Chapter 16 - Brain Rythms And Sleep Flashcards
What does the alplitude of the EEG depend on?
I’m how synchronous the activity of the underlying neurons is
What state is associated with low amplitude high frequency waves?
What can you say about the cortical activity?
Awake or dreaming stages of sleep.
Cortical activity is high and unsynchronized
What state is associated with high amplitude low frequency waves?
What can you say about the cortical activity?
Non-dreaming sleep states or coma.
- Cortical neurons are not engaged in information processing.
- large numbers of neurons excited by common slow rhythmic input
How is the generation of synchronous brain rhythms initiated?
By a central pacemaker neuron.
Synchronous timing arises from the collective behavior of all the cortical neurons
Explain what the two-neuron oscillator does and how
Constantly active excitatory input excited E cell, which excites I cell which inhibits E cell and so forth
It’s responsible for rhythmic activity
What are the two mechanisms that generate synchronous brain rhythms?
1) two neuron oscillator
2) thalami pacemaker neuron (chef d’orchestre)
What drives rhythmic activity in the cortex? How does it work?
Rhythmic activity in the thalamus
Synaptic connections between excitatory and inhibitory neurons force each neuron to conform to the rhythm of the group
What are the 3 functional states of the brain? Define each one
1) awake: EEG low voltage and fast
2) REM sleep
- EEG looks like you’re awake
- Body immobilize
- Dreams
3) non-REM sleep
- EEG high voltage and slow
- 4 stages
What can you say about parasympathetic tone, firing rates of neurons and amplitude of EEG during non-REM sleep?
- Increased parasympathetic tone: heart rate, respiration, kidney function slow down
- slow firing rates of neurons
- slow, large amplitude of EEG- neurons firing synchronously
What can you say about sympathetic tone, firing rates of neurons and amplitude of EEG during REM sleep?
- EEG almost indistinguishable from waking, fast, low voltage
- rapid eye movement
- increased sympathetic tone, increased and irregular heart rate and respiration rate
What are ultradian rhythms?
Cycles repeated throughout a 24 hour circadian day
- cycle every 90 min
- REM 25%
- Non-REM 75%
What are the 4 stages of non-REM sleep? Define each one
Stage 1:
- transitional sleep
- lasts only a few minutes
Stage 2:
- slightly deeper sleep
- lasts 5-15 minutes
- sleep spindles (hi freq, low amplitude)
- generated by the thalamic pacemaker
- K complexes
Stage 3:
- eye and body movements are few
Stage 4:
- deepest stage large EEG rhythms
Why do we sleep?
- verbal learning
- spatial learning
- sensori-motrice learning
What controls the sleep and waking?
Diffuse modulatory neurotransmitter systems
What happens during waking, which enhances awake state?
Locus coeruleus
What does orexin do?
- Strongly excites cells of the cholinergic, noradrenergic, serotonergic and dopaminergic modulatory systems
- promotes wakefulness. inhibits REM
What does a loss of orexin lead to?
Narcolepsy
What do the diffuse modulatory systems control?
Rhythmic behavior of the thalamus and in turn EEG rhythms of the cerebral cortex
What do the show sleep-related rhythms of the thalamus block?
The flow of sensory information to the cortex
What may contribute to initiating non-REM sleep?
Decrease in firing rates of neurons of the Ascending Reticular Activating System
What does the Ventrolateral Preoptic Area of hypothalamus (VLPO) do?
GABAergic neurons inhibit orexin neurons and ARAS
What activates VLPO?
- accumulation of adenosine, a metabolite of ATP
- adenosine has an inhibitory effect on the ARAS
- caffeine blocks adenosine receptors
Which cells initiate REM? Where are they located?
REM-on cells: neurons of the pons
What cells terminate REM? Where are they located?
REM-off cells: locus coeruleus and Raphe nuclei
What is another thing that REM-on cells do?
Inhibit spinal motor neurons and prevent us from acting out our dreams
What do human narcoleptics lack?
They have low levels of orexin
Element lacking from these flash cards are some of the sleep disorders
.
What do the suprachiasmatic nucleus cells of the hypothalamus do?
They are biological clocks. The light sensitive input entrains the clock.
What projects to SCN? Which is responsible for the light sensitivity?
Light-sensitive retinal ganglion cells have the visual pigment molecule melanospin. These cells project to SCN
