Sleep, wakefulness, epilepsy and EEG Flashcards
Define sleep.
a) easily reversible state of inactivity with a
b) lack of interaction with the environment.
Define unconsciousness.
Unconsciousness is an inconsistent term, can be:
-coma (depressed state of neural activity, absence of
wakefulness)
-sleep ( variation in neural activity)
Define consciousness.
Having awareness; with perceptions, thoughts and feelings. – philosophical and biological aspects
Do all vertebrates sleep ? Mammals ?
Most vertebrates, and all mammals sleep, but not all sleep in the same way as humans
What is the function of sleep ?
The true function of sleep is unknown:
suggested functions include the processing and storage of memories, recuperation of the bodies immune system and to conserve energy.
During sleep, are neurons active ?
During sleep the neurons of the brain are active, but display a different type of activity from wakefulness
Is there a difference in amount of oxygen consumed by the brain in wakefulness cf in sleep ?
The sleeping brain consumes as much oxygen as the wakeful brain , and sometimes more
What are the main forms of external discernible sleep ?
There are two main forms of externally discernable sleep, they are either:
1) when the eyes move rapidly from side to side (REM sleep)
2) when they do not (non REM, slow wave or deep sleep) however there
are other determinants also (mostly starts with non REM sleep)
How can neuronal activity during the different stages of wakefulness (including sleep) be measured ?
Neuronal activity during different stages of wakefulness (including sleep) can be measured using an Electroencephalogram (EEG)
Explain how an EEG works.
-EEG electrodes are arranged in 19 pairs (or more) at internationally agreed points on the surface of the head
-Post synaptic activity of individual neurons not picked up
-Post synaptic activity of
synchronised dendritic activity (network of neurons which fire synchronously) can be picked up
(synchronisation is either by neuronal interconnections or by pacemaker)
-The more neurons that are synchronised, the bigger the peaks on the EEG.
What frequencies are normal adult brain waves, in the following:
- Awake with mental activity
- Awake and resting
- Sleeping
- Deep sleep
- Awake with mental activity: beta (14-30 Hz)
- Awake and resting: alpha (8-13 Hz)
- Sleeping: theta (4-7 Hz)
- Deep sleep: delta (<3.5 Hz)
Identify the main components of normal sleep, including physiological changes and EEG changes.
AWAKE
- Eyes closed, alpha high frequency (8-13 Hz) and low amplitude (50 μV)
- Eyes open beta waves (14-60 Hz) waves of activity
STAGE 1 (duration 1-5 minutes, easily roused)
- Phys: Slow rolling eye movements
- EEG: Some theta waves (slower frequency 4-7 Hz and higher amplitude waves)
STAGE 2 (duration 10-15 minutes)
- Phys: No eye movement, but body movement remains possible
- EEG: K complexes and sleep spindles (8-14 Hz bursts)
STAGE 3 (duration few minutes)
- Phys: Harder to rouse
- EEG: Slower frequency, delta waves (including amplitude) appear, few spindles
STAGE 4 (duration 15-30 minutes)
- Phys: Deepest sleep, hardest to rouse, heart rate and BP lower, movement
- EEG: >50% EEG waves at 2Hz (slow waves of synchronised firing of large groups of neurons) and high amplitude (> 200μV) called delta waves
REM
- Phys: Subject easier to rouse than in stage 4, dreaming, recalled, low muscle tone (body effectively paralysed), rapid eye movement, increased HR, neural activity, respiration, and oxygen consumption, penile erection, body temperature drops as metabolism is inhibited
- EEG: Fast beta waves and REM
Graph the different stages of sleep, especially their frequency, as a function of time.
Refer to slide 8
Which stages of sleep are spindles present in ?
Stages 2 and 3
How many cycles occur in a typical night’s sleep ?
Consists of several cycles through the five stages of sleep. Note that Stage 4 is only reached in the initial cycles, thereafter the deepest sleep attained is Stage 3. Also, increasing time spent in REM sleep (and shorter intervals between REMs, towards morning tend to be dreaming more)
What is the relationship between muscle activity and depth of sleep ?
Muscle activity (head) decreases with depth of sleep.
Why can the characteristic penile erection associated with REM sleep be useful ?
Penile erection is associated with REM sleep and this characteristic can be used in discrimination between different types of erectile dysfunction.
Describe the changes in movement and breathing as subject goes deeper into non REM sleep.
As the subject goes deeper into non REM sleep, movement and breathing is depressed however movement is still possible
What is the function of slow waves ?
Slow waves are thought to be involved with inhibiting sections of the relevant cortex
Why is there no body movement but there is eye movement during REM sleep ?
One source of activity in REM is concerned with inhibiting motor output (excepting breathing and eye movement)
What are the main structures forming the reticular formation ? What is its function ?
diffuse collection of at least 100 networks of neuromodulatory neurones spanning all three divisions of the brainstem
- NOT homogeneous (main NTs are NAdr, 5HT, Ach)
- DIVERSE functions (posture, respiration, heart rate and sleep/arousal)
Where does the reticular formation project ?
It has projections to: the thalamus, the hypothalamus, some brainstem nuclei, the cerebellum, the spinal cord and, the cerebral cortex
Where does the reticular formation receive inputs from ?
It receives input from: the cerebra (collaterals from the corticospinal pathways), the visual and auditory systems, sensory spinal systems, the cerebellum, certain brainstem nuclei
Which parts of the brain are involved in sleep ?
Sleep mechanisms rely on communication between the Reticular Formation and the Thalamus (being the main relay station to and from the cortex.