Sleep Flashcards
what are features of sleep
Altered consciousness Reduced movement and responsiveness Typical posture Homeostatic regulation Daily rhythmicity
what are specific features of sleep in higher organisms
Brainwave patterns
Loss of muscle tone
Sporadic eye movement – characteristic in different phases
slow electrical stimulation of this area causes the animal to spontaneously fall asleep
the thalamus
stimulation of this area causes a state of wakefulness and arousal (caused sleeping cat to wake)
the reticular activating system - cholinergic neurons near the junction of pons and midbrain
what is an electroencephalogram
a test where an electrode is placed on the skull to record the electrical signals coming from the brain
what causes slow wave rhythmic signals
the sum of individual firing of neurons in a coordinated manner
what are the EEG characteristics during the first hour of sleep
beta wave activity (characteristic of awake state 15-60Hz) lengthens and lowers in frequency to theta waves in stage 1 (4-8Hz)
stage 2 waves further lengthens and lowers in frequency other than when the sleep spindle occurs
in stage 3 you see even slower brainwaves (2-4Hz)
the slowest waves delta waves (0.5-2Hz) are seen in stage 4 at the end of the hours
what is the slowest sleep waves
delta waves
what is NREM sleep
Non-rapid eye movement sleep - encompasses the first 3 stages of sleep characterised by Reduced physiological activity, Shift to parasympathetic activity and maintenance of Thermoregulation
what occurs during the three NREM stages of sleep
slowed breathing, muscle activity, heartbeat, and brain waves
when do dreams occur
during REM sleep
how often do REM periods occur
every 90 to 120 minutes (with the first period being the shortest)
what happens to your sleep as you age
Similar amount of REM sleep
Diminishing stage 3,4 (deep) sleep
Increasing sleep fragmentation
what is the deepest stage of sleep and when does it occur
stage 3, 4 are the deep stages and they occur early (within the first hour)
what is a polysomnogram
electrodes are put on the eyes and neck to measure heart rate, respiration, eye movemetns and penile erection to observe the patterns in sleep
what are the similarities and differences between REM sleep and the awake state
resembles wake state for • brain activity • heart rate • respiration diverges for • eye movement • muscle tone • Thermoregulation • penile erection/vaginal lubrication
what is responsible for the suppression of the somatosensory response and muscle relaxation during REM sleep
Inhibition of cells in the dorsal colum nuclei results in diminished response to somatic sensory stimuli
Inhibition of the lower motor neurons results in paralysis
gaba signals
what areas of the brain are activated during REM sleep
Anterior cingulate cortex, Amygdala, Parahippocampal gyrus (some cholinergic nuceli that are only activated during rem sleep), Pontine tegmentum
what areas of the brain are inactivated during REM sleep
Dorsolateral prefrontal cortex, Posterior cingulate cortex
what electrical features is the awake state characterised by
high frequency (15-60Hz) low amplitude activity (∼30 μV) - beta activity
descent into stage 1 NREM sleep is characterised by
decreasing EEG frequency (4–8 Hz) and increasing amplitude (50–100 μV), called theta waves
what is descent into stage 2 NREM sleep characterised by
by10–12 Hz oscillations (50–150 μV) called spindles, which occur periodically and last for a few seconds.
what are stages 3 and 4 of NREM sleep characterised by
Stage III = slower waves at 2–4 Hz (100–150 μV).
Stage IV sleep is defined by slow waves (also called delta waves) at 0.5–2 Hz (100–200 μV)
after reaching deep sleep what happens to the sleep sequence
the sequence reverses and a period of rapid eye movement sleep, or REM sleep, ensues.
what is REM sleep characterised by
REM sleep is characterized by low-voltage, high-frequency activity similar to the EEG activity of individuals who are awake.
what is the ventrolateral preoptic nucelus
The ventrolateral preoptic (VLPO) nucleus in the anterior hypothalamus is the major area of the brain that controls sleep induction and maintenance.
Its major neurotransmitter is GABA (inhibited during awake state)
during the awake state what keeps the ventrolateral preoptic nucleus off
The GABA release from the VLPO nucleus is inhibited by norepinephrine (NE) from the locus ceruleus.
what structure of the brain is responsible for the rhythmic regulation of sleep
the superchiasmatic nucleus
what loci are turned on during NREM and REM sleep
ventrolateral preoptic nucleus and the medial preoptic nucleus
what loci are turned on during wake and REM sleep but off during NREM sleep (what neurotransmitter is involved)
LDT and PPT
(laterodorsal tegmentum and PedunculoPontineTegmental Nucleus)
acetylcholine
what loci are turned on in wake state but off in both REM and NREM sleep - turned off by VLPO/MPOA toggle)(what chemicals are involved)
TMN (His) - TuberoMammillary nucleus LH (orexin) - Lateral hypothalamus LC (NE) - Locus coeruleus Raphe (5-HT) - vPAG (DA) - ventral PeriAqueductal Gray
what is considered the sleep/wake toggle switch
VLPO/MPOA
why do we need sleep
because if we dont we cant function and we die
what were the results of the study on preventing rats falling asleep and how was it carried out
Rat was put on a moving disk with an electrode measuring brain activity - as soon as they started to fall asleep the disk was moved so they fell into water and woke up - this caused the rat to start dying: they observed Debilitated appearance, Skin lesions, Swelling of the paws, Loss of motor control, Loss of EEG amplitude, Respiratory symptoms, Stomach ulcers
what are the cognitive impacts of sleep disruption
Inattention Changes in cortical EEG responses Slower computational speed Impaired verbal fluency Reduced creativity Reduced abstract problem solving Learning issues Lower IQ scores
give 5 examples of sleep disorders
primary insomnia primary hypersomnia narcolepsy breathing-related sleep disorder (snoring, obstructive sleep apnea) circadian rhythm sleep disorder
what is narcolepsy and what is the cause
are long-term brain condition that causes a person to suddenly fall asleep at inappropriate times
- symptoms daytime sleepiness, sleep attacks, cataplexy, sleep paralysis, excessive dreaming and waking at night
Orexin signalling defect caused neurodegeneration in orexinergic centre
what is cataplexy
sudden muscular weakness triggered by strong emotions such as laughter, anger and surprise
what causes the vicious cycle seen in primary insomnia
feelings of worry/ stress -> lack of sleep -> tiredness -> difficulty coping with daily life -> low self esteem -> feeling of worry/ stress
what is hypersomnia
an uncommon sleep disorder that causes you to be excessively sleepy during the day even after a good or prolonged night’s sleep
what are breathing-related sleep disorders
Primary snoring – tissues in the back of the throat vibrate
Obstructive sleep apnea – blocked airway (decrease in blood oxygenation, wake). Increased risk of cardiovascular disease, (pre-) diabetes, depression.
what are the types of circadian rhythm sleep disorders (4)
Non 24hour sleep wake syndrome - no synchronisation to the environmental light dark cycle but can maintain 24hour cycle (occurs in visually impaired people)
irregular sleep wake syndrome - no pattern (happens in chronically ill people who are in hospital, lights are always on)
delayed sleep phase syndrome - go to bed late and wake up late ( alot of the population would probably qualify)
advanced sleep phase syndrome - sleep early wake early (more similar to our ancestral state)
sleep is controlled in two ways, what are they?
Rhythmically (C) -based on circadian rhythms and light
Homeostatically (S) - based on how much sleep you’ve gotten
(rhythmic pressure alleviates in the morning but the homeostatic pressure remains if you didnt get enough sleep)
who discovered the period gene in fruit flies and is considered the father of neurogenetics
Seymour Benzer
what evidence is there for a daily timekeeper
control of overt rhythms
entrainment (alignment to external time cues)
free running rhythms (persistence of rhythms in the absence of environmental cues)
temperature compensation (maintain robust rhythm over road range of temps)
who received the Nobel prize for the discoveries of the molecules mechanisms controlling the circadian rhythm
The Nobel Prize in Physiology or Medicine 2017 was awarded to
Jeffrey C. Hall, Michael Rosbash and Michael W. Young
what is the delayed negative feedback loop that helps eukaryotes keep time
period gene makes period protein in the cytoplasm where doubletime binds it (limiting its stability so that it does not build up too quickly) - timeless binds to these two proteins and creates a heterotrimeric complex that is now able to enter the nucleus and shut down period and timeless production - once the levels of period get too low the whole process starts again (24hour cycle)
entry into the nucleus occurs around midnight
what are the mammalian equivalents of the eukaryotic timeless and doubletime proteins
timeless= Cytochrome CRY doubletime= casein kinase 1 episolon/delta (CK1ε and CK1δ)
describe the steps of the SCF mediated protein degradation of Per
double time phsophoylates period enabling recognition by SLMN (fbox adaptor protein) and recruitment of SCF complex. Attachment to the SCF complex allows E3 to add ubiquitin to period which is then recognised by 26S proteosome and degraded.
what percentage of genes are rhythmically controlled
50%
describe the mechanism of the sleep homeostat in dorsal fan shaped body of Drosphilia
1) At onset of sleep:
Sandman channels internalise and dFSB neuronal firing starts involving active Sh/Hk channels.
2) During sleep:
A-type Shaker(Sh) K+ channels turn off and tonic firing↓ when Hyperkinetic(Hk) subunit exchanges NADP+ for NADPH
3) Upon arousal (DA):
Sandman K+ leak channels relocate to plasma membrane and hyperpolarize cells.
4) During wake:
Mitochondrial metabolism produces Reactive Oxygen Species → NADPH for NADP+ exchange for Hyperkinetic turning on Sh/Hk
how does light induce the SCF mediated degradation of timeless
when CRY (cytochrome) is hit by blue light it undergoes conformational changes that allow it to bind to timeless, incurring phosphorylation of timeless by a kinase. causes recruitment of SCF complex by JET (jetlag) binding with timeless. allowing E3 to ubiquinate timeless and 26S proteosome to recognise this and degrade the protein
what happens when drosophila are exposed to light in the early night time
Cry causes destabilisation of timeless causing levels to fall and the process to start over - phase delay
what happens when Drosophilia are exposed to light in the late night
causes degradation of timeless, speeding up the time it takes for it to reach reactivation - resetting the cycle back to early dawn - a phase advance
how does light act on the mammalian clock
light hits retina which sends projections to the suprachiasmatic nucleus of the hypothalamus where the signal acts on the transcription of the period via other transcrition factors
what 3 clusters of neurons synchronise the circadian rhythm via neuropeptides
dorsal lateral neurons, small ventrolateral neurons, dorsal neurons type 1 - neuropeptides used are neuropeptide y (fly sNPF) and VIP (fly PDF)
