NEUR 201: Sleep and the Circadian Rhythm

What are ways to study someone’s sleep?

polysomnography - brain waves (EEG), eye movements (EOG), muscle movements (EMG)

What is sleep characterized by?

1. decrease in physical activity (10% less energy)

2. decoupling from external inputs (heightened threshold for detection of sensory stimuli)

3. changes in brainwave activity

Phases of Sleep

1. NREM1: drowsiness

2. NREM2: 50% of night’s sleep

3. NREM3: deep sleep, lowest physiological activity

4. REM: paradoxical sleep, muscles immobile except eyes

Awake

dominated by high-freq waves. beta band range of freqs

NREM1

beta freq amplitude decreases to alpha waves then theta waves

NREM2

theta waves predominate with two interruptions that may be related to learning and memory. k-complexes: large amplitude events observed every minute. high freq burst of rapid neural activity in low beta range that lasts for a second

NREM3

cortical neurons fire in synchronicity with one another, change in potentials cause large amplitude deflections in EEG, in delta band

REM

pattern of activity very similar to being awake

What does lack of sleep cause?

mental and physical fatigue, poor decision-making, impaired learning, emotional irritability, and an increased risk of migraine and epileptic seizures

Recuperation Theory

the body needs a period of time when energy usage decreases and the body’s natural repair systems can work without interruption

Benefits of recuperation

1. enhanced metabolic cleaning during sleep

2. immune system function improved with sleep

3. increased production of growth hormone during sleep

Glympatic system

immune system of the brain

Evolutionary Adaptation Theory

sleep patterns are different across species for reasons that most efficiently benefit the animal

Brain Plasticity Theory

brain needs some period of time for critical changes to occur

[BPT] Declarative Memory

info of facts benefits from slow-wave sleep

[BPT] Procedural Memory

motor skills learning enhanced by REM sleep

Chronobiology

the study of biological clocks and biological rhythms within an organism

Biological rhythms are…

endogenous and entrainable

Free-running period

time between waking up each day

Rhythms entrain in response to…

zeitgebers-time givers

3 sleep related NTs

1. Adenosine

2. Melatonin

3. Histamine

Adenosine

“A” in DNA and ATP. energy level consumption increases = adenosine = sleepiness. caffeine antagonizes adenosine receptors. involved in inflammation, immune response, and modulation of heart rate.

Melatonin

an endogenous hormone that helps the brain regulate the sleep-wake cycle. pineal glands convert trytophan to melatonin and releases it to the bloodstream, which signals body to prepare to sleep.

Histamine

mediates sensation of itch, participates in inflammatory response, and activates immune system. wakefulness NT (opposite of adenosine and melatonin). helps with allergies

Suprachiasmatic Nucleus

the master clock. connection to the pineal gland and melatonin

Tuberomammillary Nucleus

major site of neuronal production of the wakefulness NT histamine

Lateral Hypothalamus

has neurons that produce wakefulness NT orexin. lost in severe narcolepsy

Reticular Formation

found in brainstem, present throughout midbrain, pons, and medulla

ARAS - Ascending Reticular Activating System

upward pathway from reticular formation to cortex. ARAS from midbrain to pons required for wakefulness.

Other neurons required for wakefulness:

noradrenergic neurons in the locus coeruleus and serotonergic neurons in the raphe nucleus of the reticular formation… project to cortex