Sleep and Circadian rhythms Flashcards
What are the features of sleep?
- 1) Unconscious. We never know we are sleeping while we are asleep.
- 2) We switch from awake to sleep instantaneously, it is not a gradual process
- 3) Parts of the brain can be very active during sleep
What is an EEG?
Records the fluctuations of the electrical activity of large ensembles of neurons in the brain, mostly in the cortex.
What are the different classes of sleep?
- Short wave sleep
- Rapid-eye movement
Describe short wave sleep
can be divided into four stages and is characterized by slow-wave EEG activity
Describe rapid-eye movement sleep
characterized by small amplitude, fast-EEG waves, no postural tension, and rapid eye movements
What happens in Stage 1 SWS?
- Shows events of irregular frequency and smaller amplitude, as well as vertex spikes, or sharp waves
- Heart rate slows, muscle tension reduces, eyes move about
- Lasts several minutes
What happens in Stage 2 SWS?
- Waves of 12 to 14 Hz that occur in bursts, called sleep spindles
- K-complexes appear–sharp negative EEG potentials
What happens in Stage 3 SWS?
•Early stage 3 sleep
–Continued sleep spindles as in stage 2
–Defined by the appearance of large-amplitude, very slow waves called delta waves
–Delta waves occur about once per second
•Late stage 3 (stage 4) sleep
–Delta waves are present about half the time
What happens in REM sleep?
•REM sleep follows SWS
–Active EEG with small-amplitude, high-frequency waves, like an awake person
–Muscles are relaxed—called paradoxical sleep
How do sleep patterns and needs change with age?
- Infants spend about 8 hrs in non-REM sleep and about 6 hours in REM sleep
- Children spend about 10-12 hrs a night sleeping (2-4 hrs of REM)
- Adolescents through adults sleep about 7-8 hrs (1-2 hrs in REM)
- Starting at about 50 REM sleep= 30-1hr and they only sleep about 6 hours
What parts of the brain are involved in neural control of sleep?
- Recticular formation
- Hypothalamus
- Forebrain
- Pontine system
What are some of the chemical controls of arousal?
•Histamine
–Cell bodies in tuberomammillary nucleus of the hypothalamus
–Increases cortical activation and arousal
•Hypocretin
–Cell bodies in lateral hypothalamus
–Has an excitatory, wakefulness-promoting effect
•Acetylcholine (Ach)
–Basal forebrain Ach neurons that activate cortex
•Norepinephrine (NE)
•Serotonin (5-HT)
What is the locus coeruleus involved in?
Norepinephrine
Arousal
-firing rate significantly decreases during SWS and REM sleep compared to waking
Describe the activity of the 5-HT neurons in the raphe nuclei
-firing rate decreases as we progress from active waking to quiet waking, to drowsiness, through stage 1, 2, and 3 sleep. It reaches its lowest during REM sleep and then the first second after REM sleep the firing rate significantly increases (past active waking level)
What area of the brain are involved in sleep promotion?
•Ventrolateral preoptic area (VLPA) of hypothalamus
–lesions produce total insomnia, leading to death
–electrical stimulation induces drowsiness
What part of the brain generates SWS?
•Basal forebrain
–Subset of GABA releasing neurons
-Need to have a connection between your basal forebrain and pontine system to have cycles between wakefulness and sleep
Why do we sleep?
- Energy conservation
- Adaptive value
- Body restoration
- Memory consolidation
What are some of the features of REM sleep?
–Dreaming
–Paralysis with some twitching: subceorelor nucleus sends out signals to motor neurons in the spinal cord
–Breathing heart rate irregular
–Rapid eye movements: pons sends signals to the tectum which causes this
What are dreams?
activation of the cortex which activates some memories and the cortex tries to tie bits of information together and they seem to make sense in the dream
What can sleep deprivation do to us?
•Cognitive function •Alterations in mood –Aggressive oppositional kids •Death (rats) –Immune function •Beauty sleep –Rated less attractive
What is insomnia?
•Insomnia: Difficulty falling asleep or waking early
–Transient- lasting one to several days
–Chronic- lasting weeks, months or years
•Causes:
–Hyperarousal due to stress, anxiety or excitement
–Time zone changes
–Sleep environment, e.g. noises
What is snoring?
•Snoring:
–Narrowing of airway
–Vibration of soft tissue
What is Apnea?
–Airway closes shut during snoring for a few seconds up to 1 minute.
–Obesity increases risk of apnea
-treated with continuous positive airway pressure
What do pontine lesions result in?
•REM sleep –Atonia/paralysis –Inhibition of spinal motor neurons •REM sleep behavior disorder –Act out dreams
