Brain Rhythms Flashcards
What neurons do EEGs take readings from primarily?
Pyramidal neurons in the cerebral cortex being synaptically excited. EEGs do not record from single neurons and electrodes are placed in pairs to observe differences between two or more points on a scalp
Why must many neurons be sampled from in an EEG recording?
Single neuron electrical output is really small and must travel through non-neural tissue like the meninges and skull.
What type of recording can sense the magnetic fields of neurons firing in synchrony and their location in the brain?
Magnetoencephalography (MEG)
What is the frequency range of beta waves, what do they signal?
Anything greater than 14 Hz, activated cortex
What is the frequency range of alpha waves, what do they signal?
8-13 Hz, quiet, waking states
What is the frequency range of theta waves, what do they signal?
4-7 Hz, some sleep states
What is the frequency range of delta waves, what do they signal?
Less than 4 Hz, large in amplitude, hallmark of deep sleep
What are two ways in which synchronous rhythms of the brain can arise?
- From thalamic pacemaker cells
- From the collective behaviour of all participating neurons (think audience clapping falling in sync) by mutually inhibiting and exciting each other
What is a generalized seizure?
A seizure of the entire cerebral cortex of both hemispheres
What is a seizure that only affects a circumscribed area of the cortex called?
A partial seizure
Why do EEGs record very large patterns during seizures?
Neurons within an effected area fire with synchrony that is not seen during normal behaviour
What is the definition of sleep?
Sleep is a readily reversible state of reduced responsiveness to, and interaction with, the environment.
What is sleep paralysis called in clinical terms?
Atonia, a complete loss of muscle tone
What is more active during REM sleep, the sympathetic or parasympathetic ANS?
Sympathetic, causing increased (though irregular) heartbeat and breathing.
What are ultradian rhythms? How do they differ from circadian rhythms?
They are transitions through the cycles of sleep, therefore they are much quicker than circadian rhythms.
What type of brain rhythms are prevalent during REM sleep?
beta
What are spindles and K complexes? What stage of sleep do they occur in?
Spindles - High frequency
K complex - High amplitude
Occur during stage 2 non-REM sleep
How many stages of sleep are there in a single cycle?
4, non including REM and awake.
Lesioning the ascending reticular activating system (midline tegmentum and other) causes what?
A state similar to non-REM sleep
The locus coeruleus in also involved in waking, along with serotonergic diffuse modulatory systems
What diffuse modulatory systems go silent and become active with the onset of REM?
Silent
- Serotonergic
- Locus Coeruleus (norepinephrine)
Active
- Cholinergic
All within the brain stem, especially the pons. These may regulate REM sleep
What are common molecules that stimulate sleepiness?
Peptides that effect the immune system such as interleukin-1 and muramyl
Adenosine levels increase during the day with increasing sleepiness and decrease during sleep
Caffeine is an antagonist to what type of receptor?
Adenosine receptors
How does adenosine work to increase sleepiness?
It inhibits diffuse modulatory systems that maintain wakefullness, the locus coeruleus, serotonergic and cholinergic ones
What are zeitgebers?
German for time givers. Things that can calibrate a biological clock, such as the rise and fall of the sun.
Which nuclei are human’s biological clock for wake and sleep? Where is it located?
The suprachiasmatic nuclei, located in the hypothalamus. Smallest neurons in the brain
How can a retina without rods and cones detect light levels?
Ganglion cells with melanopsin directly innervate the suprachiasmatic nuclei in the hypothalamus.
What happens when suprachiasmatic nuclei neurons are isolated form the rest of the brain? What happens when they are treated with tetrodotoxin?
Isolated
- Still keep 24 hour cycle, can’t be calibrated with light
Tetrodotoxin
- Don’t make action potentials, but still keep 24 hour cycle
How do clock genes work?
mRNA is made and then translated into protein which stops transcription. When transcription is stopped, the protein is not made and the inhibition is slowly lessened until more protein inhibitor is made. This whole cycle takes about 24 hours.
