overview

Outline
OVERVIEW
24.3
LE S S O N
Le s s o n
Unit1.2
Rationale: This lesson presents the concept of the neural circuit. Using
the sleep-wake circuit as an example, this lesson demonstrates how different
parts of the brain work together to regulate behaviors. In addition to learning
the brain structures involved in controlling the sleep-wake cycle, students
will learn that this cycle is controlled by a switch sensitive to outside stimuli.
Students will also be introduced to the key concept that circuits rely on both
inhibition and excitation to regulate function. Finally, this lesson introduces the
idea of using an animal model to study a human disorder.
Objectives:
■■ Students will be able to identify the components of the sleep-wake
circuit.
■■ Students will be able to describe how these components work together
to control our sleep-wake cycle.
Activity: Students begin the lesson by trying to determine what makes
us fall asleep and what makes us wake up. To challenge their answers to
these questions, they will be shown a video about Skeeter, a narcoleptic
poodle. Students will then work through a PowerPoint with the teacher that
describes the sleep-wake circuit. The PowerPoint is interactive and students
will be required to make deductions and answer questions about how the
circuit works. After learning about the sleep-wake circuit, students will be
asked to predict what causes Skeeter’s narcolepsy. The lesson concludes
with a video about research being done on dogs with narcolepsy.
Homework: Students will complete a worksheet about the research
being done on the role of orexin in the sleep-wake circuit. Students are also
asked to bring in their sleep journals as well as their ND Lesson 4.2 Activity
Worksheet for tomorrow’s lesson.
The
Lesson
Plan
Lesson 4.3: What makes us go
to sleep and wake up?
1. Do Now (5 min):
The students answer questions about what makes us fall asleep and what
makes us wake up to introduce the concept of the stimuli required to keep
us awake and allow us to sleep.
2. Discussion (15 min):
The discussion begins with a video of Skeeter, a narcoleptic poodle and
the students are asked – what makes this happen?
Using the PowerPoint, the class will piece together the flip-flop switch
which underlies the sleep-wake circuit.
3. Activity (15 min):
Students work in small groups to determine what could be wrong with
Skeeter’s sleep-wake circuit.
4. Wrap-up (10 min):
The lesson concludes with a video about research done on narcoleptic
dogs as an illustration of defects in the sleep-wake circuit.
5. Homework:
Students will complete a worksheet about the research being done on the
role of orexin in the sleep-wake circuit.
6. Materials:
1. Printed Materials
• Homework worksheet
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1.
DO
NOW
Have the students work with a partner to answer the questions on the slide.
Powerpoint
Slide 2
■■ After giving the students 5 minutes to complete this task, ask the
students to share some of their responses.
■■ Students will likely answer that we fall asleep because we’re tired,
relaxed or bored. We will also fall asleep when it’s dark or we’ve just
eaten a big meal.
■■ Students will likely answer that we wake up because we’ve just slept
or we feel stress. We also wake up because of light or noise.
2.
Discussion
So, what makes this happen?
Powerpoint
Slide 3
■■ Show the students the video of Skeeter, a narcoleptic poodle. This
video is embedded in the PowerPoint so you can just click on the
image and the video will play.
Ask the students – So what makes this happen?
■■ Most likely none of their answers will explain narcolepsy, but this
video is used as a jumping point to show the students what we have
learned about the sleep wake circuit.
_______________________________________
LE S S O N
4.3
Specific brain areas keep us awake and
other areas put us to sleep.
This slide (next page) introduces the idea that specific areas of the
brain need to interact with each other in order to regulate behavior. This
concept of multiple parts of the brain working together is the idea of the
circuit. There are many circuits within our brains, but for this lecture we will
focus on the sleep-wake circuit to introduce the concept of the circuit to
the students.
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2.
Discussion
Powerpoint
Slide 4
Tell the students that specific regions in our brain keep us
awake and others cause us to fall asleep.
Tell the students that the ‘wake up’ area is made of arousal
neurons found in the brainstem.
Ask the students – How could these neurons
control wakefulness?
■■ The arousal neurons function because they connect directly with the
cortex.
■■ One of feature of these neurons is that they make synapses all the way
along their path to the cortex so they can influence many areas.
Tell the students that the “go to sleep” area is located in
the hypothalamus and that the hypothalamus is critical in
maintaining body homeostasis.
LE S S O N
4.3
Ask the students – What is homeostasis?
Specific brain areas keep us awake and
other areas put us to sleep.
The slide abstracts the two brain areas and shows them as a schematic.
Powerpoint
Slide 5
Tell the students that you can represent the two brain
areas pictured on the previous slide with this schematic.
■■ We will use the schematic to describe how the brain areas work.
Ask the students – But how do these areas
know what the other is doing? (This is the
classic - Does the right hand know what the
left hand is doing?)
■■ Based on their previous studies on pain, the students should be able
to immediately say that there would be axonal connections between
the two areas. Make sure they understand that the connections have
to go in two directions.
■■ Students are likely to think that communication between the two
areas requires them to activate each other. This is not necessarily the
case as the next few slides will demonstrate.
■■ Homeostasis is the balance that is required to maintain physiological
function.
Tell the students that neurons in the ventrolateral preoptic
nucleus (VLPO) of the hypothalamus help to regulate sleep.
__________________________________________
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2.
Discussion
The two areas connect with each other.
They inhibit each other.
The two areas connect with each other.
Can you predict how they connect?
Powerpoint
Slide 7
Powerpoint
Slide 6
Ask the students – How would these two areas
connect?
■■ Since the two areas have opposing actions, they should inhibit each
other.
If the students need help getting to the answer,
ask them - what type of synapse would the
“wake up” area need to make with the “go to
sleep” area in order for it to stop the action of
the “go to sleep” area?
■■ An inhibitory synapse.
Explain to the students that as the circuit is drawn now,
when each area is active it will inhibit the activity of the
other area.
Ask the students whether it could work as
drawn?
■■ No because each component inhibits the output of the other.
■■ We would either constantly be asleep or constantly be awake, there
is no balance between the two.
__________________________________________
To wake up, the ‘wake up’ area needs
to be more active than the ‘go to sleep’
area.
__________________________________________
LE S S O N
4.3
Powerpoint
Slide 8
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2.
Discussion
Ask the students - what would happen if the
‘wake up’ area was more active than the ‘go to
sleep’ area?
■■ We would wake up because the ‘wake up’ area will inhibit the activity of
the ‘go to sleep’ area.
___________________________________________
But how is the transition from sleep to
wake (and vice versa) controlled?
Powerpoint
Slide 10
To sleep the ‘go to sleep’ area needs to be
more active than the ‘wake-up’ area.
Ask the students – What makes us feel tired
and sleepy?
Powerpoint
Slide 9
■■ This question was initially asked in the “Do Now” of the lesson, so
take just a minute to review their answers.
■■ Typical answers could include:
They feel tired when it’s dark, which could apply to rainy or grey days, as well as to nighttime.
They feel tired when they haven’t slept in a while – this gets into the circadian clock.
■■ They feel tired after a big meal or when they are really relaxed.
Ask the students – what needs to happen for us
to be able to go to sleep?
LE S S O N
4.3
■■ For us to be able to go to sleep, the ‘go to sleep’ area needs to be more
active than the ‘wake up’ area so that it can inhibit the ‘wake up’ area
and put us to sleep.
____________________________________________
■■ Animate the slide to show the students three possible answers.
Ask the students - What makes us feel awake
and alert?
■■ This question was initially asked in the “Do Now” of the lesson, so
take just a minute to review their answers.
■■ Typical answers could include:
They feel awake when it’s light.
They feel awake and alert when they just slept or when they feel stressed.
They feel awake and alert when they just slept or when they feel stressed.
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2.
Discussion
■■ Animate the slide to show the students three possible answers.
■■ Remind the students that we needed an external stimulus to drive the
circuit. The light/dark cycle acts as that stimulus.
Orexin neurons are activated by signals
that keep us awake, and then activate
the arousal neurons.
Use this slide to show the students how the orexin neurons fit into the
circuit.
Tell the students that neurons that are sensitive to these
signals, particularly light and dark, switch the “wake up” and
“go to sleep” areas on and off.
_______________________________________
Powerpoint
Slide 12
The Orexin neurons in our hypothalamus are activated by signals that keep us
awake.
Powerpoint
Slide 11
Walk the students through this schematic drawing. They
have seen a similar drawing earlier in this lesson, and the
only addition is that the orexin neurons are now stimulating
the arousal neurons.
Ask the students – What is the effect of the
orexin neurons activating the arousal neurons?
Tell the students that orexin neurons in the hypothalamus
actually drive the sleep/wake cycle.
LE S S O N
4.3
■■ These neurons are called orexin neurons because they use a chemical
neurotransmitter called orexin.
Tell the students that the orexin neurons are stimulated by
light as well as the other signals that keep us awake.
■■ The students should be able to answer that the arousal neurons can
then inhibit the VLPO neurons, and we wake up.
_______________________________________________
Orexin neurons are activated by signals
that keep us awake, and can activate the
arousal neurons.
__________________________________________
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2.
Discussion
Powerpoint
Slide 13
Ask the students – what happens when the
orexin neurons are switched off?
■■ The students should be able to predict that you would fall asleep
because the “go to sleep” neurons are no longer inhibited, and so
they then can inhibit the “wake up” area.
■■ When orexin neurons are not stimulated (its dark, your blood fat
levels are high, you feel calm) they do not activate the arousal center.
■■ Now the arousal center cannot activate the sleep center, so sleep
occurs.
■■ Use the next slide to answer this question for the students.
______________________________________
Ask the students – Other than light, what keeps
us awake?
What happens when the orexin neurons
are switched off (2)?
■■ The students will probably answer things like stress and/or caffeine.
Use this slide to show the students how the circuit switches to sleep.
■■ Animate the slide to show the students that orexin neurons are
sensitive to signals other than light which then keeps us awake
Tell the students that orexin neurons are not only responsive
to light they can also respond to energy balance and
emotional states – that is why you can’t sleep sometimes
when you’re tense or stressed, or why you wake up too
early.
Powerpoint
Slide 15
_______________________________________________
What happens when the orexin neurons
are switched off?
Use this slide to show the students how the circuit switches to sleep.
LE S S O N
4.3
Tell the students that when the orexin neurons are
switched off, arousal neurons are switched off too, which
removes the inhibition to the VLPO. So the VLPO can now
become active, and we fall asleep.
Powerpoint
Slide 14
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3.
4.
Wrap Up
Activity
Think, Pair, Share.
Narcolepsy
Use this slide to remind the students of how we started
this discussion – Skeeter and his inability to stay awake.
Show the class the video which describes how researchers have used
dogs with narcolepsy to discover a gene that underlies the disorder. The
video has been embedded into the PowerPoint so you can just click on the
picture and the video will play.
Powerpoint
Slide 16
Ask the students – Given what you just learned
about the sleep-wake circuit, can you predict
what causes Skeeter’s narcolepsy?
■■ Have the students work in small groups to determine what might be
wrong with Skeeter’s sleep-wake circuit.
■■ After 5 minutes, have some of the student groups present their ideas of
what causes Skeeter’s narcolepsy.
LE S S O N
4.3
Powerpoint
Slide 17
Tell the students that researchers have studied dogs with
narcolepsy to learn more about the human condition.
Tell students that in 1999 researchers identified the gene
responsible for causing narcolepsy in dogs.
■■ The gene identified was a mutation in the receptor for orexin. The
mutation caused the receptor to be defective. Make sure the
students know that this means dogs with this gene would not be able
to detect orexin.
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4.
Wrap Up
Tell the students that for homework they will apply what they
have learned about the sleep-wake circuit to figure out what
causes narcolepsy.
The homework worksheet is included in
the Materials Folder
for this lesson.
■■ Additionally, have the students bring in their sleep journals as well
as their activity worksheet from Lesson 4.2. The students will need
the data contained in these documents to complete an activity in
tomorrow’s class which investigates circadian rhythms.
Homework: Worksheet narcolepsy
■■ Have the students write a
Powerpoint
Slide 18
LE S S O N
4.3
Homework
■■ For homework have the students complete the homework worksheet.
This homework is designed to walk students through the research
done on the role of orexin in the sleep-wake circuit.
paragraph to advise a government agency on whether
or not insurance companies
should be required to cover
the cost of treatment for
addiction. Instruct the students to include evidence
that they have learned in
class.
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