This document discusses sleep, including what it is, what happens during sleep, what causes sleep, and the functions of sleep. It notes that sleep consists of different stages, including non-REM sleep with four stages and REM sleep. It discusses factors that cause sleep accumulation in the blood and CSF of sleep deprived animals. It also discusses how caffeine and tetrahydrocannabinol affect sleep and potential reasons why sleep is needed, including neural maturation, memory consolidation, and energy conservation, though the physiological functions of sleep remain speculative.

1. Sleep
Csilla Egri, KIN 306 Spring 2012
KIN306, 8:30am: excellent time to catch some Zzz’s

2. Outline
 What is sleep?
 What happens during sleep?
 What causes sleep?
 Functions of sleep??
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3. What is sleep?
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Sleep is an actively induced and highly
organized brain state with different phases.
Characterized by:
1.Reduced motor activity
2.Decreased response to stimulation
3.Stereotypic posture
4.Relatively easy reversibility

4. What happens during sleep?
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Pace-Schott Nature Reviews Neuroscience 2002
 We cycle thru
different stages of
sleep
 Non-REM
 Four stages
 “deep sleep”
 REM
 Rapid eye
movement
 Irregular heart rate
and breathing
 “paradoxical sleep”
 dream state?

5. What causes sleep?
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 Neuronal connections thru reticular
formation play a role
 Above pons – contributes to
wakefulness
 Below pons – has inhibitory
connections to wakefulness centers in
pons area reticular formation
 Role of sleep factors?
 accumulate in blood and CSF of sleep
deprived animals
 Induces sleep when injected into other
animals
 Circadian regulation of sleep wake cycles
 Does not cause sleep, but regulates
sleep timing
pons
thalamus

6. Effects on sleep: Caffeine
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 Caffeine has similar molecular
structure to adenosine
 Adenosine thought to be one
type of sleep factor
 Caffeine blocks adenosine
receptors (adenosine
antagonist)
 Stimulates wakefulness
 Potency and duration of effect
is highly variable and
subjective

7. Effects on sleep:
tetrahydrocannabinol7
 Chronic use of drug:
 Sleepiness, calming effect
 Reduced REM sleep
 Reduced dreaming/remembering of dreams
 Abrupt cessation of drug use
 Vivid dreams
 Sleep disturbances; insomnia, poor sleep quality
 Mechanism?
 Binds to CNS cannabinoid receptor CB1
 How/why this affects sleep is unknown

8. Why do we sleep?
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 Almost all animals require sleep
 Sleep deprivation causes irritability, reduced
cognitive functions, general malaise, death
 Sleep is required but physiological function is
speculative at best
 Neural maturation?
 Facilitation of learning, consolidation of
memories?
 Facilitation of development?
 Importance of REM sleep?
 Conservation of metabolic energy?

9. Objectives
After this lecture you should be able to:
 List the four characteristics of sleep
 Understand that sleep consists of different stages
 Compare the effects of caffeine and
tetrahydrocannabinol on sleep
 Describe some theories as to why we sleep
 Be really curious about the mechanism of sleep and
dreams and pursue a career as a researcher
After this section of the course you should:
 Be really fascinated about the complexities, intricacies
and mysteries of nervous system physiology and
pathophysiology and pursue a career as a scientist
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10. 10
1. If the brainstem is cut as per the dotted line in slide 5,
would sleep be stimulated or inhibited?
2. Caffeine binds to ______________ receptors and
stimulates wakefulness.
3. Why is REM sleep sometimes referred to as
paradoxical sleep?
Test your knowledge