Sleep Flashcards
What are the two main processes of sleep-wake regulation?
- Circadian Process C: internal clock
2. Homeostatic Process S: sleep pressure
What are the major nuclei of the hypothalamus involved in sleep-wake regulation?
suprachiasmatic nucleus and ventrolateral preoptic area
What area of the pons is involved in the regulation of sleep-wake cycle?
the ascending reticular activating system
What is the human circadian rhythm generator and to where is it localized?
the internal clock that has been localized to the suprachiasmatic nucleus (SCN)
When does the output of the SCN peak?
Through the end of a major sleep period and into the middle of the subsequent wake period in each 24 hour cycle.
when is the minimum output from the SCN?
as the wake period ends and sleep begins
What is the crucial role of the SCN circadian rhythm generator?
What process is it associated with?
maintain wakefulness
It is associated with process C
How does light promote wakefulness?
Light hits the retinal ganglion cells that contain melanopsin. The ganglion cell depolarizes and tranduces its signal which travels along the retinalthalamic tract to the SCN of the anterior hypothalamus.
The SCN projects to the PVN which projects to the sympathetic pathway to cervical ganglion.
The postsynaptic of the cervical ganglion regulates the pineal gland which releases melatonin.
Which process drives the homeostatic drive to sleep?
Process S
When is S at at minimum?
It is at a minimum when we have had enough sleep. It increases over the course of the day as we get sleepier. It decreases while we are sleeping.
If you stay up too late, what happens to Process S? What happens to slow waves?
It is highly increases, because you want to sleep. There are increased slow wave activity and longer sleep the next day.
Who demonstrates more significant slow wave response after sleep deprivation?
young people are more affected by sleep deprivation
What does sleep deprivation show on the graph of visual task test?
There is huge standard deviation between people on the effects of sleep deprivation, but overall, sleep deprivation delays response time to visual tasks.
What are the five major stages of sleep?
1-2 are light sleep, 3-4 are deep sleep, and 5 is REM sleep.
What is REM sleep?
transitional step between sleep and wakefulness. It is characterized by rapid eye movements on the EOG
What is the posterior dominant rhythm?
8-12 Hz called the alpha rhythm which is normal brain activity with the eyes closed
What is alpha rhythm?
the normal brain eelctrical activity of an adult when the eyes are closed
What are the two overarching categories of sleep?
REM- rapid eye movement
NREM- non-rapid eye movement
What is the test to record human sleep?
polysomnography
Which sleep stage is more crucial for performance of mental tasks, REM or NREM?
NREM
What three recordings are taken when recording someones sleep cycle?
EEG- occipital and central scalp
EOG- extraocular eye movement
EMG- chin muscle movement
There are two kinds of REM. What are they and what are they characterized by?
Tonic REM- no eye movement
Phasic REM- eye movement
What does the EEG pattern most closely resemble when the person is in REM sleep?
Is the amplitude of spikes high or low?
What is the frequency?
What does this suggest about cerebral activity?
Awake
low amplitude waves
frequency in the alpha (8-12Hz) or beta (13-20Hz) range
This suggests that the cerebral cortex is active with desynchronized neuronal activity
How do you distinguish REM from Awake on the EEG?
Look at the EOG lines to identify rapid eye movement and look at the EMG to see if there is low amplitude chin activity
what percent of a nights sleep is REM?
20-25% ( the second 3-4 hours of the nights rest)
What is the main difference between REM and NREM activity on the EEG?
REM is not synchronized
NREM has synchronized EEG activity
What part of the sleep cycle is associated with synchronized EEG recordings?
What does the waveform look like?
What frequency are the waves in this stage?
NREM sleep has lower frequency, higher amplitude waves
The frequency will be in the theta (4-7Hz) and delta (1-3Hz range)
What are the different wave frequency ranges from lowest to highest?
delta (1-3 Hz)
theta (4-7 Hz)
Alpha (8-12 Hz)
Beta (13-20 Hz)
What four stages was NREM sleep formerly divided into?
1-2 light sleep
3-4 deep sleep
Currently what three stages are NREM sleep divided into?
N1- transitional stage
N2- cessation of conscious stimuli
N3- slow wave sleep
What are the characteristics of N1 stage of sleep? What do you see on the EEG?
it is the transitional stage where you feel yourself getting sleepy
EEG - replaces alpha waves with irregular theta waves. Vertex sharp transients occur sporadically
EOG- slow rolling of eyes
EMG- reduced chin movement amplitude from wake
What stage of sleep is most important for restoration, survival funcitons, mental tasks, conservation of the days memories, regenerate cells from the previous day?
N3- slow wave sleep
What are the characteristics of N2 on the EEG?
Irregular lower amplitude theta waves (like N1) but with sporadic high voltage K-complexes and 12-16Hz sleep spindles
What is a sleep spindle? In what sleep stage do you see them? what is the frequiency?
12-16 Hz wave seen in the N2 stage
Which sleep stage is the predominant stage of the sleep cycle?
N2 is about half the night sleep
How much of the night is slow wave sleep?
20-25%
What are the characteristics of N3 sleep on the EEG?
Delta frequency waves with very high amplitude
What sleep stage is most important for cognitive function?
What stage is most important for motor memory?
Deep
REM
When we are experiencing drowsiness, what two stages of the sleep cycle are we transitioning between and what would we see on the EEG?
Wake and N1 and we would see alpha to theta to alpha to theta
Why are cells in the wake cycles (and REM) desynchronyzed?
When we are awake, the cells are processing the world around them and each set of neurons is performing a specific and different task. They depolarize easier to incoming stimuli
Why are neurons synchronized in sleep?
They are recharging and not performing different tasks.
There is no incoming stimuli so the cells are hyperpolarized
Sleepiness is correlated with a lesion in what structure?
Sleeplessness is correlated with what structure?
Sleepiness- ARAS (which promotes wakefulness)
Sleeplessness- the anterior thalamus
What is the encephale isole preparation?
A lesion just below the medulla that spares the ARAS. Sleep-wake cycle is NOT disrupted.
What is cerveau isole?
A lesion transection the brainstem and the pontomesencephalic junction that disrupts the ARAS
What is seen on the EEG with an encephale isole preparation
Normal EEG
What would be seen on the EEG for a cerveau isole preparation
You would not have wakefulness so you would see sleep spindles, slow waves, and the low frequency high amplitude waves characteristic of NREM sleep
If the rostral reticular formation is stimulated, what would you see on the EEG and why?
You would see a transition from synchronous sleep waves to asynchronous alpha waves associated with the wake state
If you lesion the preoptic area of the thalamus, what would the person present with?
A persistant wake state, because the ARAS would promote wake and the preoptic area of the thalamus modulates it by promoting sleep. INSOMNIA
What are the six neurotransmitters that promote arousal and wakefulness?
- Ach
- NE
- Dopamine
- histamine
- Orexin
- Serotonin
Which neurons are cholingeric?
What are they responsible for?
pedunclepontine tegmental area and lateral dorsal tegmental area (PPT and LDT) make Ach to wake the person up.
This promotes low amplitude, higher frequency desychronized waves
When is the firing rate of cholingeric neurons in the brainstem and basal forebrain the highest? What does it promote?
Highest during wake and REM sleep. It promotes the release of Ach
What nucleus produces NE?
Locus ceruleus in the brainstem
When are Locus Cerulues neurons most active?
They are most active during wake, less active in NREM and least active in REM
When is NE cortical activation the strongest?
during periods of high stress
What neurons produce histamine?
Tuberomamillary nucleus of the posterior hypothalamus
When is tuberomamillary nucleus activity the highest?
Wake, then NREM and least active in REM
What do histamines do?
Promote wakefullness (why antihistamines like benadryl make you sleepy)
What nucleus secretes 5-HT (serotonin)?
the medial and dorsal raphe nucleus
When are the dorsal and median raphe nucleus most active?
most active during wake, less active in NREM and REM
What type of wake state does serotonin promote?
restful, quiet wake state. Low serotonin promotes lethargy
What nuclei make dopamine?1
Substantia nigra (pars compacta)
Ventral Tegmental Area
Posterior hypothalamus
When are extracellular levels of dopamine highest?
during the wake state.
What is frequently used to promote wakefulness and supress sleep?
Amphetamines that are dopamine receptor agonists (leaving more extracelluar dopamine available)
What do antipsychotic drugs block?
Dopamine receptors so they depress alertness
Where are orexins produced?
lateral and posterior hypothalamus
When are orexin levels highests?
during locomotion and arousal to promote feeding and foraging
Where are neurons known to promote sleep largely limited to?
What neurotransmitters are made in these neurons?
the ventral lateral preoptic area of the hypothalamus VLPO.
These neurons make GABA and galanin which inhibit neuronal firing in the ARAS
How does the VLPO promote sleep?
Negative feedback on the ARAS by secreting GABA and galanin inhibitors to the ARAS neurons
Drugs that enhance what neurotransmitter will induce sleeP?
GABA
What molecule increases in neurons over the course of wakefulness that contributes to sleep? Where do these molecules bind to promote sleep?
Adenosine binds to neurons in the basal forebrain to promote sleep because the basal forebrain activates the VLPO
Why do physically and mentally taxing activities promote sleep?
Adenosine builds up in the neurons, binds to neurons in the basal forebrain, signal to the VLPO which negatively feedsback on neurons in the ARAS.
Why does caffeine promote wakefulness?
It blocks adenosine receptors in the basal forebrain
In addition to adenosine, what other small peptides promote sleep?
inflammatory cytokines like tumor necrosis factor alpha
Once NREM is obtained, it cycles between what two stages while it waits for what neurotransmitters to stop firing?
N2 and N3 while it waits for NE, Serotonin and Histamine to stop firing
When HA, NE and 5-HT stop firing in NREM, what happens?
Cholingeric cells in the PPT and LDT are disinhibited which send Ach to the thalamus to desynchronize EEG activity and direct the person into REM sleep.
In addition PPT and LDT inhibit descending motor pathways which slow the muscle movement of the chin
What are the characteristics of Behaviorly Induced Insufficient Sleep Disorder?
daytime sleepiness, short sleep episodes, recovery on weekends
What are the characteristics of Delayed Sleep Phase?
What age group is this phase associated with?
Normal sleep time but stay up later at night and wake up later in the day. Common in adolescence
What is dream enacting behavior?
What neurological disorder is it associated with?
Excessive motor activity during REM sleep.
PArkinsons, Lewy Body Dementia, Multiple Sclerosis, pontine neoplasms
What is REM Behavior Disorder?
What drugs can it be a side effect for?
Where violent or confrontational dreams are acted out causing harm to sleeping partner.
Side effect for selective serotonin reputake inhibitors
What is narcolepsy?
What two forms can be witnessed?
Absence of what neurotransmitter is it associated with?
REM sleep intrudes into the wake state episodically.
With or without cateplexy.
It is caused by a lack of orexin
What is cataplexy?
loss of muscle tone with excitable or pleasurable stimuli. Associated with narcolepsy
