8. Consciousness, Unconsciousness, Sleep, EEG Flashcards
What is consciousness?
Self-awareness, perception, ability to respond to stimuli and act with judgement
What is sleep?
A state of altered consciousness
Person can be aroused by stimuli
Which cycle controls when we sleep?
Circadian rhythm
What is a coma?
Inability to sense or respond to stimuli
Loss of sleep/wake cycle
What is the scale used to measure a coma?
Glasgow scale
What categories are used in the Glasgow scale?
Eye opening
Verbal response
Motor response
What are the ranges for severe to mild coma on the glasgow scale?
<8 severe
9-12 moderate
>13 mild
What are causes of comas?
Intoxication Acute neurological injury Metabolic disorders CNS infection Stroke Hypoxia
How long can a coma last before the patient enters a vegetative state or dies?
5 weeks
What is a vegetative state?
Unconsciousness in patients with severe brain injury
Have a certain degree of wakefulness (may be able to track objects with eyes)
Lack awareness and cognitive function
What is brain death?
Irreversible coma
Loss of pain response and cranial nerve reflexes (fixed pupils, no blink reflex)
Loss of spontaneous respiration
How long does an infradian rhythm last?
> 1 day
How long does an ultradian rhythm last?
<1 day, > 1 hour
Where is melatonin secreted from?
Pineal gland
What stimulates the pineal gland?
SCN
What are the functions of melatonin?
Induce sleep at night time
Help adjust to seasons and other time zones
What sort of brain waves are characteristic of NREM sleep?
Slow
What happens to HR, BP and temperature during NREM sleep?
Decrease: autonomic instability
How long are REM cycles?
90 mins
How many times do REM cycles occur during the night?
5-6
What are the three parts of a polysomnography?
Electroencephalogram
Electroculograph
Electromyogram
What is tracked by an EEG?
Changes in frequency, amplitude and synchronisation of brain waves
What is tracked by an EOG?
Eye movements
What is tracked by an EMG?
Muscle tension in face and leg
What are the uses of an EEG?
Sleep
Seizures
Altered consciousness
What rhythm is present when awake with eyes open?
β rhythm
What rhythm is present when awake with eyes closed?
α rhythm
What are the EEG, EOG and EMG results during NREM 1?
Theta waves (high amplitude, low frequency)
Slow, rolling eye movements
Slow muscle activity
What are the EEG, EOG and EMG results during NREM 2?
Slow waves but occasionally rapid spindles/k complexes
Eye movements stop
Spontaneous muscle tone and relaxation
What are the EEG findings during NREM 3?
Slow delta waves (also stage 4)
Interrupted by smaller, faster waves
What are the EEG, EOG and EMG results during REM?
Fast, small amplitude brain waves
Rapid eye movements
Flaccidity
What are the benefits of sleep?
Improves cognitive ability Solidify memory Increase decision making skills 'Eraser' theory Lack of sleep: increase HR, BP and obesity risk GH secreted during REM Increase immunity
What controls NREM/REM cycles?
Reticular activating system
What 2 ascending systems of reticular formation contribute to the RAS?
Neurons with ACh
Neurons with NA, serotonin, histamine
What happens to neuronal activity during NREM?
Both cholinergic and monoaminergic pathways slow down
What happens to neuronal activity during REM?
Cholinergic neurons fire rapidly
Monoaminergic neurons sop firing
What controls the sleep/wake cycle?
Suprachiasmatic nucleus in the hypothalamus
What does the SCN receive input from?
Retina
What does the SCN provide signals to?
Pre-optic nucleus
Orexin neurons
