Stimulus and Response
BSC 231: Presentation/Write-Up
Matthew D. Schaidle
April 26, 2008
Stimulus and Response; Reaction vs. Reflex (30-40 minute activity)*
*Adapted from Stimulus/Response Lesson Plan [http://ed.fnal.gov/lincon/w98/projects/vitalsigns/stim-response.html]
Objectives: This experiment is designed to teach the students the differences between
stimulus/responses and stimulus/reflexes. It also explains what neuronal reflex arcs and neuronal
reaction arcs are. It allows students to experiment with the effect of conscious decision making on
response time as well as the effect of practice on response time.
Rational: This experiment supports the standards 12.A.4b, 11.A.4b, and 11.A.4c. The experiment is also
a good supplement to the following topics: muscle movement, neurology, senses, stimulus, and cell
structure. It can be use as a bridge between neurology and the senses.
Overview:
Review Movement. Ask the students to review the systems in their bodies that come into play when
they move (Skeletal, joints, Muscles). When all of these systems work together to provide Movement, it
is called coordination.
Introduce Stimulus. Tell students that coordinated movements of the human body don’t happen by
themselves. Movements are directed by the Central Nervous System (CNS)—the brain, spinal column,
and nerves. The CNS gets information from the outside through special systems called senses (sight,
sound, touch, taste, and smell).
Introduction. We interact with out environments through a complex web of stimuli (from the
environment) and responses (to the environment). Our basic senses are our faculty to receive incoming
stimuli. The Central Nervous system (CNS) then interprets them into understandable messages that the
brain can use as a basis for choosing an appropriate response.
The actual work of interpreting and responding to the stimuli is all done by neurons (CNS cells). A
stimulus neuron sends a signal to the spinal cord or brain that a certain stimulus has occurred (light for
photoreceptors, vibrations striking the eardrum etc.). The brain then interprets the message [into sight
or a sound in the previous examples] and decides upon a course of action—to catch the falling cup or
dance to the rhythm of the music. Once the decision about a response has been made a response
neuron carries a signal back to the target organ.
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Material List.
For each pair of students:
* 1 plastic cup with hole
* 1 lid for the cup with hole
* 1 dowel, with cm dashes on it
* clothes pins (1 per pair)
* 2 student lab sheets for Stimulus/Response data
* Stop watch
* Reflex hammer (only one for the class if the teacher is going to demonstrate part 2)
Preparation. Before class the teacher should make 1cm dashes on each of the dowel rods and secure
them to a base (Bunsen burner stands work good for this). The teacher should also practice with the
reflex hammer so he/she can help the students to use them properly without hurting each other. Total
preparation time should be less than 15 minutes (all of which can be done the day in advance).
Special Safety Instructions:
Some Students should not be allowed to handle a hammer in class and as such the teacher should be
the one to demonstrate the reflex part of the experiment. The dowel rods can also be used by students
as weapons (they could poke an eye out!!!).
Experiment:
Part 1. Assembly of the falling cup device.
In Stimulus and Response one student will mark a location on the dowel rod with the clothing pin as the
start location for the top of the cup for the experiment. He/she will drop the plastic cup and use the
stop watch to measure how long the second student takes to catch the falling cup. The time of the first
few trials and last few trials will be recorded on the data table. The distance is to be measured by using
the cm dash marks on the dowel rod. This data will also be recorded in the data table. Once the first
student has done ten trials the two students will switch rolls and the second student will perform ten
trials. Once both students have had a turn; they will repeat the experiment using their other hand.
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Discussion Questions: How do we interact with our environment? What are some examples of stimuli
from the environment? What are some other ways that we could measure response efficiency to the
stimulus?
Between your right and left hands which one do you think will be the quicker of the two? What about
ambidextrous people? Your primary hand should be faster. Ambidextrous people still usually favor
(practice more) with one hand or the other so they should still have one faster hand.
How else, besides time and distance could we measure response time? Ability to remove hand from
underneath cup before being hit, lower the cup the faster response time.
Trial Number
Right/Left hand
Distance fell (cm)
Response time (s)
Right/Left hand
Distance fell (cm)
Response time (s)
1
2
3
8
9
10
(4pts for graph)
Trial Number
1
2
3
8
9
10
(4pts for graph)
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Discussion Questions: What was the stimulus for the experiment? What was the response? What was
your best time (write them on the board)? What might explain these individual differences? Is there a
limit to how efficient one can be with their response time? Why?
Questions. Why does the distance that the cup fell decrease as you performed more trials in the
experiment? (2pts) Training, repetitive use of neurons increases their efficiency (better response time).
Is there a statistical difference between your right and left hands? Why? (2pts) Yes, there should be.
Amount of use with each hand is different.
Are there any other ways that you could improve your response time? If yes what are they? (2pts) Yes.
Practice and concentration.
Part 2. Reflex Hammer.
For the second part two students will come up to the front of the class. One student should sit relaxed
with his/her legs off of the floor. The second student will strike the first student below the knee with
the reflex hammer and time (with the stop watch) how long it takes for the first student to react. Due to
the inherit danger of giving students a hammer the teacher may want to be the only one to use the
reflex hammer. In this case the teacher should demonstrate the activity to the class using two student
volunteers (one to time and the other to be the guinea pig).
The timer should strike the other student below the knee while he/she is relaxed. The timer should
start the stop watch when the knee is struck and stop it when there is movement of the leg.
Trial Number
Response time (s)
1
2
3
(2pts for graph)
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Discussion Questions: What was the stimulus for the experiment? What was the response? Do you think
that the response time would be different for different people? Why or why not? Why would automatic
responses be useful and make sense in an evolutionary light?
Questions. Which is faster, your response of catching the falling cup or responding to the reflex
hammer? Why might this be? (2pts) Reflex hammer is a reflex and does not involve the brain or any
cognitive processes which take time.
Are there any ways to improve your reflex time? If yes what are they? (2pts) No [Yes, proper
diet/nutrition and exercise will help keep the body working properly and improve the reflexes].
Extension to the experiment: Instead of catching the cup you could switch to seeing how low the cup
can be with the students still being able to remove their hand from underneath of it. Students could
then compare the response times (how low the cup can be) of different parts of their bodies and discuss
whey the differences occur.
References and extra sources:
Stimulus/Response Lesson Plan [http://ed.fnal.gov/lincon/w98/projects/vitalsigns/stim-response.html]
http://www.biologymad.com/NervousSystem/nervoussystemintro.htm
http://www.mpipf-muenchen.mpg.de/CA/RESEARCH/rr_kompatibel_e.html
http://www.biopac.com/SecondaryEducation.asp?Pid=4695
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Student Work Sheets:
____________________Name
Stimulus and Response; Reaction vs. Reflex
Introduction: We interact with out environments through a complex web of stimuli (from the
environment) and responses (to the environment). Our basic senses are our faculty to receive incoming
stimuli. The Central Nervous system (CNS) then interprets them into understandable messages that the
brain can use as a basis for choosing an appropriate response.
The actual work of interpreting and responding to the stimuli is all done by neurons (CNS cells). A
stimulus neuron sends a signal to the spinal cord or brain that a certain stimulus has occurred (light for
photoreceptors, vibrations striking the eardrum etc.). The brain then interprets the message [into sight
or a sound in the previous examples] and decides upon a course of action—to catch the falling cup or
dance to the rhythm of the music. One the decision about a response has been made a response
neuron carries that signal back to the target organ.
Experiment:
Part 1: Assembly of the falling cup device.
In Stimulus and Response one student will mark a location of the dowel rod with the clothing pin as the
start location for the top of the cup for the experiment. He/she will drop the plastic cup and use the
stop watch to measure how long the second student takes to catch the falling cup. The time of the first
few trials and last few trials will be recorded on the data table. The distance is to be measured by using
the cm dash marks on the dowel rod. This data will also be recorded in the data table. Once the first
student has done ten trials the two students will switch rolls and the second student will perform then
trials. One both students have had a turn; they will repeat the experiment using their left hands.
Trial Number
Right/Left hand
Distance fell (cm)
Response time (s)
1
2
3
8
9
10
8|Page
Trial Number
Right/Left hand
Distance fell (cm)
Response time (s)
1
2
3
8
9
10
(4pts for each graph)
Questions. Why does the distance that the cup fell decrease as you performed more trials in the
experiment? (2pts)
Is there a statistical difference between your right and left hands? Why? (2pts)
Are there any other ways that you could improve your response time? If yes what are they? (2pts)
Part 2: Reflex Hammer.
For the second part two students will come up to the front of the class. One student should sit relaxed
with his/her legs off of the floor. The second student will strike the first student below the knee with
the reflex hammer and time (with the stop watch) how long it takes for the first student to react. The
timer should strike the other student below the knee while he/she is relaxed. The timer should start the
stop watch when the knee is struck and stop it when there is movement of the leg.
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Trial Number
Response time (s)
1
2
3
(2pts for graph)
Questions. Which is faster, your response of catching the falling cup or responding to the reflex
hammer? Why might this be? (2pts)
Are there any ways to improve your reflex time? If yes what are they? (2pts)
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