Johan Dahlin
178e5fe7c0
4.2 KiB
Cirkadiansk rytm, sömn och medvetande.pdf
OCR Transcript
- Pages: 25
- OCR Engine: pymupdf
- Quality Score: 1.00
Page 1
Cirkadiansk rytm, Sömn och Medvetande Eric Hanse HT 2025
Page 2
Circadian rhythms appeared 2-3 billions years ago Sleep, like ageing17,18, may be an inescapable consequence of aerobic metabolism.
Page 3
Circadian organization in mammals Hastings et al 2018 Nat Rev Neurosci 19:453-469
Page 4
The central clock in nucl. suprachiasmaticus (SCN) synchronizes circadian rhythms Control After lesion of the SCN
Page 5
Model for the circadian clock
Page 6
The molecular clock is based on delayed negative feedback
Page 7
The SCN does not keep an exact 24 hour cycle if not entrained ”The third eye” -melanopsin-containing ganglion cells sleep wake
Page 8
SCN signals to the rest of the brain and body both electrically and with hormones Higher frequency of action potentials during the day Homones, for example: Cortisol – highest levels when we wake up Melatonin – a “dark hormone”, released from corpus pineale Welsh et al (1995) Neuron 14:697
Page 9
Pracucci et al 2023 Nat Comm 14:7108 Alfonso et al 2023 Nat Neurosci 26:64-78 I.c.[Cl-] is higher during wake and lower during sleep in cortical pyramidal neurons
Page 10
Sleep “Sleep is the readily reversible state of reduced responsiveness to and interaction with the environment”
Page 11
Why do we sleep? Processing of memories ”Brain wash” Hauglund et al 2025 Cell 188: 1-17 Brodt et al 2023 Neuron 111: 1050-1075
Page 12
NA, 5-HT, Histamin High Low Very Low Ach High Low High Orexin High Low Low Energy consumption High Somewhat lower High Awake, NREM and REM Hobson (2005) Nature 437:1254
Page 13
The ”wake nucleus” in the hypothalamus (LHA) excites the modulatory transmitter systems using Glu/Orexin Saper et al (2005) Nature 437:1257 LC –Locus Coeruleus BF – Basal forebrain LH – Lateral Hypothalamus VLPO – VenteroLateralPreOptic TMN - TuberoMammillary Nucl LDT/PPT – LateroDorsal- and PeduncoPontine Tegmental nucl
Page 14
The ”sleep nucleus” in the hypothalamus (VLPO) inhibits the modulatory transmitter systems using GABA/Galanin Saper et al (2005) Nature 437:1257
Page 15
The cells in LHA and VLPO are under circadian control by the SCN via the DMH in the hypothalamus Saper et al (2005) Nature 437:1257
Page 16
SCN DMH VLPO GABA/Galanin NA, 5-HT, NA, ACh Light Meals, Temperature, Emotions / Cognition
LHA Orexin +
Somnogenic factors Somnogenic factors +
Sleep control
Somnogenic factors
Page 17
Adenosine is an ”somnogenic” factor contributing to sleep pressure
Page 18
Three different brain states: Wake, NREM & REM Wake Non-REM REM NA, 5-HT, Histamin High Low Low ACh High Low HIGH Orexin High Low Low EEG Desynchronized Synchronized Desynchronized Energy consumption High Moderate High Muscle tonus High Moderate Low Breating / Heart rate Regular Regular Oregelbunden Temperature regulation Functioning Functioning Non-functioning Eye movements Vision Slow Fast (REM)
Page 19
Timofeev & Chauvette (2018) Neuron 97:1200-1202 Modulatory transmitters and changes of e.c. ion conc. regulate the activity of cortical neurons EMG I.c. EEG
Page 20
An optimal level of neuronal network activity in the brain - Criticality Hengen & Shew (2025) Neuron 113:1-17
Page 21
Loss of consciousness during sleep and anaesthesia because ”decoupling” of cortical pyramidal neurons? Marvan et al (2021) Neurosci Conscious 7: 1-17
Page 22
Cortical pyramidal neuron with two action potential initiation zones comparing Content with Context Granato et al 2024 Neurosci and Biobehav Rev 161: 105688 ”Predictive coding” and ”Predictive error”
Page 23
Simultaneous apical feedback and basal feedforward inputs provide synergistic firing output Larkum (2012) TiNS 36:141-149
Page 24
Promoting apical and basal coupling enables consciousness Suzuki & Larkum (2020) Neuron 180: 666-676
Page 25
(No content)