Physiological responses and methods
What are the three most commonly measured physiological responses and using what methods?
Electrical activity of the brain – EEG
Muscle tension – EMG
Eye movements – EOG
What are the four main internal biological mechanisms that influence the regulation of our sleep-wake patterns?
Circadian rhythm, suprachiasmatic nucleus (SCN), melatonin secretion, ultradian rhythm
Around what percentage of our total sleep time is spent in NREM sleep?
75-80%
Around what age does an infant sleep 14-15 hours a day with most of it occurring as a single sleep episode in the evening?
12 months
Refers to our awareness of something either internal or external to ourselves including objects, events, sensations, mental experiences and our own existence.
Where are the electrodes placed for EEG, EMG and EOG respectively?
EEG: around the scalp
EOG: around the eyes
EMG: near muscles on the face and body
True or false: although endogenous, the sleep-wake cycle can be influenced by exogenous factors.
True (e.g. external cues such as light can affect our sleep-wake cycle)
REM: no stages, sleep with an active brain and paralysed body
NREM: stages, relatively inactive brain in a body that can move
Both: occur in virtually all mammals and birds, linked to specific brain waves and changes in bodily activity
List some reasons why the number of hours spent sleeping decreases as humans move from infancy to childhood.
Maturation of other biological factors, and social factors like decreased daytime napping, preschool and other routines.
Sleep can be described as...
A regularly occurring altered state of consciousness that typically occurs naturally and is primarily characterised by partial or total suspension of conscious awareness.
List the four different types of brain waves and describe their characteristics.
Beta pattern: fastest brain wave patterns, associated with alertness and intensive mental activity during normal waking consciousness. Also present when dreaming during the REM period.
Alpha pattern: Occurs when we are awake and alert but mentally relaxed and internally focused. Happens especially when closing your eyes while doing something like reflecting.
Theta pattern: Occurs most commonly when we are very drowsy and also when engaged in creative activities during waking period.
Delta pattern: Most commonly associated with deep, dreamless sleep or unconsciousness.
Define and distinguish circadian and ultradian rhythms.
Circadian rhythm: behavioural, psychological and physiological changes that occur throughout the 24-hour cycle
Ultradian rhythm: behavioural, psychological and physiological changes that fluctuate in cycles throughout each day and occur more than once a day (e.g. human sleep, heartbeat, respiration, hunger, etc.)
What does a complete sleep cycle consist of?
A period of NREM sleep with transitions between its three stages and a period of REM sleep
Besides biological factors, what might be a reason for adolescents getting less sleep than they need to function at their best?
Irregular sleep patterns across the week (staying up late on weekdays and even later on weekends)
Being in FFF mode, fatigue, feeling drowsy, being asleep, daydreaming, being in a meditative state, being under the influence of external chemicals like alcohol, medication or illicit drugs.
Give an example where of an activity where each of the brain wave patterns would be seen.
Beta pattern: taking a test
Alpha pattern: meditating
Theta pattern: struggling to stay awake on a plane
Delta pattern: deep sleep
When is melatonin secreted? Why?
When activated, the pineal gland produces and secretes melatonin only when it is dark outside. This occurs so that an individual maintains their sleep-wake cycle aligned with the day/night cycle and does not fall asleep when they should be awake, even if the pineal gland is signalled to do so by the SCN.
What is the pattern that best describes a typical sleep cycle (that occurs 4-5 times a night)?
N1, N2, N3, REM, N1, N2, N3, REM ...
Why do older adults tend to report more frequent awakenings during the night?
The decrease (and in some cases disappearance) of NREM sleep causes a higher frequency of awakenings during the night, as we are harder to awaken during slow delta wave sleep.
Name and describe the two distinctions between the two altered states of consciousness (ASC).
Naturally occurring: sleep, dreaming during sleep, daydreaming when awake --> occur without the need for any aid
Induced: meditation, hypnosis, alcohol ingestion, medication, illegal drugs (intentionally) / accident, disease, concussion, epilepsy, comatose state from brain trauma (unintentionally)
How can sleep diaries supplement objective data collected through EEGs, EMGs and EOGs?
It provides qualitative data that these machines cannot measure or detect such as how well-rested an individual feels, how sleepy the individual may feel throughout the day and events that can affect sleep (naps, caffeine, alcohol, medication, exercise, etc). Furthermore, it may help suggest explanations/provide understanding for the data obtained or anomalies found in it.
*any reasonable response is accepted*
Explain the role and importance of the suprachiasmatic nucleus (SCN) in the sleep-wake cycle.
It adjusts our sleep-wake cycle according to the information about the amount of incoming light it receives. It does so by sending neuronal messages to the pineal glad to secrete either more or less melatonin into the blood. Furthermore, when light is detected, the SCN will increase body temperature and release stimulating hormones to promote awareness and wakefulness, a chain reaction that is suppressed when it is dark.
It maintains our sleep-wake cycle in sync with the 24-hour day/night cycle.
Explain the three stages of NREM sleep
Stage 1 (N1): Relatively light sleep and lower level of bodily arousal (sometimes we may experience muscle twitches called hypnic jerks due to the relaxation of the muscles). Brain waves also start to slow down. Lasts for around 5-8 minutes and accounts for 4-5% of the total sleep time. It is easily to be awoken during this period (low arousal threshold).
Stage 2 (N2): A period of light sleep that gradually becomes deeper. Brain wave pattern is overall slower but is distinguished by sleep spindles (occur every 3-6 seconds), which signal transition to N2. People become less responsive to external stimulus as we approach the second half of this stage. This stage lasts 10-25 minutes in the firs cycle and lengthens with each successive cycle. It is the stage we spend the most time in when sleeping.
Stage 3 (N3): A period of deep sleep where heart rate and breathing slow to slowest levels, and we barely move. Brain waves become even slower (delta waves). This stage has the highest arousal threshold and people find it difficult to re-orient themselves after awakening, especially if it occurs abruptly. As the night progresses, we successively spend less and less time in this stage (20-40 minutes in the first cycle, making up for 10-15% of total sleep time).
True or false: sleep needs decline with age. Explain
False. Sleep needs remain the same throughout adulthood. However, people have a harder time falling and remaining asleep as they age, as well as having a higher likelihood of developing sleep disorders like sleep apnea or insomnia.
Explain why it is reasonable for consciousness to exist along a continuum between total awareness and complete lack of awareness instead of having arbitrary dividing lines.
It is reasonable for consciousness to exist along a continuum because of how often it varies throughout the day. Furthermore, there are no exact boundaries for where one state of awareness starts and the other ends.
*any reasonable response is accepted*