Learning Outcomes:

• Define homeostasis and negative feedback• Predict how a sleepiness factor will fluctuate

throughout a 24 hour period• Graph a sleepiness factor’s fluctuation

throughout a 24 hour period under various conditions

• Provide feedback to peers about their predictions and graphs

Think/Pair/Share:

• Define Homeostasis• How is it like driving a car on a highway?

Your body’s thermostat in the brain is set at 98.6F (unless you have a fever).

What does your body specifically do to maintain this constant body temperature if the ambient temperature is cold? What is your body’s effector mechanism? Will your body just get warmer and warmer and warmer?

What is your body’s effector mechanism for when you are too warm?

Think/Pair/Share:

Brainstorm: what else in the body is “maintained” through homeostatic mechanisms besides temperature?

SLEEPINESS CAN BE DEADLY• Approximately 100,000 automobile crashes

each year result from drivers who were “asleep at the wheel.”

• In a survey of drivers in New York State, approximately 25 percent reported they had fallen asleep at the wheel at some time.

• Crashes in which the driver falls asleep are especially common among young male drivers. One large study found that in over 50 percent of fall-asleep crashes, the driver was 25 years old or younger.

• In addition to the high risk of automobile crashes, problem sleepiness can cause difficulties with learning, memory, thinking, and feelings, which may lead to poor school and work performance and difficulty with relationships

http://science.education.nih.gov/supplements/nih3/sleep/guide/info-sleep.htm

• Consider that the longer an individual remains awake, the stronger the desire and need to sleep become. This pressure to sleep defines the homeostatic component of sleep.

• The precise mechanism underlying the pressure that causes us to feel a need to sleep remains a mystery.

• A sleepiness factor appears to “keep track” of lost sleep and may induce sleep. We usually sleep once daily because the homeostatic pressure to sleep is hard to resist after about 16 hours.http://science.education.nih.gov/supplements/nih3/sleep/guide/info-sleep.htm

What about sleep homeostasis?

Scientists are still looking for and learning about a possible “sleepiness factor” (SF).

AWAKEASLEEP

SF levels rise

SF levels decrease

Sleep homeostasis

Graphing a “sleepiness factor”(10 minutes)

Predict, by drawing a line graph, the relative concentration levels of the “sleepiness factor” throughout a normal 24 hr period.

1. Use paper. Put names on your graph; I

will be collecting these.

2. Label the X axis and the Y axis and give

your graph a title.

3. Make sure awake and asleep periods are

obvious on your appropriate axis.

4. Draw the line that makes your prediction

about the sleepiness factor in a normal 24

hour period.

5. Draw a second graph predicting what

would happen to a student that stays up

studying and only gets a very small

amount of sleep. How is the line

different?

AWAKEASLEEP

SF levels rise

SF levels decrease

Sleep homeostasis

Peer evaluation and feedback(10 minutes)

• Swap papers with a partner. • Give written feedback on the graph about

whether you agree or disagree with their graph.

• Write any questions you have for them.• Discuss.

Which of these two graphs is a college student cramming late into the night?

Which of these two graphs is a college student cramming late into the night?

Normal: Student won’t be tired until the entire day passes.

Sleep deprivation: student will be tired in a few hours.

The precise mechanism underlying the pressure that causes us to feel a need to sleep remains a mystery.

• There is recent evidence that the molecule adenosine (composed of the base adenine linked to the five-carbon sugar ribose) is an important sleepiness factor: it appears to “keep track” of lost sleep and may induce sleep.

• Interestingly, caffeine binds to and blocks the same cell receptors that recognize adenosine. This suggests that caffeine disrupts sleep by binding to adenosine receptors and preventing adenosine from delivering its fatigue signal. (COMPETITIVE INHIBITION).

http://science.education.nih.gov/supplements/nih3/sleep/guide/info-sleep.htm

Think/Pair/Share:

If this student cramming into the night and sleeping only a few hours drinks caffeine when waking, what will happen to the sleepiness factor?

A.It will decreaseB.It will increaseC.Nothing, it will not be affected by caffeine