Wakefulness and Sleep Flashcards
Name some internal mechanism that operate on a 24 hour cycle.
Sleep, frequency of eating and drinking, body temperature, secretion of hormones, urination and sensitivity to drugs.
Explain circannual rhythms.
Internal mechanisms that operate on an annual or yearly cycle, like birds migratory patterns, or animals storing food for the winter.
What is the purpose of the circadian rhythm?
To keep our internal workings in phase with the outside world.
Explain the concept of zeitgeber.
Meaning time-giver, referring to the stimulus that resets the circadian rhythm.
Give some examples of zeitgeber.
Sunlight, tides, exercise, meals, and temperature of the environment.
Give three examples of the effect of using something other than sunlight as a zeitgeber.
Depression, irritability, and impaired job performance.
What is jet lag?
The disruption of the circadian rhythms due to crossing time zones.
Travelling west phase-____ our circadian rhythms.
Delays.
Travelling east phase-____ our circadian rhythms.
Advances.
How do people adjust best to night work?
If they sleep in a very dark room during the day and work under bright lights.
Give three mechanisms of the circadian rhythms.
The suprachiasmatic nucleus, genes that produce certain proteins, and melatonin levels.
What is the suprachiasmatic nucleus?
The main control centre of the circadian rhythms of sleep and temperature.
Where is the suprachiasmatic nucleus (SCN) located?
Above the optic chiasm and part of the hypothalamus.
What does damage to the SCN result in?
Less consistent body rhythms that are no longer synchronised to environmental pattern of light and dark.
How is the SCN reset?
Via a small branch of the optic nerve called the retinohypothalamic path, travelling directly from the retina to the SCN.
What does the retinohypothalamic path consist of?
Specialised ganglion cells that respond directly to light and require no input from rods or cones.
Name the two genes that are responsible for generating the circadian rhythm.
Period and timeless.
What proteins do period genes produce?
PER
What proteins do timeless genes produce?
TIM
What do mutations of the PER gene result in?
Odd circadian rhythms or decreased alertness if deprived of a good night’s sleep.
What do PER and TIM proteins increase the activity of?
Certain neurons in the SCN that regulate sleep and waking.
What does the SCN regulate?
The pineal gland.
Where is the pineal gland located?
Posterior to the thalamus.
What does the pineal gland secrete?
Melatonin.
What is sleep?
A state that the brain actively produces, characterised by a moderate decrease in brain activity and decreased response to stimuli.
Name some states that sleep differs from.
Coma, vegetative state, minimally conscious state, and brain death.
Explain stage 1 sleep.
Alpha waves are present when one begins a state of relaxation, brain activity begins to decline, and the EEG is dominated by irregular, jagged, and low voltage waves.
What waves are present in stage 2 sleep?
Sleep spindles and K-complex.
Describe a sleep spindle.
12-14 Hz waves during a burst that lasts at least half a second.
Describe a K-complex.
A sharp wave associated with temporary inhibition or neuronal firing.
What do stage 3 and 4 sleep constitute?
Slow wave sleep.
What occurs in stage 3 and 4 sleep? (4)
Slowing of heart rate, breathing rate and brain activity, as well as highly synchronised neuronal activity.
What do EEG readings show during stage 3 and 4 sleep?
Slow, large amplitude waves.
Give another name for REM sleep.
Paradoxical.
Explain deep sleep.
Postural muscles of the body are more relaxed than other stages.
Explain light sleep.
EEG waves are irregular, low-voltage and fast.
What does NREM refer to?
Stages other than REM sleep.
How long does it take fore a person to cycle back trough the stages of sleep?
An hour.
What is the sequence of sleep stages when a person cycles back through them?
4, 3, 2, REM.
How long does each complete sleep cycle last?
90 minutes.
What is the reticular formation?
Part of the midbrain that extends from the medulla to the forebrain.
What is the reticular formation responsible for?
Arousal.
What is the pontomesencephalon?
Part of the midbrain that contributes to cortical arousal.
Where do the pontomescencephalon’s axons extend? (3)
The hypothalamus, thalamus and basal ganglia.
What do the pontomescencephalon’s axons produce?
Acetylcholine and glutamate, which produce excitatory effects in widespread areas of the cortex.
What is the locus coeruleus?
A small structure in the pons whose axons release norepinephrine.
What does the locus coeruleus increase?
Wakefulness.
When is the locus coeruleus dormant?
When asleep.
What does the hypothalamus produce that enables anti-histamines to cause sleepiness?
Histamines, that produce widespread excitatory effects through the brain.
What does orexin do?
Enhances wakefulness, and is important for staying awake.
What is acetylcholine?
An excitatory neurotransmitter the increases arousal.
When is acetylcholine released?
During REM and wakefulness.
What is GABA?
An inhibitory neurotransmitter.
How many neurons rely on GABA in the SCN?
20’000
Explain lucid dreaming.
Dreaming but being aware of being asleep and dreaming.
How do sleepwalkers exist?
They are awake in one part of the brain and asleep in others.
What causes an inability to move upon waking?
The pons remaining in REM while the rest of the brain is awake.
Where does activity increase in the brain during REM? (2)
In the pons and limbic system.
Where does activity decrease in the brain during REM? (3)
In the primary visual cortex, the motor cortex, and the dorsolateral prefrontal cortex.
Explain PGO waves.
High-amplitude electrical potentials that pass through the pons, lateral geniculate and occipital lobe.
What is each PGO waves synchronised with?
An eye movement in REM.
Name some factors causing sleep disorders.
Noise, stress, pain, diet and medication.
Name some disorders causing sleep disturbance.
Epilepsy, Parkinson’s, depression, anxiety, and more.
Dependence on what two things an result in insomnia?
Sleeping pills or alcohol.
Describe sleep apnea.
A sleep disorder characterised by the inability to breathe while sleeping.
What are the consequences of sleep apnea? (4)
Sleepiness during the day, impaired attention, depression and sometimes heart problems.
Name some causes of sleep apnea.
Genetics, hormones, old age, obesity, and deterioration of the brain mechanisms that control breathing.
Describe narcolepsy.
A sleep disorder characterised by frequent periods of sleepiness.
Explain occasional cataplexy.
Muscle weakness triggered by strong emotions.
Describe sleep paralysis.
Inability to move while falling asleep or waking up.
What are hypnagogic hallucinations?
Dreamlike experiences.
What is periodic limb movement disorder?
The repeated involuntary movement of the legs and sometimes the arms while sleeping.
How often does leg movement occur in periodic limb movement disorder?
Once every 20-30 seconds for minutes to hours.
When does periodic limb movement generally occur?
During NREM.
What is REM behaviour disorder?
Associated with vigorous movement during REM sleep, usually associated with acting out dreams.
What may be responsible for REM behaviour disorder?
Inadequate GABA and other inhibitory neurotransmitters.
What are night terrors?
Experiences of intense anxiety from which a person awakens screaming in terror.
When do night terrors occur?
NREM sleep.
When does sleepwalking occur?
Stage 3 or 4 sleep.
What is sleepwalking not associated with?
Dreaming.
Name some functions of sleep.
Resting muscles, decreasing metabolism, performing cellular maintenance in neurons, reorganising synapses, strengthening memories, and conserving energy.
What happens to body temperature during hibernation?
It decreases until it is only slightly above that of the environment.
What happens to heart rate and brain activity during hibernation?
They drop to almost nothing.
What are the effects of hibernation on neurons? (2)
The cell bodies shrink, and dendrites lose branches.
What do animals sleep habits depend on? (3)
Whether they are predatory or prey, how many hours they spend each day devoted to looking for food, and safety from predators while they sleep.
How does sleep affect memory?
It enhances learning an strengthens memory.
What suggests that the brain replays its daily experiences during sleep?
Patterns of activity in the hippocampus during learning are similar to those shown in sleep.