Exam 2 Flashcards
What was seen in patients who died of insomnia
Inflammatory lesions of the anterior hypothalamus
What part of the brain is important for spindles and high amplitude slow waves
thalamus
Describe the ascending arousal system in the brain.
Sensory inputs that are critical for wakefulness go from midbrain and brainstem (pons and medulla) to the cortex
What does wakefulness depend on?
Activity of neurons within the brainstem and reticular formation
Where is REM sleep located in the brain?
Pons (upper brainstem)
Does wakefulness/sleep require input from the periphery?
no
What is the Raphe nucleus
Produces serotonin which is important for the transition from wake to sleep
What is the role of the hypothalamus in sleep?
Primary active NREM sleep promoting region
Describe the role of each part of the brain in the control of wakefulness.
- Locus coeruleus, Raphe, vPAG, TMN, Lateral hypothalamus, basal forebrain, LDT, PPT
Locus coeruleus: norepinephrine important for arousal and attention
Raphe: seratonin in upper brainstem, promotes wakefulness, transition to sleep –> drugs that impact seratonin = effect REM sleep
vPAG: dopamine important for arousal
TMN: in hypothalamus, histamine (wake promoting neurotransmitter)
Lateral hypothalamus: orexin - stabilizes wakefulness–> activate REM off cells
Basal forebrain: ACh promotes wakefulness
LDT: ACh –> active during REM, inhibit REM off cells (one way)
PPT: ACh –> active during REM, inhibit REM off cells (one way)
Which of these project to straight to the cortex vs going through thalamus?
LDT and PPT project to the thalamus and then to cortex, all others project straight to the cortex
What is the PB?
Parabrachial complex: in the pons, uses glutamate which is an excitatory neurotransmitter that promotes arousal - is inhibited by GABA from the VLPO
What is the VLPO/MnPO?
Median preoptic nucleus/ventrolateral preoptic nucleus: active sleep system in the hypothalamus - secretes GABA (dominant inhibitory neurotransmitter in the brain) which inhibits other neuron groups to promote sleep
Which neuron groups are inhibited by the VLPO?
TMN, PeF, Raphe, vPAG, LC, PB, LDT, PPT (not BF)
What is the PFZ?
Parafacial zone: in the medulla - promotion of SWS (NREM) by inhibiting PB
How do the wake and sleep centers work together?
They mutually inhibit each other, whichever has stronger inhibition tells whether someone is awake or asleep
What is adenosine?
Sleep promoting neurotransmitter
Where and how does adenosine act?
Basal forebrain: inhibited by adenosine
Ventral lateral preoptic area (VLPO): excited by adenosine
Cortex: inhibited by adenosine
Where does adenosine come from?
Byproduct of cellular metabolism (breakdown of ATP)
How is adenosine involved in the control of sleep (general) and how was this discovered?
Involved in process S: builds up with time and dissipates with sleep
Discovered by measuring ECF in the basal forebrain of sleep deprived rats
How do glia (astrocytes) contribute to sleep?
Need to deactivate glutamate to sleep. Astrocytes surround a synapse and when glutamate is released, it binds to the postsynaptic cell as well as astrocytes. This releases calcium and ATP which is converted to adenosine. Adenosine binds to inhibitory receptors on both neurons and inhibits them
What is the result of this pathway with astrocytes?
Similar to negative feedback - can cause local sleep in these neurons (which can result in performance impairments)
How does the SCN influence sleep/wake centers in the brain?
Has input to both
SCN enhances arousal during the day through input to the dorsal medial hypothalamus (DMH) which projects to arousal centers
SCN enhances sleep during the night by projecting to the VLPO
What parts of the brain and neurotransmitters are important for NREM sleep?
Basal forebrain (GABA)
PFZ (GABA): SWS specifically
Anterior hypothalamus (5-HT): transition to sleep, initiates NREM
Immune factors (prostaglandins and cytokines)
Thalamus: sleep spindles and slow waves
What parts of the brain and neurotransmitters are important for REM sleep?
Pons
Increase in acetylcholine
Suppression of NE, 5-HT, Hist (practically silenced)
How does REM affect emotion in memories?
REM strips emotion from memories
Which groups in the brain are essential to the REM-NREM sleep switch?
vlPAG/LPT (REM-off) and SLD/PC (REM-on) - both in the pons
How do these groups (REM-on vs REM-off) work together?
Mutually inhibitory using GABA: if REM-on is more active → have REM and vice versa
What else contributes to the REM-NREM sleep switch
VLPO: promotes REM by inhibiting REM-off
Lateral hypothalamus: releases orexin which activates REM-off cells
LDT/PPT: promote REM by inhibiting REM-off
LC/Raphe: activate REM-off cells
What is the pattern of firing during the transition from NREM sleep → wake?
Norepinephrine (LC) begins increasing → basal forebrain starts → transition occurs → VLPO stops immediately → TMN starts firing
What is the pattern of firing during the transition from wake → light NREM sleep?
LC and TMN quiet → VLPO starts → transition occurs → BF inhibited by adenosine takes longer to quiet
What can cause chronic insomnia?
Damage to the hypothalamus
How much effect does genetics have on sleep patterns?
Small to moderate genetic contributions
What is a cause of the genetic difference in sleep and what factors of sleep are affected?
Genetic variation of adenosine deaminase (breaks down adenosine) affects the duration and intensity of sleep in humans
Describe the effect of this genetic difference.
G/A population (small proportion) has much more deep sleep than the majority
What is the ADORA2A and how is it affected by genetics?
Adenosine receptor that is responsible for the effects of caffeine and modafinil (wakefulness promoting drug) - can have two haplotypes: HT4 and non-HT4
HT4 haplotypes are insensitive to caffeine but sensitive to modafinil, non-HT4 haplotypes are sensitive to both (increase performance and sleep is disturbed by caffeine)
Describe the data on the short sleep family.
Short duration of sleep with no negative effects due to a point mutation in the DEC-2 gene (transcriptional repressor), unknown whether there are long term consequences of less sleep
What genes affect obstructive sleep apnea?
Sleep wake genes, craniofacial morphology genes, ventilatory control genes, obesity genes, pleiotropic genes (i.e. leptin) - all increase risk
Describe the mammalian SCN clock gene model.
Process that takes ~24 hours
BMAL and CLOCK proteins bind to the promoter regions of Per and Cry genes in the nucleus to activate transcription → ribosomes in the cytoplasm translate the mRNA into two versions of PER and CRY proteins: one that’s large and stays in the cytoplasm and one that’s small and goes back into the nucleus → small protein binds to the BMAL/CLOCK proteins to remove them from the promoter (inhibit their own transcription) → eventually protein complex dissociates and BMAL/CLOCK can rebind
What is CK1ε and how does it fit into this process?
Enzyme that helps with translocation of PER/CRY protein complex back into the nucleus, also interacts with CLOCK and BMAL
How is BMAL produced?
Produced when RORa protein binds to its promoter (RORa is inhibited by REV-ERBɑ)
What happened when the SCN was removed and how was it measured?
Bioluminescence oscillated for a long time → shows SCN is truly independent of neural stimulation
Measured this way because when PER2 is produced, so is LUC → bioluminescence
How does the BMAL/CLOCK process compare with other species?
Many things on earth have molecular clockwork - players different but process similar
What is the clockwork due to?
Expression of genes/proteins have delays - coordinated delays create a molecular cycle
Describe the anatomy of the SCN.
Has inner core and outer shell - core sends info to the shell
Describe the neurochemistry of the SCN.
Photic info received by the core from the retina - use glutamate and PACAP (excitatory) → 2 dominant peptides in the SCN (AVP, vasoactive intestinal peptide (VIP)) that are important for communication within the SCN → SCN neurons are GABAergic - allows coordinated firing to sync with eachother
How does light affect the neurochemistry of the clock cycle?
Light induces expression of the PER gene and CLOCK gene
What is the importance of the shell of the SCN?
Important in phase advance/delay
How does caffeine affect the circadian clock?
Causes a phase delay - lengthens circadian period through ADORA1 receptors
What are ADORA1 receptors?
Adenosine receptors, levels show circadian rhythm
How does caffeine affect ADORA1 receptors?
Acts as an inverse agonist (causes the opposite effect) → increases intracellular cAMP
What are the PER34//4 and PER35/5 polymorphisms?
Repeated sequence of DNA, PER34/4 repeated 4 times, PER35/5 repeated 5 times
Did PER34//4 and PER35/5 have differences in PER3 RNA, melatonin and cortical levels (circadian markers) across the day?
No
What was different between PER34//4 and PER35/5 subjects?
The shorter allele (PER34/4) of PER3 is related with delayed sleep phase syndrome (DSPS) and eveningness whereas the longer allele of PER3 (PER35/5) is related with early morning type.
Greater performance decrement during the biological night in PER35/5
Describe familial advanced sleep-wake phase disorder?
Very early sleep onset: 4 hour advance of the sleep/wake cycle - autosomal dominant, highly penetrant, higher rates of occurrence in seniors, 1% of adults have it
Describe delayed sleep-wake phase disorder?
Delayed sleep onset, may have a genetic component, higher occurrence in younger adults, associated genes include AA-NAT (rate limiter of melatonin production) and CK1e
How do the majority of sleep promoting drugs work?
By GABA
What is the most common sleep promoting drug?
Zolpidem (brand name Ambien)
How does Zolpidem (Ambien) affect the GABA receptor?
Causes greater effect when GABA binds - increases GABA binding and hyperpolarization
Describe the GABA receptor.
Pentomeric receptor (GABA binds between the ɑ and β subunits, chloride channel - when opened, chloride flows in and hyperpolarizes the cell to inhibit it
What is the issue with affecting GABA receptors?
GABA receptors are all over the brain - affect more than the sleep wake system and have broad side effects
What do barbiturates do and what makes them dangerous?
Muscle relaxants - act like GABA and open channels - dangerous if used with alcohol
What are the risk factors for falls?
Biological factors, environmental factors, sleep problems (frequency of waking up at night, untreated insomnia, nocturia), use of sleep medications, daytime naps (indicates sleep issue)
How do sleep drugs affect fall risk?
Major increase in risk even with drug that has the least risk of falls
How do sleep drugs affect sleep inertia?
They make it worse, more of a cognitive effect in young adults than older adults
What is the effect of exogenous melatonin on daytime and nighttime sleep?
Daytime sleep: dose dependent effects improving sleep efficiency
Nighttime sleep: only improves latency to sleep, but not sleep quality
What are the cutoffs for a natural dose of exogenous melatonin?
<0.5mg is similar to natural levels, greater than that is not
At what age are melatonin levels highest?
Right before puberty
What are the effects of Ramelteon (melatonin agonist) on sleep?
Shortens latency to sleep at night, little influence on WASO at night, and improves daytime sleep (sleep efficiency and total sleep time)
When can caffeine affect nighttime sleep?
From 6 hours before bedtime to bedtime
What are the effects of caffeine on each factor of sleep?
Total sleep time:
Latency to sleep:
SWS and SWA:
REM sleep:
Daytime sleep:
Total sleep time: reduced
Latency to sleep: increased
SWS and SWA: reduced
REM sleep: no effect
Daytime sleep: greater disturbance
Are the effects of caffeine on sleep dose dependent?
yes
What is the effect of amphetamines on sleep and how do they work?
More disrupting to sleep than caffeine, work by release of excitatory neurotransmitters
What is modafinil and what are its effects on sleep?
Treatment for sleep disorders - increases latency to sleep, no measurable effects on sleep
What are the effects of alcohol on sleep?
Helps you fall asleep, but decreases sleep quality
Reduced latency, increased WASO, dose dependent suppression of REM, increased total sleep time, tolerance and withdrawal