Sleep Flashcards
(23 cards)
How do we measure sleep? (The machines) (3)
- Electroencephalogram (EEG): Electrodes attach to wires that sense nerve signals, which are electrical impulses.
- Electromyogram (EMG): Muscle activity and tone.
- Electrooculogram (EOG): Eye movements.
What type of states does an Electroencephalogram (EEG) detect.
• Beta:12-30Hz;typical of an aroused state. Reflects desynchronous neural activity.
• Alpha:8-12Hz;typical of an awake, relaxed state.
• Theta:4-8Hz;appears intermittently when people are drowsy and is prominent is early stages of sleep.
• Delta:<4Hz;occurs during the deepest stages of slow-wave sleep; reflected synchronized low frequency, large amplitude brain activity.
What are the two stages of sleep?
• Rapid eye movement (REM) sleep: associated with desynchronized EEG activity, rapid eye movements, dreaming, and muscle paralysis.
• Slow-wave sleep; stage 3&4 non-REM sleep: corresponds to large amplitude, low frequency oscillations of brain activity as measured with EEG. This pattern reflects synchronized bursts of action potentials in a large collection of neurons
How do animals act under extreme sleep deprivation?
Animals that underwent sleep deprivation often had cognitive problems and lost control of their metabolic processes and could not regulate their body temperature. After a short amount of time, they would soon lose too much weight and die.
What is the first theory of sleep? (Recovery & Energy Conservation)
• We sleep to conserve energy while we’re not “hunting” for food.
• Sleep lowers our metabolic rate, blood pressure, and heart rate.
Issues with the first theory…(Recovery & Energy Conservation)
• Sleep doesn’t “save” as much energy as it might seem.
• There is no clear correlation between physical/cognitive exertion and amount of sleep.
What is the second theory of sleep? (Learning & Memory/ Brain Processing)
Sleep provides a period of time when the brain can reorganize itself and stabilize memories.
• There are synaptic changes.
• Evidence of continued processing activity.
When in slow wave sleep: processes declarative learning
When in REM sleep: procedural learning
What is the third theory of sleep? (Waste Removal)
Sleep serves to clean up waste in the brain that accumulated during wakefulness.
• The glymphatic system: removes excess proteins and waste from the interstitial space via cerebrospinal fluid (CSF).
• Glial cells shrink, CSF increases.
• Economies of scale: smaller brains vs. larger brains.
What are Circadian Rhythms?
The daily change in behavior and physiological processes that follows a cycle of approximately 24 hours.
What part of the brain is the Circadian Rhythms controlled by?
Controlled by internal biological “clocks” in the suprachiasmatic nucleus (SCN) of the hypothalamus.
Light information directly from the retina helps keep the clock timed to 24 hours.
What happens when you lesion the suprachiasmatic nucleus?
SCN Lesion studies:
• Change the length and timing of sleep - wake cycles
• No effect on the total amount spent asleep
What is the Flip-Flop Circuit of Sleepiness/Wakefulness? (On and off)
ON
• Arousal systems are active
• Arousal systems inhibit vlPOA
• Animal is awake
OFF
• vlPOA is active
• vlPOA inhibits arousal systems
• Animal is asleep
What is vlPOA?
Ventral lateral preoptic area of the hypothalamus that promotes sleep.
* they also inhibit wake promoting neurons!
What is the The Sleep Molecule Hypothesis?
• Extracellular adenosine builds up over the course of the day.
• Adenosine activates vlPOA, inhibits acetylcholine neurons -> Flip-Flop circuit “OFF”
Where is Orexin Signalling from, and what does it do?
Orexin (also called hypocretin) is produced in the lateral hypothalamus (LH).
• Promotes wakefulness.
• Motivation to remain awake activates
orexin neurons.
• Most forms of narcolepsy are associated with the absence of orexin neurons.
Another flip-flop system controls REM sleep, what does the on and off too?
REM flip-flop “OFF”
vlPAG is active
vlPAG inhibits SLD
The animal is not in REM
REM flip-flop “ON”
• SLD is active
• SLD inhibits the vlPAG
• The animal is in REM
What is the SLD?
sublateral dorsal nucleus of the thalamus
What is the vlPAG?
ventrolateral periacqueductal grey
What is Narcolepsy?
• Characterized by periods of excessive daytime sleepiness and irresistible urges to sleep.
Accompanied by:
• Sleep paralysis
• Cataplexy
Related to the degeneration of orexin neurons in the hypothalamus.
What is Insomnia?
• Characterized as difficulty falling asleep after going to bed or after awakening during the night.
• 25% affected occasionally, 9% affected regularly.
What are Fatal Familial Insomnia &
Sporadic Fatal Insomnia?
Leads to hallucinations, delirium, confused states, and eventually death.
• Associated with progressive neurodegeneration around the thalamus, hypothalamus, and/or brain stem.
What are some sleep disorders that occur outside of rem sleep
Sleep disorders that occur during non-REM sleep or during transitions out of sleep.
• Walking, talking, groaning, crying, eating, masturbating, teeth grinding, etc. -> more prevalent in children
Sleep Terrors
• Overwhelming feelings of terror upon waking.
• Prevalent in people diagnosed with post-traumatic stress disorder (PTSD).
What are REM Sleep Behaviour Disorders?
• Neurological disorder in which the person does not become paralyzed during REM sleep and thus acts out dreams.
• Neurodegenerative disorder with some genetic component.
• Associated with more common neurodegenerative disorders such as Parkinson’s Disease.
