Sleep

Csilla Egri, KIN 306 Spring 2012

KIN306, 8:30am: excellent time to catch some Zzz’s

Outline

What is sleep? What happens during sleep? What causes sleep? Functions of sleep??

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What is sleep?3

Sleep is an actively induced and highly organized brain state with different phases.

Characterized by:1.Reduced motor activity2.Decreased response to stimulation3.Stereotypic posture4.Relatively easy reversibility

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?

What causes sleep?5

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

Effects on sleep: Caffeine6

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

Effects on sleep: tetrahydrocannabinol

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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

Why do we sleep?8

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?

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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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?

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