Neurobiology of Circadian Rhythms Flashcards
During what stage of sleep does an EEG most resemble wakefulness/stage 1 sleep?
REM sleep, but with muscle atonia
What are the five major brain regions that promote wakefulness? What neurotransmitters do they use?
- Ascending reticular activation system - serotonin (Raphe), norepinephrine (locus coeruleus), ACh (pedunculopontine/lateral tegmentum)
- Tuberomammillary nuclei of posterior hypothalamus - histamine
- Lateral hypothalamus - hypocretin/orexin
- Basal forebrain - ACh
- Cerebral cortex and limbic system - Glutamate
What are the two main drivers of non-REM sleep?
Ventrolateral preoptic nucleus (VLPO) and median preoptic (MnPO) areas: they are the sleep switch neurons
What two neurotransmitters do the nuclei controlling non-REM sleep use?
VLPO and MnPO use GABA and galanin and are more active during sleep; they turn off projections to wake-promoting regions
What are the 4 general brain regions associated with NREM sleep?
- Brainstem
- VLPO and MnPO
- Thalamus and cerebral cortex
- Homeostatic drive in the basal forebrain
What builds up in the basal forebrain to signal sleep?
Adenosine; blocked by caffeine
What are the key structures in REM sleep?
Activation of the lateral dorsal tegmentum (LTD) and pedunculopontine tegmentum (PPT) and the cholinergic neurons within
During what stage of sleep/wake is the EEG low amplitude and fast frequency? When is it high amplitude and slow frequency?
During wake states (and sort of REM sleep) it is fast frequency with low amplitude. During NREM sleep it is slow frequency and high amplitude
What neurotransmitters are NREM inducing?
GABA and galanin, serotonin, and adenosine
What neurotransmitters induce wakefulness?
Acetylcholine, histamine, serotonin, norepinephrine, hypocretin
What neurotransmitters induce REM sleep?
Acetylcholine
What is the biological internal clock mediating circadian rhythms?
Suprachiasmatic nuclei, controls release of melatonin from the pineal gland
What is the name of a period that is about a day long? Longer than a day? Shorter than a day?
Day = circadian Shorter = ultradian Longer = infradian
What is a zeitgeber?
An external time cue
What is an efferent of the SCN that allows it control sleep/wake cycles?
SCN has projections to the hypothalamus and thalamus, the medial preoptic area, the anterior and lateral hypothalamus, and the LGN of thalamus. The key ones are the SCN efferents to subparaventricular nucleus and the medial preoptic area of the anterior hypothalamus
