Nerves and Muscles Physiology-Virtual Experiments
Online Virtual Experiments:
1. For Virtual Experiment Visit this link. Click on "Exercise 2: Skeletal Muscle Physiology ".
Click on one of the following titles:
- Single Stimulus,
- Multiple Stimulus,
- Isometric Contraction,
- Isotonic Contraction.
- Eliciting a Nerve Impulse,
- Inhibiting a Nerve Impulse,
- Nerve Conduction Velocity.
Virtual Experiment on The effect of stimulus intensity on the degree of muscle tension:
Virtual Experiment on The relationship between muscle length on the degree of muscle tension:
Virtual Experiment on the Tetanus
Virtual Experiment on the EMG & Twitch amplitude:
INTRODUCTION: In this lab, you will examine how muscles vary the amount of tension they produce by altering the number of contracting muscle fibers. Skeletal muscles are composed of cells called muscle fibers. Each muscle fiber receives synaptic input from only one motor neuron; this synapse is, therefore, the only source of excitation for the muscle fiber. The motor neurons that supply limb muscles have their cell bodies in the ventral horn of the spinal cord. The motor axons leave the spinal cord in the ventral root and travel to the muscle in a nerve. The muscle is supplied by many motor neurons, and any one motor axon makes synaptic connections, or neuromuscular junctions, with only a portion of the fibers in the muscle. The motor neuron and the group of muscle fibers it supplies are called a motor unit. Activation of that motor unit means that there are one or more action potentials in the motor axon, and a similar number of action potentials in (and contractions of) the target muscle fibers. One of the ways that the neurons system can control the amount of tension produced by a skeletal muscle is by controlling the number of activated motor units. This is done by upper motor neurons, which have cell bodies that are located in the brain and have axons that run in descending tracts in the white matter of the spinal cord. These upper motor neurons stimulate the (lower) motor neurons in the ventral horn of the spinal cord. If only a few (lower) motor neurons are activated, only a small portion of the total muscle fibers will contract, while activation of more motor neurons will recruit more motor units and produce a larger contraction. In general, the amount of tension created by a muscle is directly proportional to the number of muscle fibers contracting. In this lab (see video) video, you will examine this general statement by recording the electric signal from contracting muscles (the electromyogram or EMG), to estimate the number of muscle fibers twitching, and the amount of tension created. You will ‘ask‘ the volunteer to quickly contract or ‘twitch’ his forearm muscles to squeeze a bulb in their hand. A pressure transducer in the bulb will monitor the amount of pressure produced by each muscle contraction and patch electrodes placed over the forearm muscles will monitor the EMG. You will measure the amount of pressure and the amplitude of the EMG at different response magnitudes. The relationship between the amount of the pressure generated by the forearm muscle contractions and the amplitude of the electric signal from contracting muscles is shown in figure. Electromyograms are monitored using three electrodes attached to the volunteer‘s skin; the ground on the right wrist and the other two electrodes on the inside-right forearm. The cables are attached to the Data Acquisition Unit. The hand dynamometer is placed in the volunteer’s right hand and is connected to the Data Acquisition Unit. When the volunteer squeezes the dynamometer, the transducer inside detects the amount of DFBSSLFB created. The volunteer is asked to produce a series of quick contractions of his fingers so that the muscle twitches briefly squeeze his hand at different intensities. The EMGs and dynamometer signal are displayed on the computer screen and analysis will reveal whether there is any correlation between the size of the EMG and the amount of pressure produced by the contractions.
Virtual Experiment on Resting potential and external [K]:
INTRODUCTION: All cells have a negative charge
across their plasma membrane. This negative membrane potential (Em) can be
attributed to an asymmetric distribution of ions across the membrane, which is
created by charged proteins and the Na-K-ATPase pump. Proteins are composed of
several amino acids joined together by peptide bonds. Many amino acids are
negatively charged, so that the proteins they form are also negatively charged.
As a result, there is a high concentration of negatively charged proteins
trapped within the cells that produce them. This negative charge attracts
cations (positively charged ions) from the outside, most notably sodium and
potassium. However, as potassium ions enter the cell they create a
concentration gradient.
Therefore, two forces act on
potassium ions: an electrical gradient pulls them into the cell, and a
concentration gradient pushes them out. At equilibrium, the electrical and concentration
gradients would be equal and opposite so no net ion flow would occur across the
membrane. In living cells, however, the potassium ions are not in equilibrium; rather,
there is a constant flux of potassium out of the cell, down its concentration gradient.
This flow is counterbalanced by the Na-K-ATPase pump, which transports two potassium
ions into the cell in exchange for three sodium ions out. Sodium is also
attracted into the cell by the negatively charged proteins, but the permeability
of the membrane to sodium is much lower than that to potassium. In addition,
the Na/K-ATPase pump moves sodium out of the cell. As a result, any sodium ions
that enter the cell are quickly removed, creating a lower sodium concentration
inside the cell. Thus, both the electrical and the concentration gradients push
sodium into the cell, while the Na/K-ATPase pump removes sodium from the cell. Because
of the asymmetric distribution of cations across the cell membrane, the inside
has a high potassium concentration and a lower sodium concentration than the outside.
These two ions constantly diffuse down their concentration gradients, only to
be returned to their original locations by the Na-K-ATPase pump. Clearly, any
change in the composition of the fluid on either side of the membrane will alter
the gradients and change the membrane potential. This simulation examines the
effect of changing extracellular potassium levels on the membrane potential
(Em) of muscle cells in crayfish. At this point, you can examine this
mathematically by changing the ion concentrations across the membrane and
seeing the effects on the membrane potential.
The crayfish is anesthetized by
placing it on ice for 5 to 10 minutes. The crayfish is decapitated and the tail
is removed. Scissors are used to cut the flexor muscles and the m along each
side of the tail. The two halves of the tail are pulled apart, and the dorsal
half is pinned to the base of a sylgard-lined Petri dish. The preparation is
immersed in crayfish saline solution, and the gut and connective tissue are
removed from the preparation to expose the fast abdominal extensor muscles. A
microelectrode is mounted in the adapter, which is attached to the electrometer
probe. The probe is held in a micrornanipulator, and the tip of the
microelectrode and an indifferent electrode are placed in the saline solution
bathing the preparation. The two electrodes are connected to the electrometer,
which is interfaced with a data acquisition unit and a computer. The potential
difference between the two electrodes is monitored using software that displays
a line on the computer screen. When the microelectrode tip is placed inside a
muscle fiber, the line on the computer screen deflects down. The amount of line
deflection depends upon the size of the membrane potential. Because the
computer software can be used to measure the deflection distance, it is possible
to obtain an accurate value for the membrane potential. Fresh saline is
constantly perfused into the preparation dish and the saline level is
maintained by suction. This perfusion system is used to change the solution
bathing the preparation. Two modified crayfish solutions are made: one with no
potassium chloride (KCI) and the second with 100 mM KCI. The two solutions are
mixed in different proportions to make solutions with final KCI concentrations
of 5, 10, 20, 50, and 100 mM. Starting with the saline solution containing 5 mM
KCI, the dish is perfused with the new solution and left for about 5 minutes
for the preparation to equilibrate to its new environment. Several muscle fibers
are impaled and their membrane potential values are obtained by measuring the
vertical deflection of the line on the computer screen. This process of
perfusion with a new saline equilibration, and then measurement is repeated
using solutions with increasing amounts of KCI (see video) video. The resting
membrane potentials at various extracellular K concentrations were recoded and
are shown in table. Questions: 1. Does hyperkalemia affect excitability of the membrane? Explain. 2. Does hypokalemia affect excitability of the membrane? Explain.
Virtual Experiment on Resting potential and external [Na]:
INTRODUCTION: All cells have a negative charge across their
plasma membrane. This negative membrane potential {Em} can be attributed to an
asymmetric distribution of ions across the membrane, which is created by
charged proteins and the Na-K-ATPase pump. Proteins are composed of amino acids
joined together by peptide bonds. Many amino acids are negatively charged, so
that the proteins they form are also negatively charged. As a result, there is
a high concentration of negatively charged proteins trapped within the cells
that produce them. The negative charge created by intracellular proteins
attracts cations (positively charged ions like sodium) from the outside, but
the permeability of the membrane to sodium is very low; there are very few open
sodium channels in the cell membranes of most cells. In addition, the
Na-K-ATPase pump moves three sodium ions out of the cell and exchanges them for
two potassium ions. As a result, any sodium ions that enter the cell are
quickly removed by the Na-K-ATPase pump. Therefore, there is a small
concentration of sodium inside the cell and a much higher concentration of
sodium outside. Thus, both the electrical and the concentration gradients
attract sodium ions into the cell, while the Na-K-ATPase pump removes sodium
from the cell. Potassium is also attracted into the cell by the negatively
charged proteins. This electrostatic gradient and the Na-K-ATPase pump move
potassium ions into the cell and create a concentration gradient, which pushes
potassium out of the cell. The asymmetric distribution of cations across the
cell membrane is such that the inside has a high potassium concentration and a
lower sodium concentration than the outside. These two ions constantly diffuse
down their concentration gradients, only to be returned to their original
locations by the Na-'K-ATPase pump. In this lab, you will measure the membrane
potential from muscle cells (or fibers) of a crayfish, and you will see what
happens to the membrane potential if you artificially alter the sodium
concentration gradient across the membrane. The crayfish is anesthetized by
placing it on ice for 5 to 10 minutes. The crayfish is decapitated and the tail
is removed. Scissors are used to cut the flexor muscles and the m along each
side of the tail. The two halves of the tail are pulled apart, and the dorsal
half is pinned to the base of a sylgard-lined Petri dish. The preparation is
immersed in crayfish saline solution, and the gut and connective tissue are removed
from the preparation to expose the fast abdominal extensor muscles. A
microelectrode is mounted in the adapter, which is attached to the electrometer
probe. The probe is held in a micromanipulator, and the tip of the
microelectrode and an indifferent electrode are placed in the saline solution
bathing the preparation. The two electrodes are connected to the electrometer,
which is interfaced with a data acquisition unit and a computer. The potential
difference between the two electrodes is monitored using software that displays
a line on the computer screen. When the microelectrode tip is placed inside a
muscle fiber, the line on the computer screen deflects down. The amount of line
deflection depends upon the size of the membrane potential. Because the
computer software can be used to measure the deflection distance, it is possible
to obtain an accurate value for the membrane potential. Fresh saline is
constantly perfused into the preparation dish and the saline level is
maintained by suction. This perfusion system is used to change the solution
bathing the preparation (see video) video. Two modified crayfish solutions are
made: one with no sodium chloride {NaCl) and the second with 200 mM NaCl. The
two solutions are mixed in different proportions to make solutions with final
NaCl concentrations of 10. 20, 50, 100, and 200 mM. Starting with the saline
solution containing 200 mM NaCl, the dish is perfused with the new solution and
left for about 5 minutes for the preparation to equilibrate to its new
environment. Several muscle fibers are impaled and their membrane potential
values are obtained by measuring the vertical deflection of the line on the
computer screen. This process of perfusion with a new saline, equilibration,
and then measurement is repeated using solutions with decreasing amounts of
NaCl. The resting membrane potentials at
various extracellular Na concentrations were recoded and are shown in Table. Questions:
1. Does change in extracellular Na concentration affect excitability of the membrane? Explain.
2.
Why does a change in extracellular Na concentration has a much smaller
effect on resting membrane potential than a change in K concentration?
Virtual Experiment on Compound action potential:
Introduction: Proteins are
usually made inside cells and do not easily move across the membrane because of
their size. In many cells these trapped proteins contain large amounts of
negatively charged amino acids, like aspartate and isothionate, creating an
electrostatic gradient so that the inside is charged negatively with respect to
the outside. This negative charge attracts cations (like sodium and potassium)
into the cell. In the case of potassium,
the electrical charge pulling potassium ions into the cell is counteracted by a
concentration gradient pushing potassium out; the concentration of potassium
inside the cell is greater than outside. Because the cell membrane is permeable
to potassium, potassium flows freely across the membrane with the net direction
of flow being out of the cell. In the case of sodium, the concentration of
sodium inside the cell is much less than outside. As a result, the negative
charge inside the cell and the concentration gradient both push sodium ions
into the cell. However, there are very few open sodium channels in the resting
cell membrane, so the permeability is low and only a few sodium ions enter the
cell. The constant diffusion of potassium out of the cell and sodium into the
cell is counterbalanced by the sodium/potassium-ATPase pump, which exchanges
two potassium ions for three sodium ions and maintains their concentration
gradients. 'Excitable' cells like
nerves and muscles can generate action potentials, a phenomenon in which the
charge on the inside of the cell changes from negative to positive and back to
negative in a few milliseconds. The ability to produce action potentials is
dependent upon the presence of voltage-gated channels, which are usually closed
when the cell is at rest. If the cell membrane is depolarized (i.e., made less
negative) beyond a certain ‘threshold’ level, the voltage-gated channels open
and produce an action potential. Voltage-gated sodium channels quickly open
when the membrane is depolarized to (and beyond) threshold and this allows
sodium to cross the membrane and produce the rapid 'upstroke' of the action
potential and the inside of the cell becomes positive. The sodium channels
quickly close, but the membrane depolarization also opens voltage-gated
potassium channels; this takes place at a much slower rate than for sodium. As
a result, there is a slight delay in the movement of potassium out of the cell
and the return of the membrane potential back to resting levels.
Nerve cells have
long extensions called axons down which action potentials can be rapidly
conducted, sometimes for long distances. In this experiment you will record
action potentials as they are conducted down axons in an excised frog sciatic
nerve (see video) video. Many axons in this nerve conduct action potentials at
the same speed. If action potentials are produced at the same time in one such
group or population of axons, the action potentials will travel at the same
speed and arrive at the other end of the nerve at the same time. In this lab
you will record action potentials from one such population of axons. You will
apply a brief electrical shock to one end of the nerve to produce an action
potential in one or more axons, and you will record the action potentials as
they pass over electrodes at the other end of the nerve. You will vary the
intensity of the electrical shock applied to the nerve to demonstrate threshold
and recruitment, as more and more axons are stimulated to produce action
potentials.
The Dissection:
A frog is anesthetized with MS-222, and then pithed. The skin is cut and
removed from the trunk and legs. From this point the exposed tissue is kept
moist with frog Ringer's solution. Scissors are used to cut the tissue on
either side of the urostyle and the urostyle is removed close to the vertebral
column. A short piece of thread is used to ligate the sciatic nerve on one side
close to the vertebral column, and the nerve is cut between the knot and the
vertebral column. The thigh muscles are separated to locate the sciatic nerve.
A short piece of thread is used to ligate the nerve close to the knee and
scissors are used to cut the nerve between the knot and the knee. The nerve is
dissected from the surrounding tissue, and the excised nerve is placed in a
nerve chamber filled with frog Ringer's solution (see figure for experiment setup).
The Response: Recording electrodes are attached to one
end of the nerve and stimulating electrodes to the other. The nerve chamber is
drained and brief electrical shocks are applied to one end of the nerve to
produce action potentials. Evoked action potentials travel down the axons and
over the recording electrodes at the other end of the nerve. The currents
associated with the action potentials are detected by the electrodes, and the
signal is digitized by the data acquisition unit and displayed on the computer
screen.
The Experiments:
If a nerve is stimulated with a shock of zero volts no response is recorded
because the shock is insufficient for the axon membranes to reach threshold. In
this experiment, the shock voltage is increased in small increments to produce
a compound action potential. The
relationship between stimulus voltage and response amplitude is determined and
represented graphically (see table). Question: What is the relationship between
the stimulus intensity and the amplitude of a compound action potential?
Explain the plateau seen at high stimulus intensity (refer to table).
Virtual Experiment on Conduction velocity and amplitude:
Virtual Experiment on Excitatory post synaptic potential (EPSP):
Virtual
Experiment on Conduction velocity and amplitude:
Download this folder. Open the folder and double click on "index". Click on "OBJECTIVES & INTRODUCTION" and read it. Read the file "Steps" in the main "Conduction velocity and amplitude" folder and follow the steps. You start your virtual experiment by clicking on "LABORATORY EXERCISE" and follow the steps in "Steps" file. You can also browse through the following titles "PRE-LAB QUIZ, WET LAB, LABORATORY EXERCISE, POST-LAB QUIZ & LAB REPORT".
Virtual
Experiment on Excitatory post synaptic potential (EPSP):
Download this folder. Open the folder and double click on "index". Click on "OBJECTIVES & INTRODUCTION" and read it. Read the file "Steps" in the main "Excitatory post synaptic potential (EPSP)" folder and follow the steps. You start your virtual experiment by clicking on "LABORATORY EXERCISE" and follow the steps in "Steps" file. You can also browse through the following titles "PRE-LAB QUIZ, WET LAB, LABORATORY EXERCISE, POST-LAB QUIZ & LAB REPORT".
Virtual
Experiment on Refractory periods:
Download this folder. Open the folder and double click on "index". Click on "OBJECTIVES & INTRODUCTION" and read it. Read the file "Steps" in the main "Refractory periods" folder and follow the steps. You start your virtual experiment by clicking on "LABORATORY EXERCISE" and follow the steps in "Steps" file. You can also browse through the following titles "PRE-LAB QUIZ, WET LAB, LABORATORY EXERCISE, POST-LAB QUIZ & LAB REPORT".
Virtual
Experiment on Measuring ion current-Voltage clamp:
Download this folder. Open the folder and double click on "index". Click on "OBJECTIVES & INTRODUCTION" and read it. Read the file "Steps" in the main "Measuring ion current-Voltage clamp" folder and follow the steps. You start your virtual experiment by clicking on "LABORATORY EXERCISE" and follow the steps in "Steps" file. You can also browse through the following titles "PRE-LAB QUIZ, WET LAB, LABORATORY EXERCISE, POST-LAB QUIZ & LAB REPORT".
Virtual
Experiment on Spacial summation of Excitatory post synaptic potentials:
Download this folder. Open the folder and double click on "index". Click on "OBJECTIVES & INTRODUCTION" and read it. Read the file "Steps" in the main "Spacial summation of Excitatory post synaptic potentials" folder and follow the steps. You start your virtual experiment by clicking on "LABORATORY EXERCISE" and follow the steps in "Steps" file. You can also browse through the following titles "PRE-LAB QUIZ, WET LAB, LABORATORY EXERCISE, POST-LAB QUIZ & LAB REPORT".
Virtual
Experiment on Temporal summation of Excitatory post synaptic potentials:
Download this folder. Open the folder and double click on "index". Click on "OBJECTIVES & INTRODUCTION" and read it. Read the file "Steps" in the main "Temporal summation of Excitatory post synaptic potentials" folder and follow the steps. You start your virtual experiment by clicking on "LABORATORY EXERCISE" and follow the steps in "Steps" file. You can also browse through the following titles "PRE-LAB QUIZ, WET LAB, LABORATORY EXERCISE, POST-LAB QUIZ & LAB REPORT".
Virtual
Experiment on - Physiology simulator
- Nervous system
- Muscles
Biphasic or Monophasic Whether an action potential will give a biphasic or monophasic record depends on the recording arrangement. If we use bipolar electrodes, the record depicts the potential difference between the tips of the electrodes. To start with, a muscle (or nerve) fibre is polarised, and both electrodes are at the same potential. As an impulse travels along the surface of the muscle fibre, first it reaches one of the electrodes (A), which makes A negative as compared to electrode B, if the electrodes are extracellular, as in case of EMG. That gives an excursion in the record. Then the impulse reaches B, and both electrodes A and B are at the same potential (depolarisation potential). Accordingly the record returns to the baseline. Next, A repolarises while B is still depolarised. Now B is negative as compared to A, which gives an excursion opposite in polarity to the previous one. Finally, B is also repolarised, and points A and B are both at the same potential. Hence the record returns to the baseline. Thus a single action potential gives a biphasic record while travelling from one to the other member of a bipolar electrode pair. In contrast, if we use a monopolar electrode, it records the absolute potential in the vicinity of the active electrode because the indifferent electrode is at a constant potential. To start with, the muscle fibre is polarised, and the electrode records a certain potential which becomes the baseline. When the action potential reaches near the electrode, the membrane is depolarised. Therefore, the electrode records an excursion. After the action potential has passed away from the vicinity of the electrode, the membrane is repolarised and the record returns to the baseline. Thus a monopolar electrode gives a monophasic record.
1. The relationship between muscle
length on the degree of muscle tension:
The contraction strength of a muscle is very dependent on the degree
of pre-stretching but how contraction strength is affected by
pre-stretching varies between different types of muscle. The effect of
pre-stretching can be readily observed in the isolated skeletal muscle.
When a skeletal muscle is detached from a tendon, it is clearly seen to become
shorter. If the isolated skeletal muscle is then stretched by attaching
a weight, as will be seen in this practical class, it can return to its
in vivo length and it acquires a contraction strength that is close to
that which it had in vivo.
It is important to note here that this phenomenon, as it is seen in
vivo, differs between skeletal muscle, heart muscle and smooth muscle.
Whereas the normal basal, unstimulated pre-stretched state of skeletal
muscle provides for maximal muscle strength, heart muscle and smooth
muscle have a considerable reserve of potential muscle strength when in
their basal state. The strength of the heart muscle is increased as it
is stretched during filling of a heart chamber (the Frank-Starling
mechanism) and intestinal and vascular smooth muscle only become active as they are stretched in response to increased luminal pressure.
The video video of this experiment shows the effect of muscle length on the degree of muscle tension. The muscle is an isolated animal skeletal muscle. The results of this experiment are shown the following figure:
Questions: Why is the muscle tension (level A) at 26.1 mm muscle length is lower (level B) than at muscle length of 28.7 mm? Why is the muscle tension (level C) at 34.3 mm muscle length is lower than that at muscle lengths of A and B levels?
2. The effect of stimulus intensity on the degree of muscle tension:
The video video of this experiment shows the effect of stimulus intensity on the degree of muscle tension. The muscle is an isolated animal skeletal muscle. The results of this experiment are shown the following figure:
Questions: Explain why the muscle tension is increased with an increase stimulus intensity? Why at stimulus intensities of 350 and 400 mV, no change in muscles tension was observed?
3. The effect of two successive stimuli (twin stimuli) on the degree of muscle tension:
This
experiment shows the effect of two successive stimuli (twin stimuli)
separated by 75 ms on the degree of muscle tension (video) video. The muscle is an isolated animal skeletal muscle. The results of this experiment are shown the following figure:
Questions:
Explain why is the muscle tension in response to second stimulus (level
B) is higher than the muscle tension in response to first stimulus
(level A)?
4. The effect of increasing the frequency of stimulation on the degree of muscle tension (tetanization):
The video video of this experiment shows the effect of increasing the frequency of stimulation on the degree of muscle tension. The muscle is an isolated animal skeletal muscle. The results of this experiment are shown the following figure:
Questions:
Explain why is
the muscle tension in response 63 successive stimuli (level D) is higher
than the muscle tension in response to three successive stimuli (level
C), which in turn is higher than the muscle tension in response to two
(twin) successive stimuli (level B), which in turn is higher than the
muscle tension in response to one stimulus (level A)?
5. Stimulation of a nerve fiber and a nerve trunk:
The video video of this experiment shows the effect of changing the stimulus intensity (voltage in mV) on the generation of a action potential. The nerve fiber stimulation and the response recording is achieved by surface electrodes. The nerve fiber used is isolated from animal nerve trunk. The results of this experiment are shown the following figure:
Questions: Why do you think that action potential is generated at specific stimulus intensity? What do you call this level of stimulus intensity? Explain why? Explain why the action potential shape and magnitude does not change even with an increase in the stimulus intensity?
In another virtual experiment, demonstrated by this video video, a nerve trunk was stimulated. The nerve trunk stimulation and the response recording is achieved by surface electrodes. As the intensity of the applied stimulus is increased, the magnitude of the action potential recorded (compound action potential, CAP) is increased until we approach a level a further increase of the applied stimulus is not associated with a further increase in the magnitude of the CAP. The results of this experiment are shown the following figure.
Questions: Why there is a graded increase in the magnitude of the CAP recorded in a nerve trunk in response to a graded increase in the stimulus intensity? Why there is a difference in the type of response to stimulation between a nerve fiber and a nerve trunk? Explain.
6. The effect of stimulus duration:
The effect of a pulse stimulus is dependent not only on the amplitude but also the duration of the stimulus pulse. This relationship is demonstrated by the virtual experiment in this video video. In this experiment a nerve trunk was used. The results of this experiment are shown the following figure.
Question: Why it is important to successfully stimulate a nerve fiber, the applied stimulus has to be of enough duration? Explain.
7. Nerve conduction velocity:
The video video of this virtual experiment is to show you the simplest way of measuring the nerve conduction velocity. The nerve is an isolated animal nerve trunk. The nerve trunk stimulation and the response recording is achieved by surface electrodes.The results of this experiment are shown the following figure.
The following video shows the effect of temperature changes on the nerve conduction velocity. The results of this experiment are shown the following figure:8. Refractory period:
The following video video demonstrates the experiment involve an application of twin stimuli separated (delay) by 1, 2, 3, 4, and 5 ms. The experiment involves the use of nerve fiber. The results of this experiment are shown the following figure.
Question:
1. Why the second stimulus did not generate an AP? Explain.
2. Why does the 3ed & 4th 5th stimuli generated smaller AP in magnitude?