Sleep Flashcards
Polysomnography
A set of physiological measures that includes electroencephalography, electrooculography, and electromyography.
Electrooculography (EOG):
Recording of eye movements through changes in the electrical activity of eye muscles.
Electromyography (EMG):
Recording of movements of the body through measuring changes in the electrical activity of muscles.
Alpha ( 8 to 13 hz) , beta( 13 to 30 hz) , theta 4 to 8 hz , and delta 0.5 to 4 hz
Brain waves that differ in amplitude and /or frequency identified by an EEG
NREM
Non-rapid eye movement sleep . Sleep that s subdivided into 4 stages of progressively deeper sleep
75 % of our sleep are spent there.
As sleep progresses, the amount of time spent in the deeper stages of sleep is reduced and the time spent in REM sleep is increased.
Stage 1 sleep
transition between wakefulness and deeper stages of sleep. Stage 1 is characterized by theta waves, which are of slightly higher amplitude compared to that of beta and alpha waves but are of lower frequency (3 to 7 Hz).
Stage 2 sleep ( sleep spindles and K-complexes )
Sleep spindles are series of high-frequency spikes of activity lasting anywhere from 0.5 to 1.0 seconds.
K-complexes are slightly negative deflections in a wave (the wave’s movement is exaggerated downward) followed by a positive deflection (exaggerated upward).
Stage 2 is a light form of sleep from which a person is easily awakened.
Stage 3 and 4 ( slow waves sleep )
These stages are marked by high-amplitude and low-frequency wavelengths, ranging from 1 to 4 Hz, known as delta waves
The appearance of delta waves is associated with stage 3. Stage 4 sleep is characterized by delta waves consisting of more than 50% of recorded brain waves. Stages 3 and 4 are also known as slow-wave sleep (SWS).
REM
REM sleep is marked by brain activity that resembles wakefulness. The rhythm observed during REM sleep is remarkably similar to that of beta waves. For this reason, REM sleep is sometimes referred to as paradoxical sleep.
the eyes are moving back and forth under the closed eyelids.
At the same time, there is a significant loss of muscle tone resulting in the sleeper becoming relatively paralyzed as detected by an EMG.
REM sleep is the sleep stage mostly associated with dreams. It was, therefore, hypothesized that this temporary paralysis occurs to prevent people from acting out their dreams.
25 % of sleep
wakefulness
The waking state is characterized by what are known as beta waves. These are low-amplitude waves of high frequency, ranging from 13 to 30 Hz.
Relaxed state
relaxed state, alpha waves, which are more regular and of lower frequency, are observed. Alpha waves range from 8 to 13 Hz. These waves become more frequent if the relaxing person’s eyes are closed.
Factors that control the wake/ sleep switch :
1- homeostatic influence :
the degree of wakefulness is related to the accumulation of somnogens that lead to the homeostatic drive for sleep.
somnogens.
Substances in the body that produce sleep
2- Circadian influence
circadian rhythm : Physiological, behavioral, or psychological events that occur over an approximate 24-hour cycle.
they can be Entrained rhythm or Free running rhythm
Entrained rhythm
A rhythm regulated by external cues, such as light or heat.
Free running rhythm:
A rhythm that is self-regulated, not requiring any external cues.
Suprachiasmatic nucleus (SCN)
The region of the hypothalamus thought to control circadian rhythms (sometimes called the master clock).
he SCN is influenced by light-dark cycles through projections from photoreceptor cells in the retina that contain the photopigment melanopsin
Melanopsin
A pigment in certain photoreceptor cells of the retina, which influences the light-dark cycle through projections to the suprachiasmatic nucleus.
Retinohypothalamic projections
The projections of photoreceptors containing melanopsin from the retina to the hypothalamus.
his ultimately leads to the release of melatonin from the pineal gland shortly before sleep. In turn, melatonin binds to receptors in the SCN, closing a feedback loop that provides the brain with a mechanism for determining circadian time.
Zeitgebers:
Factors in the environment that influence circadian rhythms.
wakefulness hormones
norepinephrine, serotonin, histamine, glutamate, and acetylcholine. he neuropeptide hypocretin (also known as orexin) is important for the maintenance of wakefulness.
Sleep hormones
GABA, glutamate, and adenosine. melanin are also involved in promoting sleep. These chemicals, which promote sleep, also suppress the activity of the excitatory neurotransmitters that promote waking.
Ascending arousal system (AAS)
A wakefulness-promoting system that includes areas of the brainstem.
includes the pedunculopontine/laterodorsal tegmental nuclei (PPT/LDT), locus coeruleus (LC), raphe nucleus (RN), and tuberomammillary nucleus (TMN), which are the sources of cholinergic, noradrenergic, serotonergic, and histaminergic neurons, respectively.
Projections from the AAS excite the cortex through two distinct pathways, an indirect pathway and a direct pathway.
he indirect pathway consists of cholinergic neurons in the PPT and LDT that activate the cortex through connections in the thalamus. The direct pathway (Figure 9.23b) consists of noradrenergic, serotonergic, and histaminergic neurons situated in the LC, RN, and TMN, respectively, that directly activate the cortex.
Executive system for wakefulness:
Activity in the AAS itself is stimulated by the input from orexinergic neurons in the lateral hypothalamus A system that includes orexinergic neurons in the lateral hypothalamus.
Sleep maintenance
Sleep is maintained by inhibitory connections to the orexinergic neurons of the LH and histaminergic neurons of the TMN from GABA and galanin neurons in the ventrolateral preoptic area of the hypothalamus (VLPO).
wakefulness maintenance
maintenance of wakefulness occurs when orexin neurons in the LH stimulate the LC, RN, and TMN neurons of the AAS. At the same time, neurons in the VLPO are inhibited by projections from neurons in the AAS.
