NEUR200 - Exam 2 "What is Sleep"

Define Sleep

a suspension of consciousness characterized by specific patterns of brain activity

(decreased motor output, dreaming, and cyclical pattern of EEG)

What are the two waveform patterns when we are awake?

beta and alpha

Characteristic of Beta waves

• occurs during wakefulness

• fast frequency (13-13 Hz)

• low amplitude waves

• when you’re actively thinking/engaged

• high muscle tone

• eye movement

Characteristics of Alpha waves

• occurs during wakefulness

• slow frequency (8-12 Hz)

• high amplitude waves

• when you’re resting, relaxed, or not engaged

• lower muscle tone

Characteristics of Theta waves

• occurs in stages 1 and 2 of non rem

• high amplitude

• low frequency (3.5-7.5Hz)

Characteristics of sleep spindles

• stage 2 of non-REM

• occurs 2-5 times per minutes in stages 1-4 of sleep

• short medium frequency waves

• helps keep person asleep and plays role in memory consolidation

Characteristics of K complexes

• occurs only in stage 2 of non-REM

• sudden sharp spindles

• occurs one time per minute (but can be triggered by noises)

• appears before delta waves

Characteristics of Delta Waves

• appears less than 50% in stage 3 and greater than 50% in stage 4

• high amplitude

• low frequency (less than 3.5 Hz)

What is slow wave sleep?

synchronized EEG activity in deeper sleep stages of non-REM (3&4)

• moderate muscle tone

• slow or no eye movement

What are the two types of sleep?

Non-Rapid Eye Movement (Non-REM) and Rapid Eye movement (REM)

How long does one typical sleep cycle last?

about 90 minutes (mostly NREM and about 20-30min REM)

When falling alseep, which type of sleep do you enter first?

NREM before REM

What 4 waveform patterns are in non-REM sleep?

theta waves, K-complexes, spindles, and delta waves

What occurs in stage 1 of non-REM

person is drifting into sleep, characterized by theta waves

What occurs in stage 2 of non-REM

theta waves with sleep spindles to keep person alseep and consolidate memory and k-complexes appearing before delta waves

What occurs in stage 3 of non-REM

• characterized by less than 50% of delta waves

• decreased breathing and pulse

• relaxed muscles

• hard to awaken

• where people experience sleep walking, bed wetting and night terrors

What occurs in stage 4 of non-REM

• characterized by more than 50% of delta waves

• very difficult to awaken person; if awakened person is groggy/confused

• where people experience sleep walking and sleep talking

What is REM sleep?

• characterized by increased fast eye movement

• person doesn’t react to most noises unless called by their name; if awakened person is alert and attentive

• where dreaming occurs

• EEG desynchrony

• lasts a few minutes up to an hour in a period of sleep

• 4-5 cycles in an 8hr period of sleep

• avg. 20 minutes of REM per 90 minute cycle

What characterizes the waveforms of REM sleep?

EEG waves look like alpha and beta waves that occur during wakefulness (supports the theory that REM sleep is an alternative to being awake!)

What physical/physiological characteristics occur in REM sleep?

• loss of muscle tone/”paralyzed”

• increased heart rate, bp, and breathing

• facial and finger twitching

• penile erection and vaginal secretion

What is the progression through the sleep stages?

• most slow wave sleep occurs in the first half of the night

• as night goes on, more and more stage 2 of non-REM and less stage 3&4

• as night goes on, more time in REM

How does sleep change as we age?

the quality of sleep decreases as we age

in childhood: more of stage 3 and 4 in non-REM

in early adulthood and old age: less stages 3 and 4 and people are more easily awakened

What are the hypotheses for the purpose of sleep?

biological adaptation, restorative, and memory consolidation

Why might sleep be a biological adaptiation?

• animals conserve energy during food scarcity

• predators sleep more than prey (predators are less threatened so they don’t need to be as constantly alert like prey)

• ex: dolphins adapting to having one hemisphere sleep at a time to stay alert in case of predators)

Why might sleep have a restorative purpose?

researchers believe that slow wave sleep allows the brain to rest (metabolic activity is decreased)

Why might sleep have a role in memory consolidation?

sleep facilitates information transfer from the hippocampus to cortex; a study showed that people who who had REM vs just slow wave sleep alone during a nap performed better on an implicit memory task

What are the hypotheses for the functions of REM sleep?

increased REM sleep for learning and memory, increased REM sleep when sleep deprived, and REm sleep might just be an alternative to being awake

What are the 5 neurotransmitters that play a role in sleep?

Orexin, Acetylcholine, Norepinephrine, Serotonin, and Histamine

Orexin

also known as hypocretin; if there’s high orexin then you are awake. Orexin neurons can be inhibited by the VLPO

Ventrolateral Preoptic Are

as adenosine builds up, VLPO activity increases to make you sleepy; there’s a also a group of GABAergic neurons which also promotes sleepiness/suppresses wakefulness

How does the suprachiasmatic nucleus control the VLPO?

The SCN has a brake on the VLPO by responding to light. If there’s light, the SCN inhibits VLPO activity by keeping you away in response to light. If there’s no light, the brake on the VLPO is released, resulting in promotion of sleep.

What brain regions are involved in sleep regulation and Orexin?

The ventrolateral pre optic area and the suprachiasmatic nucleus in the hypothalamus

destruction of orexin characterizes what disorder?

narcolepsy (falling asleep at any given time)