The Brainstem, Arousal and Sleep Flashcards
What does the reticular formation do?
Sleep regulation Motor control Cardio/Respiratory control Autonomic functions Motivation and reward
Where is the reticular formation found?
In the brainstem, the pons
What is the ascending reticular activating system?
Formed by projections of the RF
Specific effects throughout the CNS to raise levels of consciousness
Filters incoming signals (LSD knock this out giving overwhelming senses)
Inhibited by hypothalamic sleep centres
How does the neuronal circuit work to keep us awake?
The brainstem send two projections to the thalamus,
One to activate the thalamus (ACh)
One to inactivate an inhibitory interneuron
So when awake or in paradoxical sleep, the brainstem is sensitising the thalamus to sensory signals and inhibiting the ‘off’ switch
What is an EEG?
Electroencephalography
Algebraic sum of the electrical activity (both excitatory and inhibitory) of neurones, from scalp
How do you interpret an EEG?
When eyes are shut, it is synchronised, the waves are low frequency and high amplitude
When eyes are open, it is desynchronised, the waves are high frequency and low amplitude
This is because when there are lots of signals they cancel each other out creating a low amplitude
Alpha waves - 8-13Hz (50muV), (mainly occipital) awake, quiet, eyes shut
Beta >14Hz, (parietal and frontal lobes) awake + eyes open
Theta 4-7Hz, (parietal and temporal lobes) Children, concentrating or meditating adults
Delta
What does consciousness require?
Requires adequate function of both the cerebral cortex and RAS
What is a coma?
A state of unconsciousness from which the person cannot be roused using pain, sound, light. Patient does not initiate any voluntary movement
Causes: intoxication, metabolic, neurological, trauma
Evaluation: GCS, Scans, blood work, EEG
Why do wee need sleep?
CNS resetting/clearance
Memory
Homeostasis (reduced sleep switches on ‘bad’ genes)
(Energy conservation - discredited, don’t save that much)
Might be a glymphatic system that is washed down with CSF
How is sleep controlled?
Reticular Formation
Hypothalamus
(Inhibits RF to promote sleep)
Biological clocks
What are the different sleep states?
Non REM Slow wave sleep 'active body, inactive brain' Sleepwalking 4 stages
REM
Rapid eye movement
‘active brain, inactive body’
EEG as if awake (paradoxical)
How does someone going to sleep look like on an EEG?
Alpha waves (awake)
Sleep
Stage 1 - Theta waves
Stage 2 - decreasing amplitude
Stage 3 - decreasing amplitude with some k complexes
(High amplitude peaks)
Stage 4 - Delta waves - Thalamocortical oscillations
REM - paradoxical - similar to awake
What functions occur during non-REM sleep?
Restorative - 'neurological rest' Neuroendocrine - 90% are released Decreased: - Cerebral blood flow - O2 consumption - Body temperature - BP - Respiratory
Hence BMR reduced
What happens during REM sleep?
EEG waves spread from pons to thalamus then occipital lobe Dreaming Difficult to disturb Irregular heart rate and respiratory rate Increased BMR Descending inhibition of motorneurones Penile erection Reduced by alcohol
What is the pharmacology of sleep?
During waking
- 5-HT/NA constantly active
- ACh neurones active during a novel input
Non-REM sleep
- 5-HT and NA active
- ACh inactive
REM
- 5-HT inactive, NA inactive
- ACh fully active
Coming out of REM
- Increase NA activity
