1  

Monosynaptic and Polysynaptic Reflex in Human Body

Submitted by: Janice Leung

Partners: Garvin Tan, Lawrence Luu, Yan Wah Ng

Section: NPB 101L 062

TA: Phung Thai

Date: 22 July 2013

2  

Introduction

Reflexes are involuntary and stereotyped movement that responses to the stimulation on

the receptor. The response is directly proportional to the strength of stimulation which is known

as graded potentials. On the other hand, the pathway of reflex response contains 5 components –

receptor, afferent, integrator, efferent, and effector. These 5 components work together to form

the reflex arcs. When there is a stimulus acts on the receptor; for example, skin, muscles, or

tendons, it will convert the stimulus into an electrical signal and starts an action potential in

afferent neuron. Then, the afferent neuron delivers the impulses from the receptor to the

integrator, the central nervous system. The fire impulses will then conduct through the efferent

neuron to the effector such as cells, muscles, or organs to proceed reflex responses. (Rohkamm,

2003, p40)

There are two types of reflex responses - monosynaptic and polysynaptic reflex.

Monosynaptic reflex has only one synapse between afferent and efferent neuron which means

the receptors and effectors are locating at the same place. The stretch reflex is one of the

examples of monosynaptic reflex. In monosynaptic reflex, the stimulation on the receptor would

activate the 1a afferent neuron and it would connect to the efferent neuron, α motor neuron,

through monosynaptic connection. This pathway to activate α motor neuron produces the

Hoffman Reflex which is known as H-reflex. When the stimulation increases, the α motor

neuron activates directly by the stimulus and this pathway of stimulation generates the second

wave, M-wave. During experiment, H-wave and M-wave is recorded by EMG; it is a technique

for recording the electrical activity of muscles at a specific time. Polysynaptic reflex has several

interneurons lie between afferent and efferent neuron. The vestibular-ocular reflex is one of the

examples of polysynaptic reflex; it is a reflex that response to the angular acceleration and

3  

deceleration of body. Since polysynaptic reflex has more than one synapse in between, the

latency of stimulus to response would increase and the intensity of response would reduce if the

stimulus repeats. (Rohkamm, 2003, p40)

There are two parts in this Human Reflexes experiment. In the first part of the experiment,

it focuses on the stretch reflex and observes the changing pattern of H-wave and M-wave by

stimulating the tibial nerve in the gastrocnemius with different voltage or frequency. In the

second part of the experiment, it focuses on the saccadic eye movement of vestibular-ocular

reflex. The rapid and slow eye movement of the subject will be recorded along with angular

acceleration or deceleration of the body and head.

In the Part 1, it is expected that the H-wave will appear on the EMG first and then the M-

wave when the electrical voltage starts to increase. When the stimulus intensity increases

continuously, the amplitude of M-wave will increase, but the amplitude of H-wave will decrease

or disappear at the end. Besides, it is expected that the amplitude of H-wave will decrease with

the increase of frequency at a fixed voltage. However, the M-wave will have no response to the

change of frequency. These results are expected because of the relationship between stimulus

intensity and frequency with the H-wave and M-wave. In Part 2, it is expected that the direction

of perceived rotation is the same as the direction of spinning when it is accelerating and it is

opposite to the direction of spinning when it is decelerating. Also, the rapid eye movement of the

subject is always opposite to the spinning direction if the rotation is fast and it is in the same

direction as the spinning direction if the rotation is slow. Besides, the head position would affect

the direction of eye movement too. These results are expected because of the sensation and

response of vestibular apparatus to the angular acceleration and deceleration.

4  

Materials and Methods

The subject of this experiment was human and the details about the materials and

methods can be found in Experiment 3 in the lab manual. In Part 1 of this experiment, electrode

leads connected to the tibial nerve of the subject and he was stimulated by the stimulus produced

by the stimulator. The data was collected by the BioPac program in the computer and performed

as an EMG graph. On the other hand, there was a deviation in the Effect of Stimulus Frequency

part. We used 80V as the stimulus instead of the stimulus voltage of Intermediate H-wave. In

Part 2 of this experiment, the subject sit on a spin chair and his eye movement was recorded

while he was rotating at different speed, direction or body position during the experiment.

(Bautista, E., & Korber, p19-29)

Results

In Part 1 of the experiment, the effect of stimulus voltage on the H-wave and M-wave is

recorded in Table 1. Table 1 is showing the stimulus voltage required for H-wave threshold, M-

wave threshold, maximal H-wave, Intermediate H-wave and H-wave abolished and the segment

number of each response that appears on the EMG recording.

Table 1 Data table for stimulus voltage responses

H-wave Threshold

M-wave Threshold

Maximal H-wave

Intermediate H-wave

H-wave Abolished

Stimulus Voltage (V)

42.5

58

60

51

80

Segment Number

13

25

32

57

63

5  

Based on the data from Table 1 and the EMG recording for part 1, the amplitude of M-

wave and H-wave could be measured. The data for stimulus voltage versus M-wave and H-wave

amplitude is recorded in Table 2. It shows the relationship between the stimulus voltage and

amplitude of M-wave and H-wave under conditions of H-wave threshold, M-wave threshold,

maximal H-wave, Intermediate H-wave and H-wave abolished. It shows that the amplitude of H-

wave is increasing from 0.065002mV to 0.523986mV with the stimulus voltage increasing from

42.5V to 60V. However, the amplitude of H-wave decreases to 0mV when the stimulus voltage

is 80V. From Table 2, the amplitude trend of M-wave could observe. M-wave would not appear

until the stimulus voltage reaches the M-wave threshold which is 58V. The M-wave starts to

recognize from 58V to 80V and its amplitude is increasing as the voltage increase. The

amplitude of M-wave is the highest at 80V with amplitude of 1.957703mV.

Table 2 Data table for stimulus voltage versus M-wave and H-wave amplitude

H-wave Threshold

M-wave Threshold

Maximal H-wave

Intermediate H-wave

H-wave Abolished

Stimulus Voltage (V)

42.5

58

60

51

80

H-wave Amplitude (mV)

0.065002

0.354309

0.523986

0.216369

N/A

M-wave Amplitude (mV)

N/A

0.813904

1.016845

N/A

1.957703

According to the data on Table 2, a graph of Stimulus Voltage versus M-wave and H-

wave Amplitude has made. The relationship between voltage and M-wave amplitude is showed

6  

as the graph below. The trend of M-wave amplitude is increasing as it reaches the M-wave

threshold (58V). The relationship between voltage and H-wave amplitude is showed as the graph

below. The trend of H-wave amplitude is increasing from its threshold value (42.5V) to the

maximal stimulus voltage (60V). Then, the trend starts to decrease 0mV at 80V stimulus. A

detail of the graph description is showed in the legend of the graph.

In the effect of stimulus frequency part, the data for frequency response is recorded in

Table 3. It shows the file name of the EMG that recorded in stimulus frequency 0.5 Hz, 1.0 Hz,

2.0 Hz, and 3.0 Hz and the fixed stimulus voltage 80V that used during the experiment.

7  

Table 3 Data table for frequency response

Stimulus Frequency (Hz)

File Name

0.5 Freq 0.5

1.0 Freq 1.0

2.0 Freq 2.0

3.0 Freq 3.0

Stimulus Voltage (V) 80

Based on the EMG recording of the effect of stimulus frequency at fixed voltage 80V, the

segment number and the amplitude of M-wave are recorded in Table 4. The amplitude of M-

wave has a range from 0.101929mV to 0.127563mV. It does not have an obvious change by

comparing the amplitudes; the change of amplitude of each condition is less than 9%. Besides,

the amplitude of H-wave does not show on the EMG recording because of an error during the

experiment. The fixed stimulus voltage used in this part reaches the H-wave abolished voltage

(80V), so no H-wave could be generated.

Table 4 Data table of stimulus frequency versus M-wave and H-wave

Stimulus Frequency (Hz)

0.5

1.0

2.0

3.0

Segment number

87

23

53

72

Amplitude of M-wave (mV)

0.110779

0.122985

0.127563

0.101929

Amplitude of H-wave (mV)

N/A

N/A

N/A

N/A

8  

According to the Table 4, a graph of Stimulus Frequency versus M-wave amplitude has

made. The graph is showing the relationship between frequency and M-wave amplitude at a

fixed voltage. Based on the trend of the curve, the change of M-wave is not obvious at different

frequency. Detail descriptions of the graph are showed below the graph.

In Part 2 of the experiment, the data of vestibular apparatus and eye movements is

recorded. The data of Case 1 (Perceived Motion Following a Spin with Closed Eye) is recorded

in Table 5. The table shows the direction of perceived rotation and duration of perceived motion

under different conditions – Start of spin, Middle of spin, and Chair stopped. Details of the result

refer to Table 5 below.

9  

Table 5 Observations for chair spins

Experimental Condition

Observations

Case 1

Direction of perceived rotation

Duration of perceived motion (seconds)

Start of spin

With spin

17

Middle of spin

None

22

Chair stopped

Opposite to spin

24

The direction of fast and slow eye movement under three different conditions is showed

in Table 6. In the table, Case 2 represents the experimental condition of optokinetic system and

moving visual fields, Case 3 represents the angular acceleration and the vestibule-ocular reflex

with forward tilt, and Case 4 represents the angular acceleration and the vestibule-ocular reflex

with lateral tilt. Detail of results shows in Table 6 below.

Table 6 Direction of fast and slow eye movements

Experimental Condition

Direction of fast eye movement

Direction of slow eye movement

Case 2

With spin

Opposite to spin

Case 3

With spin, flutters

Opposite to spin

Case 4

Look up, opposite to spin

Look up, with spin

10  

Discussion

In Part 1 of the experiment, the reflex arcs of stretch reflex contains 5 components – the

tibial nerve (receptor), 1a afferent neuron (afferent), spinal cord (integrator), α motor neuron

(efferent), and muscles (effector). Therefore, we stimulated the tibial nerve of the subject and

then measure the muscle contraction by the EMG. During the experiment, the 1a afferent neuron

received electrical stimulation from the receptor. Then, it will connect to the α motor neuron and

then to the receptor. According to the results in Table 1 of stimulus voltage responses, the

threshold of H-reflex is lower than that of M-wave; the threshold of H-reflex is 42.5V and the

threshold of M-wave is 58V. Based on the Rohkamm’s article (2003), this result is accepted.

Since the diameter of 1a afferent neuron is larger than that of α motor neuron, so the resistance of

1a afferent neuron is lower than that of α motor neuron. Therefore, lower stimulus voltage is

required for the stimulation of H-reflex. As we mentioned in the introduction, H-wave is

generated by the activation of 1a afferent neuron and the connection of the α motor neuron, but

M-wave is produced by directly activation of α motor neuron. Therefore, the stimulus voltage

that required for M-wave threshold is higher than that of H-wave. (Rohkamm, 2003)

Based on the graph of Stimulus voltage versus M-wave and H-wave amplitude, it shows

that the amplitude of M-wave and H-wave increases with the increases of stimulus voltage, but

the H-wave disappeared when the stimulus voltage increases continuously to 80V. This result is

supported because the higher the stimulus intensity is, the more the motor neuron is activated and

so the larger the amplitude is. Rohkamm (2003) mentioned that the H-wave disappeared as the

stimulus voltage increases continuously because of the collision of the reflex discharge with the

antidromic motor volley in the motor axons. (Rohkamm, 2003)

11  

The results from Table 4 and the graph of Stimulus frequency versus M-wave Amplitude

show the relationship between frequency and M-wave. Table 4 and Stimulus frequency versus

M-wave Amplitude graph showed that the frequency does not have any significant influence on

the M-wave amplitude. However, the Stimulus frequency versus M-wave Amplitude graph

showed some deviations because the inaccuracy of the experimental processes. Since the

electrode lead which connected on the subject did not hold in place during the experiment, so it

might affect the amplitude which showed on the EMG. Our experimental result of unchanged M-

wave with changing of frequency is supported by the article of Ishikawa, Porter, Stuart (1996). It

also mentioned that high frequency stimulation would depress the monosynaptic reflex because

the stimulus frequency in afferent neuron increases and the amount of motor neuron stayed at

refractory period would increase. This would cause the decrease of the amplitude of H-wave

because the motor neurons are unable to transducer the signal to the effector. (Ishikawa, Porter,

Stuart, 1996) In general, the change of frequency does not influence the amplitude of M-wave

because the generation of M-wave is produced by the direct activation of efferent neuron, but not

the stimulation input from the afferent. Unfortunately, our group did this part of the experiment

wrong. We used a wrong stimulus voltage, 80V, which has reached the H-wave abolished, so no

H-wave could be generated in the EMG recording. We could not prove if our data of H-wave

agree with the Ishikawa, Porter, Stuart’s study (1996) of the relationship between H-wave

amplitude and stimulus frequency.

In Part 2 of the experiment, we examined the saccadic eye movements of the vestibule-

ocular reflex (VOR) that caused by polysynaptic reflex. The VOR contains three major

components; the peripheral sensory apparatus including 3 semicircular canals and the otolith

organs, a central processing mechanism, and the eye muscles. The 3 semicircular canals are

12  

located in the ear at right angles with about 30° to each other. One canal is located in a plane and

the other two canals are in vertical planes. Also, it contains hair cells (mechanoreceptors) which

could sense the angular acceleration in order to detect the head rotation. Also, the otolith organs

could detect the linear acceleration of the head in order to sense the position of the head relative

to gravity. In Case 1 of the experiment, the perceived motion following with a spin with closed

eye is recorded. The result of this part is related to the mechanism of the semicircular canals and

the sensation of hair cells.

In Case 1, when the chair starts to spin in clockwise direction, the subject starts to

accelerate and rotate in clockwise direction. Then, the base of the hair cells would move in the

clockwise direction with acceleration. And the kinocilium and stereocilia would move in

anticlockwise direction. (Buttner, Straube, 2007) However, there is no perceived rotation at the

beginning of rotation because of the inertia of the fluid inside sensory apparatus. (Baker, Evinger,

McCrea, 1981) Our results on Table 5 showed that the perceived direction of rotation is “with

spin” which is not supported by the Baker, Evinger, McCrea’s study (1981). Also, our result

recorded during the middle of spin is “no rotation”; it is an unexpected perceived direction. In

general, the inertia of the fluid inside sensory apparatus has disappeared during the middle of

spin, so the subject should have the perceived motion of “with spin”, but not “no rotation”. This

error occurred because of observation errors or the subject controlled his eye movement

consciously. The perceived direction of rotation when the chair stopped is under our expectation

because the chair stopped which means the direction of rotation sensed by the hair cells is under

the condition of deceleration. Therefore, the perceived direction of rotation is opposite to the

spinning direction; it is the same as our results.

13  

In Case 2, the relationship between optokinectic system and moving visual fields is

performed. According to the study of Buttner and Straube (2007), optokinetic nystagmus is a

short latency and involuntary eye movement in response to large moving visual fields. Under

normal conditions, our eye and head would follow the small moving visual object. When the

head is fixed at a position, a large moving visual fields causes slow compensatory eye

movements. As the movement of visual fields continues, fast eye movement occurs which is

called saccades. The slow and fast eye movement is the response of nystagmus. (Buttner, Straube,

2007) Table 5 shows that the direction of fast eye movement is “with spin” and the slow eye

movement is “opposite to spin”. These results are under our expectation because the fast eye

movement is “with spin” when the rotation speed is slow.

In Case 3, the subject’s head tilted forward at 30° and rotated with very fast speed. When

subject’s head tilted forward for 30°, one of the semicircular canal located in a plane that is about

30° from horizontal brings into horizontal plane and the two other canals are in vertical plane.

Thus, the gravity acts on the otolithic membrane changes and there is a new force that displaces

the hairs to the side. In Table 5, the direction of fast eye movement is “with spin” and the

direction of slow eye movement is “opposite to spin”. It is an unexpected eye movement that the

fast eye movement is “with spin” when the rotation’s speed is fast.

In Case 4, the subject’s head lean over the left shoulder and rotated with very fast speed.

When subject’s head lean over the left shoulder, the orientation of the three semicircular canals

changed. It could change the gravity of otolithic membrane and the position of hairs cells. In

Table 5, the direction of fast eye movement is “Look up, opposite to spin” and the direction of

slow eye movement is “Look up, with spin”. It is under our expectation; the fast eye movement

14  

is “opposite to spin” when the rotation is fast. Also, the subject’s eye not only moves with spin or

opposite to spin, it also looks up because of the new orientation of the semicircular canals.

In conclusion, monosynaptic reflex and polysynaptic reflex has different reflex arcs.

Monosynaptic reflex

15  

References

Baker, R., Evinger, C. and McCrea, R. A. (1981), Some thoughts about the three neurons in the

vestibular ocular reflex. Annals of the New York Academy of Sciences.

Bautista, E., & Korber, J. Npb 101l systemic physiology lab manual. (pp. 19-29).

Buttner, U., & Straube, A. (2007). Neuro-ophthalmology neuronal control of eye movements.

(Vol. 40, pp. 35-51, 77).

Deseilligny, E. P., & Mazevet, D. (1999). The monosynaptic reflex: a tool to investigate motor.

Rohkamm, R. (2003). Color atlas of neurology. (2nd ed., p. 40).

Ishikawa, K., Ott, K., Porter, R. W., & Stuart, D. (1996). Low frequency depression of the h wave

in normal and spinal man.