Lec 19 Sleep

sleep is naturally recurring state characterized by

reduced or basent conciousness, suspended sensory activity, inactivity of most voluntary muscles

sleep occurs in what animals

all mammals, birds, and most reptiles

sleep is controlled by

brainstem nuclei with projections to brain and spinal cord

does brain remain active while you sleep

yes, brain is active while sleeping

humans spend … of their lives sleeping, or … hours

1/3, 7.5 hrs

how is sleep measured

EEG which records electrical activity on scalp from thousands of cells

EEG’s are ___ spatial resolution, and has leads in which parts?

low spatial res, frontal, temporal, central, parietal, occipital leads

What are the two main phases of sleep?

Non-REM and REM sleep

What are 3 major reasons for sleep?

ecological adaptation, energy conservation/restoration, memory consolidation

eco adaptation

difficult for predators to hunt in the dark at night, so prey sleep then to save energy

in terms of energy conservation/restoration, what happens to glycogen and metabolism when you sleep?

glycogen replenishes, metabolism decreases to reduce heat loss on colder nights

What effect does sleep deprivation have on the immune system?

It compromises it

how does sleep affect memory consolidation?

strengthens synaptic connections induced during waking hours, spatial location info is consolidated in rats

rat experiment sleep

experimental rat was kept awake and control rat could sleep, exp rat lost body weight and total sleep deprivation led to death in 3-4 weeks

What type of animals have single long periods of sleep?

Predators like humans, long period of nocturnal or diurnal sleep

How do prey animals sleep differently?

They sleep in short intervals of minutes to maintain vigilance

What is unique about dolphin and seal sleep?

One brain hemisphere sleeps while the other stays awake

first hour of sleep is

non-rem

What characterizes Stage I sleep?

drowsy, EEG has decreased frequency, increase in amplitude

What characterizes Stage II sleep?

Light sleep; lower frequency, increase amplitude, spike clusters/sleep spindle

What characterizes Stage III sleep?

Moderate-deep sleep; even lower frequency and higher amplitude

What characterizes Stage IV sleep?

Deep sleep; delta waves, low frequency, high amplitude

What is the EEG trend from wakefulness to Stage IV sleep?

Amplitude increases and frequency decreases

When does REM sleep occur?

After non-REM sleep stages

How long does the first REM period last?

About 10 minutes, gets longer as sleep continues

How does EEG during REM compare to wakefulness?

It looks similar to being awake

How many REM periods occur per night?

About 5

What brain waves are associated with wake?

beta eyes open, alpha eyes closed

What brain waves are associated with sleep?

Theta(stage 1) and delta waves(stage 4)

deep sleep is characterized by …. activity in….

synchronous activity in pyramidal cortical neurons

What does synchronization of neurons cause in EEG?

Increased amplitude (delta waves)

How do heart rate and respiration change in non-REM vs REM sleep?

slow down in non-REM sleep and increase in REM sleep.

REM sleep increases from 10 minutes to

50 minutes in final cycle

which stage of sleep is only present in the first 2 sleep cycles?

stage 4 non-REM

EOG

electroOCULOgram, eye movements in REM

EMG

electroMYOgram, muscle movement at onset of sleep and right before waking

When does sleepwalking and talking occur?

During non-REM sleep

When does dreaming occur?

Mostly during REM sleep, combo of memory and hallucinations

dreams last … hrs for both REM and n-REM

2 hrs, mostly in REM

What are dreams like in REM vs non-remsleep?

in REM, dreams are vivid and emotional, bizarre

in non-REM, dreams are less vivid, less emotional, more related to everyday activities, Sigmund Freu’s day residue

What are two possible functions of dreams?

Memory consolidation and unwanted memory disposal(would otherwise become intrusive+compulsive)

What is the activation synthesis theory?

Dreams result from random cerebral cortex firing during REM, forebrain creates a story to make sense of nonsensical sensory info, this explains irrationality of dreams in REM

how brain knows its night/day

Light sensed by photosensitive retinal ganglion cells (with melanopsin photopigment) sets the biological clock by sending signals to the suprachiasmatic nucleus (SCN), then via the paraventricular nucleus(hypothalamus) and preganglionic sympathetic neurons(spinal cord) to the pineal gland, which releases melatonin.

What brain structure is central site for circadian control?

Suprachiasmatic nucleus (SCN) of the hypothalamus, evidence is SCN lesion in rat abolished sleep-wake cycle

SCN controls which circadian rhythms

sleep • physical activity • alertness • hormone levels • body temperature • immune function • digestive activity

SCN neurons hae internal endogeneous 24-hr rhythm that persists when…

external time cues are removed

human in a cave, deprived of time clues would…

begin free-running on a cycle of 24-hrs based on internal clock.

What hormone is called the "Dracula of hormones"?

Melatonin, only comes out at night

in darkness, SCN turns on pineal gland to make melatonin starting from

9PM for 12 hrs

body temp and motor activity when we sleep is decreased due to…

melatonin

What happens to melatonin production in elderly people?

It decreases, so elderly sleep less at night

during REM sleep, which happens to limbic activity and frontal cortex activity?

increased limbic activity (amygdala, hippocampus, pontine tegmentum, anterior cingulate cortex)

decreased frontal cortex activity (dorsolateral prefrontal cortex, posterior cingulate cortex inactivated)

stimulation of what woke the cat in experiment?

Cholinergic neurons (Reticular Activating System)

low-frequency pulse stimulation of … caused cat to sleep

lamina medullaris interna of the thalamus

sleep has interactions btwn which 3 brain structures

brainstem, thalamus, cortex

role of Cholinergic nuclei near the pons-midbrain junction

low activity during non-REM, increases during REM, high when awake

What is the role of noradrenergic neurons from the locus coeruleus (LC)?

inactive during sleep, active during waking,arousal,stress

What is the role of serotonergic neurons from the raphe nuclei?

Active during waking, decreased or inactive when asleep

What is the role of histamine neurons in the TMN?

slow firing when tired, stop firing when asleep, fires rapidly when waking, modulates LC and raphe

which 2 chemicals promote wakefulness?

orexin and histamine

antihistamines cause

drowsiness

TMN is activated by ….

orexin from lateral hypothalamus

VLPO lesion causes

insomnia

VLPO of hypothalamus inhibits..

wake circuits, causes onset of sleep

Antihistamines make people drowsy because they A. inhibit the cholinergic nuclei in the brainstem. B. excite several classes of neurons in the raphe. C. mimic noradrenaline and serotonin at several metabotropic receptors. D. are selectively taken up by VLPO neurons. E. block the effects of tuberomammillary hypothalamic neurons.

E, block effects of TMN

chart of sleep wake centers

Projections from brainstem modulate activity of thalamocortical projections

Ascending projections from LC (NE), raphe (5HT), reticular activating system (ACh) and tuberomammillary nucleus (histamine) ➔ thalamocortical neurons ➔ pyramidal cortical neurons

What are the two states of thalamocortical neurons?

Intrinsic bursting oscillatory(sleep) and tonic active (wake)

What happens during intrinsic bursting of thalamocortical neurons?

sleep, thalamocortical neurons synchronize with cortex

oscillation decreased by activation of ascending systems causes what…

diminishes the high amplitude, low frequency waves of sleep

What is tonically active firing of thalamocortical neurons associated with?

awake, thalamocortical neurons depolarized by RAS, transmit info encoding peripheral stimuli to cortex

What is insomnia?

Inability to sleep long enough or deeply enough, caused by stress, jetlag, depression, caffeine, age altering NT’s

What is sleep apnea?

Breathing interruptions during sleep causes little to no slow-wave sleep and less REM, caused by pharynx muscle problems or compressed by obesity, rise in CO2 causes person to inhale by reflex and wakes person up

What is narcolepsy?

frequent 30 sec to 30 min REM sleep attacks without entering non-REM, animal studies show mutation in ORX2 gene

causes of jet lag aka desynchronosis

internal vs external clock, eating chocolate for breakfast prevents jetlag

Delayed sleep phase vs advanced sleep phase

DSPS- out of phase with 24 cycle, later everyday

ASPS- out of phase with 24 cycle, earlier everyday

What is non-24-hour sleep-wake syndrome?

Circadian rhythm not synchronized to 24-hour day

What is shift work disorder or situational circadian rhythm disorder?

Circadian disruption from work schedules

What is somniphobia?

Fear of falling asleep

What is hypopnea syndrome?

Abnormally slow respiratory rate during sleep

What is parasomnia?

Disruptive or inappropriate behaviors during sleep

What is bruxism?

Grinding or clenching teeth during sleep

What is periodic limb movement disorder (PLMD)?

Involuntary limb movements during sleep

What is restless legs syndrome (RLS)?

Uncontrollable urge to move legs, without PLMD

What is sleep paralysis?

Temporary paralysis before or after sleeping

What is nocturia?

Frequent nighttime urination

What is enuresis?

Bedwetting during sleep without waking