, the muscle is in a state known asYou 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, themuscle has reached itsYou 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 iscalledYou 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 ResultsPredict Question:Predict Question: If the stimulator is briefly turned off for defined periods of time, what will happen to the length of time thatthe 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 inmaximal 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 tensiononce 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) Sustained Maximal Force(sec)

8.5 120 0 5.86 108.5 120 0 5.86 108.5 120 8 5.86 0.208.5 120 21 5.86 5.40

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1. During cross bridge cycling in skeletal muscle, force is created by theYou correctly answered: c. power stroke of the myosin heads.

2. The term tetanus refers toYou 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 iscalledYou correctly answered: c. fatigue.

4. During fatigueYou 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 muscleYou correctly answered: c. the development of fatigue will be delayed.

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Review Sheet Results1. When a skeletal muscle fatigues, what happens to the contractile force over time?Your answer:Una disminucin en la capacidad del msculo para mantener una fuerza de contraccin constante tras una estimulacinrepetida 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 acumulacin de cido lctico, ADP y Pj en losmsculos.

3. Turning the stimulator off allows a small measure of muscle recovery. Thus, the muscle will produce more force for alonger 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 enel 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 respiracin, para poder llevar oxigeno a la sangre.-adecuarse a entrenamientos si el ejercicio es para periodos cortos o largos.

Exercise 2: Skeletal Muscle Physiology: Activity 6: The Skeletal Muscle Length-Tension Relationship Lab Report


1. During an isometric contractionYou 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 isYou correctly answered: a. passive force.

3. Active forceYou 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 will not be indicated on yourscreen?You correctly answered: c. tetanic force

5. Passive force in skeletal muscle is largely caused byYou correctly answered: c. the protein titin.

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Experiment ResultsPredict Question:Predict Question: As the resting length of the muscle is changed, what will happen to the amount of total force the musclegenerates 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 yetincreased to a significant value.

Experiment Data:

Voltage Length Active Force Passive Force Total Force8.5 75 1.82 0.00 1.828.5 70 1.75 0.00 1.758.5 65 1.55 0.00 1.558.5 60 1.21 0.00 1.218.5 55 0.73 0.00 0.738.5 50 0.11 0.00 0.118.5 80 1.75 0.02 1.778.5 90 1.21 0.25 1.468.5 100 0.11 1.75 1.86

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1. When a skeletal muscle is stimulated and generates force but remains at a fixed lengthYou 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 lengthsYou 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 whenYou correctly answered: a. the fiber is at its resting length.

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Review Sheet Results1. What happens to the amount of total force the muscle generates during the stimulated twitch? How well did the resultscompare 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 fuerzatotal 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 msculo intente soportar una carga que es igual a la fuerzaque l genera, el msculo se contraeisomtricamente. Durante la contraccin isomtrica elmsculo se mantiene con una longitud fija (isomtrico significamisma longitud.

3. Based on the unique arrangement of myosin and actin in skeletal muscle sarcomeres, explain why active force varieswith 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 generava 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.

Exercise 2: Skeletal Muscle Physiology: Activity 7: Isotonic Contractions and the Load-Velocity Relationship Lab Report


1. During an isotonic concentric contraction, theYou correctly answered: b. force generated by the muscle is greater than the weight of the attached load.

2. During an isotonic concentric contractionYou correctly answered: b. the latent period increases with heavier loads.

3. During the latent period for an isotonic concentric contractionYou correctly answered: c. cross bridges cycle and, when muscle tension exceeds the load, muscle shortening occurs.

4. Muscle shortening velocityYou correctly answered: a. decreases with heavier loads.

5. An isotonic contraction of a muscle is one in whichYou correctly answered: a. the length of the muscle changes.

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Experiment ResultsPredict Question:Predict Question: As the load on the muscle increases, what will happen to the latent period, the shortening velocity, thedistance 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 thecontraction 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 acontraction? You correctly answered: c. isometric

Experiment Data:

Voltage Length Weight Velocity(mm/msec)

Twitch Duration(msec)

Distance Lifted(mm)

8.5 75 0.5 0.100 78.00 4.08.5 75 1.0 0.057 49.00 2.08.5 75 1.5 0.022 30.00 0.58.5 75 2.0 0.000 0.00 0.0

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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 whichYou correctly answered: a. the length of the muscle changes.

6. When lifting a heavy loadYou correctly answered: d. the muscle shortening velocity is decreased in comparison with lighter loads.

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Review Sheet Results1. If you were using your bicep muscles to curl a 7-kg dumbbell, when would your muscles be contracting isotonically?Your answer:si el bicep participa en el levantamiento de 7 kg, el objeto se levantara a una velocidad menor, porque esta en unacondicion isotonica.

2. Explain why the latent period became longer as the load became heavier in the experiment. How well did the resultscompare with your prediction?Your answer:El perodo de latencia aumenta a medida que aumenta el peso de la carga. Cuando la fuerza generada por el msculosupera el peso de a carga, el msculo se acorta y esto hace que el peso se mueve.

3. Explain why the shortening velocity became slower as the load became heavier in this experiment. How well did theresults compare with your prediction?Your answer:a velocidad se acorta porque aumenta el peso que es levantado.

4. Describe how the shortening distance changed as the load became heavier in this experiment. How well did the resultscompare with your prediction?Your answer:a medida que el peso aumenta la distancia de acortamiento disminuye .

5. Explain why it would take you longer to perform 10 repetitions lifting a 10-kg weight than it would to perform the samenumber of repetitions with a 5-kg weight.Your answer:las musculos que levantaran 10 repeticiones de 10kg comparadas con las de 5 kg, tendran una menor velocidad y unamayor concentracion isotonica.

6. Describe what would happen in the following experiment: A 2.5-g weight is attached to the end of the isolated wholeskeletal muscle used in these experiments. Simultaneously, the muscle is maximally stimulated by 8.5 volts and the platformsupporting the weight is removed. Will the muscle generate force? Will the muscle change length? What is the name for thistype of contraction?Your answer:El musculo genera ms fuerza cuando un peso acorta su longitud isotonica; pero si el peso es superior al de la capacidadde fuerza que puede ejercer el musculo, este no podra ser levantado.

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Fisiologia Del Musculo Esqueletico Ejercicio 2 Cod 20120353