The Physiology of Sleep Flashcards
Define Sleep
a natural period state of rest for the mind and body, in which the eyes usually close and consciousness in completely or partially lost, so that there is a decrease in bodily movement and responsiveness to external stimuli
Sleep Deprivation can lead to:
- grumpiness
- grogginess
- irritability
- forgetfulness
- language, memory, planning and
sense of time are severely affected
How do we measure sleep?
- questionnaire
- physiological measurements EEG
Analysis of Sleep: Questionnaire:
- eg do you feel your sleep is not
refreshing or restful - results can be limiting due to
increased error due to bias
Analysis of Sleep: Physiological Measurements:
- more complex approach
- eg brain waves, neurochemicals,
sleep models, pharmacology - results are limited by methods
used, mostly free from bias and
are reproducible
EEG stands for
Electroencephalography
EEG: Method:
involves the recording of a gross average of electrical potentials of the cells and fibers in the brain areas closes to each electrode attached to the scalp
EEG: Basic Principle:
- neurons generate electrical action
potentials - the firing of many neurons creates
a large electrical field in particular
brain regions
Generation of small fields in pyramidal cells:
insert diagram
What are the 2 basic requirements for signal detection?
- a whole population o fneurons
must be active in synchonicity to
generate a large enough electrical
field at the level of the scalp - this population of neurons must
be aligned in a parallel orientation
so that they summate rather than
cancel out
The amplitude of EEG signals depends upon:
- the synchronous activity of
underlying neurons - number of active cells, total
amount of excitation, timing of
activity are key contributors
What type of cells generate synchronous rhythmns?
Thalamic cells have a set of voltage-gated ion channels that allow each cell to generate rhythmic, self-sustaining discharge patters even in the absence of external inputs
the rhythmic activity of each thalamic pacemaker neuron then becomes synchronised with many other thalamic cells through cellular and chemical communication
Function of Brain Rhythms?
- sensory input travels to thalamus,
then directed to functional area of
cortex - meaningless by-product of
feedback circuits and connections
EEG Recordings:
- electrical potentials are recorded
from either the entire skull surface
or from specific points - electrical potentials are recorded
as traces - increased, synchronised activity is
displayed as a larger amplitude
than the baseline recording
Interpreting Sleep Through EEGs:
- EEG recorded whilst asleep
- observes monitored behavioural
changes during sleep - traces obtained were analysed
from amplitude and frequency of
wave patterns
EEG:
- flat line
- peak
- trough
Flat line = half the neurons recorded are firing, half are inhibiting
Peak = all are firing in that area
Trough = none are firing in that area
Whilst sleeping, heart rate, breathing rate and brain activity
decrease
Major behavioural changes whilst sleeping:
- lack of gross movement (large
amounts of muscle movement) - presence of Rapid Eye Movement
(REM) cycles throughout a period
of sleep
Correlating EEG with Behaviour:
All are different stages:
insert slide
EEG:
insert figure
How many stages in sleep?
- 4 stages non-REM sleep (N1,2,3)
- 1 stage REM sleep
Sleep: N1:
- non-REM sleep
- dominated by irregular, jagged,
low voltage waves - brain activity is high but will start
to decline
Sleep: N2:
- non-REM sleep
- sleep spindles
- K-complexes
Sleep: N2: Sleep Spindles:
- 12-14Hz burst for at least 500msec
- generated by oscillating
interactions between cells in the
thalamus and the cortex
