brain and behavior exam 2 (biological rhythms and sleep)

circadian rhythms

about 24 hours in humans

ultradian rhythms

repeat more than once a day

infradian rhythms

repeat less frequently than once a day

entrainment

when the 24 hour light cycle is shifted

phase shift

cycle of behavior that is shifted as a result of entrainment

free-running

with no light cycle the animal shows a later start of activity each day…an indication that the animals endogenous clock is longer than 24 hours

slow wave sleep (SWS)

it can be divided into three main stages and is characterized by slow-wave EEG activity. also its non-REM

rapid eye movement sleep (REM)

characterized by small amplitude, fast-EEG waves, no postural tension, and rapid eye movements

delta waves

its in stage 3 sleep. they are large-amplitude, very slow waves. they are about one per second

REM

active EEG with small-amplitude, high frequency waves, like an awake person. the muscles are relaxed in paradoxical sleep

sleep in young adults

there is the first REM episode and then brief awakenings and then a fianl REM episode.

sleep in older adults

there is only a First REM episode. no breif awakenings or final REM episodes

Energy conservation for sleep

muscular tension, heart rate, blood pressure, temperature, and respiration rate are reduced

niche adaptation for sleep

avoid predators by sleeping during the part of the day when animals are more vulnerable

body restoration for sleep

replenish metabolic requirements, such as proteins; growth hormones release during SWS; immune function

memory consolidation for sleep

especially REM

What part of sleep does the forebrain affect?

SWS. it releases GABA into the tuberomammilary nucleus in the hypothalamus. the electrical stimulation of the basal forebrain make the animal sleepy so lesions in the forebrain can cause insomnia.

what part of sleep does the brainstem affect?

active forebrain. this part contains the ascending arousal system wheich projects mostly monoaminergic axons to the brain. the electric stimulation promotes wakefullness and alertness. lesions here can produce constant sleep states.

what part of sleep does the pons affect?

REM. the subcoeruleus sends widespread projections to promote REM sleep. the medullary axons projecting to the spinal cord profoundly inhibit motor neurons so that they cannot fire, causing muscle atonia.

what part of sleep does the hypothalamus affect?

it affects the forebrain, brainstem, and pons. it uses hypocretin to send axons to the other sleep centers and coordinate them, enforcing a pattern of sleep. loss of hypocretin can lead to disorganized sleep and narcolepsy

where do hypocretin neurons reside?

the hypothalamus

where do hypocretin project to?

other sleep system centers such as the basal forebrain, reticular formation, the locus coeruleus, and tubero-mamillary nucleus

What happens when hypocretin is inhibited?

it induces SWS