Wakefulness and Sleep Flashcards
Endogenous circadian rhythm
Internal mechanisms that operate on a 24 hour cycle. i.e.. wakefulness & sleep, eating & drinking, body temp.
Human circadian rhythm is longer/shorter than 24 hours?
Longer
External cues are important for keeping circadian rhythms on track - true/false
true
Zeitgeber “time giver”
A stimulus that resets circadian rhythm - tides, sunlight, arousal, meals, environmental temp.
Jet lag
stems from mismatch of circadian clock, and external cues
Mechanisms of the biological clock include:
Suprachiasmatic nucleus (SCN), Genes that produce certain proteins, Melatonin levels (neurotransmitter)
Suprachiasmatic Nucleus (scn)
Part of the thalamus, main control centre of circadian rhythms of sleep and temperature, located above the optic chiasm.
Neurons in the SCN respond to light through the …
Retinohypothalamic path
There are two types of genes that are important for circadian rhythms. Period and Timeless. They produce genes called …
PER and TIM. Oscillate. Low during day and high during night. Promote sleep and inactivity.
The Pineal gland
secretes melatonin to increase sleepiness, located posterior to the thalamus, controlled by the SCN.
Sleep is a state that the brain actively/passively produces
actively
Electroencephalography (EEG) revealed…
that sleep occurs in stages.
Relaxed, awake
Alpha waves, 8-12 Hz
Stage 1 sleep
irregular, jagged, low voltage waves. Desynchronized neural activity.
Stage 2 sleep
Sleep spindles (bursts of 12-14 Hz activity - 1/2 second), K-complexes (sharp decrease in activity, followed by sharp increase).
Stage 3 & 4
Slow wave sleep (SWS). Slow, large waves. Highly synchronized neural activity. Slow heart rate and breathing rate. 4 More common earlier in the night.
REM - Rapid eye movement
Paradoxical, with characteristics of light and deep sleep. More common later in the night.
Reticular Formation
Part of the midbrain that extends from the medulla to the forebrain. Responsible for arousal.
Pontomesencephalon
Part of the reticular formation. Axons extend to the hypothalamus, thalamus, and basal forebrain (acetylcholine, glutamate). Maintains and increases arousal.
Locus Coeruleus
Small structure in the pons. Axons release norepinephrine to arouse various areas of the cortex and increase wakefulness. Dormant while asleep.
Hypothalamus
Releases neurotransmitter Orexin. Stimulates acetylcholine releasing cells in the basal forebrain. Excitatory projections to thalamus and cortex.
In sleep, cells of the basal forebrain release the inhibitory neurotransmitter…
GABA, which is inhibitory. It decreases body temp, metabolic rate, and stimulation of neurone throughout the brain.
Insomnia
Sleep disorder associated with inadequate sleep
Phase delay
results in difficulty getting to sleep
Phase advance
results in difficulty staying asleep
Sleep apnea
Inability to breathe while sleeping for long periods of time. Caused by genetics, hormones, old age, obesity
Narcolepsy
Frequent periods of sleepiness. Sudden attacks of sleep, sometimes cataplexy, sleep paralysis, hypnagogic hallucinations. Produced by lack of hypothalamic cells that produce and release orexin.
Cataplexy
sudden weakness of muscles triggered by strong emotions
Sleep paralysis
inability to move while falling asleep or waking up
Hypnagogic hallucinations
dreamlike experiences
Functions of sleep
Energy conservation, restoration of the brain and body, memory consolidation
Energy conservation is achieved by
decreasing body temperature and muscle activity. Animals increase sleep time during food shortages.
Sleep enhancing learning
activity in hippocampus similar to learning, brain strengthens some synapses and weakens others.
