Sleep & Anaesthesia Flashcards
What is the circadian rhythm?
- 00 - Midnight
- 00 - Deepest sleep
- 30 - Lowest body temperature
- 00 - Morning
- 45 - Sharpest rise in blood pressure
- 30 - Melatonin secretion stops
- 00 - Highest testosterone secretion
- 00 - Highest alertness
- 00 - Noon
- 30 - Best coordination
- 30 - Fastest reaction time
- 00 - Greatest cardiovascular efficiency + muscle strength
- 00 - Evening
- 30 - Highest blood pressure
- 00 - Highest body temperature
- 00 - Melatonin secretion starts
- 00 - Midnight
The hormone ______ is involved in
melatonin
synchronising circadian rhythm
Clock - A circadian clock
is a 24hour timing mechanism that is composed of molecular oscillators
Circadian rhythm
a biological rhythm with an approx. 24 hr period that persists in constant conditions
Oscillator is
a system of components that interact to produce a rhythm that occurs with a definable period length.
A circadian oscillator can drive a rhythmic output but needs other oscillators (known as pacemakers) for its function.
A circadian oscillator can therefore be self-sustained but cannot operate properly independently of other oscillators.
Circadian pacemaker
is a specialised oscillator that operates independently of other oscillators to drive rhythmic outputs, either directly or through other oscillators, and is entrained by environmental cues.
Entrainment
Process by which an environmental rhythm e.g light-dark cycle, regulates the period and phase relationship of a self-sustained oscillator
Zeitgeber
Any external or environmental cue that synchronises an organism’s biological rhythm to Earth’s 24-hour light/dark cycle and 12 month cycle e.g. light, temperature, exercise
What is the suprachiasmatic nucleus?
A small region of the brain that sits on top of the optic chiasm in the anteroventral region of hypothalamus
SCN is a type of
specialised oscillator - pacemaker
SCN can regulate process such as
locomotor activity
electrical firing
Where may some other oscillators be present?
Heart
Lung
Liver
Kidney
Heart Lung Liver Kidney all may regulate processes such as
heart rate, systolic blood pressure, vasodilation, gene expression, melatonin levels
How is the brain kept awake? What may lead to constant sleep?
the activity of the Ascending Reticular Formation
lesions to this brain area
Melatonin has ______ actions on SCN
inhibitory
EEG stands for __________________. It measures
electroencephalograpgh.
electrical activity produced by the brain (cerebral cortex) and recorded from electrodes placed on scalp.
From highest to lowest frequency, what waves do EEGs detect?
beta
alpha
theta
delta
Which radio wave is present during alert wakefulness?
beta
Which radio wave is present during quiet wakefulness?
alpha
Which radio wave is present during Stage 1 sleep?
low voltage and spindles
Which radio wave is present during Stage 2 and 3 sleep?
Theta waves
Which radio wave is present during Stage 4 slow wave sleep?
Delta
Which radio wave is present during Stage 5 REM sleep?
Beta
Stages and what happens during sleep cycle
Stage 1 - interim between consciousness and sleep
Stage 2 - Heat rate slows, brain does less complicated sleep
Stage 3 - Body makes repairs
Stage 4 - Body temperature and BP decrease
Stage 5 - Increase in eye movement, heart rate, breathing, BP and temperature
The awake stage is characterised by
high frequency activity with variable amplitude, combined with active electromyography (EMG)
The REM stage is characterised by
high frequency activity with high amplitude and no active EMG
The non-REM stage 4 sleep is characterised by
low frequency and high amplitude
Stage 4 occurs during the
first hour of going to sleep
REM has _____ body muscle activity than Stage 4
more
Stage 5/ REM sleep is also known as
paradoxical sleep
What is the most refreshing part of sleep? What occurs during this stage?
REM sleep
- muscle relaxation
- increased heart rate
- dreaming
- deep regular breathing
Prolonged activity of the brain may cause production of a ‘sleep producing substance’
Glucose is the main nutrient of the brain, carried by blood.
The more the brain is active, the more glucose needed.
Surrounding astrocytes supply extra energy in the form of glycogen
Glycogen metabolism increases adenosine level
Adenosine accumulation induces higher delta activity in the next sleep session
If sleep does not take place, accumulation of adenosine causes cognitive and emotional effects seen after sleep deprivation
Sleep regulatory substances seem to be involved in ________ scaling
synaptic
Synaptic scaling is a slow
homeostatic process that occurs over hours/ days; it serves in part to balance/ to scale Hebbian plasticity changes that occur rapidly as a consequence of neuronal activity
During wake period
- synaptic __________
-
- ________ regulation
potentiation
learning
circadian