Sleep Physiology and CNS Respiration Control (Bond University) PDF

The Physiology of Sleep …and a bit of breathing MEDI11-102...

The Physiology of Sleep …and a bit of breathing MEDI11-102 Dr Jacob Thorstensen Assistant Professor (Medicine) [email protected] CRICOS Provider Code: 00017B TEQSA: PRV12072 1 Please remember to check in via Osler! CRICOS Provider Code: 00017B TEQSA: PRV12072 2  Copyright Warning. This material has been reproduced and communicated to you by or on behalf of Bond University in accordance with section 113P of the Copyright Act 1968 (Act). The material in this communication may be subject to copyright under the Act. Any further reproduction or communication of this material by you may be the subject of copyright protection under the Act. DO NOT REMOVE THIS NOTICE CRICOS Provider Code: 00017B TEQSA: PRV12072 3 What are our objectives for today? LO1) Describe what EEG is and identify common patterns of brain activity LO2) Describe consciousness clinically LO3) Explain the components of sleep LO4) Describe how the reticular formation controls wakefulness LO5) Outline the importance of sleep and define some common sleep disorders LO6) Review how the CNS controls respiration LO7) Explain how breathing is controlled during sleep CRICOS Provider Code: 00017B TEQSA: PRV12072 4  But first…why do we sleep? HINT: What is sleep? Sleep “is an active state of unconsciousness produced by the body where the brain is in a relative state of rest and is reactive primarily to internal stimuli” Brinkman JE, Reddy V, Sharma S. Physiology of Sleep. CRICOS Provider Code: 00017B TEQSA: PRV12072 5  But first…why do we sleep? Answer: We don’t know…we can only guess! Inactivity theory: Evolutionarily advantaged if inactive at night (less likely to be prey in dark) Hunting for food is less effective at night, so ↓ brain metabolism at night by Energy conservation theory: sleeping to conserve calories (aka during periods with limited food availability) We repair body tissues when we sleep (hormones for growth released in The restorative theory: sleep) Sleep is needed for brain reorganization (CLUE: Infants can sleep for more Brain plasticity theory: than 14 hours a day, a period of life when plasticity is highest!) CRICOS Provider Code: 00017B TEQSA: PRV12072 6  LO1) Describe what EEG is and identify common patterns of brain activity CRICOS Provider Code: 00017B TEQSA: PRV12072 7 LO1) Describe what EEG is and identify common patterns of brain activity So how can we study sleep and best quantify it? Maybe we can non-invasively measure the activity of the brain (cortex)? Enter the…electroencephalogram (EEG) Yet, polysomnography (PSG, aka a sleep study) also involves HR recordings (ECG), muscle activity measures (EMG), eye muscle activity (EOG), oxygen saturation and other measures. Electrical activity = EEG trace EEG activity = summed firings of many neurons But how does the EEG trace change Source: Clinical Neuroscience Johns, Paul, BSc BM MSc FRCPath © 2014. across different brain states/sleep? Source: Costanzo Physiology Costanzo, Linda S., PhD © 2022. CRICOS Provider Code: 00017B TEQSA: PRV12072 8 LO1) Describe what EEG is and identify common patterns of brain activity How does EEG differ between “brain states”? Which one are you ↓ amplitude Awake (but somewhat ↑ frequency focused) Beta β right now? 13-30 Hz Awake (but Alpha α AROUSAL LEVEL relaxed) 8-13 Hz Very deep Theta relaxation 4-8 Hz θ Delta ↑ amplitude Deep sleep