brain states Flashcards
the 2 main brain states during sleep
slow wave sleep (SWS) and rapid eye movement (REM)
SWS
slow wave sleep; characterised by high amplitude and low frequency brain waves; indicates that many cortical neurones switch their activity from depolarised (more excitable) to hyperpolarised (less excitable) and vice versa in synchrony.
the longer a person is awake the longer SWS state is.
during SWS no actual dream occur.
REM
rapid eye movement; characterised by the rapid eye movements people have in this state; brain waves have much lower amplitude than SWS since neurones are less synchronised; in EEG REM activity is similar to an awake state. REM brain activity is accompanied by atone (reduced muscle tone to a temporary paralysis)
night/sleep cycles
each sleeping cycle is about 90 minutes long with 75-80 min SWS state followed by 10-15 min REM state
how does the brain regulate sleep
wakefulness is maintained by the brain’s arousal systems, mainly in the upper brainstem, where neurones connect with the forebrain use NT like acetylcholine, norepinephrine, serotonin and glutamate that keep us awake.
Orexin- producing neurons, located in the hypothalamus, send projections to the brainstem and spinal cord, the thalamus and basal ganglia, as well as to the forebrain, the amygdala, and dopa- mine-producing neurones- exert excitatory effects.
orexins
small neuropeptides that increase metabolic rate, activated by insulin induced low blood sugar (involved in energy metabolism); orexin producing neurones are important in preventing sudden transition to sleep.
VLPO neurons
Ventrolateral preoptic neurons release NT galanin and GABA that suppress arousal systems. damage to VLPO–> irreversible insomnia
suprachiasmatic nucleus
a small group of neurons in hypothalamus that function as master clock and express “clock proteins” that go through a biochem. cycle of 24 h.
directing daily cycles of activity, sleep, hormone release, among others, and receive info from retina to adapt the body cycles to light/dark in the outside world–>
regulate the circadian system.
Sleep apnea
occurs when airway muscles in the throat relax to the point of collapse–> patient wakes up from short of breath during sleep that prevents them from entering deeper stage of SWS
REM sleep behavior disorder
nerve pathway in the brain that are responsible to atonia during REM sleep do not work properly–>patient is “acting out his dreams”; can be treated with medications for Parkinson’s disease.
Narcolepsy
sleep attacks during the day, causing to suddenly fall asleep. cause is in a loss of orexin neurons in the lateral hypothalamus. patient tend to enter REM very quickly and sensing dreaming even while being partially awake. narcolepsy is often accompanied by cataplexy
cataplexy
attacks of “paralysis” or loss of muscle tone, similar to during REM sleep but while being awake.
neurotransmitters involved in arousal
dopamine (for movement), norepinephrine (for alertness), serotonin (for emotion) and acetylcholine and histamine (help the brain communicate with body to induce arousal)
the autonomic nervous system
affects heart rate, blood flow, and breathing–> the reticular activating system sets up physical state for arousal
sexual arousal
similar to general arousal, but the activation of sex hormones such as oestrogen and testosterone is the distinguishing factor. these hormone then lead to release of Its like dopamine, serotonin, and GABA (similar to general arousal). regions in hypothalamus, hippocampus and amygdala, and nucleus accumbens have many sex hormone receptors.
