SLEEP AND BIOLOGICAL RYTHMS PART 1

circadian rythms

functions of a living organism that display a rythm of about 24 hours

physical, mental, biochemical and behavioral changes

synchronize behavior & body states to changes in the environment

diurnal

active during the day (humans, dogs, etc.)

nocturnal

active during the dark (bats, skunks)

crepuscular

active during twilight, the time shortly before sunrise and after sunset (house cats, rabbits, deers)

photic zeitgeber

light is what synchronizes the endogenous rhythm

nonphotic zeitgeber

cues for entraining the internal clock (food, physical activity, social time, etc.)

free running

when the zeitgeber (external cues) is removed and animal becomes subject only to internal timing mechanisms

suprachiasmatic nucleus (SCN)

the main biological clock

a subregion of the hypothalamus located above the optic chiasm

circadian rhythm is disrupted if this area is injured

frankenhamsters

genetic mutation (tau) to hamsters made them have 22/20 hours

transplanting SCN from 22 hour hamster to 20 hour hamster

proves again that specific areas in brain have specific jobs

endogenous clock

enables animals to anticipate & prepare for events best done in light or darkness

retinohypothalamic pathway

intrinsically photosensitive retinal ganglion cells

Light transmitting cells are ganglion cells that use melanopsin as a photopigment

light information goes from SCN to…

melanopsin

the photopigment that make intrinsically photosensitive retinal ganglion cells sensitive to light (especially blue light)

opsin

retinal protein

blind people

melanopsin containing ganglion cells STILL transmit light information to SCN allowing them to have normal circadian rhythm

pupillary light reflex (PLR)

a rapid constriction of the pupil to protect the retina from intense light energy

Some ipRGCs project to the brainstem & help control this reflex

SCN clock ticking

controlled by the time it takes to produce and degrade a set of proteins

(it takes about 24 hours for this process to be complete)

clock and cycle

the proteins that the SCN make

dimer

clock and cycle proteins bind to form…

period (per) and cryptochrome (cry) genes

The dimer promotes transcription of…

Per and Cry proteins

dimerize and inhibit transcription of Clock/Cycle genes

No new Clock/Cycle proteins are made until the Per/Cry proteins degrade; the cycle takes approximately 24 hours

depolarized

retinal ganglion cells are ____ by light (APs release glutamate onto SCN neurons)

This promotes Per protein production

larks

morning people

likely have different alleles of the Clock and per genes

infraradian rhythm

biological rhytyhms that are longer than a day (EX: reproductive cycles)

ultraradian

rhythms shorter than a day

EX: bouts of activity, feeding, and hormone release

circannual

type of infraradian rhtythm thats has a period of 365 days / a year

Mechanism seems to be separate from the SCN

(EX: seasonal animals)

melatonin

produced and released by the pinneal gland

Light information from the retina to the SCN suppresses its release

influential in seasonal depression and hibernation

sleep

most pronounced feature of circadian rhythm

eyes are closed and postural muscles are relaxed

purpose is unclear but is need to be alive

electroencephalography (EEG)

records electrical active in the brain

Electro-oculography (EOG)

records eye movements

Electromyography (EMG)

records muscle activity

brain wave activity

Sleep states are characterized by changes in ____

Records coordinated extracellular electrical activity from many neurons (EEG), the eyes (EOG), or muscle cells (EMG)

Delta, Theta, Alpha, Beta

Ranges of activity In order from low to high

frequency

synchronized

Low frequency activity

desynchronized

Active mental states / high frequency activity

beta

desynchronized

pattern of activity in an awake person contains many frequencies

awake with mental activity (14-30Hz)

alpha

awake with resting (8-13Hz)

delta

deep sleep (<3.5Hz)

theta

sleeping (4-7Hz)

NREM 1

Stage 1

Transition between sleep and wakefulness

Alpha activity slows to theta activity

Experience hypnic jerks (muscles contract & relax)

Lasts about 10 minutes

NREM 2

Stage 2

Continued Theta activity

Sleep spindles (possible memory consolidation function)

K complexes (spontaneously ~1/min. & in response to noise)

Lasts about 15 minutes

NREM 3

stage 3

slow wave sleep

high amplitude delta activity

deepest stage of sleep synchronized cortical activity

Lasts about 1 hour

REM

rapid eye movement

AKA paradoxal sleep

occurs about 90 minutes into sleep

rapid eye movements under closed lids, irregular breathing and pulse rates, and vivid dream

REM sleep

EEG activity is like an awake person (desynchronized)

BUT muscles are relaxed and limp (atonia)

brainstem regions are inhibiting motor neurons

Easily awoken by meaningful stimuli

the sleep cycle

The last REM is just before waking

Typical night of sleep is 4 – 5 cycles of the sleep stages

reflects a basic ultradian rest- activity cycle (90–

110 minutes)

infant sleep

characterized by: Shorter sleep cycles & More REM sleep (~50%)

24-hour rhythm develops around 16 weeks of age

elderly sleep

total time asleep declines & number of awakenings increase

greatest decline in stage 3 (NREM3)

age of 60 = half the amount of time; age 90 it is gone completely

4-5 cycles

a typical night of sleep has ____ of the sleep stages

dreaming

during REM characterized by visual imagery and sense that he dreamer is “there”

Vivid dreams in NREM can be predicted from high- frequency EEG activity in POSTERIOR CORTEX regions

Lucid dreaming

awareness that dream is happening

results from activation of normally inactive PREFRONTAL CORTEX during sleep

extrastriate cortex

high activity during REM, reflects visual hallucinations during dreaming mostly coming from memory

striate cortex

low activity during REM; due to lack of visual input (eyes are closed)

prefrontal cortex

low activity during REM; reason for lack of organization and planning that occurs in dreams

nightmares

long frightening dreams that awaken the sleeper from REM sleep

night terrors

sudden arousals from NREM sleep marked by fear and autonomic activity (fight or flight)

usually no memory of dream just the feeling of fear or suffocation

sleep deprivation

partial or total prevention of sleep

EFFECTS: increased irritability, difficulty in concentration, episodes of disorientation

comprises the immune system and leads to death

Cognitive functions are disrupted (tasks that require attention or vigilance)often compared to being drunk

mental health

sleep is more important for _____ than it is for physical recuperation and function

rat experiment

total sleep deprivation caused stop in grooming, an increase in metabolism, development of sores on body and death

no high stress hormones, no internal organ damage, no inflammation

disc over water method

disc rotates when EEG shows that animal is falling asleep so that it stays awake

fatal familia insomnia

inherited neurological disorder when in midlife people stop sleeping (slow wave sleep disappear)and die 7-24 months after

cause is unknown but autopsy shows degeneration in the cortex and thalamus

sleep recovery

process of sleeping more than normal after a period of deprivation

night 1 of sleep recovery

stage 3 sleep is increased, usually at the expense of stage 2 sleep

night 2 of sleep recovery

most recovery of REM sleep; more intense than normal with more rapid eye movements