Sleep Science Overview

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Questions and Answers

What occurs in the EEG when a person first closes their eyes?

Alpha dropout and loss of posterior rhythmicity (correct)

Dominance of delta waves

Increase in high-frequency beta waves

Stable theta wave patterns

During which stage of sleep is a person most easily awakened?

Stage 2 non-REM sleep

Stage 1 non-REM sleep (correct)

REM sleep

Stage 3 non-REM sleep

What characterizes Stage 2 non-REM sleep according to EEG features?

Presence of sleep spindles and K-complexes (correct)

Increased presence of delta waves

Low amplitude mixed frequency activity

Consistent alpha rhythms throughout

What does an electroencephalogram (EEG) primarily measure?

Cortical activity and brain wave patterns (D) Signup and view all the answers

What are vertices sharp waves in Stage 2 sleep associated with?

Intermittent high amplitude complexes (B) Signup and view all the answers

What structure forms the primary barrier between the bloodstream and the brain?

Tight junctions between endothelial cells (B) Signup and view all the answers

How are endothelial cells in the central nervous system connected?

By tight junctions (D) Signup and view all the answers

What type of capillaries is found in organs outside the nervous system?

Fenestrated capillaries (C) Signup and view all the answers

What role do astrocytic foot processes play in the capillaries of the central nervous system?

They provide structural support and contribute to the blood-brain barrier. (B) Signup and view all the answers

What are the small openings between the endothelial cells of fenestrated capillaries called?

Pores (D) Signup and view all the answers

What frequency range is associated with alpha waveforms?

8-13 Hz (C) Signup and view all the answers

Which of the following statements best describes beta waveforms?

They are irregular and occur during focused attention. (C) Signup and view all the answers

Which EEG waveform is primarily associated with deep sleep and has lower frequency?

Delta (A) Signup and view all the answers

What physiological function is primarily related to gamma wave activity?

Arousal and focused attention (D) Signup and view all the answers

What characteristic distinguishes sleep spindles in EEG readings?

Sinusoidal wave pattern at 12-14 Hz (D) Signup and view all the answers

What common sleep disorder is indicated by loud snoring and pauses in breathing?

Obstructive sleep apnea (B) Signup and view all the answers

Which stage of sleep is characterized by highly synchronized brain activity and occasional delta spikes?

Stage 3 NREM (C) Signup and view all the answers

What two distinctive patterns are seen in normal sleep cycles?

Rapid eye movement (REM) and non-rapid eye movement (nREM) (B) Signup and view all the answers

What is the predominant EEG activity observed in Stage 4 nREM sleep?

Delta spikes with maximum amplitude (A) Signup and view all the answers

Which neurotransmitter is primarily associated with the inhibition of preoptic neurons in the hypothalamus during sleep?

GABA (B) Signup and view all the answers

During the initial stages of sleep, which waves are predominantly observed in the EEG?

Alpha waves (A) Signup and view all the answers

What characterizes the sleep of children during Stage 4 nREM sleep?

Deep sleep resistant to awakening (B) Signup and view all the answers

Which of the following statements about neurotransmitters in sleep is correct?

Histamine inhibits preoptic neurons. (C) Signup and view all the answers

What happens to Orexin levels during Stage 4 nREM sleep?

They decrease. (C) Signup and view all the answers

What is typically observed in the EEG during the awakening of an individual from deep sleep?

Low voltage fast activity is predominant (D) Signup and view all the answers

Which neurotransmitter's activity is decreased during deep sleep?

Acetylcholine (C) Signup and view all the answers

What is primarily responsible for the pressure-controlled mechanism of cerebral autoregulation?

Myogenic responses (D) Signup and view all the answers

At what mean arterial blood pressure range does cerebral autoregulation occur?

60-150 mmHg (D) Signup and view all the answers

Which statement accurately describes the role of neurogenic control in cerebral autoregulation?

It includes both extrinsic and intrinsic influences. (B) Signup and view all the answers

What happens to cerebral blood flow when there is an increase in pH (alkalosis)?

Vasoconstriction occurs. (D) Signup and view all the answers

Which mechanisms are involved in cerebral autoregulation?

Chemical-metabolic, neurogenic, and myogenic (B) Signup and view all the answers

What defines cerebral autoregulation as a major homeostatic mechanism?

It ensures constant blood flow under varying pressures. (A) Signup and view all the answers

Which factor is NOT typically a determinant of cerebral blood flow (CBF)?

Intracranial pressure levels (A) Signup and view all the answers

Which of the following describes a characteristic of cerebral autoregulation?

It occurs in both large and small arterioles. (A) Signup and view all the answers

What physiological changes occur during REM sleep?

Penile erections may occur (D) Signup and view all the answers

What is the typical pattern of sleep cycles in young adults?

nREM and REM sleep cycles lasting about 90 minutes (B) Signup and view all the answers

What is a common symptom associated with disturbances during sleep?

Waking up in unusual places (A) Signup and view all the answers

How does sleep change with aging?

Slow wave sleep decreases steadily (C) Signup and view all the answers

What triggers REM sleep according to current understanding?

Activity in the pontine reticular formation (A) Signup and view all the answers

Which of the following is characteristic of neonate sleep patterns?

Up to 16 hours of sleep with REM predominating (A) Signup and view all the answers

Which statement about bruxism is true?

It is associated with dreaming (C) Signup and view all the answers

What happens to nREM sleep periods during the first half of the night?

They tend to be longer and deeper (B) Signup and view all the answers

How does the distribution of sleep stages change throughout a typical night?

nREM periods are less deep in the latter half of sleep (C) Signup and view all the answers

What is the role of PGO spikes in REM sleep?

They facilitate the maintenance of REM sleep (C) Signup and view all the answers

Study Notes

Sleep

Sleep is a normal, cyclic, temporary loss of consciousness, readily reversed by stimuli.
It's a result of interaction between the reticular formation and sleep-producing brain centers.
The brain is still active during sleep.
Electroencephalography (EEG) records cortical activity via scalp electrodes.
Waveforms represent summed postsynaptic potentials (EPSPs/IPSPs) and reflect cortical activity and consciousness levels.
EEG is used to identify sleep stages.
Visual input is lost with eyes closed increasing the summation of (EPSPs/IPSPs) on the posterior brain area (vision).
Alpha waves (8-13 Hz) are prominent when eyes are closed and attention is relaxed.
Beta waves (13-30 Hz) are irregular and associated with active attention.
Gamma (30-80Hz) waves occur during high-attention and alertness.
Theta (4-7 Hz) and Delta (0.5-3 Hz) waves are more prevalent in pathological conditions showing lower brain function.
Sleep periods are categorized as REM (rapid eye movement) and nREM (non-rapid eye movement).
nREM sleep is predominant in the first half of sleep cycles, offering restorative properties.

nREM Sleep Stages

Stage 1: Lightest sleep, marked by drowsiness and slowing of brain activity; loss of posterior rhythmicity and alpha dropout.
Stage 2: Light to medium sleep. EEG features include sleep spindles (12-14Hz, sinusoidal waves) and K complexes (high voltage biphasic waves). Common time for obstructive sleep apnea to be observed.
Stage 3: Deeper sleep with increased difficulty waking characterized by slow wave activity, higher amplitude, lower frequency and a greater synchronization of EEG.
Stage 4: Deepest sleep. EEG shows maximum slowing with large amplitude waves and increased delta spikes. Common for young children.

REM Sleep

Also called paradoxical sleep, with brain activity levels similar to wakefulness; however, skeletal muscles are inactive to prevent acting out dreams.
Associated with muscle paralysis and dreaming.
REM sleep behavior disorder (RBD) occurs when muscle paralysis is lost.
REM sleep shows rapid, low-amplitude, desynchronized EEG waves, fluctuations in autonomic functions like heart rate, blood pressure, respiration, and potentially increases risk for cardiovascular events.

Sleep Distribution and Age

Sleep patterns change with age. nREM periods are longest during the first half of sleep, with REM periods increasing throughout the night as sleep progresses.
Neonates need more sleep than adults.
REM sleep is predominant in infants.
Slow-wave sleep (stage 3 and 4) is maximal in children.
The proportion of REM sleep decreases throughout life, plateauing at around 25% in adulthood.

Circadian Rhythm

Circadian rhythm is a roughly 24-hour cycle of processes (e.g. sleep-wake cycle, hormone secretion).
It is driven by the suprachiasmatic nucleus (SCN) in the hypothalamus, the master biological clock.
It is adjusted to the external environment through zeitgebers (time givers) such as light-dark cycles, temperature, and social cues.

Blood-Brain Barrier (BBB)

The BBB is a protective barrier between the blood and the brain, formed by capillaries with tight junctions and astrocyte foot processes.
It controls movement of substances from the blood to the brain.
Lipid-soluble substances can easily traverse the barrier.
Substances need to travel through the plasma membrane to reach/enter the brain.
BBB is absent in very specific areas of the brain like the 3rd ventricle, tuber cinereum of hypothalamus, pineal gland, and area postrema

Cerebral Blood Flow (CBF)

The brain (1.5-2% of body mass) receives about 15-20% of the cardiac output.
CBF is driven by mean arterial pressure (MAP) and inversely proportional to cerebrovascular resistance (CVR).
The brain maintains a relatively constant CBF over a range of blood pressures.
Changes in CO2 most potently influence CBF, with increased CO2 leading to vasodilation and increased CBF.
Normal CBF is sustained by tightly coupled mechanisms—myogenic, neurogenic, and biochemical/metabolic.

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Description

This quiz explores the mechanisms and stages of sleep, including the roles of brain activity and EEG in monitoring sleep states. Understand the different types of brain waves associated with sleep and consciousness, as well as the physiological changes that occur during sleep cycles. Test your knowledge about the intricacies of sleep and its importance to brain function.