Neural Networks
An APS Workshop
& Classroom Unit
This unit updated June 2002
Marsha Lakes Matyas, Ph.D.
APS Education Office, [email protected]
Adapted from a unit developed by the Columbus, Ohio Frontiers in
Physiology Local Outreach Team, 1997, Bethesda, MD: American
Physiological Society.
Purpose:
The purpose of this learning cycle unit is to engage students in an exploration
of reflexes and reactions through inquiry-based activities.
Objectives
Students will:
• Make active observations about various reflexes and reactions and what the
difference is between the two;
• Connect their own experiences with reflexes and reactions to the observations
they make;
• Express their current understanding of reflexes and reactions to allow
identification and correction of possible misconceptions; and
• Develop skills in experimental design, methods, and data collections and
analysis.
Major concepts
• Reflexes are involuntary responses to stimulation from the environment.
• Reflexes require sensory neurons, interneurons, and motor neurons to the
effector system in which the reflex behavior is seen.
• Reflex behavior has three main properties:
o Speed of response
o Purposefulness
o Stereotyped nature
• Reactions are voluntary responses to stimulation from the environment.
• Reactions require neural networks in the brain that are involved with
conscious behavior.
• Reactions require more time than reflexes do.
• Reaction times may be decreased slightly by practice.
Page 1 of 87
Neural Networks Workshop Outline
Start
time
8:15
am
Total Segment
time
15
Jurassic
min Park clips
8:30
am
15
min
8:45
am
20
min
Overview
This “engage” activity is
designed to get students
thinking about reflexes
and reactions.
Procedure
1. Make sure students have
pen and paper to write down
observations. Ask students to
write down every reflex or
reaction they see in the film
clip.
2. Begin the movie from
Chapter 11 and continue
until the bathroom scene
without sound (muted).
3. Run it a second time with
sound.
Brainstorm
This segment generates
1. Divide an overhead
list
a list of observations
transparency into two
and hypotheses about
columns: “reflex” and
reflexes and reactions
“reaction.”
that will be addressed
2. Ask students to share their
throughout the unit.
observations from the clip
Make sure you do not
and indicate whether they
react to the
think it’s a reflex or reaction.
classifications, just write DO NOT define these terms or
them as they are given.
indicate whether they are
correct or incorrect.
Concept
Student groups generate 1. Review concept
map
a concept map of what
map/graphic organizer
development they “know” about
principles. Concepts should
reflexes and reactions.
be written on sticky notes
Use large Post-It paper
(they should use one color),
and have groups share
and write relationships on
their concept maps by
lines (use one color of pen or
posting them around the pencil).
room.
2. Use transparency to
provide a list of key words
that should be included in the
concept map.
3. Set Teach Timer for
students to view.
9:05
am
55
min
Open
inquiry
10:00
am
10
min
Break
10:10
am
20
min
“Explain”
phase
In this segment, the
PIRs will review the
key concepts for the
unit and will review
the brainstorming list
in a class
discussion…what was
correct? What was
not? What do we still
have questions about?
10:30
20
min
Review
your
concept
map and
correct in
another
color
In this segment,
students will review
their concept maps,
adding new material
and correcting
misconceptions
This segment engages
students in an open
inquiry about one of
two reflexes in humans
(pupillary or knee jerk).
1. Show procedure on overhead
projector and review. Allow 20
minutes for hypothesis and
experimental design
development and approval. Use
Teach Timer. Allow 35 minutes
for data collection, analysis, and
poster development. Use Teach
Timer.
2. IMPORTANT: Groups MUST
have approval from an
instructor before carrying out
their procedure!
3. Each group should create a
poster summarizing their
procedure and their findings. It
should include hypothesis,
methods, results table, and
conclusions. When completed
groups should display posters to
be reviewed by other groups as
they finish and during break.
Groups should post their
posters on the wall and review
the other groups’ findings.
1. Refer to the background
material at the front of the unit.
Use overhead transparency of
key concepts on reflexes and
reactions.
2. Ask each group how their
findings relate to the key
characteristics of a reflex.
3. Go back to the original
brainstorm list. Were we correct
in our original thoughts on
reflexes and reactions?
1. List on transparency the
things that should be added
(key concepts, experimental
results from their experiments
which is the bottom half of the
transparency used earlier).
2. They should use DIFFERENT
color of sticky note and
pen/pencil to distinguish from
original map. Have them share
their work as time allows.
10:50
am
40
min.
Assessment
via Webquest
Students will use the
Webquest to apply what
they have learned about
reflexes and reactions,
along with info on the
effects of drug use on
physiology and health,
to write a persuasive
email to a friend. DO
NOT have them
complete the website
evaluation portion. Use
20-25 min. for activity
and 10-15 min. for peer
grading using rubric in
lesson.
11:30
pm
20
min
Wrap up
activities and
presentations
followed by
the
debriefing
The instructors will use Use debriefing sheet and
this time to finish
follow debriefing procedure.
presentations and to tie
the unit together. Follow
with a discussion of how
Six Stars are integrated
as well as possible
adaptations for different
classroom/course
needs.
There are three different
ways to do the Webquest:
1. At the APS website,
2. Using printouts of the web
sites, or
3. At the APS Blackboard site
(“The Choice is Yours”).
Groups should do the
Webquest as written. They
can pick which email they
want to respond to, but
should read 1-2 websites for
information to use in
preparing their response.
Print out responses and
display alongside posters.
Neural Networks Workshop Materials List
Activity Handouts (25 copies)
• Page 13 from Neural Networks booklet
• Page 15 from Neural Networks booklet
Unit Handouts (40 copies – three hole, stapled)
• Full teaching packet:
o Cover Sheet
o Purpose/Objectives/Concepts
o Workshop Outline
o Key words transparency master
o Debriefing Sheet
• WebQuest printout & Internet pages packet
• Neural Networks Unit booklet
Transparencies
• List of key words
• Procedure for Module One
• Debriefing sheet
• Page two from Neural Networks unit
Technology/AV
• Jurassic Park tape
• Video player
• Teach Timer
• Extra batteries for Teach Timer
• Overhead projector, blank transparencies & overhead transparency pens
• Internet access, Project WISE Usernames & passwords
Materials (for six groups of three-four persons)
Each group should have:
• Blank white paper
• Table basket supplies: pens, sticky notes in multiple colors, colored pencils,
colored markers
• Large Post-It poster sheets
• Percussion mallet
• Penlight
• Timer
• Graph paper
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Neural Networks
Pre-unit keywords
Reflex
Reaction
Examples
Voluntary response
Involuntary response
Nervous system
Post-unit keywords
Reflex
Reaction
Examples
Voluntary response
Involuntary response
Nervous system
Neurons
Sensory neurons
Interneurons
Motor neurons
Speed of response
Purposefulness
Stereotyped nature
Conscious behavior
Reaction time
Effector systems
Stretch
Knee jerk
Pupillary
Transparency Master
Page 66of 87
APS Lab/Lesson Debriefing
Integrating Inquiry, Equity, and Technology
Inquiry:
This lesson includes an open inquiry activity in the Engage section (experiment on knee
jerk/pupillary reflex). It fosters skills in:
• Developing questions (brainstorm list, concept map, open inquiry hypothesis
development, Explain Phase: Class Discussion),
• Observation (Engage activity: Jurassic Park, Explore experiment),
• Information and data analysis (Engage activity: Jurassic Park, Explore experiment,
and Presentation), and
• Presentations (Presentation).
Note: The Elaborate and Evaluate phases of this Learning Cycle unit further expand on
these skills. We will not be doing these phases today, but they build on the components
that we are doing today.
Equity:
This lesson includes a variety of modalities for learning, including
• Tactile (hands-on experiments);
• Visual (observations, presentations, web review);
• Auditory (discussion, presentations); and
• Written (concept maps, observation notes, presentations, web notes).
It also can include cultural/local connections since many students are involved in sports
and activities that require quick reactions and reflexes. Also, the issues of drug use and its
effects on human physiology are applicable to all students.
Technology:
The activity uses basic audiovisuals for the Engage activity (Jurassic Park video) and
classroom discussion (overhead projector). The web is integrated via a WebQuest, used for
part of the unit assessment. Further technology integration possibilities: 1) use of digital
camera to record reflexes; 2) student presentations could utilize transparencies, powerpoint
presentations, web pages, WISE posters, etc. 3) A video on reflexes, reactions, and the
nervous system also might be used.
Possible Extensions:
• Additional experiments to follow up on questions raised
• Schedule a classroom visit with neurologist or physiologist. An exercise physiologist
could talk about how practice improves reaction times.
• Explore the physiology of the nervous system and diseases that affect it such as
multiple sclerosis, Parkinson’s disease, and Alzheimer’s disease.
Adaptations for Your Classroom:
• An alternative “Engage” activity could be a video on the nervous system, including a
review of reflexes. If so, be sure to have students take notes or discuss the video
afterwards.
• Do concept map as class discussion, homework, or as final assessment.
• Do the WebQuest as homework.
• Let students find credible sources on the web or in the media center to address the
question raised by their “friend.”
• In Mission 2, assign different questions to specific lab groups to test.
Page 77of 87
•
Do a lab report instead of presentation.
PEDAGOGY EMPLOYED IN THIS LESSON
Teaching Strategies
Broad Teaching Strategies
Active learning/discovery learning
‰ Bicultural/bilingual education
Cooperative learning/small group
instruction
Critical analysis/Critical thinking
Hands-on learning
Inquiry-based learning
‰ Large-group instruction
‰ Parent involvement
Student-centered instruction
Teacher-centered instruction/traditional
instruction
‰ Tutorial or self-directed instruction
Use of Instructional technology
Computer-assisted learning
Multimedia/audiovisual instruction
‰ Other instructional technology use
Additional Teaching Strategies
‰ Block time teaching
‰ Case-based instruction/Case study
approach
Class/group discussion
Data analysis, collection, interpretation
‰ Demonstrations
‰ Field laboratory experience/Field trips
Hypothesis testing
‰ Independent study
Laboratory experiment
‰ Learning centers
Learning cycles
‰ Peer teaching
‰ Problem sets/word problems
Problem-based learning
Assessment
Authentic & Alternative Assessment
‰ Peer evaluation
Performance-based assessment
Portfolios
‰ Self-evaluation
Tests & Testing
‰ Cognitive tests
‰ Computer-assisted testing
‰ Essay tests
Group testing
‰ Multiple-choice test
‰ Norm referenced tests
‰ Objective referenced tests
‰ Open book tests
‰ Standardized tests
‰ Testing techniques
‰ Timed-tests
‰ True-false tests
‰ Verbal tests
Other pedagogies
‰ _________________________
‰ _________________________
‰ ________________________
Notes
Page 88of 87
National Science Education Standards Addressed in this Lesson
K-12:
Unifying Concepts and Processes:
Systems, order, and organization
Evidence, models, and explanation
Change, constancy, and measurement
‰ Evolution and equilibrium
Form and function
Grades 9-12
Grades 5-8
Science as Inquiry:
Abilities necessary to do scientific inquiry
Understandings about scientific inquiry
Physical Science:
‰ Properties and changes of properties in matter
‰ Motions and forces
‰ Transfer of energy
Life Science:
Structure and function in living systems
‰ Reproduction and heredity
Regulation and behavior
‰ Populations and ecosystems
Diversity and adaptations of organisms
Earth and Space Science:
‰ Structure of the earth system
‰ Earth’s history
‰ Earth in the solar system
Science and Technology:
‰ Abilities of technological design
‰ Understanding about science and technology
Science as Inquiry:
Abilities necessary to do scientific inquiry
Understandings about scientific inquiry
Physical Science:
‰ Structure of atoms
‰ Structure and properties of matter
‰ Chemical reactions
‰ Motions and forces
‰ Conservation of energy and increase in disorder
‰ Interactions of energy and matter
Life Science:
The cell
‰ Molecular basis of heredity
‰ Biological evolution
‰ Interdependence of organisms
Matter, energy, and organization in living systems
Behavior of organisms
Earth and Space Science:
‰ Energy in the earth system
‰ Geochemical cycles
‰ Origin and evolution of the earth system
‰ Origin and evolution of the universe
Science in Personal and Social Perspectives:
Personal health
‰ Populations, resources, and environments
‰ Natural hazards
Risks and benefits
‰ Science and technology in society
History and Nature of Science:
‰ Science as a human endeavor
‰ Nature of science
‰ History of science
Science and Technology:
‰ Abilities of technological design
‰ Understanding about science and technology
Science in Personal and Social Perspectives:
Personal and community health
‰ Population growth
‰ Natural resources
‰ Environmental quality
Natural and human-induced hazards
‰ Sci. & tech. in local, natl. & global challenges
History and Nature of Science:
‰ Science as a human endeavor
‰ Nature of scientific knowledge
‰ Historical perspective
Page 99of 87
NEURAL
NETWORKS
MIDDLE SCHOOL leveL
The American Physiological Society
DEVELOPED BY The COLUMBUS, OH
LOCAL OUTREACH TEAM
Page 10 of 87
This classroom unit was developed as part of
the American Physiological Society’s
Frontiers in Physiology project
by a Local Outreach Team
of physiologists and middle/high school faculty
from the Columbus, OH area.
Columbus, OH Local OUTREACH Team
Kris Ledford
Monroe Traditional Middle School
LOT Team Leader:
Jack Wood
Ohio State University
Gloria C. Letts
Columbus Public Schools
Neil Baker
Project Discovery
Mary Lightbody
Columbus Public Schools
Constance Barsky
Project Discovery
Robert L. Stephens
Ohio State University
Michael E. Beeth
Ohio State University
Patrick E. Ward
Ohio State University
Jack A. Boulant
Ohio State University
Mae J. Welch
Champion Middle School
Jean-Pierre L. Dujardin
Ohio State University
Lynn Elfner
Ohio Academy of Sciences
Edited By:
Marsha Lakes Matyas
The American Physiological Society
© 1997 — The American Physiological Society.
Permission to reproduce the information in this publication is granted for classroom, home,
or workshop use only. Appropriate citation must be included. For all other purposes, request
permission from the APS Education Office at (301) 634-7132 or [email protected].
The Local Outreach Team component of the Frontiers in Physiology project is supported by grants
from the National Science Foundation and the National Institutes of Health. Any interpretations and
conclusions in this publication are those of the authors and do not necessarily represent the views of
the National Science Foundation, the National Institutes of Health, or the American Physiological Society.
Page 11 of 87
Neural Networks
TEACHER’S GUIDE
Introduction
This unit covers aspects of neurophysiology and neural responses that are important to the functioning of many body
systems. It is designed to provide students with a scientific basis for understanding “reflexes,” especially why reflexes
are special types of responses and how reflexes can/cannot be modified. The unit can be used as an integrative review of
these topics, or selected activities can be used to introduce some of the topics. It was designed by a team of middle
school teachers and research physiologists to be useful for “Biology” and “Life Sciences” classes. It can serve as an
introduction for basic understanding of the nervous system.
The unit utilizes the Learning Cycle approach (Karpus & Thier, 1967; Lawson, 1988), where various modules can be
used to engage students in thinking about the topic(s) (Module #1); offer them opportunities to explore via hands-on and
inquiry approach activities (Module #2); explain their findings and how they relate to the concepts included in the unit
(Module #3); elaborate on the concepts (Modules #4 and 5); and evaluate students’ understanding of the unit concepts
via authentic assessment (Module #6). The unit also makes use of concept mapping and inquiry approach activities. The
relationship of each activity to both content and pedagogy standards, as described by the National Science Education
Standards, is outlined in the table on page 2.
The modules are designed to teach the students general physiological principles that are based on physical and
biochemical principles. An important educational objective of the unit is that students should be able to relate what they
learn about the nervous system to its many important interactions with other systems in the body.
Suggestions for Teachers are provided for each module; these contain information necessary to teach the units. The
Background Information section is designed to supplement the information available in any good physiology or biology
textbook used in middle or high school. Boldfaced terms typically can be found in the index of your textbook or other
references.
This unit was developed as part of an American Physiological Society program designed to form partnerships between
scientists and teachers. Therefore, the units also can be used in consultation with research scientists, such as a university
faculty member or pharmaceutical researcher. The Education Officer of the American Physiological Society can assist
you in making connections with physiologists in your area (301-634-7132; [email protected]).
References
Karplus, R. & Thier, H.D. (1967). A new look at elementary school science. Chicago: Rand McNally.
Lawson, A.E. (1988). A better way to teach biology. American Biology Teacher, 50 (5), p. 266-289.
Background Information — Neural Networks
Why are neural networks important?
Neural networks are responsible for the basic functions of our nervous system. They determine how we behave as individuals. Our emotions experienced as fear, anger, and what we enjoy in life come from neural networks in the brain.
Even our ability to think and store memories depends on neural networks. Neural networks in the brain and spinal cord
program all our movements including how fast we can type on a computer keyboard to how well we play sports. Our
ability to see or hear is disturbed if something happens to the neural networks for vision or hearing in the brain. Neural
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1
Neural Networks
Relationship of Neural Networks Unit to
National Science Education Standards for Content and Teaching
Selected Content Standards
Neural Networks
Grades 5-8
Structure and function in living systems
*
Regulation and behavior
*
Personal health
*
Risks and benefits
History and nature of science
*
Grades 9-12
Matter, energy, and organization of living systems
*
Behavior (responses to stimuli)
*
Personal and community health
*
History and nature of science
*
Pedagogy
Unit Activities
Hands-On
#1: What Can You Observe About Reflexes and
Reactions?
#2: What Do You Know About Reflexes?
Inquiry
Authentic
*
*
*
#3: Reflexes and Reactions — An Overview
*
#4: Is Heart Rate Constant?
*
*
*
#5: Effects of External Stimuli on Reaction Times
*
*
*
#6: What Do You Know Now About Reflexes and
Reactions?
*
2
*
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Neural Networks
networks also control important functions of our bodies. Keeping a constant body temperature and blood pressure are
examples where neural networks operate automatically to make our bodies work without us knowing what the networks
are doing. These are called autonomic functions of neural networks because they are automatic and occur continuously
without us being aware of them.
Who should know about neural networks?
Workers in areas dealing with people’s health must understand neural networks. Doctors and nurses must understand
them in order to take care of their patients. Paramedics (firefighters and ambulance teams) need the knowledge to make
quick decisions for saving the lives of accident victims. Doctor’s assistants in many different areas of special medical
treatment use their understanding of the nervous system to do their jobs. Scientists must know what is already known in
order to design studies that will produce new knowledge of how the nervous system works and new ways to treat
diseases of the nervous system. Finally, it is important for each of us to understand how our own bodies work.
What is a neural network?
Simply, neural networks are groups of select neurons that are connected with one another. Neural networks are
functional circuits in the brain that process information and create useful activities by sending outputs to the body.
Some neurons (nerve cells) transmit this neural network information over a distance much the same as information is
transmitted over a telephone line. Neurons have a cell body and a fiber that carries the information (Figure 1, page 4).
Electrical impulses, called action potentials, are used by neurons to transmit information over the distance from the cell
body to the end of the fiber. Nerve fibers from one neuron in a network are connected to others in the network by
synapses, the tiny gaps between the end of one neuron and the beginning of another. The fibers do not make direct
contact with the other neuron at a synapse. Instead, each impulse triggers release of a chemical substance from the end
of the fiber. The chemical, called a neurotransmitter, then carries the information across the synaptic space on to the
next neuron. Neurons make and release over 50 different kinds of neurotransmitters. Some neurotransmitters, called
excitatory neurotransmitters, start a new electrical impulse in the neuron at the other side of the synapse. Other
neurotransmitters prevent impulses from occurring in the neuron at the other side of the synapse. These are called
inhibitory neurotransmitters.
Large numbers of neurons are interconnected by synapses to form a network. Depending on the job to be done, a
network can have a few hundred to more than a million neurons. Each neuron in the network may receive a synaptic
input from one hundred or more other neurons in the network. Moreover, one network may have connections for sharing
information with other networks. For example, neural networks in the brain share information with networks in the
spinal cord. Neural networks are complex and much remains to be learned before we fully understand how they work.
This is why neuroscientists in universities, industry, and government continue with research on the nervous system.
Sensory neurons
Sensory neurons, interneurons, and motor neurons are important parts of neural networks. Sensory neurons, interneurons, and motor neurons are connected to perform the control for most of the things we do (Figure 2, page 4). Most of
the time, this is control of the movement of our muscles and of the function of body organs, such as the heart and stomach. The job of sensory neurons is to detect what is happening outside and inside the body and report the information to
networks of interneurons. Sensory neurons have a specialized receptor region at some point on the body where sensation
occurs, a cell body, and a fiber that transmits information in the form of nerve impulses to the brain for processing.
There are sensory neurons that detect changes in mechanical forces, light, sound, and temperature for the body. Sensory
neurons in the skin detect touch. Others detect when something may be happening that could damage the skin and body.
Without light detectors, we could not see. Without sound detectors we could not hear. Without temperature detectors we
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3
Neural Networks
Figure 1
Neuron
Cell Body
Synaptic
Gap
Synaptic
Transmission
Nerve Fiber
Nerve Fiber
Synaptic
Input
Neuron
Cell Body
Two major parts of a neuron are the cell body and a nerve fiber that may extend over long distances. Information in
the form of nerve impulses is transmitted by nerve fibers. Nerve fibers meet other neurons in neural networks at
synapses. Information is transmitted across the synaptic gap by a chemical signal (neurotransmitter substance) released
at the terminals of nerve fibers. Arrival of each nerve impulse at the terminal of a nerve fiber releases a burst of
neurotransmitter substance that then excites or inhibits the next neuron. This is rather like a runner in a relay race
handing off the baton (neurotransmitter) to the next runner.
Figure 2
Cross-section of the spinal cord to illustrate
the connections of a sensory neuron,
interneuron, and motor neuron in a neural
network. Each neuron in the illustration
represents a pool of several hundred neurons
in the actual network. The cell bodies of
sensory neurons are found outside the gray
matter of the spinal cord. Cell bodies of
interneurons and motor neurons are within
the gray matter. In this example, sensory
fibers transmit information of muscle
contraction to interneurons for processing.
After processing, information for control of
the muscle is transmitted by motor neurons.
The muscle in this example is the effector.
4
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could not know if it was warm or cold and our nervous system could not adjust our bodies to changes in outside
temperatures. Without touch receptors, we could not feel the wind blowing on our skin or when someone touches us.
Without damage receptors, we could burn our skin and not know it.
Interneurons
The “inter” of interneurons comes from the position of this kind of neuron between sensory and motor neurons in a
neural network. Interneurons are connected one with another by synaptic connections to form networks that receive
information from sensory neurons (Figure 2). The interneuronal networks have two main jobs. One job is to receive
information about the outside environment or inside state of the body from sensory neurons. The other is to activate
motor neurons. Interneuronal networks interpret and make sense of the streams of information coming from sensory
neurons. This function is sometimes called information processing.
Motor neurons
Motor neurons are the pathways for transfer of information from interneuronal networks to effector systems. Effector
systems are parts of our bodies like muscles, glands, and internal organs. Nerve fibers of motor neurons can be very
long. Those extending from the neural networks in the spinal cord to muscles in the lower leg may be three or more feet
in length. The interneuronal networks tell the motor neurons when to “fire” and transmit the signal to the effector cell. If
the effector is a muscle cell, the signal makes the muscle contract and move the body. Patterns of movement like
shooting a basketball require precise timing of the contraction of different groups of muscles. The timing of movements
are organized by interneuronal networks and the signals are then sent over motor neurons to the different muscles. Some
of the networks for complex movements, like shooting a basketball or playing the piano, include components in both the
brain and spinal cord. Some less complex movements, called spinal reflexes, are determined by networks in the spinal
cord without involvement of networks in the brain. Other kinds of reflexes, such as the response of the pupil in the eye
to light, involve neural networks in the brain.
Reflexes
Local reflex circuits are organized at various locations in the nervous system. The constriction of the pupil of the eye in
a bright light is an example of a local reflex response. Reflexes require sensory neurons, interneurons and motor neurons
to the effector system in which the reflex behavior is seen. In this exercise, we will study tendon reflexes in muscles as
the effector, and light reflexes in which the pupil of the eye is the effector.
Reflexes are part of our day-to-day experience of living. For example, if someone accidentally touches the hot burner of
a cook stove, the hand is immediately and rapidly withdrawn from the source of danger. This is a reflex that includes
the added behavior of extending the arm and leg on the opposite side of the body to provide balance as the other arm is
bent to withdraw the hand from the hot surface. If you have had this experience, you will recall that the withdrawal of
the hand from the hot surface and the extension of the arm and leg on the opposite side took place before you realized
that the hand had been in danger of injury and the source of the danger. Two main networks were involved in the
experience. One in the spinal cord processed the information from sensory neurons for the hand and organized
withdrawal from the source of injury while the information from the same neurons was being transmitted to processing
networks in the brain. Networks in the brain determined what had happened and brought about conscious awareness of
the event.
Reflex behavior has three main properties. The first is speed of response. In the above example, reflex behavior
organized by networks in the spinal cord removed the hand from danger during the longer time required for the
information to reach the brain networks for processing to the level of consciousness.
The second property of reflex behavior is purposefulness. Reflex responses generally accomplish a useful purpose like
withdrawing the hand from danger in the above example. An experiment performed on a frog is often used to show the
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Neural Networks
purposeful nature of reflexes. The experiment begins by an operation that severs the frog’s brain from the spinal cord.
This is called a spinal animal and is the same situation as seen in a paraplegic or quadriplegic human. The frog is
suspended so the lower legs hang free. When a small piece of paper soaked with vinegar is placed on the thigh, the frog
raises its foot, locates the source of irritation with the foot and kicks it away. If the foot on the irritated leg is held so the
frog cannot move that leg, the opposite leg will be used to kick away the paper irritant. Watching this, you may feel that
the spinal cord knows what it is doing as if it has consciousness. If fact, the behavior is a purposeful reflex organized by
a neural network in the spinal cord apart from the brain.
The third property of locally organized reflexes is their stereotyped nature. This means that a reflex response
behaves in the same way each time it is evoked. Reflex responses are, therefore, predictable. In the above examples, the
withdrawal reflex in humans is always the same. The hand is always withdrawn from the source of irritation — never
extended toward the danger. Likewise, in the frog experiment the leg always moves in the same way to remove the
source of irritation.
Reactions
Reactions are voluntary responses to stimulation from the environment. Unlike reflexes, which are involuntary, reactions require neural networks in the brain that are involved with conscious behavior. Reactions require more time for a
response due to the more complex processing of information in the brain networks. Reaction times are defined as the
length of time required for a voluntarily response to the stimulation of sensory neurons. The average reaction time for
humans to a visual stimulus is about 0.25 second; for hearing, 0.17 second; for touch about 0.15 second.
Reaction times vary among individuals. Some persons react faster than others to a stimulus. Star athletes usually have
faster reaction times than non-athletes. Reaction times may be decreased slightly by practice. They are increased when
you are tired, emotionally upset, or under the influence of alcohol. The length of an individual’s reaction time is of great
importance in many situations such as driving a car and the tasks required by many industrial jobs.
Experiments with reflexes
Tendon reflexes in humans are examples of reflexes readily demonstrated in the classroom. The knee jerk in response to
tapping the patellar tendon is an example of a tendon reflex. Extension of the foot (ankle jerk) evoked by tapping the
Achilles tendon is another example. These are also called stretch reflexes because they reflect the action of neural
networks in the spinal cord to counteract the effects of stretch on the muscle.
Many stretch reflexes automatically maintain tone in the muscle that offsets the pull of gravity. The fibers of sensory
neurons for these reflexes are connected to structures in the muscle called “spindles” (Figure 3). When the muscle is
stretched, the muscle spindles initiate nerve impulses in the sensory fibers. The impulses are then conducted from the
muscle to the networks of interneurons where they are processed. The more the muscle spindles are stretched, the more
impulses are fired per second. Frequency of impulses then becomes the sensory code for the degree of stretch of the
whole muscle. A faster frequency is interpreted by the interneuronal networks as lengthening of the muscle. The
interneuronal networks compensate by activating motor neurons to make the muscle contract and shorten to the desired
length. This reflex operates continuously to keep the muscle at the needed length for it to do its job in supporting the
body.
Figure 4 illustrates the knee jerk reflex. The patellar tendon connects the muscle of the front of the thigh to the lower
leg. This is called an extensor muscle because it extends the lower leg when it contracts. A tap on the patellar tendon
produces a quick stretch of this muscle. This also stretches the spindles in the same muscle which, in turn, fire impulses
at a higher frequency. The increased frequency of impulses reaches the interneuronal networks by way of the sensory
neurons. The interneuronal networks interpret the information as a rapid increase in length of the muscle and compensate
by sending signals that contract the muscle. Contraction is seen as rapid extension (forward jerk) of the lower leg. The
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Figure 3
Skeletal muscles have sensory structures that
detect the length of the muscle. These are called
muscle spindles. They detect and signal the
spinal cord when the muscle is stretched and the
length increases. When the length of the muscle
is increased, the muscle spindles send impulses
along sensory fibers into the spinal cord. The
frequency (number per second) of impulses
increases as the length increases. Consequently,
the frequency of firing represents the information code for the moment-to-moment length of
the muscle. In this example, the sensory neuron
connects directly to the muscle’s motor neuron.
This allows for rapid activation of contraction of
the muscle in response to a stretch.
Figure 4
Diagram of the neural connections for the
“knee jerk” reflex. A sharp tap on the patellar tendon stretches the extensor muscles for
the lower leg. Stretch of the muscle also
stretches the sensory detectors within the
muscle. Stretch of the detectors (muscle
spindles) fires impulses in the sensory fibers
to the spinal cord. The sensory fibers make
a direct synapse with the motor neurons to
the same extensor muscle. Release of a neurotransmitter at the terminal of the
sensory neuron excites the motor neuron
and impulses are transmitted to the extensor
muscle. This triggers contraction of the
extensor muscle that is seen as extension of
the lower leg.
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reflex time is that required for impulses to travel into the spinal cord from the muscle spindles, be processed, and be
returned in motor neurons to contract the muscle.
Because of the complexity of the nervous system and the large number of stimuli constantly impinging on the body, the
activity of neural networks in one part of the nervous system often modifies another. This is the case for reflexes, such
as the knee jerk. The magnitude of the knee jerk is greater when the contractile tone in the extensor muscle is higher.
Conditions that increase muscle tone, such as mental excitement increase the extent of the knee jerk. A decrease in
mental excitement (sleep, a restful state, etc.) is associated with a decrease in the reflex. The strength of the “tap”
required to evoke the reflex is higher after physical or mental work. The knee jerk may be reinforced by a second
stimulus, such as a loud noise when the noise is appropriately timed with respect to the tapping of the tendon.
Pupillary reflexes
Pupillary reflexes affect the size of the pupil of the eye. By changing the size of the pupil, reflex responses control how
much light enters the eye. A special kind of muscle, called the pupillary muscle, surrounds the pupil. The pupillary
muscle is the effector in pupillary reflexes. When the pupillary muscle contracts, it reduces the size of the pupil and the
amount of light entering the eye. Impulses in motor neurons to the muscle produce the contraction.
The pupillary light reflex is seen readily by observing the pupil of an individual when the light from a pen light is
directed to the eye. Another term for the constriction of the pupil is photopupil reflex. The “purpose” of the reflex is to
shield the eye from too great and sudden light exposure. This protects the sensitive light detecting parts of the eye called
the retina.
The neural network for a pupillary reflex consists of a light detector (sensory neuron), interneurons and motor neurons
back to the pupillary muscle. Some parts of the neural network are located in or near the eye itself and others are found
in the mid-regions of the brain (Figures 5 and 6).
There are three kinds of pupillary reflexes. One called the direct light reflex consists of constriction of the pupil of the
same eye when light is directed into the eye. The second is called the consensual light reflex. It consists of constriction
of the pupil of the opposite eye from one in which light is directed. The consensual reflex is demonstrated by shining
light into one eye and observing constriction of the pupil in the opposite eye that receives no light stimulus. The third
kind of pupillary reflex is called the accommodation reflex. This is observed as constriction of the pupil as an object is
brought progressively closer to the eye.
Pupillary reflexes are important indicators of the state of the brain. Because they require neural networks in the brain,
damage to parts of the brain containing the networks may be seen as a malfunction of the reflex. Shining a penlight into
the eyes of an accident victim provides emergency personnel with a quick assessment of potential head trauma.
For the practicing anesthesiologist, pupillary size can be an indicator of depth of general anesthesia during surgical
procedures. In Stages I and II of anesthesia, the anesthesiologist knows that the pupils are dilated due to emotional
stress. In Stage III anesthesia, which is surgical anesthesia, the pupil constricts. In Stage IV, which is paralysis of the
neural networks in the brain, the pupils become dilated.
Background Information — Autonomic Nervous System
What is the autonomic nervous system?
There is a part of your nervous system that is called the autonomic nervous system. “Autonomic” means that most of the
time it acts all by itself without you consciously trying to control it.
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Figure 5
Constriction and dilation of the pupil is
determined by two groups of muscles. The
dilator muscle enlarges the radius of the pupil
(mydriasis) when it contracts. The constrictor
muscle reduces the size of the pupil when it
contracts (miosis). Nerves that release the
neurotransmitter substance, acetylcholine,
evoke contraction of the constrictor muscle.
Nerves that release the neurotransmitter,
norepinephrine, evoke contraction of the dilator
muscle. There are three kinds of pupillary
muscle reflexes: (a) direct; (b) consensual;
and (c) accommodation. The direct light
reflex is the case where bright light evokes
pupillary constriction in the same eye (a). The
consensual light reflex is the case where bright
light in one eye evokes pupillary constriction
in both eyes (b). The accommodation reflex is
pupillary constriction that occurs as a distant
object 1 meter or less from the eye is moved
progressively closer to the eye (c).
light
light
direct light
response
a
consensual light
response
convergence response
b
c
Figure 6
pupil
oculomotor nucleus
ciliary (Edinger-Westphal
ganglion
accommodation
pretectal
visual
constrictor
LIGHT
pupil
dilator
superior
cervical ganglion
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ciliospinal
center
autonomic
regions in
brainstem
Neural networks for pupillary reflexes are interconnected
inside and outside the brain. The retina of the eye detects
changes in light intensity and focus. The retina codes the
changes as neural signals that are transmitted to the
pretectal region of the brain for processing. If the
processing networks in the tectal region determine to
activate constriction of the pupil, information is
transmitted to the region of the brain stem called the
oculomotor nucleus. From the oculomotor nucleus,
signals are transmitted to a network of neurons in the
ciliary ganglion located at the back of the eye socket.
Nerve projections from the ciliary ganglion to the
constrictor muscle evoke pupillary constriction. If the
processing networks in the tectal region determine to
activate dilation of the pupil, information is transmitted
to the spinal cord, down the cord to the neck region and
then out of the cord to a group of neurons in the superior
cervical ganglion. Nerve projections from the superior
cervical ganglion to the dilator muscle evoke contraction
and increased pupil size.
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As an example, the autonomic nervous system determines how fast your heart beats (this is called your heart rate). If
you would measure your heart rate at different times during the day, you would get many different values. At times your
heart rate is higher and at other times it is lower. You may have noticed, for example, that your heart beats faster after
you have just walked from one classroom to another, especially if you had to walk up some steps. You don’t have to
think about raising your heart rate when you climb steps; the autonomic nervous system takes care of that.
There are control centers in the central nervous system (brain and spinal cord) that determine how fast the heart should
beat and there are neural connections between these areas and the heart. It is along these connections that messages are
sent to speed up or slow down the heart. These neural connections are part of the autonomic nervous system.
Not only the heart but all of the organs and blood vessels in the body receive messages from the brain and the spinal
cord along neural connections that are part of the autonomic nervous system. After you eat a meal, for example, your
stomach receives messages to work harder so that the food will be digested.
Autonomic reflexes
How high your heart rate is at any particular time depends on a lot of factors, for example how much oxygen your body
needs or how nervous or how calm you are. Your heart rate also plays a role in regulating your blood pressure. Your
blood pressure is very important. When you visit a doctor, she or her nurse will almost always measure your blood
pressure to make sure it is not too low or too high. It is very important that your blood pressure is close to normal. The
autonomic nervous system helps control your blood pressure. If your blood pressure would suddenly fall a bit, your heart
rate will increase and the contraction of your heart will become stronger so that your heart pumps out more blood and
increases your blood pressure until it is normal again. What we just described is an example of an autonomic reflex. It is
called the baroreceptor reflex.
How does the baroreceptor reflex work? Since it controls blood pressure you may expect that there will be something
that keeps an eye on your blood pressure so that it can be compared to a normal value. Indeed some large blood vessels
contain blood pressure sensors that measure blood pressure. Physiologists call them baroreceptors. The blood pressure
that they measure is sent via nerves to an area of the brain where it is compared to a normal value. If blood pressure is
too low, for example, this area of the brain will send a message to the heart to increase the heart rate via neural networks. In this way the blood pressure will be brought back to normal.
An experiment
Two people work together. First the subject lies down on the floor or a table for three minutes. After the three minutes
the other person measures the subject’s heart rate and writes it down. then the subject stands upright for three minutes.
Again at the end of these three minutes the other person measures the subject’s heart rate and writes it down. Compare
the two heart rates.
Explanation
After standing up for three minutes the heart rate will normally be increased when compared to lying down. The reason
is that as a result of standing up, blood pools in the legs and less blood is in the heart. If you looked on an X-ray you
would see that the heart appears smaller because it contains less blood when a person stands up. As a result, the heart
pumps out less blood volume with every beat and that causes the blood pressure to fall a bit. The baroreceptor reflex we
talked about increases the heart rate to bring the blood pressure back to normal. That is why we measure a higher heart
rate initially in a person who stands upright.
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Suggestions For Teachers
Module #1 (Engage)
What Can You Observe About Reflexes and Reactions?
Purpose
Engage students in exploring reflexes and reactions.
Objectives
1. Engage students in making active observations about various reflexes and reactions and what the difference is
between the two.
2. Allow students to connect their own experiences with reflexes and reactions to the observations they make.
3. Assess students’ current understanding and possible misconceptions about reflexes and reactions.
Materials
●
●
●
videotape of the movie, Jurassic Park
overhead transparencies
transparency pens
Procedure
1. Find the sequence in Jurassic Park (or a similar type of movie sequence) where the cars are stranded in the rain by
the Tyrannosaurus rex enclosure. In the encounter with the T. rex, there are a number of good reactions and reflexes
displayed, including a pupillary reflex of the dinosaur when a flashlight is shined into its eyes. Stop the sequence
when the archaeologist begins waving flares at the dinosaur. Show the sequence first with the sound muted; this
allows students to focus on the responses that they can pick up visually. Ask students to write down every reflex or
reaction that they see, either by people or animals. Then repeat the video sequence with the sound on; students will
pick up many more responses from the audio track (gasps, exclamations, etc.).
2. Using the overhead projector, divide your transparency into two columns: Reflexes and Reactions. Ask students to tell
you the responses that they saw in the movie and to say whether they thought that response was a reflex (such as
removing your hand from a hot stove) or a reaction (such as grabbing for a basketball when it’s tossed your way).
3. As you complete this activity with students, note any misconceptions that you hear voiced. You can reconfirm these
using the concept map activity that follows and work to correct the misconceptions in the third activity (the “explain”
activity).
Safety Issues
None.
Suggestions for Assessment
Monitor student participation. Try to assure that every student contributes one or more responses to your listing. The
video segment is rich in possible answers.
References and Resources
Spielberg, S. (1994). Jurassic Park. Universal City, FL: MCA Universal Home Video.
Note: There is no student handout for Module #1.
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Suggestions For Teachers
Module #2 (Explore)
What Do You Know About Reflexes?
Purpose
Assess students’ understanding of reflexes and give them a real life example of a reflex.
Objectives
1. Engage students in making active observations about various reflexes and reactions and the difference between them.
2. Allow students to connect their own experiences with reflexes and reactions to the observations they make.
3. Assess students’ current understanding and possible misconceptions about reflexes and reactions.
Materials
●
●
●
●
●
●
poster board
Post-Itfi notes
colored markers or pencils
percussion mallets (or something to generate a knee jerk reaction)
pen lights or flashlights
various materials to generate a distraction (water, radio, reading material, etc.)
Procedure
1. Starting with the list they generated during Module #1, assign groups of students to generate a concept map of what
they know about reflexes. They should put concepts on the Post-It® notes and connect concepts using pencil-drawn
lines and text on the poster board so they can be changed later, as needed. (Information on concept mapping follows.)
2. Students can present their concept maps and/or they can be used as a pre-assessment by the teacher.
3. Next, ask students to define a simple question and design a corresponding experiment to learn more about the
pupillary reflex or the knee jerk reflex. Their experiments must use only those materials made available to them. Each
group must design their experiment and clear their plan of action with the teacher before proceeding.
4. Allow students to conduct their experiments, gather and analyze their data, and present their findings briefly to the
class. Part of their presentation should be a list of two to three additional questions they have about reflexes.
Safety Issues
The percussion mallet should be used gently to elicit the knee jerk response. Students should design experiments that
will not harm the subject. Extremely loud noises may damage hearing and any stimulus that results in pain must be
avoided. This is a good opportunity to discuss the need for human and animal protocol approval for experimentation. All
experiments must be approved by the teacher before they are begun.
Suggestions for Assessment
Student concept maps (both pre- and post-lesson) and experimental reports or posters can serve as assessment tools.
Develop a rubric for evaluation of group activities. Require students to keep detailed records of the experiments they
conduct and collect these for evaluation. Finally, students could write a research paper on their experiments in the form
of a scientific poster that they can present to the class.
References and Resources
Spielberg, S. (1994). Jurassic Park. Universal City, FL: MCA Universal Home Video.
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BUILDING CONCEPT MAPS
Step 1:
Identify the major concepts, principles, components, and contributing factors.
How To Do It: While “brainstorming” the subject, write down each possible item on
paper. After editing and amending the list, write each final selection on a card, small
piece of paper, or Post-It® note.
Step 2:
Organize the items. Rank each in a hierarchy of importance(s), or sequence(s), or
interactive relationship(s), or from general to specific, or start to finish.
How To Do It: Arrange concept label cards (generated in Step 1) on a table or board
or place Post-It® notes on a large sheet of paper to best fit the selected hierarchy and
lead into Step 3.
Step 3:
Determine the relationships and interconnections between the concepts, principles,
components, etc.
How To Do It: Draw connecting lines in pencil (so they can be changed as needed)
and write appropriate verbs and/or phrases on the lines to describe the connections.
Step 4:
Neatly lay out the final concept map, either by hand on poster board or by using a
computer graphics program.
References and Resources on Concept Mapping
Wesley, W.G., & Wesley, B.A. (October 1990). Concept mapping: A brief introduction. The Teaching Professor, p. 3-4.
Novak, J. (October 1991). Clarify with concept maps: A tool for students and teachers alike. The Science Teacher,
p. 45-49.
NOTE: The concept map on the following page was developed by a group of middle and high school science teachers
during an APS workshop on neural reflexes.
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SAMPLE CONCEPT MAP
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Student Activity Sheet
Module #2
What Do You Know About Reflexes?
PART I:
Materials
●
●
●
poster board
Post-It® notes
colored markers or pencils
Procedure
Construct a concept map detailing what you know about reflex actions (such as a knee jerk response). Place each
concept on a Post-It® note. Each concept must be connected by a line labeled with the relationship of the concepts. For
example:
Apple Tree
produces
Apples
contains
Seeds
PART II:
Materials
●
●
●
percussion mallets (or something to generate a knee jerk reaction)
pen lights or flashlights
various materials to generate a distraction (water, radio, reading material, etc.)
Procedure
The knee jerk and pupil reflexes are simple responses that can be studied easily. With your group, define a question
concerning one of these responses and design a simple experiment to answer your question. Check with your teacher
before proceeding with your experiment.
Be sure to include the following in your experiment:
● your question (purpose)
● your hypothesis (what you think will happen)
● materials
● methods (how you will do the experiment)
● chart to record your data
● results
● conclusions
● additional questions you’d like to explore (where would you go from here?)
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Suggestions for Teachers
Module #3 (Explain)
Reflexes and Reactions — An Overview
Purpose
Provide students with additional information on reflexes and reactions to explain the results and questions they
generated in the previous two activities.
Objectives
1. Engage students in developing and sharing their questions about reflexes and reactions.
2. Allow students to connect their own experiences with reflexes and reactions to the observations they make.
3. Increase students’ understanding and correct misconceptions about reflexes and reactions.
Materials
●
●
●
overhead projector
overhead transparencies
transparency markers
Procedure
1. Ask students to share some of the questions they have about reflexes and responses. They should have generated
questions as they developed their concept maps and as they did the experiment in Module #2.
2. Review the concepts presented in the background material in this unit on reflexes, reaction times, and neural
networks. You may want to duplicate the illustrations on pages 2, 5, and 7 for students.
Questions to Ask
What is the difference between a hand jerk reflex following contact with a hot object and a reflex reaction to catch or
block an object thrown towards your face? Is the brain involved in either response? Explain. Draw a simple diagram
of the neural paths for the two reactions.
● What impact do drugs, including alcohol, diet, and tobacco use have on reaction times?
● Is the saying “Practice makes perfect” true? Can you design an experiment to test the hypothesis that practice can
improve reaction time?
● What exactly is a reflex? What tissues are involved and what controls them?
●
Safety Issues
None.
Suggestions for Assessment
Students can revise their concept maps on reflexes or generate a new one on reflexes and reactions.
References and Resources
Textbooks on anatomy and physiology.
Note: There is NO student handout for Module #3.
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Suggestions for Teachers
Module #4 (Elaborate)
Is Heart Rate Constant?
Purpose
Explore further the concept of reflexes in terms of the heart’s response to various stimuli via a hands-on, inquiry
approach laboratory.
Objectives
1. Engage students in making active observations about the baroreflex and how it can be stimulated.
2. Improve student skills in developing experimental questions, designing experiments, collecting and analyzing data,
and drawing conclusions.
Materials
●
●
●
stopwatches
pulse or heart rate monitors (desirable but optional)
stethoscopes (desirable but optional)
Procedure
1. Ask the class if heart rate is constant. Obviously, it is not, but what sort of stimulus might raise or lower heart rate?
2. Ask them to design an experiment to test the effect of a stimulus, e.g. standing from a prone position or mild exercise,
on heart rate. They will need a way to measure heart rate. The pulse is an obvious method, but it is not necessarily the
most accurate. If possible, have stethoscopes and/or heart or pulse monitors available.
3. Have them share their experimental design, results, and analysis.
4. Ask them if heart rate can be controlled just by thinking about it — by and large no, but some degree of biofeedback
is possible.
Safety Issues
Students should design experiments that will not harm the subject. Extremely loud noises may damage hearing and any
stimulus that results in pain must be avoided. This is a good opportunity to discuss the need for human and animal
protocol approval for experimentation. All experiments must be approved by the teacher before they are begun.
Suggestions for Assessment
Class presentations of experiments, results, and conclusions. Develop a rubric for evaluation of group activities.
References and Resources
Textbooks on anatomy and physiology.
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Student Activity Sheet
Module #4
Is Heart Rate Constant?
Materials
●
●
●
stopwatches
pulse or heart rate monitors (desirable but optional)
stethoscopes (desirable but optional)
Procedure
Does heart rate change in response to a stimulus? Measure the heart rate or pulse of the members of your group. Are
they all the same? Compare your heart rates to those of others in the class. Do you see any patterns? Did everyone
measure their heart rates the same way? Decide on a method of measurement and design an experiment to test the effect
of a stimulus, e.g. going from a prone to a standing position, on heart rate. DO NOT include strenuous exercise in your
protocol. After obtaining approval from the instructor, run the experiment. Carefully record the experimental design,
results and interpretation. Summarize your experimental design, results and conclusions for presentation to the class.
Be sure to include the following in your experiment:
● your question (purpose)
● your hypothesis (what you think will happen)
● materials
● methods (how you will do the experiment)
● chart to record your data
● results
● conclusions
● additional questions you’d like to explore (where would you go from here?)
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Suggestions for Teachers
Module #5 (Elaborate)
Effects of External Stimuli on Reaction Times
Purpose
Explore further the concept of reactions and how they can be altered via a hands-on, inquiry approach laboratory.
Objectives
1. Engage students in making active observations about reactions and how they can be altered.
2. Improve student skills in developing experimental questions, designing experiments, collecting and analyzing data,
and drawing conclusions.
Materials
●
●
●
●
●
meter sticks
reaction time strips
stopwatches
poster board
colored markers or pencils
Procedure
1. Have the students design and complete an experiment to determine the effect of an external stimulus on reaction time.
This will require that they first develop a way to measure reaction time. One very simple way is to have one student
hold a meter stick suspended near the 0 cm end between the fingers of another student. This student must catch the
meter stick when it is released without warning. (Precalibrated reaction time sticks are available from scientific supply
catalogs). The distance the stick falls is recorded and reaction time recorded as:
Reaction time (in seconds) =
2 x distance (in cm)
980 cm/sec2
2. Another is to record the time it takes a student to sequentially touch 16 numbers randomly distributed in a 4x4 pattern
on a sheet of paper. Similar patterns can be setup with letters that spell out a name or word. This may useful for
introducing a new word such as neurophysiology. Electronic reaction time devices are also available from scientific
supply catalogs.
3. Review each group’s design prior to the experiment. Stimuli that might be tested include distractions such as external
noise or engagement in another activity (reciting the Gettysburg Address), right vs. left hand, repetition (practice),
auditory vs. visual signal, age, gender etc.
4. Have the students record their experimental design and summarize their data for presentation to the class. They should
present their experiment, the rationale for their design and the results in a manner that can be easily understood. They
should also provide their own interpretation of the results.
Safety Issues
Students should design experiments that will not harm the subject. Extremely loud noises may damage hearing and any
stimulus that results in pain must be avoided. This is a good opportunity to discuss the need for human and animal
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protocol approval for experimentation. All experiments must be approved by the teacher before they are begun.
Suggestions for Assessment
Class presentations of experiments, results, and conclusions. Develop a rubric for evaluation of group activities.
References and Resources
Textbooks on anatomy and physiology.
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Student Activity Sheet
Module #5
Effects of External Stimuli on Reaction Times
Materials
●
●
●
●
●
meter sticks
reaction time strips
stopwatches
poster board
colored markers or pencils
Procedure
Design and conduct an experiment to test the effect of an external stimulus on reaction time. Before you do this you
must develop a method to measure reaction time. Get approval of your method to measure reaction time and of your
experimental design before proceeding. Summarize your experimental design and results for presentation to the class.
Be sure to include the following in your experiment:
● your question (purpose)
● your hypothesis (what you think will happen)
● materials
● methods (how you will do the experiment)
● chart to record your data
● results
● conclusions
● additional questions you’d like to explore (where would you go from here?)
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Suggestions for Teachers
Module #6 (Evaluate)
What Do You Know Now About Reflexes and Reactions?
Purpose
Assess students’ understanding of reflexes and reactions.
Objectives
1. Allow students to revise their concept maps to correct misconceptions and add new concepts gained.
2. Provide students with opportunities to see their progress in understanding of the nervous system and its function.
Materials
●
●
●
poster board
Post-It notes
colored markers or pencils
Procedure
1. According to your preference, students can either revise their existing concept map on reflexes to add what they’ve
learned about both reflexes and reactions or they can generate a new concept map.
2. In either case, students should have an opportunity to see their progress in understanding the nervous system and its
functions.
Safety Issues
None.
Suggestions for Assessment
Compare pre- and post-concept maps. Develop a rubric for evaluation of concept maps.
Where to Go From Here
Explore in more detail the mechanism of reflex actions including muscle contraction and transmission of impulses.
Explore through literature research the mechanism of action of neurotoxins such as botulism toxin, tetanus toxin,
curare, etc. Do any of these have medical application?
● Discuss the importance of controlling emotional responses in reflex reactions, such as the anger response.
● Interview a scientist who does research on reflex reactions.
●
●
Extension
The above activities work from a simple reflex action involving a simple neural network (pain receptor — spinal cord
— neuromuscular signal) to more complex reactions requiring the brain. But these networks are still somewhat simple
compared to the mechanisms of visual and auditory perception. These can be explored by introducing the students to
optical illusions. Numerous examples can be found but a few are included on the following pages. More than likely the
students have seen the 3D images that have become popular recently. Simple observation of the images can lead to
further study of perception and why different people may come away with different interpretations of the same
observations.
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References and Resources
None.
Note: There is NO student handout for Module #6.
The American Physiological Society
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87
NEURAL NETWORKS
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The American Physiological Society
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