4.2.2 EEG and Sleep Flashcards
The reticular activating system is comprised of?
Cerebral cortex
Thalamic nuclei - Intralaminar and thalamic reticular nuclei
Pontomesencephalic reticular formation
What are the two EEG activities associated with wakefulness in normal adults?
Beta activity - Greater than 20Hz; low amplitude and high frequency, occurs during periods of alert wakefulness
Alpha waves - 8-12Hz; higher amplitude and lower frequency; relaxed wakefulness with eyes closed
What is the distribution of alpha and beta waves in the brain?
Alpha rhythm is largest over parietal , occipital and temporal lobes.
Alpha rhythm is replace by beta rhythm when eyes are opened
Beta rhythm is most prominent in the front of the brain
What is the source of the current measured in EEGs?
This is changes in resting membrane potential
-Synaptic potentials, Summed EPSP and IPSP
NOT ACTION POTENTIALS DONT YOU DARE PUT ACTION POTENTIALS ON THE TEST SO HELP ME DOG
What is synchronization and what controls it in the brain?
Synchronization is the pacemaking of the oscillations of the cortical membrane potentials
Under control of the thalamic reticular nucleus
Thalamic renticular nucleus receives excitatory input for where? What is the neurotransmitter? (YOU BETTER NOT MISS THIS)
Receives excitatory input from thalamocortical and corticothalamic axon collaterals.
TRN neurons are GABAergic
The reticular activating system has input to the TRN to regulate?
Wakefulness
What are the characteristical EEG findings of the different stages of sleep and what are they?
Awake - alpha and beta
Stage 1 (drowsy) - Alpha drops out and appearance of theta waves
Stage 2 - sleep spindles and K complexes
Stage 3 and 4 - Slow wave sleep Delta waves (Stage 3 < 50% delta waves Stage 4 > 50% delta)
REM
What are the physiological characteristics of REM sleep and how does it compare to non-REM?
The brain is metabolically active during REM sleep, as if it were awake.
Non-REM the brain is less physiologically active
What are the terms synchronized and desynchronized used for? When would you observe these different phenomenom?
Synchronized - high amplitude and low frequency waves such as sleep spindles, alpha and delta rhythms - Occurs in deeper states of sleep
Desynchronized - Low amplitude, and high frequency waves, beta waves - found is states of wakefulness and REM
Describe the sleep cycle and what happens during it?
A. Upon falling asleep a person enters stage 1 of slow-wave sleep.
B. After approximately 90 minutes the first REM sleep period occurs.
C. Cycles of slow-wave and REM sleep continue throughout the night with a period of about 90 minutes.
D. REM sleep periods increase in duration throughout the night.
E. REM sleep usually occurs just prior to waking in the morning.
F. The early sleep cycles are deepest, reaching stage III and IV. Later sleep cycles are shallower reaching only stage II.
How does a sleep cycle change with age?
As a person ages they will experience less stage 3 and 4 sleep. More waking during the night and more stage 1 and 2 sleep
What are the physiological characteristics of slow wave sleep?
Neuronal activity is low and brain temp is lowest
Sympathetic output decreases
Muscle tone is low and reflexes are slightly present
What are the characteristics of REM sleep?
Dreaming
Rapid eye movements
EEG - low amplitude and high freq
Irregular changes in BP
Penile erection and clitoral engorgement
What is atonia associated with REM?
Active inhibition of alha motorneurons preventing movements occurring in the reticulospinal tract
What is the role of cholinergic projections?
Works in the initiation of sleep
What are the characteristics of the tonic and phasic control in the slow waves of sleep?
Thalamic and cortical neurons have unusual membrane properties that have important functional implications for the generation of the EEG, and for understanding sleep and wakefulness. During wakefulness and REM sleep, neurons operate in the tonic mode, and are capable of high-frequency continuous discharge of action potentials. In this state, neurons transmit and integrate information very efficiently. During slow-wave sleep, neurons operate in the phasic mode, and are characterized by rhythmic discharges. A discharge of one or a few action potentials is followed by a prolonged period of post excitatory hyperpolarization lasting 100-200 milliseconds, and then another phasic discharge. In this state, neurons are very inefficient in transmitting information. The tonic and phasic modes are due to intrinsic membrane properties. Raising the membrane potential a few millivolts has the effect of converting the phasic mode of firing to the tonic mode. During the tonic mode, prolonged hyperpolarization does not follow a discharge, so neurons are capable of high-frequency firing.
What is the circadian rhythm and what is it under the control of?
Suprachiasmatic nucleus - monitors light/dark cycles
