Sleep (8) Flashcards
The study of biological rhythms
Chronobiology
Which cycle dominates the human biorhythm?
Circadian (daily) rhythm of daylight activity and nocturnal sleep
What are the behaviours associated with biological rhythms driven by?
External cues from the environment as well as internal cues (endogenous control)
A neural system that times our behaviours
Biological clock
Yearly rhythm (ex. migratory cycles)
Circannual
Daily rhythm (ex. human sleeping)
Circadian
Rhythm that is less than a day
Ultradian
Rhythm that is more than a day
Infradian
How would one determine if a behaviour is produced by a biological clock?
Observe it in the absence of external cues
Rhythm of the body’s own devising in the absence of all external cues
Free-running rhythms
Why would the human circadian rhythm for the sleep-wake cycle become obsolete over time if not for it being reset?
The natural sleep-wake rhythm is 25-27 hours, which over time would not correspond to night/day times
A “clock-setting” cue from the environment that resets biological rhythms (ex. light/dark)
Zeitgeber
Main pacemaker of circadian rhythms located at the base of the hypothalamus that gives input about the appropriate timing of behaviours
Suprachiasmatic nucleus
What would happen to sleep if the SCN is damaged?
The total amount of sleep would be maintained but the timing would be off
The SCN receives information about light through this pathway, which extends from the retina through to the SCN
Retinohypothalamic pathway
Describe the retinohypothalamic pathway
Specialized RGCs become excited when stimulated by light and pass the message passes to the SCN
Describe the role of the SCN in relation to the Circadian Timing System
Light entrains the SCN and the SCN then drives a number of slave oscillators, each of which controls the rhythmic occurrence of one other behaviour (through hormone release)
Using recording equipment to measure the electrical activity of the brain and body during sleep
Polysomnography
What are the three measures of polysomnography and their uses?
Electroencephalogram (EEG - brain activity)
Electromyogram (EMG - muscle activity)
Electrooculogram (EOG - Record of ocular activity)
What are the five sleep stages?
W, N1, N2, N3, R-sleep
What are characteristics of the W stage?
Beta rhythm (small amplitude, fast frequency waves)
Active EMG and EOG shows eye movement
If relaxed with eyes closed, alpha rhythms are produced
Waves that are 15 to 30 Hz in frequency, indicative of wakefulness
Beta rhythm
What are characteristics of the N1 stage?
From beta to theta wave activity
EMG is slightly active
EOG largely absent
Waves with low amplitude and mixed frequency
Theta waves
Varying behaviour from alertness to drowsiness
W (waking)
Behavioural state of a person at sleep onset
N1
When a person becomes fully asleep
N2
What are characteristics of the N2 stage?
Continue to produce theta waves
Sleep spindles are produced
Production of K-complexes
Brief high-frequency bursts
Sleep spindles
Deep sleep
N3
What are characteristics of the N3 stage?
Delta rhythms
EMG still active
No activity with EOG
Large amplitude, slow frequency
Delta waves
What are some characteristics of R-sleep?
No activity on EMG
EOG activity returns
Beta rhythms similar to W and N1
No muscle activity
Atonia
A sleep graph of an individual cycling through the
sleep stages over the course of a night
Somnogram
In which pattern do we experience the sleep stages during a typical night’s sleep?
Beginning with W, we proceed through the stages in order, ending with REM. The cycle then proceeds in reverse order, until REM is reached again, replacing W. This pattern continues until W stage is reached again.
How often does the sleep cycle repeat?
About every 90 minutes
What differentiates sleep early in a typical night from later?
REM dominates later sleep, whereas N sleep dominates early stages. Body temperature is also lower in early sleep and rises later in the night.
Describe how sleep patterns change with age.
Overall time asleep gets lower with age
REM sleep is longest in infancy, during growth spurts and during pregnancy.
REM sleep declines into middle age.
What are characteristics of NREM sleep that differ from REM sleep?
Muscle tone is maintained, movement can occur (teeth grinding, sleep walking)
Body temperature and heart rate drop
Growth hormone release increases
Dreaming can occur but is often less vivid (Lucid dreaming can occur)
Uncontrollable leg movement
Restless leg syndrome
Aware of dreams as we dream them
Lucid dreaming
What are characteristics of REM sleep that differ from NREM sleep?
Eyes move
Erections in males
Mechanisms that regulate body temperature stop
Paralysis and atonia (Only small twitches are possible)
Why does atonia occur during REM?
Sleep regions of the brainstem send inhibitory signals to motor neurons.
What is one theory as to why some twitching still occurs during REM?
An involuntary response to keep blood flowing throughout the body at night while we sleep.
How does recollection differ between dreams during REM and NREM?
People are more likely to indicate that they were experiencing vivid dreams and are more likely to remember them when woken from REM.
What is the relationship between time and dreaming?
Dreams take place in real-time, in that it takes the same amount of time to perform an activity in a dream as it does in real life.
What was Freud’s major theory regarding the content of dreams?
Dreams are the symbolic fulfillment of unconscious desires and wishes, often emphasising sexual desires and wishes
What was Jung’s major theory regarding the content of dreams?
Dreams allow us to relive the memories/history of the human race (our “collective unconscious”)
What does current research suggest regarding the content of dreams?
Most dreams are related to recent events and ongoing problems (80% recent past, 20% older events)
Calvin Hall et al. demonstrated that dreams occur in response to emotional states and are more likely to involve emotional stress.
Explain Hobson’s activation-synthesis hypothesis regarding dreams as meaningless brain activity.
When dreaming, the cortex receives signals from the brainstem (producing patterns similar to waking during REM)
The cortex proceeds to generate random images, actions and emotions in response to the excitatory signals, potentially drawing from personal memory
Explain why sleep is a biological adaptation.
Sleep is an energy-conserving strategy.
How does average sleep time vary depending on the type of animal?
Herbivores tend to sleep the least (predation, long time collecting food, not very energy-rich)
Carnivores sleep the most (not as subject to predation and more nutrient-rich foods)
Omnivores fall between herbivores and carnivores
Why is sleep a restorative process?
Chemical processes that provide energy to cells are depleted while awake and replenished during sleep.
What are some consequences of interrupted sleep?
Issues with attention, reaction times, mood
What are two effects of REM sleep deprivation?
Subjects take less time than usual to get back to REM sleep
The need for the brain to enter REM sleep increases (REM rebound- almost double the amount of time in REM than normal)
What are three consequences of losing REM sleep?
Impact our immune system and resistance to disease
Reduce neurogenesis in the hippocampus
Impacts our body’s ability to cope with stress
What is the impact of sleep on memory?
Helps solidify and organize memories in addition to aiding memory retention
Hippocampal neurons, for spatial memory, that fire when one is in a location in an environment that one was previously in
Place cells
Hormone secreted from the pineal gland of the brain in response to darkness that causes sleepiness
Melatonin
What evidence suggests that melatonin alone is not responsible for sleep?
Sleep behaviour survives the removal of the pineal gland
Large reticulum (mixture of cell nuclei and nerve fibers) that runs through the center of the brainstem, associated with both sleeping behavior and our ability to wake up from sleep
Reticular Activating System (RAS)/Reticular formation
A prolonged state of deep unconsciousness that resembles deep sleep, resulting from damage to the RAS
Coma
What are the two brainstem nuclei in the ascending pathway of the RAS that influence waking EEG?
Basal forebrain nucleus and the median raphe nucleus
Contains cholinergic cells and is active when the animal is alert, but not moving
Basal forebrain nucleus
Contains cholinergic cells and is active when the animal is alert, but not moving
Basal forebrain nucleus
Contains serotonergic neurons and is active when the animal is moving
Median raphe nucleus
Part of RAS, cholinergic nucleus in the dorsal brainstem that projects to the medial pontine reticular formation
Peribrachial area
What is the purpose of the peribrachial area?
Initiates REM sleep and REM behaviours (eye movements and emotional content of dreams)
Nucleus in the pons participating in REM sleep and REM-related behaviors
Medial pontine reticular formation (MPRF)
What is the purpose of the MPRF?
Produces atonia
Disorder of slow-wave sleep resulting in a prolonged inability to fall or stay asleep
Insomnia
A REM-sleep disorder producing atonia and dreaming when a person is still “awake”, usually after just falling asleep or more commonly right
before waking up
Sleep paralysis
Slow-wave sleep disorder in which a person uncontrollably falls asleep at inappropriate times
Narcolepsy
The inability to breathe during sleep causing someone to repeatedly wake up during the night to breathe.
Sleep apnea
A form of narcolepsy in which an animal suddenly experiences atonia, as if they are in REM, while still awake, sometimes accompanied by hallucinations
Cataplexy
