Biological Rhythms and Sleep

Midterm 3

sleep and weight benefits

• lack of sleep leads to increased hunger signals in brain and decreased satiety (or fulls) signals

• poor sleep causes decreased glucose tolerance and insulin sensitivity (both of which are associated with obesity)

sleep and skin benefits

• poor sleep is linked to poor collagen formation which can lead to increased signs of aging

• poor sleep can also leave your complexion dull and lifeless

sleep and cognitive abilities

• poor sleep leads to decreased academic performance

• children who do not get enough sleep have more learning difficulties

• adults with insufficient sleep have more issues with memory and poor decision makings

sleep and mental health

• studies show that people with insomnia are as much as 10x more likely to suffer from depression

• anxiety can lead to issues sleeping, which in turn can worsen a person’s anxiety

sleep and immune system

• this functions its peak while you are sleeping

• you are more likely to get sick if you do not get enough sleep

7+

how many hours should adults sleep?

increased mortality

graph:

• sleeping less or MORE than 7 hr/day was associated with ___________

biological rhythms

• the sleep/wake cycle is just one example of a behavior w/ a daily rhythm of activity

24-hr cycle

most rhythms in animals follow a ______

remove the cues

how to study if our rhythms merely follow the sun’s behavior, or do they exist without these cues?

REM sleep

Nathaniel Kleitman discovered what with sleeping in a cave

free-run according to endogenous circadian rhythm

what happens when daily cues are removed?

biological clock

what is circadian rhythm known as?

biological clock synchronizes to new cycle

if 24 hr cycle is reintroduced our ___________

entrainment

what is it called when the biological clock synchronizes to the new cycle?

limitations to entrainment

most people have difficulty adapting to shorter than (<22 hr) or longer than (>28 hr) a 24-hr cycle

zeitgebers

cyclic environmental cues that are used to synchronize circadian rhythms to the outside world

light

in humans and many mammals, ______ is the most important and effective

daily temperature, tides, etc

other animals depend on cues like _____

phase shift

when the light onset/offset is changed (______), the activity re-entrains to the new cycle

suprachiasmatic nucleus (SCN)

what part of brain in hypothalamus is responsible for organizing many of body’s circadian rhythms

two clusters of neurons above optic chiasm

where and what is the suprachiasmatic nucleus

in vivo

SCN show rhythms of activity _______

vasopressin

hormone released from SCN that occurs cylically even after the SCN are removed from the brain and kept in a dish

“tau”

this hamster has a mutation that creates a circadian rhythm is only 20 hr

retinohypothalamic tract

a specialized pathway to the SCN from the retina

melanopsin

• specialized ganglion cells send projections to SCN and these contain photopigment __________

master oscillator

SCN is the _______ that controls other rhythms

other rhythms are disrupted

is SCN is lesioned, __________

pineal gland

melatonin is a hormone produced by the _____, located deep in the brain

melatonin

• released under control of SCN input

• affects many tissues and helps coordinate the circadian responses throughout the body

• used as a sleep aid; treatment for jet lag

secondary zeitgeber

melatonin tablets may serve as a ______ to help blind/sightless people entrain their rhythms

Cl/Cy proteins turn on Per/Cry genes

first step of SCN neuron

Per/Cry proteins interfere with Cl/Cy function

second step of SCN neuron

with Per/Cry genes OFF the Per and Cry proteins degrade

third step of SCN neuron

C/C proteins active again

fourth step of SCN neuron

endogenous rhythm

in the absence of light, the whole process of SCN takes ~24 hours

RHT input

the presence of light signaled by _______ activates Per directly to reset the daily rhythm to exactly 24 hr

shift work

natural zeitgebers are unchanged, but the sleep-wake cycle must be altered

• indoor lighting is a poor zeitgeber

jet lag

sleep urge is out of sync with the new time zone

• zeitgebers now occur at a different time, so our cycles must adapt, like the rodent in the running wheel

wrong side of town

people on west vs east side of time zone

zeitgeber

stimulus that occurs with a regular period of 24 hr, like the appearance of light at dawn

west

which side of the nation experience fewer days with natural morning light, but an extra hour or more of natural light in the evening?

electroencephalogram (EEG)

• reveals “brainwaves”

• 1968: guidelines for sleep stages establushed

electrooculogram (EOG)

records eye movements seen during rapid eye movement (REM) sleep

electromyogram (EMG)

detects loss of activity in neck muscles during some sleep stages

beta waves

awake, normal alert consciousness

alpha waves

relaxed, calm, meditation, creative visualisation

• still awake

theta waves

deep relaxation and meditation, problem solving

• still awake

delta waves

deep sleep

• slow waves

stage 1

stage of sleep

• similar to awake EEG, but with theta (4-7 Hz)

stage 2

stage of sleep

• K complexes

• sleep spindles

• both of the above: linked to sensory stimulation and/or to learning/memory?

stage 3 & 4

stage of sleep

• recent convention is to refer to a single stage 3

• large and slow delta waves appear: slow wave sleep (SWS)

REM sleep

stage of sleep

• last stage

• theta and beta activity

K complexes

a large up and down deflection wave

sleep spindles

bursts of 12-14 Hz waves

rapid eye movement (REM) sleep

• Kleitman and Aserinsky

• period of desynchronized EEG activity that is similar to the awake state

• also called paradoxical sleep

• dreaming, eye movements, and absence of muscle tone are seen

SWS, REM <30 mins, transitions stepwise to different stages, 4-5 series per night

stages of sleep patterns during a night’s sleep

features of slow wave sleep (SWS)

• cerebral metabolism decreases by 75%

• brain areas active while awake show highest levels of delta waves during sleep

• parasympathetic system dominence

• increased release of growth hormone

• “brainwashing” during delta wave activity: waste removal?

features of REM

• darting eyes, fluctuations in heart and breathing rates

• increased cerebral blood flow and oxygen use

• subjects easily awakened

• PGO waves

• dreaming

PGO waves

electrical activity from the pons to geniculate to occipital regions just prior to and during REM

• must be measured with intracranial electrodes

• presumed to exist in humans

freudian dream theory

• allow us to reconcile with unacceptable repressed wishes

• manifest dreams

• latent dreams

• limited supporting evidence

manifest dreams

what we experience

latent dreams

the underlying meaning

activation-synthesis theory

• dreams result from the cortex’s attempt to make sense of random brain activity

neurocognitive theory

• similar to waking consciousness but disconnected from external stimuli and self-awareness

• coherent narrative sequences

• no function per se, but have meaning

• damage to brain areas involved in mental imagery: no dreams