Chapter 6: Demand for sleep Flashcards
what is sleep
It is an active state of unconsciousness produced by the body where the brain is in a relative state of rest and is reactive primarily to internal stimulus
key characteristics of sleep
Reversibility
a sleeper can always be awoken with a strong enough stimulus.
Disengagement
Sleeper has no awareness sensory stimuli in their external environment
Unresponsiveness
To environmental stimuli, although a strong enough sensory stimulus may awaken a sleeper. When this occurs, the exact nature of the stimulus is not perceived by the sleeping person as it would be by an awake person
what is normal waking consciousness and altered state of consciousness
Normal Waking Consciousness (NWC) – awareness of your thoughts, feelings and behaviours, including internal and external events.
Altered State of Consciousness (ASC) – any state characteristically different from normal waking consciousness in terms of awareness, thoughts, feelings and behaviours.
Three ways of measuring physiological responses to sleep
electrical activity of the brain, measured using an EEG;
muscle tension, measured using an EMG;
eye movements, measured using an EOG.
whats a sleep log
a self report on sleep, including the recording of relevent data such as amount of sleep times of waking up etc,
whats video monitoring
record externally observable physiological
responses throughout a sleep episode, including
behaviours when falling asleep and when waking.
four factors that regulate the sleep wake pattern
circadian rhythm
ultradian rhythm
suprachiasmatic nucleus (SCN)
Melatonin
whats a biological clock
A biological clock is an innate timing mechanism that regulates the cycle ofa biological rhythm. Its functioning is geneticallydetermined and occurs at the cellular level.
what are circadian rhythms
a biological rhythm that involves changes in bodily functions or activities that occur as part of a cycle with a duration of about 24 hours.
what are ultradian rhythms
A biological rhythm that involves changes in bodily functions or activities that occur as part of a cycle shorter than 24 hours.
what does the suprachiasmatic nucleus (SCN) do
The SCN receives information about the amount of incoming light from the eyes and adjusts our sleep–wake cycle accordingly.
It does so by sending neuronal messages to the nearby pineal gland to secrete more or less of the hormone melatonin into the blood
how does the SCN induce sleepiness
When there is less light, the SCN signals the pineal gland to secrete more melatonin which makes us drowsy & induce sleepiness. This only will happen if it is dim enough
whats melatonin
is a hormone that is involved in the initiation of sleep and in the regulation of the sleep–wake cycle. It is produced by the pineal gland in the brain and released into the blood stream, through
which it reaches every organ in the body. The amount of melatonin present in the blood is associated with alertness. A higher melatonin level is associated with greater drowsiness and vice versa.
whats REM sleep
20-25% of total sleep time
REM sleep is characterised by rapid bursts of eye movement, heart and breathing rate is faster (than NREM) and blood pressure rises.
whats N-REM sleep
NREM sleep is traditionally subdivided into four stages
75-80% of total sleep time spent in NREM
Typically the first half of the night has more NREM sleep than the second half of the night.
Characterised by: reduction in physiological activity. Each successive stage is indicative of a deeper sleep, with stage 1 as the lightest and stage 4 as the deepest.
As sleep gets deeper, the brain waves get slower and bigger, breathing and heart rate slow down, and blood pressure drops. We also transition back again from the deep sleep of stage 4.
