EEG and Sleep Flashcards
T/F: Melatonin synchronizes the hypothalamus to daylight
False — melatonin is released at nighttime (darkness) and is part of the signal that triggers the hypothalamic neurons that are active at dusk to fire
Which of the following brain regions is responsible for generating circadian rhythm?
A. Preoptic nucleus
B. Suprachiasmatic nucleus
C. Paraventricular nucleus
D. Arcuate nucleus
B. Suprachiasmatic nucleus
T/F: Neurons of the suprachiasmatic nucleus will continue to generate a circadian rhythm even if the nucleus is removed from the brain and placed on a petri dish with appropriate O2 and nutrient supplies
True - because circadian rhythm is generated genetically rather than in response to external day/night cycle
T/F: humans have a circadian rhythm that generates a 24 hr day even in the absence of light cues
False - in the absence of light cues, the human circadian rhythm is actually somewhat longer than 24 hours. The younger a person is, the longer their “day” is; for older people, the “day” is closer to 24 hrs, but still longer
Which of the following genes/gene products is required to produce the circadian rhythm in a normal person?
A. PER (period) B. Clock C. BMAL1 D. CRY (cryptochrome) E. All of the above
E. All of the above
Clock (CLK) — no circadian rhythm on its own
BMAL1 — increase at night
[CLK and BMAL1 increase transcription/translation of Period genes and cryptochrome genes; negative feedback loop results in circadian rhythm]
Entrainment of the genetically determined circadian rhythm: Light/dark information travels via the ____________ , a direct relay to the hypothalamus, and is completely separate from the visual tract
Information related to light is transmitted via the NT _________
Information related to darkness is transmitted via the NT _________
Retino-hypothalamic tract
Glutamate
Melatonin
Melatonin promotes sleep; how is melatonin itself controlled to be released at night?
Light/dark info is detected by melanopsin receptors which transmit signal via retino-hypothalamic tract to the SCN
During daylight, inputs from the RHT to the SCN inhibit the pineal gland, while at night the pineal gland is not inhibited and releases melatonin
The melatonin can act at 2 different receptors (MT1 and MT2). MT1 is associated with inhibition of neurons in the SCN that are active during the day, while MT2 works on the neurons of the SCN to activate those neurons that are active at dusk. If taken orally, the action on MT2 receptors is what advances the sleep cycle and is presumed to help alleviate jet lag
The pineal gland receives _____ innervation as its only input
Sympathetic
Which of the following genes/gene products has an intrinsic circadian rhythm to its transcription and translation?
A. Per (Period) B. Clock C. Cry (cryptochrome) D. BMAL1 E. All of the above
D. BMAL1
BMAL1 is translated and transcribed with an intrinsic circadian rhythm. Clock, Period, and cryptochrome derive their circadian rhythms based on BMAL1 and other feedback signals.
Release of melatonin in the human brain is inhibited by activity in the:
A. Optic nerve
B. Pineal gland
C. Arcuate nucleus
D. Retinohypothalamic tract
D. Retinohypothalamic tract
What NT is released by the retinohypothalamic tract?
A. NE
B. Glutamate
C. GABA
D. ACh
B. Glutamate
T/F: Alpha waves occur when you are alert and focused on a task
False; although alpha waves do occur while you are awake, they appear only when your eyes are closed
T/F: hypercapnia causes the EEG to slow and become lower voltage
True
Which of the following brain waves is associated with functional dissociation of the thalamus and cortex?
A. Delta
B. Theta
C. Beta
D. Gamma
A. Delta
Delta = largest and slowest of the waves on adult EEG; occur during deep sleep when thalamocortical neurons are strongly hyperpolarized leading to functional disconnection of the thalamus from the cortex
Which of the following is involved in frustration?
A. Gamma waves
B. Beta waves
C. Delta waves
D. Theta waves
D. Theta waves
Which of the following is involved in being alert and focused?
A. Gamma waves
B. Beta waves
C. Delta waves
D. Theta waves
B. Beta waves
Which of the following is involved in deep sleep?
A. Gamma waves
B. Beta waves
C. Delta waves
D. Theta waves
C. Delta waves
Which of the following is involved in planning a motor response?
A. Gamma waves
B. Beta waves
C. Delta waves
D. Theta waves
A. Gamma waves
The EEG changes with …
Degree of activity in the brain
Arousal/awareness
Sensory input
Most of the time there is no distinct pattern; clear “patterns” are often considered pathological
Characteristics of alpha waves
High frequency, low amplitude
Occur during quiet wakefulness (thinking) with EYES CLOSED
Most prevalent over OCCIPITAL cortex; Disappear during sleep
[Origin: requires connecton between thalamus and cortex; GABAergic neurons “force” coordination of neuronal activity]
Characteristics of beta waves
High frequency, low amplitude
Occur during wakefulness with EYES OPEN
Most prevalent over frontal cortex; also over parietal cortex
[Probably same origin as alpha; sensory input “disrupts” oscillation to some extent]
What is an alpha block?
Occurs with sensory input (in particular, opening eyes) - alpha waves cease = alerting response
At this time, beta waves begin and will persist as long as awake and alert
Characteristics of gamma waves
30-80 Hz (slower!)
Occur when individual is aroused or focused on something; replaced by even more irregular activity if planning a motor response
[not recognized by all textbooks]
Characteristics of theta waves
Slower, higher amplitude
Occurence: normal in children, particularly over parietal and frontal cortex; in adults, may occur in frustration or disappointment; also during sleep
[Origin still unclear; possible involvement of hippocampus]
Characteristics of delta waves
Slowest and largest waves
Occur in deep sleep in adults, occur in infants regardless of sleep; appearance during “wakefulness” in adults is a sign of “serious organic brain disease”
Origin: does NOT require connection between thalamus and cortex
In general, increased mental/neural activity is associated with _____ activity on EEG
Increased
Note: often, mental activity will lead to desynchronization of activity and reduced amplitudes
In infance, there is a fast ____-like activity, but over the occipital region there is a slow 0.5-2.0 Hz activity
Important to note that in babies, ____ activity during wakefulness is considered normal
Beta
Delta
[So generally in infancy the slower waves predominate, even in wakefulness; adolescence is when EEG starts following typical adult pattern]
The EEG activity over the ______ region will gradually increase in frequency throughout childhood. The adult _____-wave pattern will appear during adolescence
Occipital; alpha
What physiologic conditions decrease the frequency of alpha waves?
Hypoglycemia
Low body temp/hypothermia
Low adrenal glucocorticoids
High PaCO2
A pt presents with a TBI that has severely damaged the thalamus. What wave is most likely to appear on the pts EEG?
A. Alpha
B. Gamma
C. Beta
D. Delta
D. Delta
Which of the following conditions would be expected to cause a generalized slowing of the EEG?
A. A pt suffering from heat exhaustion
B. A pt taking oral glucocorticoids to tx a severe reaction to poison ivy
C. A pt with chronic respiratory alkalosis
D. A diabetic in insulin shock
D. A diabetic in insulin shock
[suffering from hypoglycemia d/t excess insulin —> slowing of EEG as neurons decrease their activity in response to decrease in ATP production; the rest of the answer choices increase activity on EEG]
Which of the following will produce an alerting response on EEG?
A. Opening the eyes
B. Attempting a task that requires greater knowledge than one has
C. Plan a double front snap kick to break 2 boards simultaneously
D. Wake up from a deep sleep
A. Opening the eyes
[the alerting response = alpha-block — occurs when person opens their eyes from a relaxed but aware state; waking from a deep sleep will replace delta waves that occur in deep sleep with either alpha or beta pattern, but will not lead to alerting response]
In terms of REM vs. Non-REM sleep, most time asleep is considered ______
Non-REM
Describe Non-REM sleep in terms of stages and ability to produce dreams
3 stages — 1, 2, and deep sleep — each with progressive slowing of EEG waves
Dreams do occur during non-REM sleep, but they are generally rehashing of day’s events (contributes to consolidation of learning/memory)
Describe REM (rapid eye movement) sleep in terms of EEG and dreaming
EEG shows low amplitude, higher frequency waves
Associated with vivid, often bizarre dreams that you remember (final consolidation step, linking knowledge to previous experience)
Sleep homeostasis, or the “need for sleep” drives the induction of ______ sleep
The circadian clock primarily drives the induction of _____ sleep
NREM
REM
The ______ area in the hypothalamus is crucial to induction of Non-REM sleep
How does it do this?
Ventral preoptic area (VPO)
PGD2 in blood binds cells of leptomeninges —> release of adenosine into CSF —> adenosine binds cells in VPO (express adenosine 2a receptors) and inhibit the ascending reticular activating system (ARAS) inputs to the cortex —> fall asleep
[adenosine levels accumulate as long as you’re awake]
Caffeine blocks the _____ receptors in the VPO
A2a — so adenosine cannot bind and sleep cannot be induced
Cytokines and hormones involved in induction of sleep
IL-1b
TNF-alpha
GHRH —> induces sleep during growth!
[All of these act on NFkB —> NOS —> NO]
REM sleep is initiated independently of sleep (generated primarily by circadian rhythm). What is the mechanism of this induction?
Cholinergic neurons in the lateral pontine tegmentum release ACh in geniculate body which sends input to the occipital cortex
Muscle paralysis during REM sleep is crucial to prevent muscle activation during dreaming. What is the mechanism of muscle paralysis in REM sleep?
Locus ceruleus —> inhibitory input to alpha-motoneurons (paralyzes large muscle groups but spares diaphragm and some other respiratory mm)
Antihistamines effects on non-REM vs. REM sleep
Promote non-REM sleep and interfere with REM sleep (this is because they have 2 different mechanisms of induction)
Describe how arousal from sleep occurs (waking up)
The hypothalamus controls arousal by different mechanism from sleep-induction
Lateral hypothalamus is one of the only sources of Orexin A and B (aka hypocretin 1 and 2) in the brain. Orexigenic inputs are sent to neurons in the tuberomamillary nucleus which release histamine
Histamine binds to H1 receptors, activating the LC neurons which then release NE and suppress REM sleep [antihistamines block this process]
Describe stage N1 of slow wave sleep
Drowsiness/earliest stage of sleep
Physical characteristics: slow, rolling motions of the eyes, EMGs show muscle activity
EEG: low voltage, slowing of frequency
How does sleep cycle differ in children?
Children spend more time in REM and deep sleep, as well as more total sleep time overall
How does sleep cycle differ in elderly?
Fewer REM epochs (but they can be long)
Almost no deep sleep (this is where brain is clearing adenosine, so they may feel increased homeostatic need for sleep)
More frequent awakenings
Less total sleep (more likely to nap)
Describe stage N2 of slow wave sleep
True sleep
Physical characteristics: EMGs show muscle activity but relatively quiet
EEG: increasing voltage, slowing of frequency, sleep spindles
Sleep spindles begin to appear during stage ____ but are most prominent in ______. These are bursts of _____-like activity interrupting the slower EEG of sleep, and may be preceded by a sharp wave (K complex)
N1; N2; alpha
Describe stage N3 of slow wave sleep
True sleep
Physical characteristics: deep sleep
EEG: increasing voltage, slowing of frequency — theta and delta waves prominent
Changes seen on polysomnogram with obstructive sleep apnea
Upper airway collapses —> No air flow occurring as well as paradoxical motion of thorax and abdomen
O2 sat may start to fall; snoring is often occurring at this time
