4 - Sleep Physiology Flashcards
How long do most people need to sleep?
7-8 hrs
Familial Insomnia
Plaques and thalamus degenerates
Lose ability to nap, then sleep
Death within one year
***Circadian Cycle***
Depends on?
Key Receptors/Pathway?
Presence of light
Retinal Ganglion Cells detect light, send info along retinohypothalamic tract, projects to Suprachiasmatic Nucleus (SCN) of Anterior Hypothalamus
What is the key structure for controling circadian rhythm of sleep-wake cycle?
Suprachiasmatic Nucleus (SCN)
What is the key hormone for regulating sleep?
Where is it produced?
Melatonin
Produced in Pineal Gland
Synthesis increases and light decreases
Alerting Signals
Major component of sleep load?
Generated by the SCN
Alerting Signals counters the sleep load‘built’ throughout the day
Adenosine major component of sleep load
Four Stages of Sleep (defined by EEG)
Stage 1 - N1/S1
Stage 2 - N2/S2
Stafe 3 - N3/S3
REM
What stage are sleep spindles found in, and what is their importance?
What other patterns are found here?
Stage 2
Important for consolidation of motor skill memory in young adults
- - -
K-Complex (higher amplitude)
Stage 3 sleep characteristics
Slow Wave Sleep
Deepest level of sleep; Delta waves
Hard to wake people up
Physiological Changes in NREM sleep?
Decrease muscle tone, heart rate, bp, body temp
Can still move
Sleep walk/talk
REM Sleep
Physiological changes?
Dreams?
Infants vs Adults
“Paradoxical” - Brain as active as when awake
Increase in BP, hr, metabolism
Paralysis of large muscles (not diaphragm)
Penile erection
MOST dreams occur during REM Sleep
Infants spend more time than adults
REM Rebound
If deprived, can go directly into REM sleep at next opportunity
Cycles of REM / NREM sleep?
After REM, brain cycles back through NREM
N3 occurs in 2nd cycle, not again
REM occurs ~ 90 minutes; duration increases with each cycle
Autonomic Activity in Sleep
REM vs NREM
REM - Sympathetic (erection)
NREM - Parasympathetic
What is a major characteristic of Stage 3 Sleep?
Low frequency, high amplitude EEG waves
Neural Circuit Governing Sleep?
Neurotransmitter/Location?
What is the counter area that will put you to sleep?
Reticular Activating System (RAS) = awake
Cholinergic near Pons/Midbrain Junction
Thalamus = sleep
What role does the Thalamus play in sleep?
Stimulation causes sleep
Gates sensory information, blocks input during sleep
Neurotransmitters:
Wakefullness
vs
Sleep
Wakefullness:
- Monoamines (dopamine, norepinephrine, serotonin)
- Acetylcholine
- Histamine (antihistamines block, make you sleepy)
- Orexin/Hypocretin
Sleep:
- Adenosine
- GABA
- Melatonin
- Galanin
VLPO
Ventrolateral Preoptic Nucleus
Sleep State; inhibit neurons responsible for wakefullness
Clinical: Insomnia
Cause: Stress, Anxiety, caffeine (adenosine), depression, medication
Clinical: Obstructive Sleep Apnea
Interupted breathing caused by partial or complete blockage of upper airway (loud snoring)
Wake up often, increased bp, obesity
CPAP machine treatment
Clinical: SIDS
Infants unable to arouse from SWS
Immature breathing control system may fail
Infants should sleep on their backs
(could be related to sleep apnea)
Clinical: Restless Legs Syndrome
Discomfort in legs at night
Helped by moveing legs
Middle-aged to older adults
Clinical: Narcolepsy
Excessive daytime sleepiness; may go directly into REM sleep
Defect in Orexin/Hypocretin-synthesizing Neurons
Lose muscle control (cataplexy) during episodes of emotion–fall down and immediately sleep
Clinical: REM Sleep Behavior Disorder (RBD)
Affected individuals can fight during sleep; mostly men over 50
Brainstem disorder; increased incidence of Parkinson’s
Sleep and Aging
Older = lighter, shorter times
Older = less SWS, less sleep spindles
Older = wake up frequently
Older = less melatonin
Older = less VLPO
