Lab 10: Nervous System and Senses Worksheet (30 points)
Name:__________John Gibson_________________________
Lab Section, Day, Time:_____807, wednesday 1pm________________
Instructor/TA:_________George Gikas_____________________
(2 pts) In your own words, describe how the knee-jerk reflex works.
The patella has nerve sensors connecting to the spinal cord and synapses to 2 motor neurons. One is for extending the quadriceps with excitatory EPSP, and another is for stopping flexing the hamstring with inhibitory IPSP.
When the patella is struck, the sensor generates an action potential toward the synapse with the 2 motor neurons. The motor neuron body toward the quadriceps is given (through its dendrite) an action potential toward the quadriceps to extend the lower leg. In contrast, the dendrite of the neuron body toward flexing the hamstring is hyperpolarized. So, the lower leg extends and kicks up.
The IPSP of the hamstring can be modulated (reduced) by willpower from the brain with another synapse with an EPSP signal to reduce the hyperpolarization of the hamstring motor neuron, but not completely. The IPSP and EPSP sum determines whether an action potential will be fired. So, even with the brain power to try to stop the kick, when the patella strikes hard enough, and the IPSP trumps the EPSP on the hamstring that counters the kick, the lower leg still kicks just a bit.
(1 pt) Was your partner able to prevent it from happening while watching you strike the hammer? Describe how their response compared to when they were not looking.
When my partner was not looking, and I struck his patella while he was trying to hold back the kick, the resulting kick was smaller than when he was not trying to hold back.
My partner couldn’t completely stop the reflex kick even if he watched me strike his patella with the hammer, however the kick was much, much smaller than when he was looking.
(5 pts) Make a Column Graph in Excel showing the time to catch vs. the trial number or experiment for both you and your lab partner. Show each of the three tests (with all trials) on the same graph. Remember to include axis labels, a descriptive title and descriptive legend. The graph may directly compare the trials within each test or it may compare each test to the next (there are two ways to plot this data, examples will be provided in class).
Figure 1. Reaction Time In Various Setups
Legend: stu. 1 means student 1; stu. 2 means student 2; regular drop means dropping the ruler without other signals;
(2 pts) Interpret/compare the data from the initial ruler reaction time, to the second test (where the dropper said a word) to the third test when the dropper said a word and the subject had to make an association. Which test did you perform the best in? The worst? Provide an explanation for your results.
As shown in Figure 1, overall, both students performed best with shortest bars in the second test (word prompting while dropping). Overall, both students performed the worst with longest bars in the first test (dropping without any word prompt).
The dropping with a word prompt was best in generating multiple EPSP neuron signalings with dual sensory inputs so that the frequency of signalings was doubled, resulting in stronger and faster motor neuron firing and muscle contraction to catch the ruler faster.
Student 1 performed best on the second test. The worst for student 1 was the first test, dropping the ruler without a second neuronal path of sound prompt to the brain to increase the frequency of EPSP toward motor neurons.
Student 2 also performed best on the second test with the short reaction times of the dark orange bars for the same reason as student 1. The worst for student 2 was also the first test for the same reason as student 1.
(2 pts) Did your graph help you interpret these results? Would it have been easier to interpret if you had plotted the data differently?
Yes, Figure 1’s bar graph helps interpret the results. The bars are generally tallest with the first test and shortest with the second test. So, that implies that the regular dropping test had the worst-performing trials by both students.
If, hypothetically, plotting the 10 trials among two students together so that only one bar is taller than another bar for each setup test, it would make it easier to interpret.
An alternative plotting in Figure 2 with separate trials spread out allows comparing different trials more clearly. For example, occasionally (in trials number 1 and 2), the word association resulted in longer reaction times (light orange bars longer than blue bars) than without any word prompts because the student tried to give a verbal response to word association before catching the ruler. This is not obvious with Figure 1.
Figure 2. Reaction Time In Various Setups
Legend: stu. 1 means student 1; stu. 2 means student 2; regular drop means dropping the ruler without other signals;
(2 pts) How did your own results compare to your partner’s?
I am student 1 in the Figure 2. My blue bars (the first test) are not consistently taller than the orange bars (the third test); my partner’s green bars (the first test) are consistently taller than the cyan (the third test) bars.
My red bars (the second test) are consistently the shortest in all trials, the same as my partner's, who consistently produces the shortest dark orange bars (the second test).
However, the overal trends are the same between the 2 students. Both performed best in second test with word prompt; both performed worst in first test without any word prompt.
(1 pt) Who performed the activity first?
Student 2 first. My partner first.
(1 pt) Explain how this may have impacted the results.
The first student to perform the catching first test (dropping without word prompts) was unfamiliar with the setup with the subtle body movements of the student making the drops. This was evident in the extra tall green bars of Figure 2, performed by student 2, who performed first.
The second student (me) to perform the catching had a better performance because I learned from my own subtle body movement before dropping, and that gave me familiarity with the cues of a dropping events when I was performing the catchings, as evidenced by the blue bars that were shorter than the green bars and nearly as tall as the light orange bars for the first 2 trials.
However, the overall conclusion that the first test had the longest reaction time withstands even with the bias. So, the influence of familiarity was no significant.
(4 pts) Based on the distance between the two-point discriminator required to perceive two distinguished contact points, which area tested has the highest density of touch receptors? Which has the least? Explain.
The fingertip has the highest density of touch receptors. The two points can be distinguished between 0.2 and 0.3 cm. Humans use their fingers to manipulate objects, sometimes in the dark. So, being able to distinguish two points in the dark when setting traps to capture prey food items gave humans an evolutionary advantage and was selected for.
The outer shoulder has the least density of touch receptors. Both students cannot distinguish the two points at the maximum 1.5 cm of the measuring instrument. The outer shoulder is used primarily for motion anchoring for arms. It only needs to detect if an obstruction is there and avoid the obstruction, regardless of the shape and pointy points in contact with the outer shoulder skin. So, there is no advantage to selecting for extra neuron distribution to the skin at the outer shoulder.
(3 pts) How did your finger that had been in the 20oC water bath compare to that in the 44oC water bath when both were placed in the 33oC water bath? Did the temperature feel the same to both or different? Explain.
It felt different when both hands moved to the 33oC water bath. The hand initially in 20oC water bath now felt hot in the 33oC water bath; the hand initially in 44oC water bath now felt cold in the 33oC water bath.
The temperature is sensed by different sensors of different sensing ranges. The hand in the hot bath initially felt hot by the hot sensor covering the 44oC range. The neuron of that hot sensor adapted to the hot temperature after 1 minute and slowed or stopped firing the hot action potential to the brain. Then, when the hand is submerged in the 33oC water bath, only the cold sensors covering the 33oC range fire action potential to the brain, so the brain interprets it as cold.
On the other hand, the hand in the cold bath initially felt cold by the cold sensor covering the 20oC range. The neuron of that cold sensor adapted to the cold temperature after 1 minute and slowed or stopped firing the cold action potential to the brain. Then, when the hand is submerged in the 33oC water bath, only the hot sensors covering the 33oC range fire action potential to the brain, so the brain interprets it as hot.
(2 pts) After fixing your eyes on the white dot in the center of the peace symbol and then looking at the black dot, what did you see? Explain what is going on.
I saw a peace symbol with a white ring instead of a black ring, with a white fork instead of a black fork, and with a black center dot instead of wa hite center dot.
Human vision is achieved by image light forming on the retinal neurons. When staring at the black peace symbol, the retina neurons under the black image adapt to the black color and slow or stop firing the black action potential to the brain (The retina is one of the few unique neurons in humans that uses IPSP with Opsin G-protein as the signal when stimulated, instead of the more general EPSP. So, the black color, lacking light, indeed makes the neuron fire action potentials.), and the retina neurons under the white background image adapt to the white color. When moving the view to a blank white background (the black dot is just to keep the vision fixed, overall it is just a white background), the retina neurons initially under the black image does not fire black action potentials, and only have white sensing to the brain (due to the retina IPSP nature, lacking action potential firings is interpreted as white), so the brain interprets the white sense image as a white peace sign with white fork.
(2 pts) Describe how sound conduction through air compares with sound conduction through bone. Why are vibrations perceived longer through one medium than the other?
In the Rinne test, for a normal person, sound conduction through the air is sensed more strongly when placing the tuning fork near the auditory canal than through the bone when the tuning fork is placed on the mastoid process (bone). With conductive deafness, the sound conducted through the bone is louder than through the air. With sensory deafness, both conductions are equally suppressed.
Vibration perceived duration through a media can gague the medium’s conductivity because the tuning fork’s vibration strength diminishes over time. The longer lasting sound in a medium means the medium conducts better so that the weaker sound, after a longer duration, is delivered and sensed by the sensory neuron (in the cochlear) when otherwise conducted the sound would be lost in the medium and not be sensible.
The human hearing evolved to sense vibration of the air through tympanic membrane, incus, stapes, and cochlear hair, so air is a better conducting medium. When perceiving longer sound through air, the sound is diminished weaker and still perceivable when otherwise conducted through bone the sound would not be perceivable.
(2 pts) Fill in the table with your predictions on what each solution smelled like. How did your guesses compare to your partners? If you differed in any solutions, did you come to an agreement after revisiting them?
We are both men, and we each had 8 and 10 out 15 correct answers, but we could not agree on our disagreed items, especially Anise and pasta water. We didn’t have experience with Licorise, and pasta water smell was very faint.
(1 pt) Incorporation of what other sense(s) might have made this test easier? Why?
Color (visial sense) of the food items wight have made this test easier. The color of food items are part of the memory formation. I guessed the cranberry correctly partly because I got some cues from the dark pink color.
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