Neurofisiología Del Impulso Nervioso-Actividades Del 1 Al 9 Cod 20120353

LABORATORIO DE SIMULACIN (Physioex 9.0). Ejercicio N 3:NEUROFISIOLOGA DEL IMPULSO NERVIOSO -ACTIVIDADES DEL 1 AL 9.

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

Exercise 3: Neurophysiology of Nerve Impulses: Activity 1: The Resting Membrane Potential Lab Report

Pre-lab Quiz ResultsYou scored 100% by answering 4 out of 4 questions correctly.

1. What is the approximate concentration of K+ inside a typical cell (intracellular concentration)?You correctly answered: a. 150 mM

2. What is the approximate concentration of K+ outside a cell (extracellular concentration)?You correctly answered: b. 5 mM

3. What is the approximate concentration of Na+ inside a cell (intracellular concentration)?You correctly answered: b. 5 mM

4. What is the approximate concentration of Na+ outside a cell (extracellular concentration)?You correctly answered: a. 150 mM

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Experiment ResultsPredict Question:Predict Question: Predict what will happen to the resting membrane potential if the extracellular K+ concentration isincreased.Your answer : a. The resting membrane potential will become more negative.

Stop & Think Questions:What is the polarity of the resting membrane potential (voltage)?You correctly answered: b. negative

What does it mean that the voltage just inside the membrane is negative?You correctly answered: b. There are more negative charges than positive charges just inside the membrane.

The membrane of most cells, including neurons, contains passive, open,K+ leak channels. Given the normal K+ concentrations and the resultant concentration gradient, which direction would K+ be expected to move (diffuse) through these leak channels?You correctly answered: b. out of the cell

What effect does increasing extracellular K+ have on the net diffusion of K+ out of the cell?You correctly answered: b. It decreases the net diffusion of K+ .

Which way would Na+ move across the membrane if there were open Na+ channels?You correctly answered: a. Na+ would diffuse into the cell.

The membrane has open K+ channels, and changing extracellular K+ concentration results in a change in membranepotential. Changing the extracellular Na+ concentration does not significantly change the membrane potential. What doyour results suggest about the number or state (open or closed) of Na+ channels in the resting membrane of a neuron?You correctly answered: b. Na+ channels are mostly closed.

Experiment Data:

Extracellular Fluid (ECF) Microelectrode Position Voltage (mV)Control Cell body extracellular 0Control Cell body intracellular -70Control Axon extracellular 0Control Axon intracellular -70High K+ Axon intracellular -40High K+ Axon extracellular 0High K+ Cell body extracellular 0High K+ Cell body intracellular -40Low Na+ Cell body intracellular -72Low Na+ Cell body extracellular 0Low Na+ Axon extracellular 0Low Na+ Axon intracellular -72

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Post-lab Quiz ResultsYou scored 100% by answering 3 out of 3 questions correctly.

1. A negative membrane potential was recorded when the tip of the microelectrode wasYou correctly answered: d. both inside the cell body and inside the axon.

2. Which of the following caused a change in membrane potential from -70 to -40 in the cell body?You correctly answered: a. an increase in extracellular K+

3. Which of the following has the most negative voltage?You correctly answered: c. between the inside of the axon and the outside of the axon with control K+ ECF

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Review Sheet Results1. Explain why increasing extracellular K+ reduces the net diffusion of K+ out of the neuron through the K+ leakchannels.Your answer:Porque el potasio difusiona a favor de su gradiente de concentracion desde una region de mayor concentracion a otra demenor concentracion, en este caso encontramos mayor cantidad de potasio dentro de la celula, y poca afuera de ella; alincrementar la concentracion de potasio fuera de la celula, el trasnporte de potasio disminuyo debido a este efecto ya quehay una mayor concentracion de potasio de la que regularmente hay fuera de la celula.

2. Explain why increasing extracellular K+ causes the membrane potential to change to a less negative value. How welldid the results compare with your prediction?Your answer:Porque la concnetracion intracelular de potasio buscara equilibrarse con la nueva concentracion de potasio extracelular, porlo que disminuye su carga interna ya que se ha desplazado una mayor cantidad de potasio de lo esperado.

3. Explain why a change in extracellular Na+ did not significantly alter the membrane potential in the resting neuron?Your answer:Es porque ya hay una concentracion alta de sodio fuera de la celula, ante de agregar el ion sodio (no es una cantidadgrande), cuando este esta fuera de la celula solo interactua con el potasio (carga negativa).

4. Discuss the relative permeability of the membrane to Na+ and K+ in a resting neuron.Your answer:Cuando la neurona esta en reposo los niveles intracelulares de mV es negativo, porque los iones de potasio se difundenhacia fuera a travs de la membrana, dejando tras de s una carga neta negativa, si se agrega ms potasio extracelular, elmV intracelular se vuelve menos negativo porque habra un desplazamiento de potasio hacia dentro de la celula parabuscar el equilibrio lo que hara disminuir el voltaje; mientras que cuando se agrega sodio tiende a volverse ms negativodebido a que entran 3 iones de sodio por cada 2 iones de potasio que sale.

5. Discuss how a change in Na+ or K+ conductance would affect the resting membrane potential.Your answer:El cambIo en las concentraciones de sodio y potasio afectan el potencialk de la menbrana en reposo, cambiando lanegatividad en mV del interior de la neurona, estos cambios de potencial afectaan directamente a los receptores,potenciales sinapticos y potendciales de accion dentro del sistema nervioso.

Exercise 3: Neurophysiology of Nerve Impulses: Activity 2: Receptor Potential Lab Report


1. Assuming that the resting potential of a sensory neuron is -70 mV, which of the following represents a depolarization?You correctly answered: c. a change to -60 mV

2. Which of the following is a sensory modality (type of sense)?You correctly answered: e. all of the above

3. Which of the following is a sensory stimulus?You correctly answered: d. all of the above

4. Which of the following is true of the response of a sensory neuron to the appropriate sensory stimulus?You correctly answered: c. both a and b

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Experiment ResultsPredict Question:Predict Question 1: The adequate stimulus for a Pacinian corpuscle is pressure or vibration on the skin. Which of thefollowing modalities will induce the largest amplitude receptor potential in the Pacinian corpuscleYour answer : a. low-intensity heat

Predict Question 2: The adequate stimuli for olfactory receptors are chemicals, typically odorant molecules. Which of thefollowing modalities will induce the largest amplitude receptor potential in the olfactory receptor?Your answer : c. moderate-intensity pressure

Stop & Think Questions:Why didn't the Pacinian corpuscle respond to high-intensity light?You correctly answered: b. Light-transducing proteins are not present in the Pacinian corpuscle.

Judging from these results, does light have a smell?You correctly answered: b. no

Why did the free nerve ending respond to several different modalities?You correctly answered: c. The sensory end of this nerve is less specialized.

Experiment Data:

Receptor Modality Intensity RestingPotential (mv)

Peak Value ofResponse (mv)

Amplitude ofResponse (mv)

Pacinian corpuscle --- --- -70 -70 0Pacinian corpuscle Pressure Low -70 -60 10Pacinian corpuscle Pressure Moderate -70 -45 25Pacinian corpuscle Pressure High -70 -30 40Pacinian corpuscle Chemical Low -70 -70 0Pacinian corpuscle Chemical Moderate -70 -70 0Pacinian corpuscle Chemical High -70 -70 0Pacinian corpuscle Heat Low -70 -70 0Pacinian corpuscle Heat Moderate -70 -70 0Pacinian corpuscle Heat High -70 -70 0Pacinian corpuscle Light Low -70 -70 0Pacinian corpuscle Light Moderate -70 -70 0Pacinian corpuscle Light High -70 -70 0Olfactory receptor --- --- -70 -70 0Olfactory receptor Pressure Low -70 -70 0Olfactory receptor Pressure Moderate -70 -70 0Olfactory receptor Pressure High -70 -70 0Olfactory receptor Chemical Low -70 -64 6Olfactory receptor Chemical Moderate -70 -58 12Olfactory receptor Chemical High -70 -45 25Olfactory receptor Heat Low -70 -70 0Olfactory receptor Heat Moderate -70 -70 0Olfactory receptor Heat High -70 -70 0Olfactory receptor Light Low -70 -70 0

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Receptor Modality Intensity RestingPotential (mv)

Peak Value ofResponse (mv)

Amplitude ofResponse (mv)

Olfactory receptor Light Moderate -70 -70 0Olfactory receptor Light High -70 -70 0Free nerve ending --- --- -70 -70 0Free nerve ending Pressure Low -70 -70 0Free nerve ending Pressure Moderate -70 -70 0Free nerve ending Pressure High -70 -65 5Free nerve ending Chemical Low -70 -70 0Free nerve ending Chemical Moderate -70 -70 0Free nerve ending Chemical High -70 -70 0Free nerve ending Heat Low -70 -60 10Free nerve ending Heat Moderate -70 -40 30Free nerve ending Heat High -70 -20 50Free nerve ending Light Low -70 -70 0Free nerve ending Light Moderate -70 -70 0Free nerve ending Light High -70 -70 0

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1. A very intense stimulus can sometimes stimulate sensory neurons that have evolved for a different modality. Thus, witha blow to the eye, one "sees stars." In this example the photoreceptors in the eye are responding toYou correctly answered: c. intense pressure.

2. Olfactory receptor neurons respond to low concentrations of chemical odorants because there are membrane proteins inthe receptor ending of this sensory neuron thatYou correctly answered: b. can bind and respond to the specific odorant.

3. The sequence of events starting with a sensory stimulus and ending with a change in membrane potential is calledYou correctly answered: c. sensory transduction.

4. Starting at a resting membrane potential of -70 mV, a change to which of the following represents the largest receptorpotential?You correctly answered: d. a change to -50 mV

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Review Sheet Results1. Sensory neurons have a resting potential based on the efflux of potassium ions (as demonstrated in Activity 1). Whatpassive channels are likely found in the membrane of the olfactory receptor, in the membrane of the Pacinian corpuscle,and in the membrane of the free nerve ending?Your answer:los canales pasivos que probablemente se encuentren en la membrana del recpetor olfavtivo, corpusculo de pacini, yneurona libre, es una bomba sodio potasio

2. What is meant by the term graded potential?Your answer:son los cambios que hay en el potencial recpetor, segun los grados de estimulos correctos que recibe.

3. Identify which of the stimulus modalities induced the largest amplitude receptor potential in the Pacinian corpuscle. Howwell did the results compare with your prediction?Your answer:un estimulo correcto para el corpusculo de pacini, es un cambio en la presiono vibracion de la piel, esto lo podemoscomprobar al ver los resultados del experimento.

4. Identify which of the stimulus modalities induced the largest amplitude receptor potential in the olfactory receptors. Howwell did the results compare with your prediction?Your answer:un estimulo correcto para los receptores olfatorios, es un cambio quimico que llega a los recptores , esto lo podemoscomprobar al ver los resultados del experimento

5. The olfactory receptor also contains a membrane protein that recognizes isoamylacetate and, via several othermolecules, transduces the odor stimulus into a receptor potential. Does the Pacinian corpuscle likely have thisisoamylacetate receptor protein? Does the free nerve ending likely have this isoamylacetate receptor protein?Your answer:es poco probable que el corpusculo de pacini o el nervio libre tengan estos receptores, o en todo caso si los tuvieran noestan tan especializados como las menbranas del receptor olfatorio.

6. What type of sensory neuron would likely respond to the green light? Your answer:posiblemente para que una neurona sensorial responda a la luz verde, debe recibir seales de las mebranas de celulasligadas a la vision como por ejemplo,clulas ganglionares de la retina.

Exercise 3: Neurophysiology of Nerve Impulses: Activity 3: The Action Potential: Threshold Lab Report


1. Axons areYou correctly answered: d. long, thin structures that extend from a neuronal cell body.

2. Which of the following is easier?You correctly answered: a. extracellular recordings of the action potential

3. An action potential is usually initiated in an axon at or nearYou correctly answered: d. all of the above

4. The initiation of an action potential in a sensory neuron in the body normallyYou correctly answered: a. follows a sufficiently large depolarizing receptor potential.

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Experiment ResultsPredict Question:Predict Question: How will the action potential at R1 (or R2) change as you continue to increase the stimulus voltage?Your answer : b. The peak value of the action potential will increase.

Stop & Think Questions:Why is the action potential recorded by the second recording electrode (R2) delayed relative to the action potential recordedby the first recording electrode (R1)?You correctly answered: c. The action potential had to propagate from R1 to R2.

An increase in extracellular K+ would depolarize a neuron. This depolarization would occur if neurons were damaged. Fromwhat you have just learned about generating an action potential, what effect would this have on nearby axons? The nearbyaxonal membranes will ___________.You correctly answered: b. be depolarized to values near or above threshold voltages.

Experiment Data:

Stimulus Voltage (mV) Peak Value at R1 (V) Peak Value at R2 (V) Action Potential10 0 0 No20 100 100 Yes30 100 100 Yes40 100 100 Yes50 100 100 Yes

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1. The threshold voltage in an axon is usuallyYou correctly answered: a. less negative than the resting membrane potential.

2. If a graded receptor potential made the resting membrane potential of the axon more negative (for example, -70 mVchanges to -75 mV), you would expectYou correctly answered: d. it to be more difficult for this axon to reach the threshold voltage.

3. Failure to reach the threshold voltage in the axon of a sensory neuron could be caused byYou correctly answered: d. all of the above.

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Review Sheet Results1. Define the term threshold as it applies to an action potential.Your answer:El umbral se da cuando hay una despolarizacion, es decir un cambio en la negatividadlo que llevara a la neurona a un potecial de accion, si la neurona no alcanza, este umbral no se produce el potencial deaccion.

2. What change in membrane potential (depolarization or hyperpolarization) triggers an action potential?Your answer:Porque al ya haber una despolarizacion en el potencial de membrana , cambia la negatividad de la menrba en resposo,estoconlleva a enviar seales electricas que genren un potencial de accion.

3. How did the action potential at R1 (or R2) change as you increased the stimulus voltage above the threshold voltage?How well did the results compare with your prediction?Your answer:El potencial de accin no a cambiado a pesar de que aumento el estmulo de voltage, . Esto se debe a que una vez que sealcanza el umbral, no importa si el estimulo es mayor con tal de que alcance el nivel requerido del umbral el potencial deaccion se da. es constante, no se incrementa o disminuye.

4. An action potential is an "all-or-nothing" event. Explain what is meant by this phraseYour answer:Ssignifica que una vez que se alcanza el umbral, s o s se produce un potencial de accin. si el estmulo es demasiadopequeo no se produce un potencial de accin., y si el estimulo es muy grande se dara, pero no ms rapido seraconstante.

5. What part of a neuron was investigated in this activity?Your answer:Se investigo como se da las seales a lo largo del axon, como se da el umbral y la iniciacion del potencial de accion.

Exercise 3: Neurophysiology of Nerve Impulses: Activity 4: The Action Potential: Importance of Voltage-Gated Na+ channels Lab Report


1. Voltage-gated Na+ channels are membrane channels that openYou correctly answered: b. when the membrane depolarizes.

2. When open, Na+ channels allowYou correctly answered: a. Na+ ions to diffuse into the cell.

3. Which of the following is true of an action potential?You correctly answered: d. All of these answers are correct.

4. Which of the following can reduce the likelihood of an action potential?You correctly answered: d. All of these can reduce the likelihood of an action potential.

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Experiment ResultsPredict Question:Predict Question 1: If you apply TTX between recording electrodes R1 and R2, what effect will the TTX have on the actionpotentials at R1 and R2?Your answer : d. TTX will block the response at R1 and R2.

Predict Question 2: If you apply lidocaine between recording electrodes R1 and R2, what effect will the lidocaine have onthe action potentials at R1 and R2?Your answer : c. Lidocaine will block the response at R2 but have no effect at R1.

Stop & Think Questions:2. Enter the peak value of the response at R1 and R2 in the field below and then click Submit to record your answer in thelab report.You answered: 100 V

With a slower timescale, the appearance of the action potentials generated at R1 and R2 will appear toYou correctly answered: c. be compressed in time but have the same peak value of response.

Why do you think TTX is not used during dental procedures?You correctly answered: c. TTX irreversibly blocks voltage-gated sodium channels in axonal membranes.

Experiment Data:

Condition StimulusVoltage (mV)

Electrode Peak Valueof Response

(V) 2 sec

Peak Valueof Response

(V) 4 sec


(V) 6 sec


(V) 8 sec

Peak Valueof Response(V) 10 sec

Control 30 R1 100 100 100 100 100Control 30 R2 100 100 100 100 100

TTX 30 R1 100 100 100 100 100TTX 30 R2 100 100 0 0 0

Lidocaine 30 R1 100 100 100 100 100Lidocaine 30 R2 100 100 100 0 0

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1. In the control, the amplitudes of the action potentials at R1 and R2 are the same. Which of the following explains this?You correctly answered: d. All of these are reasonable explanations.

2. Blocking the voltage-gated Na+ channels between R1 and R2 with TTX blocksYou correctly answered: d. the propagation of the action potential from R1 to R2.

3. When voltage-gated Na+ channels between R1 and R2 are blocked with TTX, an action potential is still recorded at R1becauseYou correctly answered: b. the voltage-gated Na+ channels between the stimulus and R1 are unaffected by the TTX.

4. Puffer fish must be prepared carefully and properly before they can be eaten. Eating puffer fish can cause numbness ofthe lips, probably because You correctly answered: a. action potentials from sensory neurons in the lips are blocked.

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Review Sheet Results1. What does TTX do to voltage-gated Na+ channels?Your answer:la TTX bloquea los canales de difusion (que funcionan con valtaje) de sodio ala vez este bloqueo es irreversible

2. What does lidocaine do to voltage-gated Na+ channels? How does the effect of lidocaine differ from the effect of TTX?Your answer:al igual que la TTX, la lidocaina bloquea la difusion de sodio, pero si efecto es reversible, e spor eso que se usa comoanestia.

3. A nerve is a bundle of axons, and some nerves are less sensitive to lidocaine. If a nerve, rather than an axon, had beenused in the lidocaine experiment, the responses recorded at R1 and R2 would be the sum of all the action potentials (calleda compound action potential). Would the response at R2 after lidocaine application necessarily be zero? Why or why not?Your answer:no nesesariamente seria cero, al usarse un potencial de accion compuesto porque algunos axones quedan afectados yotros no.

4. Why are fewer action potentials recorded at recording electrodes R2 when TTX is applied between R1 and R2? Howwell did the results compare with your prediction? Your answer:por que la seal empieza en R1, es aqui donde se porpaga pero la seal va disminuyendo debido al efecto del TTX, por locual se disminuye en R2 hasta desaperecer. Los resultados del experimento lo sustentan.

5. Why are fewer action potentials recorded at recording electrodes R2 when lidocaine is applied between R1 and R2?How well did the results compare with your prediction?Your answer:tiene casi el mismo efecto del TTX, pero con la diferencia que la seal se pierde a los 6 ms, recordemos que este efecto esreversible.

6. Pain-sensitive neurons (called nociceptors) conduct action potentials from the skin or teeth to sites in the brain involvedin pain perception. Where should a dentist inject the lidocaine to block pain perception?Your answer:un dentista debe inyectarar la lidocana en las encias para bloquear los receptores evitando asi la generacin de unpotencial de accin que dara lugar a la percepcin del dolor.

Exercise 3: Neurophysiology of Nerve Impulses: Activity 5: The Action Potential: Measuring Its Absolute and RelativeRefractory Periods Lab Report


1. Which of the following occurs after the peak of the action potential?You correctly answered: d. All of these occur.

2. What is meant by Na+ channel inactivation?You correctly answered: b. The Na+ channel no longer allows Na+ ions to pass through it.

3. What happens when voltage-gated K+ channels open?You correctly answered: d. All of these occur.

4. It is harder to generate a second action potential soon after the first action potential becauseYou correctly answered: d. All of these make it harder to generate a second action potential.

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Experiment ResultsPredict Question:Predict Question: If you further decrease the interval between the stimuli, will the threshold for the second action potentialchange?Your answer : b. The threshold for the second action potential will not change.

Stop & Think Questions:Threshold can be defined as the minimum voltage needed to generate an action potential. Is the threshold for the first actionpotential the same as, or different from, the threshold for the second action potential with a 60 msec interval?You correctly answered: a. The threshold for the first action potential is lower than the threshold for the second actionpotential.

Experiment Data:

Interval Between Stimuli (msec) Stimulus Voltage (mV) Second Action Potential?250 20 Yes125 20 Yes60 20 No60 25 No60 30 Yes30 30 No30 35 No30 40 No30 45 Yes15 60 Yes7.5 60 Yes

3.75 60 No

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1. What is the original threshold for this neuron?You correctly answered: a. A 20 mV depolarization to -50 mV.

2. As the interval between stimuli decreases, the depolarization needed to generate the second action potential You correctly answered: a. increases.

3. Judging from your results, what time period after the first action potential best describes the relative refractory period(the time when a second action potential can be generated only if the stimulus intensity is increased)?You correctly answered: c. 7.5 ms-60 msec

4. At what interval between stimuli did the second action potential fail, regardless of the stimulus intensity?You correctly answered: d. 3.75 msec

5. What is the absolute refractory period for this neuron?You correctly answered: d. 3.75 msec

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Review Sheet Results1. Define inactivation as it applies to a voltage-gated sodium channel.Your answer:se puede decir que la inactivacion se da porque los canales de voltaje de sodio se inactivan cuando ya no permiten que elsodio se difunda a travez de la menbrana ..

2. Define the absolute refractory period.Your answer:es el tiempo en el que ningn potencial de accin se puede generar independientemente de la fuerza del estmulo.

3. How did the threshold for the second action potential change as you further decreased the interval between the stimuli?How well did the results compare with your prediction?Your answer:segun los datos del experimento el segundo potencial de accion disminuye (no se da) cuando los msec disminuyen por loque se nesecita un estimulo de voltaje (mV) mucho mayor (para que se pueda dar),

4. Why is it harder to generate a second action potential during the relative refractory period?Your answer:porque para que se de el potencial de accion se nesecita un mayor estimulo, ya que los canales de sodio evitan ladespolarizacion en ese intervalo de tiempo.

Exercise 3: Neurophysiology of Nerve Impulses: Activity 6: The Action Potential: Coding for Stimulus Intensity Lab Report


1. The time after an action potential when a second action potential cannot be generated no matter how intense thestimulus is called theYou correctly answered: b. absolute refractory period.

2. The time after an action potential when a second action potential can be generated only if the stimulus intensity isincreased is called theYou correctly answered: c. relative refractory period.

3. The term frequency refers toYou correctly answered: c. the number of action potentials per second.

4. The purpose of this activity is to exploreYou correctly answered: b. the relationship between stimulus intensity and the frequency of action potentials.

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Experiment ResultsPredict Question:Predict Question: What effect will the increased stimulus intensity have on the frequency of action potentials?Your answer : c. The frequency of action potentials will increase.

Stop & Think Questions:4. At the site of stimulation, the stimulus keeps the membrane of the axon at threshold for a long time, but this depolarizationdoes not spread to the recording electrode. After one action potential has been generated and the axon has fully recoveredfrom its absolute and relative refractory periods, the stimulus is still present to generate another action potential

Measure the time (in milliseconds) between action potentials. This interval should be a bit longer than the relative refractoryperiod (measured in Activity 5).

Click Measure to help determine the time between action potentials. A thin, vertical yellow line appears at the first actionpotential. You can move the line in 10 millisecond increments by clicking the + and - buttons beside the time display, whichshows the time at the line. Subtract the time at the first action potential from the time at the second action potential todetermine the interval between them.

Enter the interval between action potentials in the field below and then click Submit to display your answer in the datatable.You answered: 100 milliseconds

5. The interval between action potentials is sometimes called the interspike interval (ISI). Action potentials are sometimesreferred to as spikes because of their rapid time course.

From the ISI, you can calculate the action potential frequency. The frequency is the reciprocal of the interval and is usuallyexpressed in hertz (Hz), which is events (action potentials) per second. From the ISI you entered, calculate the frequency ofaction potentials with a prolonged (500 msec) threshold stimulus intensity. Frequency = 1/ISI. (Convert the ISI to secondsbefore calculating the frequency.)

Enter the frequency in the field below and then click Submit to display your answer in the data table.You answered: 5 Hz

7. Enter the interval between action potentials (the ISI) in the field below and then click Submit to display your answer inthe data table.

Click Measure to help determine the time between action potentials. A thin, vertical yellow line appears at the far left side ofthe oscilloscope screen. You can move the line in 10 millisecond increments by clicking the + and - buttons beside the timedisplay, which shows the time at the line.You answered: 500 milliseconds

8. From the ISI you entered, calculate the frequency of action potentials with a prolonged (500 msec) 30 mV stimulusintensity. Frequency = 1/ISI.

Enter the frequency in the field below and then click Submit to display your answer in the data table.You answered: 16.67 Hz

11. Enter the interval between action potentials (the ISI) in the field below and then click Submit to display your answer in

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the data table.

Click Measure to help determine the time between action potentials. A thin, vertical yellow line appears at the far left side ofthe oscilloscope screen. You can move the line in 10 millisecond increments by clicking the + and - buttons beside the timedisplay, which shows the time at the line.You answered: 500 milliseconds

12. From the ISI you entered, calculate the frequency of action potentials with a prolonged (500 msec) 45 mV stimulusintensity. Frequency = 1/ISI.

Enter the frequency in the field below and then click Submit to display your answer in the data table.You answered: 11.11 Hz

Experiment Data:

Stimulus Voltage (mV) Stimulus Duration (msec) ISI (msec) Action Potential Frequency (Hz)20 0.5 --- ---20 500 100 530 500 500 16.6745 500 500 11.11

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1. If the interval between action potentials (the interspike interval) is 0.1 (1/10) seconds, what frequency of action potentialswould be observed?You correctly answered: c. 10 Hz

2. With a prolonged stimulus that is just above (more depolarized than) threshold, you would expect to get additional actionpotentials when the membrane has completedYou correctly answered: b. the absolute and relative refractory periods.

3. Which of the following changes occurs when you increase the stimulus intensity?You correctly answered: c. The frequency of action potentials increases.

4. The absolute refractory period is about 3.75 msec. What intensity stimulus would produce action potentials with thisinterspike interval?You correctly answered: d. None of these stimuli would produce action potentials at this high frequency.

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Review Sheet Results1. Why are multiple action potentials generated in response to a long stimulus that is above threshold?Your answer:Sse gerena por un estimulo prolongado; este puede darse, tal como el ejemplo del olor, este estimulo tiene que ser mayor alo normal para poder ser mayor que el periodo refractario relativo.

2. Why does the frequency of action potentials increase when the stimulus intensity increases? How well did the resultscompare with your prediction?Your answer:La frecuencia aumenta debido a la intensidad del estmulo, este estimulo desencadena potenciales de accin adicionalesdentro del periodo refractario relativo, evitando asi que la la neurona se repolarise.

3. How does threshold change during the relative refractory period?Your answer:el umbral aumenta para evitar que la la repolarizacion del interior de la celula; haciendo que las seales se sigantrasnmitiendo por un tiempo mayor.

4. What is the relationship between the interspike interval and the frequency of action potentials?Your answer:La relacin entre el intervalo interspike (modelo espiga) y la frecuencia de los potenciales de accin es recproca.

Exercise 3: Neurophysiology of Nerve Impulses: Activity 7: The Action Potential: Conduction Velocity Lab Report


1. An action potential can be propagated along an axon because there are __________ channels in the membrane.You correctly answered: d. voltage-gated

2. The units of conduction velocity areYou correctly answered: d. meters/second.

3. Which of the following will affect axonal conduction velocity?You correctly answered: c. both the diameter of the axon and the amount of myelination

4. Which of the following describes an A fiber?You correctly answered: a. large diameter, heavily myelinated

5. Which of the following describes a C fiber?You correctly answered: c. small diameter, unmyelinated

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Experiment ResultsPredict Question:Predict Question 1: How will the conduction velocity in the B fiber compare with that in the A Fiber?Your answer : b. The conduction velocity in the B fiber will be slower because the B fiber has a smaller diameter and lessmyelination.

Predict Question 2: How will the conduction velocity in the C fiber compare with that in the B Fiber?Your answer : b. The conduction velocity in the C fiber will be slower because the C fiber has a smaller diameter and lessmyelination.

Stop & Think Questions:3. Note the difference in time between the action potential recorded at R1 and the action potential recorded at R2. Thedistance between these sets of recording electrodes is 10 centimeters (0.01 m).

Convert the time from milliseconds to seconds, enter the time (in seconds) in the field below, and then click Submit todisplay your results in the grid.You answered: 0.5 sec

4. Calculate the conduction velocity in meters/second by dividing the distance between R1 and R2 (0.01 m) by the time ittook for the action potential to travel from R1 to R2.

Enter the conduction velocity in the field below and then click Submit to display your results in the grid.You answered: 50 m/sec

7. Note the difference in time between the action potential recorded at R1 and the action potential recorded at R2.

Convert the time from milliseconds to seconds, enter the time (in seconds) in the field below, and then click Submit todisplay your results in the grid.You answered: 1 sec

8. Calculate the conduction velocity in meters/second by dividing the distance between R1 and R2 (0.1 m) by the time it tookfor the action potential to travel from R1 to R2.


11. Note the difference in time between the action potential recorded at R1 and the action potential recorded at R2.

Convert the time from milliseconds to seconds, enter the time (in seconds) in the field below, and then click Submit todisplay your results in the grid.You answered: 0.10 sec

12. Calculate the conduction velocity in meters/second by dividing the distance between R1 and R2 (0.1 m) by the time ittook for the action potential to travel from R1 to R2.


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Experiment Data:

Axon Type Myelination StimulusVoltage (mV)

Distance FromR1 to R2 (m)

Time BetweenAPs (msec)

Time BetweenAPs (sec)

ConductionVelocity (m/sec)

A fiber Heavy 30 0.1 2 0.5 50B fiber Light 30 0.1 10 1 10C fiber None 30 0.1 100 0.10 1

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1. Action potential conduction velocity is fastest in which of the following fibers? You correctly answered: a. A fibers

2. Action potential conduction velocity is slowest in which of the following fibers? You correctly answered: c. C fibers

3. Why did the timescale have to be changed to measure the conduction velocity of the C fibers?You correctly answered: b. The total time shown on the oscilloscope would have been too short to see the action potential atR2.

4. The axons from touch fibers are A fibers, and the axons from pain fibers are C fibers. When you stub your toe, whichwould you expect to perceive first?You correctly answered: b. your toe touching something

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Review Sheet Results1. How did the conduction velocity in the B fiber compare with that in the A Fiber? How well did the results compare withyour prediction?Your answer:la velocidad en la fibra A es ms rapida por la mielinizacion que tiene, ademas del diametro que posee el cual es muchomayor que la fibra B.

2. How did the conduction velocity in the C fiber compare with that in the B Fiber? How well did the results compare withyour prediction?Your answer:la fibra C, tiene una velocidad de conduccion menor a la de la fibra B, porque esta menos mielinizada y tiene menordiametro.

3. What is the effect of axon diameter on conduction velocity?Your answer:mientras mayor sea el diametro del axon, ms rapido sera la velocidad de conduccion; es proporciaonal

4. What is the effect of the amount of myelination on conduction velocity?Your answer:Igual al anterios, la cantidad de mielina presente es proporcional a la velocidad de conduccion, mientras ms mielinizadoeste el axon, ms rapida sera la conduccion.

5. Why did the time between the stimulation and the action potential at R1 differ for each axon?Your answer:El tiempo difiere en cada experimento porque cada axon tenia un diametro y cantidad de mielina diferente (de mayor amenor).

6. Why did you need to change the timescale on the oscilloscope for each axon?Your answer:Para poder visualisar como cambia la aceleracion (disminuye) de la velocidad de conduccion ya que se ha reducido eldiametro del axon y la mielina de cada fibra; tal y como lo podemos comprobar en cada fase del experimento.

Exercise 3: Neurophysiology of Nerve Impulses: Activity 8: Chemical Synaptic Transmission and Neurotransmitter ReleaseLab Report


1. The end of the axon where it contacts a target is called theYou correctly answered: c. axon terminal.

2. Neurotransmitter is released into the synaptic gap byYou correctly answered: a. exocytosis.

3. Exocytosis of neurotransmitter from the axon terminal is triggered by an increase in the intracellular concentration ofYou correctly answered: c. Ca2+ .

4. Neurotransmitter released into the synaptic gap reaches the target cell byYou correctly answered: b. diffusion.

5. At the target, neurotransmitterYou correctly answered: d. does all of the above.

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Experiment ResultsPredict Question:Predict Question 1: You have just observed that each action potential in a burst can trigger additional neurotransmitterrelease. If calcium ions are removed from the extracellular solution, what will happen to neurotransmitter release at the axonterminal?Your answer : c. There will be less neurotransmitter release.

Predict Question 2: What will happen to neurotransmitter release when low amounts of calcium are added back to theextracellular solution?Your answer : b. Neurotransmitter release will increase a small amount.

Predict Question 3: What will happen to neurotransmitter release when magnesium is added to the extracellular solution?Your answer : b. There will be less neurotransmitter release than in the control solution.

Stop & Think Questions:Why does the stimulus intensity affect the amount of neurotransmitter release at the axon terminal?You correctly answered: d. Both a and b are correct.

Why is there no neurotransmitter release from the axon terminal when there are no calcium ions in the extracellularsolution?You correctly answered: c. Exocytosis of the synaptic vesicles is calcium dependent.

Why did the high intensity stimulation fail to trigger the same amount of neurotransmitter release in the presence ofextracellular Mg2+ as in the control extracellular solution?You correctly answered: a. Mg2+ blocks the calcium channels in the axon terminal.

Experiment Data:

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1. How is the neurotransmitter stored in the axon terminal before it is released?You correctly answered: c. contained in synaptic vessicles

2. Are neurotransmitter molecules released one at a time or in packets?You correctly answered: b. in packets

3. With the normal extracellular calcium concentration, [Ca2+ ], when the action potential reaches the axon terminal ittriggersYou correctly answered: b. release of neurotransmitter by exocytosis.

4. Comparing the low intensity stimulus to the high intensity stimulus, the high intensity stimulus causesYou correctly answered: b. more synaptic vesicles to undergo exocytosis

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Review Sheet Results1. When the stimulus intensity is increased, what changes: the number of synaptic vesicles released or the amount ofneurotransmitter per vesicle?Your answer:de haber un mayor estimulo, esto repercutira el el numero de vesiculas sinapticas, esto lo podemos constatar al ver losresultados del experimento al aumentar el estimulo mientras esta disponible la solucion de calcio.

2. What happened to the amount of neurotransmitter release when you switched from the control extracellular fluid to theextracellular fluid with no Ca2+ ? How well did the results compare with your prediction?Your answer:la liberacon de neurotrasmisores disminuyo porque la concentracion de calcio era menor a lo habitual.

3. What happened to the amount of neurotransmitter release when you switched from the extracellular fluid with no Ca2+ to the extracellular fluid with low Ca2+ ? How well did the results compare with your prediction? Your answer:disminuyo la liberacion de trasnmisores porque habia disminuido el calcio disponible.

4. How did neurotransmitter release in the Mg2+ extracellular fluid compare to that in the control extracellular fluid? Howwell did the result compare with your prediction?Your answer:se dio la liberacion de trasmisores, pero en menor cantidad si lo comparamos cuando utilizamos calcio.

5. How does Mg2+ block the effect of extracellular calcium on neurotransmitter release?Your answer:la liberacion de magnesio en el sistema nervioso disminuye la actividad del calcio; actua como un controlador.

Exercise 3: Neurophysiology of Nerve Impulses: Activity 9: The Action Potential: Putting It All Together Lab Report


1. Sensory neurons respond to an appropriate sensory stimulus with a change in membrane potential that isYou correctly answered: b. graded with the stimulus intensity.

2. If the depolarization that reaches the axon is large and suprathreshold, the result in the axon isYou correctly answered: c. action potentials at higher frequency.

3. At the axon terminal, each action potential causes the release of neurotransmitter. This neurotransmitter diffuses to thereceiving end of an interneuron, where it binds to receptors and causesYou correctly answered: a. ion channels to open, so that the receiving end of the interneuron depolarizes.

4. Interneurons respond to chemical (neurotransmitter) stimulation with a change in membrane potential that is You correctly answered: b. graded with the stimulus intensity.

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Experiment ResultsPredict Question:Predict Question 1: If you apply a very weak, subthreshold stimulus to the sensory receptorYour answer : a. a small, depolarizing response will occur at R1, and no responses will occur at R2, R3, and R4.

Predict Question 2: If you apply a moderate stimulus to the sensory receptorYour answer : b. a small, depolarizing response will occur at R1 and R2, and action potentials will occur at R3 and R4.

Predict Question 3: If you apply a strong stimulus to the sensory receptorYour answer : c. action potentials will be generated at all 4 locations

Stop & Think Questions:Observe the two neurons in the petri dish. What do you think is the resting membrane potential at the receiving end of thesensory neuron (sensory receptor) and the receiving end of the interneuron?You correctly answered: c. -70 mV

Why is there no response at R3 when you apply a very weak stimulus to the sensory receptor?You correctly answered: c. The very weak stimulus does not depolarize the axon of the sensory neuron to threshold.

Why is there a larger, depolarizing response at R1 when you apply a moderate intensity stimulus?You correctly answered: c. The stimulus induces a graded receptor potential at R1.

Experiment Data:

Stimulus Sensory NeuronMembrane Potential

(mV) Receptor

Sensory NeuronAP Frequency(Hz) in Axon

Sensory NeuronVesicles Releasedfrom Axon Terminal

InterneuronMembrane Potential(mV) Receiving End

InterneuronAP Frequency (Hz)

in AxonNone -70 -70Weak -60 0 0 -70 0

Moderate -40 16.6 4 -50 5Strong -25 33.3 6 -40 10

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1. What determines the amplitude of the depolarization at the sensory receptor (R1)?You correctly answered: a. The strength of the stimulus applied to the sensory receptor.

2. What determines the frequency of action potentials in the axon of the sensory neuron (R2)?You correctly answered: a. The amplitude of the depolarization at the sensory receptor (R1).

3. Which of the following directly determines the amount of neurotransmitter released at the axon terminal of the sensoryneuron?You correctly answered: c. The amount of calcium that enters the sensory receptor.

4. Which of the following directly or indirectly determines the amount of neurotransmitter released at the axon terminal ofthe sensory neuron?You correctly answered: d. All of the above play a role in determining the amount of neurotransmitter released.

5. Which of the following directly or indirectly determines the frequency of action potentials in the axon of the interneuron?You correctly answered: d. All of the above play a role in determining the frequency of action potentials in the axon of theinterneuron.

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Review Sheet Results1. Why is the resting membrane potential the same value in both the sensory neuron and the interneuron?Your answer:el potencial de la menbrana en reposo es el mimso porque el potencial casi siempre es el mismo en las neuronas.

2. Describe what happened when you applied a very weak stimulus to the sensory receptor. How well did the resultscompare with your prediction?Your answer:en los experimentos se registro una respues debil en R1 (se despolariso pero poco) n no llegando a despolarisar a R2, R3y R4.

3. Describe what happened when you applied a moderate stimulus was to the sensory receptor. How well did the resultscompare with your prediction? Your answer:en los experimentos podemos ver, que cuando hay un estimulo moderado SE despolarizo R1 y R3, esto ocasiono que seprodusca potenciales de respues en R2 y R3.

4. Identify the type of membrane potential (graded receptor potential or action potential) that occurred at R1, R2, R3, andR4 when you applied a moderate stimulus (view Experiment Results to view the response to this stimulus).Your answer:los potenciales de los receptores se comportaron de forma escalonada produciendo la despolarizacion en R1 y R3, yliberando potenciales de accion en R2 y R4.

5. Describe what happened when you applied a strong stimulus to the sensory receptor. How well did the results comparewith your prediction?Your answer:susedio lo mismo que cuando se dio un estimulo moderado (de forma escalonada), pero la despolarizacion fue ms grandeen R1 y R3.

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