sleep---------- Flashcards
why do we sleep?
To conserve energy during times when it would be inefficient or dangerous to be out looking for food
To give the body and brain a chance to rest and synthesize new proteins
Repair damage sustained during the day
Strengthen memories formed during the day
what makes us want to sleep?
Endogenous Rhythms (Zeitgeber): “generated from within” Regular cycles of activity and inactivity that keep constant length in the absence of environmental cues Environmental cues may determine the start/stop time of endogenous rhythms Circadian rhythm: repeats about once every 24 hrs.
what are TIM and PER
proteins that build up all day and reach peak in the evening at sleepiness
SCN stops making Tim/Per at night, so levels fall à wakefulness
SCN- what is it
where is it?
whats it do?
- suprachiasmatic nucleus
- in hypothalamus
- SCN neurons maintain a circadian rhythm even if separated from the brain. axons in the optic nerve bring light/dark info to the SCN to entrain circadian.
melanopsin- what is it
whats it do
photopigment in ganglian cells
works independent of rods and cones to bring light info into SCN
what is melatonin
it makes you sleepy
what happens in the pineal gland?
some SCN neurons send axons here.
when PER and TIM levels are high, SCN stimulates the penal gland to release MELATONIN.
acetylcholine
Released throughout cerebral cortex
Increases arousal, promotes wakefulness
norepinephrine
involved in arousal
histamine
indicated in wakefulness
Anti-histamines block H1 receptors in the brain leading to drowsiness
orexin
Neuropeptide released by the hypothalamus
Stimulates ACh neurons
Necessary for extended periods of wakefulness
adenosine
By-product of normal neuronal activity
Builds up during the day; high levels make you sleepy
Caffeine blocks adenosine receptors (antagonist)
GABA
Released throughout cerebral cortex and thalamus
Decreases overall brain activity; promotes sleep
(many sleep aids on the market are GABA agonists)
structure of sleep
- 4 stages + REM
- Cycle through stages about 4-5 times/night
- More REM close to waking in AM
stages 1
- Irregular, low amplitude EEG waves
- Hypnic myoclonia: abrupt jerking of muscles, usually preceeded by feeling of falling