Solution Manual for Human Anatomy & Physiology Laboratory Manual 10th Edition Elaine N. Marieb

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Solution Manual for Human Anatomy & Physiology Laboratory Manual 10th Edition Elaine N. Marieb

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EXERCISE 1 Cell Transport Mechanisms
and Permeability
Advance Preparation/Comments
1. A # symbol after rate data indicates that equilibrium was not reached for that solute.
Answers to Questions/Experimental Data
Pre-lab Quiz in the Lab Manual
1. diffusion
2. b. it contains more nonpenetrating solutes than the interior of the cell. 3. d. vesicular transport
4. phagocytosis
5. active
Activity 1: Simulating Dialysis (Simple Diffusion) (pp. PEx-4PEx-6)
Predict Question 1: The correct prediction is no. Urea is too large to diffuse through this membrane.
Predict Question 2: The correct prediction is that glucose will be able to diffuse through the membrane. Albumin, however, is too large and will not diffuse.
Chart 1: Dialysis Rates (average diffusion rate in mM/sec)
Membrane MWCO
Solute
20
50
100
200
Na+Cl
0.0000
0.0150
0.0150
0.0300
Urea
0.0000
0.0094
Albumin
0.0000
Glucose
0.0040
Activity Questions:
1. No, none of the solutes tested passed through the 20 MWCO membrane. They were all too large. 2. Yes, Na+ Cl diffused through the 50 MWCO membrane.
3. Increasing the size of the solute slowed down the rate of diffusion.
4. Increasing the solute concentration increased the rate of diffusion.
Activity 2: Simulated Facilitated Diffusion (pp. PEx-6PEx-8)
Predict Question 1: Increasing the number of protein carriers will increase the glucose transport rate.
Predict Question 2: Adding Na+Cl will have no effect on the glucose transport rate because the carrier is only transporting glucose through the membrane.
Copyright 2012 Pearson Education, Inc.
1
Chart 2: Facilitated Diffusion Results (glucose transport rate, mM/sec)
Glucose concentration
2 mM
8 mM
10 mM
2 mM w/2.00 mM Na+Cl
Number of glucose carrier proteins
500
0.0008
0.0023
700
0.0010
0.0031
0.0010
100
0.0017#
Activity Questions:
1. They are moving with their concentration gradient.
2. The rate of facilitated diffusion increased when the number of carriers was increased.
3. Equilibrium was not reached with 100 membrane carriers and 10mM glucose because the carriers became saturated and unable to move the glucose across the membrane fast enough.
4. The membrane imbedded carrier in this simulation is only transporting glucose. It is not depending upon the cotransport of Na+Cl, so the addition of Na+Cl had no effect.
Activity 3: Simulating Osmotic Pressure (pp. PEx-8-PEx-10)
Predict Question 1: Increasing the Na+Cl concentration will increase the osmotic pressure.
Predict Question 2: There will only be pressure above the left beaker because the albumin is too large to diffuse. The glucose will diffuse freely, generating no osmotic pressure.
Chart 3: Osmosis Results
Solute
Membrane (MWCO)
Pressure on left (mm Hg)
Diffusion rate (mM/sec)
Na+Cl
20
170
0.0000
Na+Cl
20
340
0.0000
Na+Cl
50
0
0.0167
Glucose
100
136
0.0000
Glucose
100
0
0.0000
Glucose
200
0
0.0036
Albumin w/glucose
200
153
0.0044
Activity Questions:
1. The 20 MWCO membrane generated the most pressure. Na+Cl diffuses through the other membranes.
2. The osmostic pressure increases proportionally with increasing solute concentration.
3. No, if solutes diffuse, no osmotic pressure is generated.
4. The albumin cant diffuse, so osmotic pressure is generated on the left. The glucose is small enough
to diffuse.
Activity 4: Simulating Filtration (pp. PEx-11PEx-13)
Predict Question 1: The filtration rate should increase when the pore rate is increased.
Predict Question 2: Increasing the pressure above the beaker should increase the rate of filtration.
2
Exercise 1
Copyright 2012 Pearson Education, Inc.
Chart 4: Filtration Results
Solute
Na+Cl
Urea
Glucose
Powdered charcoal
Filtration rate (ml/min)
Filter concentration (mg/ml)
Membrane residue
Filter concentration (mg/ml)
Membrane residue
Filter concentration (mg/ml)
Membrane residue
Filter concentration (mg/ml)
Membrane residue
20
1.00
0.00
present
0.00
present
0.00
present
0.00
present
Membrane (MWCO)
50
2.50
4.81
present
0.00
present
0.00
present
0.00
present
200
10.00
4.81
present
4.74
present
4.34
present
0.00
present
200
20.00
4.81
present
4.74
present
4.34
present
0.00
present
Activity Questions:
1. The solutes filtered were too large to pass through the 20 MWCO filter.
2. The two variables that affected the rate of filtration were the size of the pores in the membrane and the pressure applied to the filter.
3. The best way to increase the filtration rate in living membranes would be to increase the pressure applied. The powdered charcoal had the largest molecular weight because it was not able to pass through the filtration membrane.
Activity 5: Simulating Active Transport (pp. PEx-13PEx-14)
Predict Question 1: No, sodium will not be transported because it must be cotransported with potassium. The sodium/potassium pump requires sodium and potassium on opposite sides of the membrane.
Predict Question 2: The addition of glucose carriers should not have an effect on the transport of sodium or potassium because the glucose carriers work independently of the sodium/potassium pump.
Activity Questions:
1. Some of the ions were transported, but there wasnt enough ATP to transport all of the ions. If no ATP were present, there wouldnt have been any movement of ions.
2. Sodium must be transported with potassium, so even though ATP was present, no sodium was transported.
3. When more pumps were added, the rate of transport of sodium and potassium increased proportionally.
4. Glucose is transported by its own carriers and is not dependent upon sodium or potassium. Nor is sodium or potassium dependent upon glucose, as evidenced from previous experimental runs.
Exercise 1
3
Copyright 2012 Pearson Education, Inc.
1REVIEW SHEET EXERCISE
Cell Transport Mechanisms and Permeability
NAME ____________________________________ LABTIME/DATE _______________________
A C T I V I T Y 1 Simulating Dialysis (Simple Diffusion)
Increasing the size of the solute decreases the rate of diffusion
1. Describe two variables that affect the rate of diffusion. ______________________________________________________
Increasing the concentration of a solute increases the rate of diffusion.
__________________________________________________________________________________________________ 2. Whydoyouthinktheureawasnotabletodiffusethroughthe20MWCOmembrane?Howwelldidtheresultscomparewith
Urea was not able to diffuse because it was too large to fit through the pores. This matched the prediction made.
your prediction? ____________________________________________________________________________________
Student predictions vary.
__________________________________________________________________________________________________ 3. Describe the results of the attempts to diffuse glucose and albumin through the 200 MWCO membrane. How well did the
Glucose was able to diffuse through the 200 MWCO; the albumin, however, was too large.
results compare with your prediction? ___________________________________________________________________
Student predictions vary.
__________________________________________________________________________________________________ 4. Putthefollowinginorderfromsmallesttolargestmolecularweight:glucose,sodiumchloride,albumin,andurea.
The following are put in order from smallest to largest: sodium chloride, urea, glucose and albumin.
__________________________________________________________________________________________________
A C T I V I T Y 2 Simulated Facilitated Diffusion
1. Explainonewayinwhichfacilitateddiffusionisthesameassimplediffusionandonewayinwhichitdiffers.__________
Similarities include: solutes move with their concentration gradient; the processes are both passive. A difference is that facilitated diffusion requires a carrier.
__________________________________________________________________________________________________ 2. The larger value obtained when more glucose carriers were present corresponds to an increase in the rate of glucose
transport. Explain why the rate increased. How well did the results compare with your prediction? ___________________
present, more glucose is able to be moved across the membrane. The correct prediction is that the rate increases.
__________________________________________________________________________________________________ 3. Explain your prediction for the effect Na Cl might have on glucose transport. In other words, explain why you picked the
choice that you did. How well did the results compare with your prediction? ____________________________________
required for the transport of the glucose. The carrier is only moving glucose.
__________________________________________________________________________________________________
Na+Cl should have no effect because it is not
With more carriers
A C T I V I T Y 3 Simulating Osmotic Pressure
1. Explain the effect that increasing the Na Cl concentration had on osmotic pressure and why it has this effect. How well
Increasing the Na+Cl concentration increased the osmotic pressure,
did the results compare with your prediction? _____________________________________________________________
because these variables are directly proportional to each other.
__________________________________________________________________________________________________
4
Copyright 2012 Pearson Education, Inc.
2. Describe one way in which osmosis is similar to simple diffusion and one way in which it is different. ________________
because it is a passive process. It is different because it is the movement of water, rather than solutes.
__________________________________________________________________________________________________
3. Solutes are sometimes measured in milliosmoles. Explain the statement, Water chases milliosmoles. ________________
of water is with its concentration gradient. This means that it moves toward the higher concentration of solutes.
__________________________________________________________________________________________________ 4. The conditions were 9 mM albumin in the left beaker and 10 mM glucose in the right beaker with the 200 MWCO mem-
brane in place. Explain the results. How well did the results compare with your prediction? _________________________
was generated by the albumin, which was too large to diffuse. The glucose diffused through the membrane.
__________________________________________________________________________________________________
appear in the filtrate because it was too large to go through.
__________________________________________________________________________________________________ 3. Why did increasing the pressure increase the filtration rate but not the concentration of solutes? How well did the results
At the lower pressure, all of the solutes were filtering through, so increasing the pressure just caused
compare with your prediction? _________________________________________________________________________
them to filter through faster.
__________________________________________________________________________________________________
A C T I V I T Y 5 Simulating Active Transport
1. Describe the significance of using 9 mM sodium chloride inside the cell and 6 mM potassium chloride outside the cell,
The osmotic pressure
Osmosis is similar
The net movement
A C T I V I T Y 4 SimulatingFiltration
1. Explain in your own words why increasing the pore size increased the filtration rate. Use an analogy to support your state-
ment. How well did the results compare with your prediction? ________________________________________________
the filtration rate.
__________________________________________________________________________________________________
2. Which solute did not appear in the filtrate using any of the membranes? Explain why. _____________________________
Increasing the pore size should proportionally increase
The powdered charcoal did not
The concentration of the ions is significant because sodium and potassium are transported
instead of other concentration ratios. ____________________________________________________________________
at a ratio of three to two, respectively, by the pump.
__________________________________________________________________________________________________ 2. Explain why there was no sodium transport even though ATP was present. How well did the results compare with your
Sodium and potassium are required to move these ions using the pump. If one is absent movement will not occur.
prediction? ________________________________________________________________________________________ 3. Explain why the addition of glucose carriers had no effect on sodium or potassium transport. How well did the results
It is moving through its own carrie.
Glucose is not tied in any way to the movement of sodium or potassium in this simulation.
compare with your prediction? _________________________________________________________________________
__________________________________________________________________________________________________ 4. Do you think glucose is being actively transported or transported by facilitated diffusion in this experiment? Explain your
Glucose is moving with its concentration gradient through a carrier. This is facilitated diffusion.
answer. ___________________________________________________________________________________________
Review Sheet 1
5
Copyright 2012 Pearson Education, Inc.
2EXERCISE Skeletal Muscle Physiology
Advance Preparation/Comments
1. Prior to the lab, suggest to the students that they become familiar with the exercise before coming to class. If students have a home computer, or access to a computer on campus, they can become familiar with the general operation of the simulations before coming to class.
2. You might do a short introductory presentation with the following elements:
Describe the basics of muscle contraction at the cellular level, focusing on the sarcomere. This explanation is especially important for the isometric part of the simulation.
Students often have problems distinguishing between in vivo stimulation via the nervous system versus the electrical stimulation we apply to whole skeletal muscle in an experiment. Mention that increasing the intensity of an electrical stimulus to the surface of whole muscle is not the same as stimulation
via the nervous system, but that the outcome of increased force production is similar in both methods.
Encourage students to try to apply the concepts from the simulation to human skeletal muscles as they work through the program.
If a demonstration computer screen is available, briefly show students the basic equipment parts.
3. Keep in mind that many students in an introductory science course are deficient in their graphing skills. Reviewing the principles of plotting before the class begins may prove helpful.
4. Be prepared to help the students answer the more difficult What if . . . questions.
Answers to Questions/Experimental Data
Pre-lab Quiz in the Lab Manual
1. potential difference 2. c. influx of Na+
3. repolarization
4. twitch
5. True
6. True
7. a. tetanus
8. a. oxygen deficit in the tissue after prolonged activity
Activity 1: The Muscle Twitch and the Latent Period (pp. PEx-18PEx-20)
Predict Question 1: No, changes to the stimulus intensity will not change the duration of the latent period. The latent period is a chemical event initiated by the stimulus regardless of its intensity.
6
Copyright 2012 Pearson Education, Inc.
Chart 1: Latent Period Results
Voltage
0.0
3.0
4.0
6.0
8.0
10.0
Active force (g)
0.00
1.04
1.32
1.65
1.81
1.82
* Students use a visual ruler to determine the latent period. A student who enters
2.80 msec as the latent period likely understood how to correctly measure the latent period (the data points at 2.80 msec and 3.20 msec look very similar in the software).
Latent period (msec)
3.20*
3.20*
3.20*
3.20*
Voltage
Active force (g)
Voltage
Active force (g)
0.0
0.00
5.0
1.51
0.2
0.00
5.5
1.59
0.8
0.02
6.0
1.65
1.0
0.15
6.5
1.70
1.5
0.43
7.0
1.74
2.0
0.66
7.5
1.78
2.5
0.87
8.0
1.81
3.0
1.04
8.5
1.82
3.5
1.19
9.0
1.82
4.0
1.32
9.5
1.82
4.5
1.42
10.0
1.82
Activity Questions:
1. A graph similar to the tracing generated in the simulation. See figure 2.3 in the simulation for comparison.
2. The events of the latent period include the events of excitation contraction coupling, most notably the release of calcium from the sarcoplasmic reticulum.
Activity 2: The Effect of Stimulus Voltage on Skeletal Muscle Contraction (pp. PEx-20PEx-22)
6. 0.8 volts
Predict Question 1: The active force will first increase and then plateau at some maximal value as the stimulus voltage increases.
12. 8.5 volts
Chart 2: Effect of Stimulus Voltage on Skeletal Muscle Contraction
Activity Questions:
1. The active force produced by the muscle increased as the stimulus voltage was increased.
2. In the body this is achieved by motor unit recruitment. More muscle fibers are recruited to increase the force generated.
Activity 3: The Effect of Stimulus Frequency on Skeletal Muscle Contraction (PEx-22PEx-23)
Predict Question 1: As the stimulus frequency increases, the muscle force generated by each successive stimulus will increase. There will be a limit to this increase.
Predict Question 2: The stimulus frequency will need to increase.
Exercise 2
7
Copyright 2012 Pearson Education, Inc.
Chart 3: Effect of Stimulus Frequency on Skeletal Muscle Contraction
Voltage
Stimulus
Active force (g)
8.5
Single
1.83
8.5
Multiple
Variable, 2.42
8.5
Multiple
Variable, 2.42
8.5
Multiple
Variable, 2.42 and 5.20
10
Multiple
Variable, 2.42 and 5.20
8.5
Multiple
Variable, 5.20
Activity Questions:
1. Treppe is known as the staircase effect because the tracing looks like a staircase, with each subsequent wave higher than the previous wave.
2. More force is generated by the muscle with each successive twitch, thought to be due to increased availability of calcium.
3. When you increase the frequency of stimulation, the amount of force generated increases.
4. Wave summation occurs in the body when muscle fibers are stimulated before they have had a chance to completely relax.
Activity 4: Tetanus in Isolated Skeletal Muscle (pp. PEx-24PEx-25)
Predict Question 1: As the stimulus frequency increases, the muscle force generated by each successive stimu- lus will increase. There will be a limit to this increase.
Chart 4: Tetanus in Isolated Skeletal Muscle
Stimuli/second
Active force (g)
50
5.12
130
5.88
140
5.91
142
5.94
144
5.94
146
5.95
148
5.95
150
5.95
Activity Questions:
1. A summation of force is occurring at a high frequency of stimulation to produce smooth muscle contraction.
2. Lockjaw is a pathological tetanus. Tetanus boosters are vaccines to prevent the development of tetanus, the disease.
Activity 5: Fatigue in Isolated Skeletal Muscle (pp. PEx-25PEx-26)
Predict Question 1: The length of the rest period will proportionately increase the length of time for sustained muscle tension.
8
Exercise 2
Copyright 2012 Pearson Education, Inc.
Chart 5: Fatigue Results
Rest period (sec)
0
0
Variable, 812
Variable, 812
Active force (g)
5.86
5.86
5.86
5.86
Sustained maximal force (sec)
10
10
Variable, 0.21.8
Variable, 4.25.8
Activity Questions:
1. Fatigue is still being investigated, but it is thought to involve the buildup of lactic acid, ADP, and inorgan- ic phosphate, and possibly oxygen debt.
2. They best way to delay the onset of fatigue with intense exercise is to schedule brief periods of rest to allow muscle recovery.
Activity 6: The Skeletal Muscle Length-Tension Relationship (pp. PEx-26PEx-28)
Predict Question 1: Total force can increase or decrease depending upon the starting resting length. Chart 6: Skeletal Muscle Length-Tension Relationship
Length (mm)
Active force (g)
Passive force (g)
Total force (g)
75
1.82
0.00
1.82
70
1.75
0.00
1.75
65
1.55
0.00
1.55
60
1.21
0.00
1.21
55
0.73
0.00
0.73
50
0.11
0.00
0.11
80
1.75
0.02
1.77
90
1.21
0.25
1.46
100
0.11
1.75
1.86
Activity Questions:
1. Changes in the resting length of the sarcomere directly affect the amount of passive, active and total force that results as described by the length-tension relationship.
2. Thedipinthetotalforcecurveisduetothefactthatataveryshortmusclelength,thereistoomuchoverlap to generate a significant amount of active force. Additionally, there is no passive force at this muscle length.
Activity 7: Isotonic Contractions and the Load-Velocity Relationship (pp. PEx-28PEx-29)
Predict Question 1: The latent period will increase, the shortening velocity will decrease, the distance will decrease, and the contraction duration will decrease.
Chart 7: Isotonic Contraction Results
Activity Questions:
1. As the weight of the load increases, the initial velocity to move the weight decreases.
2. This is because a heavier weight will have a slower velocity for the repetitions, so it will take you longer to repeat the same number of repetitions of a heavier weight.
Weight (g)
Velocity (cm/sec)
Twitch duration (msec)
Distance lifted (mm)
0.5
0.100
78.00
4.0
1.0
0.057
49.00
2.0
1.5
0.022
30.00
0.5
2.0
0.00
0.00
0.0
Exercise 2
9
Copyright 2012 Pearson Education, Inc.
2REVIEW SHEET EXERCISE
Skeletal Muscle Physiology
NAME ____________________________________ LABTIME/DATE _______________________
A C T I V I T Y 1 TheMuscleTwitchandtheLatentPeriod
1. Define the terms skeletal muscle fiber, motor unit, skeletal muscle twitch, electrical stimulus, and latent period. _________
definitions provided in the Introduction.
__________________________________________________________________________________________________
2. What is the role of acetylcholine in a skeletal muscle contraction? _____________________________________________
initiating a change in ion permeability that results in the end-plate potential.
__________________________________________________________________________________________________
3. Describe the process of excitation-contraction coupling in skeletal muscle fibers. _________________________________
release of calcium which binds to troponin, removing the blocking action of tropomyosin so that myosin can bind to actin.
__________________________________________________________________________________________________
muscle tension peaks. The relaxation period is at the end of muscle contraction.
__________________________________________________________________________________________________ 5. Doesthedurationofthelatentperiodchangewithdifferentstimulusvoltages?Howwelldidtheresultscomparewithyour
The latent period did not change with changes in stimulus voltage.
prediction? ________________________________________________________________________________________ 6. Atthethresholdstimulus,dosodiumionsstarttomoveintooroutofthecelltobringaboutthemembranedepolarization?
Sodium would move into the cell to bring about membrane depolarization.
__________________________________________________________________________________________________
Acetylcholine binds to receptors in the motor end plate,
Excitation-contraction coupling is the
Latent period is the time preparing for contraction. Contraction is when
4. Describe the three phases of a skeletal muscle twitch. _______________________________________________________
See
A C T I V I T Y 2 The Effect of Stimulus Voltage on Skeletal Muscle Contraction
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? T_h_e__ac_t_iv_e_f_o_rc_e_i_n_cr_e_a_se_d_a_s_p_r_e_d_ic_te_d__to_t_h_e_p_o_in_t_i_n_w_h_ic_h__it_r_ea_c_h_e_d_a_p_l_a_te_a_u_a_n_d_w__as__no__lo_n_g_e_r_a_b_le_t_o_i_n_cr_e_a_se_._
2. Howisthischangeinwhole-muscleforceachievedinvivo? _________________________________________________
time.
__________________________________________________________________________________________________
3. What happened in the isolated skeletal muscle when the maximal voltage was applied? ____________________________
recruited and so the maximal force has been achieved.
__________________________________________________________________________________________________
This is achieved by the recruitment of more muscle fibers over
All of the muscle fibers have been
10
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A C T I V I T Y 3 The Effect of Stimulus Frequency on Skeletal Muscle Contraction
The stimulus intensity is the electrical changes that
1. What is the difference between stimulus intensity and stimulus frequency? ______________________________________
relate to the action potential. The frequency is the number of action potentials per minute.
__________________________________________________________________________________________________
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
above 8.5 volts to achieve the active force of 5.2 grams.
With complete relaxation, it would be treppe. This is the staircase effect, where you see an
called treppe or wave summation? ______________________________________________________________________
increase in the force/tension produced.
__________________________________________________________________________________________________
3. Howdidthefrequencyofstimulationaffecttheamountofforcegeneratedbytheisolatedskeletalmusclewhenthefrequency
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? _________________________
because the tension wasnt great enough at the lower voltage. This is consistent with wave summation.
__________________________________________________________________________________________________ 4. Toachieveanactiveforceof5.2g,didyouhavetoincreasethestimulusvoltageabove8.5volts?Ifnot,howdidyouachieve
an active force of 5.2 g? How well did the results compare with your prediction? _________________________________
__________________________________________________________________________________________________
5. Compareandcontrastfrequency-dependentwavesummationwithmotorunitrecruitment(previouslyobservedbyincreasing
the stimulus voltage). How are they similar? How was each achieved in the experiment? Explain how each is achieved in
Frequency-dependent wave summation is dependent upon stimulation by the nervous system. The motor recruitment depends
vivo. _____________________________________________________________________________________________
upon the number of motor fibers available.
__________________________________________________________________________________________________
A C T I V I T Y 4 Tetanus in Isolated Skeletal Muscle
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? ______________________________________________
increases to a point.
__________________________________________________________________________________________________ 2. Indicatewhattypeofforcewasdevelopedbytheisolatedskeletalmuscleinthisactivityatthefollowingstimulusfrequen-
cies: at 50 stimuli/sec, at 140 stimuli/sec, and above 146 stimuli/sec. ___________________________________________
146 stimuli/sec: 5.95g
__________________________________________________________________________________________________ 3. Beyond what stimulus frequency is there no further increase in the peak force? What is the muscle tension called at this
After 146 stimuli/sec there is no further increase in force. This is the maximal tetanic tension.
frequency? _________________________________________________________________________________________
The force developed increases as the stimulus frequency
The voltage needed to increase
Yes, it was necessary to increase the voltage
At 50 stimuli/sec: 5.12g. At 140 stimuli/sec: 5.91g. Above
Review Sheet 2
11
Copyright 2012 Pearson Education, Inc.
A C T I V I T Y 5 Fatigue in Isolated Skeletal Muscle
1. When a skeletal muscle fatigues, what happens to the contractile force over time? ________________________________
_co_n_t_ra_c_t_il_e_fo_r_c_e_d_e_cr_e_a_se_s_o_v_e_r_t_im_e_._______________________________________________________________________ The buildup of lactic acid, ADP and inorganic phosphate are
2. What are some proposed causes of skeletal muscle fatigue? __________________________________________________
thought to be involved in muscle fatigue.
__________________________________________________________________________________________________
3. Turningthestimulatoroffallowsasmallmeasureofmusclerecovery.Thus,themusclewillproducemoreforceforalonger
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? ___________________________________
increase in the muscle tension produced.
__________________________________________________________________________________________________
4. List a few ways that humans could delay the onset of fatigue when they are vigorously using their skeletal muscles. _____
could periodically rest during vigorous exercise.
__________________________________________________________________________________________________
When skeletal muscle fatigues, the
When you increase the rest periods, you see an
They
A C T I V I T Y 6 The Skeletal Muscle Length-Tension Relationship
1. Whathappenstotheamountoftotalforcethemusclegeneratesduringthestimulatedtwitch?Howwelldidtheresultscom-
length-tension relationship of the sarcomere.
Total force can increase or decrease depending upon the starting resting length. This is due to the
pare with your prediction? ____________________________________________________________________________
__________________________________________________________________________________________________________
2. What is the key variable in an isometric contraction of a skeletal muscle? ______________________________________
important in determining the active force produced.
__________________________________________________________________________________________________ 3. Based on the unique arrangement of myosin and actin in skeletal muscle sarcomeres, explain why active force varies with
The length-tension relationship. The passive force is
The active forces vary with the number of crossbridges formed, which changes with the
changes in the muscles resting length. __________________________________________________________________
resting length of the muscle.
__________________________________________________________________________________________________
4. What skeletal muscle lengths generated passive force? (Provide a range.) _______________________________________
passive force.
__________________________________________________________________________________________________
5. If you were curling a 7-kg dumbbell, when would your bicep muscles be contracting isometrically? __________________
in length, so this would not be isometric contraction.
__________________________________________________________________________________________________
The muscle lengths from 80-100 mm generated
No, it would be changing
12
Review Sheet 2
Copyright 2012 Pearson Education, Inc.
A C T I V I T Y 7 Isotonic Contractions and the Load-Velocity Relationship
1. Ifyouwereusingyourbicepmusclestocurla7-kgdumbbell,whenwouldyourmusclesbecontractingisotonically?
Yes, because your muscle is changing in length.
__________________________________________________________________________________________________ 2. Explain why the latent period became longer as the load became heavier in the experiment. How well did the results com-
The latent period became longer because it takes more time to generate the force required.
pare with your prediction? ____________________________________________________________________________ 3. Explainwhytheshorteningvelocitybecameslowerastheloadbecameheavierinthisexperiment.Howwelldidtheresults
It takes more time to generate the force required to lift the heavier load.
compare with your prediction? ________________________________________________________________________ 4. Describehowtheshorteningdistancechangedastheloadbecameheavierinthisexperiment.Howwelldidtheresultscom-
The shortening distance decreased with the heavier load.
pare with your prediction? ____________________________________________________________________________ 5. Explainwhyitwouldtakeyoulongertoperform10repetitionsliftinga10-kgweightthanitwouldtoperformthesamenum-
The velocity of shortening decreases with a heavier load, so the repetitions will take longer
ber of repetitions with a 5-kg weight. ___________________________________________________________________
with a 10 kg weight.
__________________________________________________________________________________________________
6. Describewhatwouldhappeninthefollowingexperiment:A2.5-gweightisattachedtotheendoftheisolatedwholeskele-
tal muscle used in these experiments. Simultaneously, the muscle is maximally stimulated by 8.5 volts and the platform sup-
porting the weight is removed. Will the muscle generate force? Will the muscle change length? What is the name for this type
The muscle will still generate force and change length. The type of contraction is isotonic.
of contraction? _____________________________________________________________________________________
Review Sheet 2
13
Copyright 2012 Pearson Education, Inc.
3EXERCISE Neurophysiology of Nerve Impulses
Advance Preparation/Comments
Consider doing a short introductory presentation with the following elements:
Explain how the resting membrane potential is established and maintained.
Clearly distinguish between graded potentials and action potentials.
Explain the importance of threshold and why an action potential is considered all or none.
Describe the relationship between stimulus strength and action potential frequency.
Explain the factors that affect conduction velocity.
Extracellular fluid (ECF)
Microelectrode position
Voltage (mV)
Control
Cell body, extracellular
0
Control
Cell body, intracellular
70
Control
Axon, extracellular
0
Control
Axon, intracellular
70
High K+
Axon, intracellular
40
High K+
Axon, extracellular
0
High K+
Cell body, extracellular
0
High K+
Cell body, intracellular
40
Low Na+
Cell body, intracellular
72
Low Na+
Cell body, extracellular
0
Low Na+
Axon, extracellular
0
Low Na+
Axon, intracellular
72
Answers to Questions/Experimental Data
Pre-lab Quiz in the Lab Manual
1. Conductivity
2. a. depolarization
3. b. K
4. absolute refractory period 5. a. gastrocnemius and sciatic
Activity 1: The Resting Membrane Potential (pp. PEx-36PEx-39)
Predict Question 1: If the extracellular K+ concentration is increased, the resting membrane will become less negative.
Chart 1: Resting Membrane Potential
14
Copyright 2012 Pearson Education, Inc.
Activity Questions:
1. The resting membrane potential is the same because the permeability of the ions is the same in both locations.
2. If the sodium-potassium pump is blocked, sodium will flow in, depolarizing the membrane.
3. The resting membrane potential would become more negative because there would be more negative anions inside the cell.
Activity 2: Receptor Potential (pp. PEx-39PEx-41)
Predict Question 1: The moderate intensity pressure modality will induce a receptor potential of the largest amplitude. Predict Question 2: The moderate intensity chemical modality will induce a receptor potential of the largest amplitude. Chart 2: Receptor Potential
Receptor potential (mV)
Stimulus modality
Pacinian (lamellar) corpuscle
Olfactory receptor
Free nerve ending
None
70
70
70
Pressure
Low
60
70
70
Moderate
45
70
70
High
30
70
65
Chemical
Low
70
64
70
Moderate
70
58
70
High
70
45
70
Heat
Low
70
70
60
Moderate
70
70
40
High
70
70
20
Light
Low
70
70
70
Moderate
70
70
70
High
70
70
70
Activity Questions:
1. Graded receptor potentials can be depolarizing or hyperpolarizing. Since graded receptor potentials can be hyperpolarizing, they can make it more difficult to induce an action potential.
2. Membrane hyperpolarization is when the membrane becomes more negative than the resting potential.
3. The adequate stimulus for sensory receptors in the ear is a moderate intensity pressure stimulus. Intense pressure could inappropriately activate the sensory receptors in the ear.
Activity 3: The Action Potential: Threshold (pp. PEx-41PEx-42)
Predict Question 1: The action potential will not change when the stimulus voltage is increased.
Exercise 3
15
Copyright 2012 Pearson Education, Inc.
Chart 3: Threshold
Stimulus voltage (mV)
10
20
30
40
50
Peak value at R1 (V)
100
100
100
100
0
Peak value at R2 (V)
100
100
100
100
0
Action potential
No
Yes
Yes
Yes
Yes
Activity Questions:
1. Each region of the neuron contains distinct membrane proteins that provide the basis for the threshold differences.
2. The action potential is regenerated by the influx of sodium which establishes local currents that depolarize adjacent sections of the membrane to threshold. The action potential must be regenerated at adjacent sections of the membrane.
3. The action potential is not graded. It is all or none, so the peak value of the action potential doesnit change.
Activity 4: The Action Potential: Importance of Voltage-Gated Na Channels (pp. PEx-42PEx-44) Predict Question 1: If you apply TTX between recording electrodes R1 and R2, TTX will block the response at
R2 but have no effect at R1.
Predict Question 2: If you apply lidocaine between recording electrodes
R1 and R2, lidocaine will block the response at R2 but have no effect at R1. Chart 4: Effects of Tetrodotoxin and Lidocaine
Peak value of response (V)
Condition
Stimulus voltage (mV)
Electrodes
2 sec
4 sec
6 sec
8 sec
10 sec
Control
30
R1
100
100
100
100
100
Control
30
R2
100
100
100
100
100
TTX
30
R1
100
100
100
100
100
TTX
30
R2
100
100
0
0
0
Lidocaine
30
R1
100
100
100
100
100
Lidocaine
30
R2
100
100
100
0
0
Activity Questions:
1. The sodium channels are voltage-gated sodium channels. Closure of the inactivation gate is a delayed response to the initial depolarization to threshold which closes the inactivation gate about 1 msec after sodium channels open.
2. Careful preparation of the pufferfish requires removal of the toxic portions that contain tetrodotoxin. The poison is most concentrated in the liver, ovaries and skin of the fish.
3. Calcium channels could possibly substitute for sodium channels to provide an influx of cation.
Activity 5: The Action Potential: Measuring Its Absolute and Relative Refractory Periods (pp. PEx-44PEx-45)
Predict Question 1: If you further decrease the interval between the stimuli, the threshold for the second action potential will be higher (requiring a larger depolarization).
16
Exercise 3
Copyright 2012 Pearson Education, Inc.
Chart 5: Absolute and Relative Refractory Periods
Interval between stimuli (msec)
250
125
60
60
60
30
30
30
30
15
7.5
3.75
Stimulus voltage (mV)
20
20
20
25
30
30
35
40
45
60
60
60
Second action potential?
Yes
Yes
No
No
Yes
No
No
No
Yes
Yes
Yes
No
Activity Questions:
1. A refractory period is when the membrane is less excitable. When local currents develop, the action potential must move forward because the previous section is in the absolute refractory period.
2. A long absolute refractory period ensures that the muscle contracts fully.
3. The benefit of a relative refractory period in an axon of a sensory neuron is that it is easier to modify the intensity of the sensation by altering the frequency of stimulation.
Activity 6: The Action Potential: Coding for Stimulus Intensity (pp. PEx-46PEx-47)
Predict Question 1: Increased stimulus intensity will increase the frequency of action potentials.
Chart 6: Frequency of Action Potentials
Stimulus voltage (mV)
Stimulus duration (msec)
ISI (msec)
Action potential frequency (Hz)
20
0.5


20
500
100*
10*
30
500
60*
16.6*
45
500
30*
33.3*
* The data in these columns are populated by student calculations.
Activity Questions:
1. The action potential frequency would be increased in the hot water when compared to the warm water.
2. The two determinants that are being overcome are the frequency of stimulation required to overcome the relative refractory period, and the greater than threshold stimulus required during the relative refractory period.
3. Two ways to overcome the relative refractory period are to increase the stimulus frequency and the strength of the stimulus. Pharmacologically, this would require timed release of the medication in bursts of increasing amounts.
Exercise 3
17
Copyright 2012 Pearson Education, Inc.
Activity 7: The Action Potential: Conduction Velocity (pp. PEx-47PEx-49)
Predict Question 1: The conduction velocity in the B fiber will be slower because the B fiber has a smaller diameter and less myelination.
Predict Question 2: The conduction velocity in the C fiber will be slower because the C fiber has a smaller diameter and less myelination.
Chart 7: Conduction Velocity
Axon type
Myelination
Stimulus voltage (mV)
Distance from R1 to R2 (m)
Time between action potentials at R1 and R2
Conduction velocity (m/sec)
(msec)
(sec)
A fiber
Heavy
30
.1
2
.002*
50*
B fiber
Light
30
.1
10
.01*
10*
C fiber
None
30
.1
100
.1*
1*
* The data in these columns are populated by student calculations.
Activity Questions:
1. The conduction velocity is dependent upon both myelination and the diameter of the axon. The large diameter of the squid axon contributes to its fast reaction.
2. The sharp immediate pain is probably carried by an A fiber with large diameter and heavy myelination. The slower dull pain is probably carried by a C fiber with small diameter and no myelination.
3. The mixture of axon types contributes to the variety of responses generated. Specifically, the rate with which a response is made can vary.
Activity 8: Chemical Synaptic Transmission and Neurotransmitter Release (pp. PEx-49PEx-50)
Predict Question 1: There will be no neurotransmitter release if the extracellular calcium is removed.
Predict Question 2: When low amounts of calcium are added back to the extracellular solution, neurotransmitter release will increase a small amount.
Predict Question 3: There will be less neurotransmitter released when magnesium is added.
Activity Questions:
1. It is unlikely that sodium could substitute for calcium since the addition of magnesium blocked the calcium channels.
2. Botulinum toxin blocks the release of acetylcholine from the axon terminal. It is used in cosmetic procedures because it results in paralysis of the muscles that are contracting and causing the wrinkles.
Activity 9: The Action Potential: Putting It All Together (pp. PEx-50PEx-52)
Predict Question 1: When you apply a very weak stimulus to the sensory receptor, small, depolarizing response will occur at R1, and no responses will occur at R2, R3, and R4.
Predict Question 2: When you apply a moderate stimulus to the sensory receptor, a larger, depolarizing response will occur at R1, and an action potential will be generated at R2 and maybe at R4.
Predict Question 3: When you apply a strong stimulus to the sensory receptor, a large, depolarizing response will occur at R1 and R3, and action potentials will occur at R2 and R4.
18 Exercise 3
Copyright 2012 Pearson Education, Inc.
Chart 9: Putting It All Together
None
Weak
Moderate
Strong
Receptor
70
60
40
25
Axon
0
16.6
33.3
Peak value of response (mV)
Stimulus
Sensory neuron
Axon terminal
0
4
6
Receptor
70
70
50
40
Interneuron
Axon
0
5
10
Activity Questions:
1. All action potentials are all or none. Threshold must be met, but once it is met, all action potentials are the same.
2. If the axons were unmyelinated, the peak value of the action potential wouldnt change.
Exercise 3
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Copyright 2012 Pearson Education, Inc.
3REVIEW SHEET EXERCISE
NAME ____________________________________ LABTIME/DATE _______________________
Neurophysiology of Nerve Impulses
A C T I V I T Y 1 The Resting Membrane Potential
1. Explain why increasing extracellular K reduces the net diffusion of K out of the neuron through the K leak channels.
Increasing the extracellular potassium reduces the steepness of the concentration gradient and so less potassium diffuses out of the neuron.
__________________________________________________________________________________________________ 2. ExplainwhyincreasingextracellularK causesthemembranepotentialtochangetoalessnegativevalue.Howwelldidthe
The membrane potential became less negative because less potassium diffused out. If more
results compare with your prediction? ___________________________________________________________________
potassium stays in, it is more positive or less negative.
__________________________________________________________________________________________________ 3. Explain why a change in extracellular Na did not alter the membrane potential in the resting neuron. ________________
There are less leakage sodium channels that leakage potassium channels, and more of the potassium channels are open.
__________________________________________________________________________________________________
The resting neuron is (45) times more 4. Discuss the relative permeability of the membrane to Na and K in a resting neuron. _____________________________
permeable to potassium because of the increased number of leakage channels.
__________________________________________________________________________________________________
5. Discuss how a change in Na
A change in the potassium or K conductance would affect the resting membrane potential. _____________________
conductance would have a greater effect on the resting membrane potential than a change in sodium would.
__________________________________________________________________________________________________
ACTIVITY 2 ReceptorPotential
1. Sensoryneuronshavearestingpotentialbasedontheeffluxofpotassiumions(asdemonstratedinActivity1).Whatpassive
channels are likely found in the membrane of the olfactory receptor, in the membrane of the Pacinian corpuscle, and in the
The efflux of potassium ions is maintained by passive potassium channels.
membrane of the free nerve ending? ____________________________________________________________________
Graded potentials are brief, localized changes in the membrane potential that can be 2. What is meant by the term graded potential? ______________________________________________________________
either depolarizing or hyperpolarizing.
__________________________________________________________________________________________________ 3. Identify which of the stimulus modalities induced the largest amplitude receptor potential in the Pacinian corpuscle. How
20
The moderate intensity pressure modality induced a receptor potential of the
well did the results compare with your prediction? _________________________________________________________
largest amplitude in the Pacinian corpuscle.
__________________________________________________________________________________________________
Copyright 2012 Pearson Education, Inc.
4. Identify which of the stimulus modalities induced the largest-amplitude receptor potential in the olfactory receptors. How well did the results compare with your prediction? _T_he__m_o_d_e_ra_t_e_in_t_e_n_si_ty__ch_e_m_i_c_a_l _m_o_d_a_li_ty_i_n_d_u_ce_d__a_r_ec_e_p_to_r_p_o_t_e_nt_ia_l_o_f_t_h_e_
largest amplitude in the olfactory receptor.
__________________________________________________________________________________________________
5. The olfactory receptor also contains a membrane protein that recognizes isoamyl acetate and, via several other molecules,
transduces the odor stimulus into a receptor potential. Does the Pacinian corpuscle likely have this isoamyl acetate receptor
protein? Does the free nerve ending likely have this isoamyl acetate receptor protein? _____________________________
nerve ending are not likely to have the isoamyl acetate receptor because they did not respond to chemical stimuli.
__________________________________________________________________________________________________
6. What type of sensory neuron would likely respond to a green light? ___________________________________________
A C T I V I T Y 3 The Action Potential: Threshold
1. Define the term threshold as it applies to an action potential. _________________________________________________
an action potential.
__________________________________________________________________________________________________
2. Whatchangeinmembranepotential(depolarizationorhyperpolarization)triggersanactionpotential? _______________
the membrane potential results in an action potential. The membrane potential must become less negative to generate an action potential.
__________________________________________________________________________________________________ 3. HowdidtheactionpotentialatR1(orR2)changeasyouincreasedthestimulusvoltageabovethethresholdvoltage?How
because once threshold is met, the event is all or none, not graded.
The action potential didnt change as the stimulus voltage increased. This is
well did the results compare with your prediction? _________________________________________________________
__________________________________________________________________________________________________
4. An action potential is an all-or-nothing event. Explain what is meant by this phrase. ____________________________
an action potential occurs. If the stimulus is too small an action potential does not occur.
__________________________________________________________________________________________________
The Pacinian corpuscle and the free
Photosensory neurons would respond to green light.
Threshold is the voltage that must be reached in order to generate
A depolarization in
This means that once threshold is met
The trigger zone was investigated. This is where the axon hillock and the
5. What part of a neuron was investigated in this activity? _____________________________________________________
initial segment come together.
__________________________________________________________________________________________________
A C T I V I T Y 4 The Action Potential: Importance of Voltage-Gated Na Channels
TTX blocks the diffusion of sodium through the voltage-gated sodium channels. channels? ________________________________________________________
1. What does TTX do to voltage-gated Na
2. What does lidocaine do to voltage-gated Na channels? How does the effect of lidocaine differ from the effect of TTX?
Lidocaine blocks the diffusion of sodium through the voltage-gated sodium channels.
__________________________________________________________________________________________________ 3. A nerve is a bundle of axons, and some nerves are less sensitive to lidocaine. If a nerve, rather than an axon, had been used in the lidocaine experiment, the responses recorded at R1 and R2 would be the sum of all the action potentials (called
Exercise 3
21
Copyright 2012 Pearson Education, Inc.
a compound action potential). Would the response at R2 after lidocaine application necessarily be zero? Why or why not?
With a compound action potential, the results would not necessarily be zero because some axons could remain unaffected.
__________________________________________________________________________________________________ 4. Why are fewer action potentials recorded at R2 when TTX is applied between R1 and R2? How well did the results com-
TTX blocked the sodium channels, preventing the propagation of the action potential from R1 to R2.
pare with your prediction? ____________________________________________________________________________ 5. WhyarefeweractionpotentialsrecordedatR2whenlidocaineisappliedbetweenR1andR2?Howwelldidtheresultscom-
Lidocaine blocked the sodium channels, preventing the propagation of the action potential from R1 to R2.
pare with your prediction? _______________________________________________________________________________ 6. Pain-sensitive neurons (called nociceptors) conduct action potentials from the skin or teeth to sites in the brain involved in
pain perception. Where should a dentist inject the lidocaine to block pain perception? _____________________________
receptors to prevent the generation of an action potential that would lead to the perception of pain.
__________________________________________________________________________________________________
A C T I V I T Y 5 The Action Potential: Measuring Its Absolute and Relative Refractory Periods Voltage-gated sodium channels are inactivated when they
Lidocaine should be applied to the
1. Defineinactivationasitappliestoavoltage-gatedsodiumchannel. ___________________________________________ no longer allow sodium to diffuse through.
__________________________________________________________________________________________________
The absolute refractory period is the time in which no action potential can be generated
2. Define the absolute refractory period. ___________________________________________________________________
regardless of the strength of the stimulus.
__________________________________________________________________________________________________ 3. How did the threshold for the second action potential change as you further decreased the interval between the stimuli?
between the stimuli decreased as predicted.
The threshold for the second action potential increased as the interval
How well did the results compare with your prediction? ____________________________________________________
__________________________________________________________________________________________________
4. Why is it harder to generate a second action potential during the relative refractory period? ________________________
because voltage gated potassium channels that oppose depolarization are open during this time.
__________________________________________________________________________________________________
A C T I V I T Y 6 The Action Potential: Coding for Stimulus Intensity
1. Why are multiple action potentials generated in response to a long stimulus that is above threshold? _________________
A greater stimulus is required
The longer stimuli allow time for recovery and the above threshold allows the action potential to occur after the relative refractory period.
__________________________________________________________________________________________________ 2. Why does the frequency of action potentials increase when the stimulus intensity increases? How well did the results com-
Action potential can occur more frequently if there is a constant source of stimulation as long as the
pare with your prediction? _____________________________________________________________________________
relative refractory period is reached.
__________________________________________________________________________________________________
3. How does threshold change during the relative refractory period? _____________________________________________
original stimulus intensity during the relative refractory period.
__________________________________________________________________________________________________
The threshold that must be achieved is higher than the
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Review Sheet 3
Copyright 2012 Pearson Education, Inc.
4. What is the relationship between the interspike interval and the frequency of action potentials? _____________________
potentials is the reciprocal of the interspike interval with a conversion from milliseconds to seconds.
__________________________________________________________________________________________________
A C T I V I T Y 7 The Action Potential: Conduction Velocity
1. HowdidtheconductionvelocityintheBfibercomparewiththatintheAfiber?Howwelldidtheresultscomparewithyour
stimulation and the action potential at R1 differed for each axon because the diameter and the degree of myelination varied.
__________________________________________________________________________________________________
6. Why did you need to change the timescale on the oscilloscope for each axon? ___________________________________
potentials. The velocity changes so when it get very slow you need a longer time scale.
__________________________________________________________________________________________________
A C T I V I T Y 8 Chemical Synaptic Transmission and Neurotransmitter Release
1. When the stimulus intensity is increased, what changes: the number of synaptic vesicles released or the amount of
2 Without calcium present, no extracellular fluid with no Ca ? How well did the results compare with your prediction? _________________________
2 When a small amount of
the extracellular fluid with low Ca ? How well did the results compare with your prediction? ______________________
The frequency of the action
The velocity of the B fiber was slower because it had a smaller diameter and less myelinated.
prediction? ________________________________________________________________________________________ 2. HowdidtheconductionvelocityintheCfibercomparewiththatintheBfiber?Howwelldidtheresultscomparewithyour
The conduction velocity of the C fiber was slower because it has no myelination and a smaller diameter.
prediction? ________________________________________________________________________________________
3. Whatistheeffectofaxondiameteronconductionvelocity? _________________________________________________
4. What is the effect of the amount of myelination on conduction velocity? _______________________________________
conduction velocity.
__________________________________________________________________________________________________
5. Why did the time between the stimulation and the action potential at R1 differ for each axon? ______________________
The larger the axon diameter, the greater the conduction velocity.
The greater the myelination, the greater the
The time between the
This is necessary in order to see the action
The number of synaptic vesicles released increases when the stimulus intensity increases.
neurotransmitter per vesicle? __________________________________________________________________________ 2. What happened to the amount of neurotransmitter release when you switched from the control extracellular fluid to the
neurotransmitter was released because the exocytosis of the synaptic vesicles is dependent upon calcium.
__________________________________________________________________________________________________ 3. What happened to the amount of neurotransmitter release when you switched from the extracellular fluid with no Ca2 to
calcium is added back, a small amount of synaptic vesicles are released.
__________________________________________________________________________________________________ 4. HowdidneurotransmitterreleaseintheMg2+extracellularfluidcomparetothatinthecontrolextracellularfluid?Howwell
The neurotransmitter release was less when magnesium was added.
did the result compare with your prediction? _____________________________________________________________
2 When magnesium is added to the
5. How does Mg block the effect of extracellular calcium on neurotransmitter release? ____________________________
extracellular fluid it blocks the calcium channels and inhibits the release of neurotransmitter.
__________________________________________________________________________________________________
Exercise 3
23
Copyright 2012 Pearson Education, Inc.
A C T I V I T Y 9 The Action Potential: Putting It All Together
1. Why is the resting membrane potential the same value in both the sensory neuron and the interneuron? _______________
The resting membrane potential is the same value because this is the typical resting membrane potential regardless of the type of

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