Lecture 11 Flashcards
Sleep research is conducted where
in a sleep laboratory.
Electrodes placed around the eyes monitor eye movements recorded aswhat
an electro- oculogram (EOG).
Electrodes are also attached to the subjects chin to record muscle activity recorded as what
an electromyogram (EMG).
Electrodes are attached to the subjects scalp to record electrical activity of the brain. The amplifier records a what
electroencephalogram (EEG).
what are the stages of sleep
awake REM non-rem stage 1 non-rem stage 2 non-rem stage 3 (formerly stage 3&4)
what is the characteristics with regard to the wavelengths during stage 4 vs awake
stage 4– low frequency, high amplitudes
awake– low amplitudes, high frequency
what is Slow-wave sleep
sleep stages 3- 4; deep, non-REM sleep; associated with large amplitude, low frequency oscillations of brain activity as measured with EEG. This pattern of neural activity reflects bursts of action potentials that are synchronized across large collections of neurons.
what is Rapid eye movement (REM) sleep
also called paradoxical sleep: desynchronized EEG activity, rapid eye movements, and muscle paralysis; associated with dreaming; apart from occasional twitching, muscles are totally inactive. Cerebral blood flow and oxygen consumption increase.
what are the EEG SIGNALS DURING SLEEP
beta activity
alpha activity
theta activity
delta activity
what is Beta activity,
13–30 Hz; typical of an aroused state. It reflects desynchronous neural activity (high frequency, low amplitude oscillations)
what is Alpha activity,
8–12 Hz; typical of awake person in a state of relaxation
what is Theta activity,
3.5–7.5 Hz; appears intermittently when people are drowsy, and is prominent during early stages of slow-wave sleep
what is Delta activity;
<4 Hz; occurs during deepest stages of slow-wave sleep; reflects synchronized low frequency, large amplitude brain activity
Starting after about 10 minutes of sleep, EEG recordings of humans include a mixture of what
sleep spindles and K complexes.
what are Sleep spindles
short bursts of desynchronized activity (12-14 Hz) which occur between 2-5 times a minute during sleep stages 1-4.
what are K complexes
sudden, sharp waveforms. They are technically only found during stage 2 sleep, but they resemble the delta waves prominent during deeper stages of sleep. They occur spontaneously at approximately 1 per minute and can be triggered by unexpected noise. Older people often have more K complexes.
what happens to muscles in REM sleep
they go limp
If you don’t sleep what happens
You feel tired, but generally, physically, your body is fine. Your mind however beings to deteriorate. You start to exhibit delayed reaction times and poor judgment (as measured on performance in cognitive tests).
• You have increases in stress hormones, mood swings, and impulsive behavior.
• You exhibit worse learning and memory.
• You increase your propensity for weight gain, migraines, hallucinations, dementia, seizures, and death.
• A sleep debt is created that must be repaid (in most species).
• Microsleep states often appear, where animals fall asleep for brief episodes lasting several seconds, during which time they are perceptually ‘blind‘ and often unaware that they have fallen asleep.
• Sleep disruptions often precede and exacerbate mental illnesses
can lack of sleep cause death
yes
how do Dolphin sleep
highlights an especially remarkable solution to the problem of maintaining vigilance during sleep. Their version of sleep alternates between the two cerebral hemispheres
aka each hemisphere sleeps separately
do all animals sleep
it appears so
give an example of large developmental differences within species
50% of human infant sleep is REM sleep
• 25% of human adult sleep is REM sleep
There are even larger differences between species in what sense
Amount of sleep
• Ratio of REM to non-REM sleep
• Length of sleep cycles (average time between two REM events)
As a general rule, predatory animals indulge in long, uninterrupted periods of sleep.
Animals that are preyed upon typically sleep during short intervals that may last no more than a few minutes.
what is the correlations between sleep and body weight
The amount of time a species sleeps each day is inversely correlated with weight
the smaller the animal, the more they seep and rise versa
what is the correlation between metabolic rate and body weight
While overall metabolic rate increases as mass increases, metabolic rate per pound (or per cell) decreases as mass increases.
what is the correlation between metabolic rate and sleep
↑ body mass, ↑ brain mass, ↑ overall metabolic rate but ↓ metabolic rate per kg (or per cell), ↓ heart rate, ↑ life span, ↓ total sleep time, ↑ length of sleep cycles
• For example, large animals have low metabolic rates per cell and long life spans. They don’t sleep very much, but each sleep session is relatively long.
• Why do all these correlations exist?
- One hypothesis is that it all has to do economies of scale related to nutrient and waste distribution networks. Large animals benefit from economies of scale (i.e. heat savings and more efficient distribution networks), so each cell doesn’t have to work as hard.
- The fact that total sleep time is highly correlated with all of these variables suggests that sleep may be critical for restorative process
what are the main theories of why animals sleep
energy conservation
brain processing
restoration of some kind
explain the energy conservation theory
Ifyouusuallyspendthenightsittingquietlyhidingina cave, you might as well be sleeping and conserving energy.
Part of this theory is that sleep is a time for “serious” rest, a respite from something that takes a toll on the body. Sleep does lowers a person’s metabolic rate and energy consumption. The cardiovascular system gets a break during sleep (20 to 30% reduction in blood pressure,10 to 20% reduction in heart rate).
what is the problems with the energy conservation theory
The amount of sleep people get does not correlate with how much or
how little they exercise.
• The caloric difference between humans sleeping and humans sitting
still across 8 hours is negligible (about 110 calories).
explain the Brain Processing theory
(learning and memory) – How can the brain update synaptic weights while it is currently operational and constantly receiving new information?
• Sleep gives the brain an opportunity to reorganize data and archive memories, which maybe cannot be done efficiently during the wake state.
• Synaptic modifications clearly occur during sleep
• Learning and memory are clearly impacted by sleep. The amount of slow- wave and REM sleep people get correlates with improvements in declarative and procedural memory, respectively.
• During sleep the brain appears to be actively processing information and transferring it between different areas, both within cells (with gene transcription) and between cells (through network oscillations)
explain the theory about Restoration of some kind
restore, replace, rebuild
• Maybe sleep is required to complete a particular biochemical task, some kind of repair or clean up
• The fact that total sleep time is highly correlated with all of these variables (body mass, brain mass, metabolic rate, heart rate, life span) suggests that sleep may be critical for either the distribution of nutrients or the removal of waste products.
Some evidence suggests sleep is required for efficient removal of waste products from the brain.
• It has been reported that the concentration of certain proteins in the brain increases across periods of wakefulness and decreases across periods of sleep.
• Recent research has shown that the clearance of proteins and waste products from the brain is almost nonexistent during wakefulness but really high during sleep
In the brain, the volume of interstitial space increases 60% across wake-sleep transitions, and grows from 14% to 23% of total brain volume. This increase in interstitial volume promotes what
the diffusion of cerebrospinal fluid into the brain, which results in increased clearance of waste products.
It seems that sleep-wake cycles regulate the volume of interstitial space. Why do big animals sleep less than small animals?
Maybe the clearance of waste products from the brain benefits from economies of scale. Maybe larger brains have a relatively larger volume of interstitial space to “buffer” the accumulation of sleep-driving molecules.
explain the The Glymphatic System
Cerebrospinal fluid (CSF) is a clear, colorless fluid that is continually being made and deposited into the ventricles of the brain. From there it circulates around the outside of the brain and acts as a cushion or buffer (mechanical support). Some CSF diffuses into the brain, into the interstitial space, which is just the space between cells. As CSF filters through the interstitial space it acts to clear waste and provides basic immunological protection. CSF exits into the cardiovascular system blood. This process is known as the glymphatic system. It is the waste clearance pathway of the brain. It removes excess proteins and other metabolic waste from the interstitial space in the brain.
The clearance of proteins and waste products from the brain occurs when
almost nonexistent during wakefulness but really high during sleep.
(In contrast, the waste clearance system in the rest of the body – the lymphatic system – is always active.)
Evolutionarily, we didn’t we just evolve bigger brains that allowed for CSF diffusion all the time?
Nobody knows
• However, almost all signaling molecules in the brain act via diffusion. And, putting constraints on diffusion is a prominent aspect of regulatory control.
• Promoting or constraining diffusion may be one of the principal ways brain function (cellular function) is regulated.
• So, there may be evolutionary pressure to control and contain diffusion within the brain to such an extent, that waste products cannot be effectively cleared while the brain is functioning.
• Thus, sleep evolved as a way to let the brain perform optimally for most of the day
what is circadian rhythm
The daily change in behaviour and physiological processes that follows a cycle of approximately 24 hours is known as a circadian rhythm
Circadian rhythms are controlled by what
internal biological clocks. Regular daily variation in light levels keeps the clock adjusted to 24 hours.
Circadian rhythms are controlled by internal biological clocks. Regular daily variation in light levels keeps the clock adjusted to 24 hours.
Rats are normally active at night. If we shift the cycle by a couple hours what happens
the rat’s activity cycle changes as well - the body adapts to this change
Rats are normally active at night. If we shift the cycle by a couple hours, the rat’s activity cycle changes as well - the body adapts to this change.
If the light is constantly dim, the rat does what
finds it own source of rhythmicity (due to an internal biological clock). They will maintain their circadian rhythms to a large extent, but these rhythms will drift over time (23 or 25 hour cycles). A brief period of bright light will reset their internal clock.
where is the suprachiasmatic nucleus (SCN)
hypothalamus
The suprachiasmatic nucleus (SCN) of the hypothalamus regulates what
sleep-cycles cycles. It receives a direct input from the retina
Lesioning the SCN does what
dramatically alters circadian rhythms (such as sleep-wake cycles and hormone secretions).
SCN lesions alter what
the length and timing of sleep-wake cycles, but they do not change the total amount of time that animals spend asleep
What makes SCN neurons tick?
Circadian rhythms are maintained by the production of several genes and two interlocking feedback loops. Basically, when expression of one of the proteins reaches a certain level in the cell, it inhibits its own production and promotes the expression of a different protein.
what is Advanced sleep phase syndrome
mutation of a gene called per2 (period 2) causes a 4-hour advance in the biological clock (rhythms of sleep and temperature cycles) – a strong desire to fall asleep at 7pm and wake up at 4am.
(in relation to SCN neurons)
what is Delayed sleep phase syndrome
a mutation of a gene called per3 causes a 4-hour delay in rhythms of sleep and temperature cycles – a strong desire to fall asleep at 2am and wake up at 11am
(In relation to SCN neurons)
SCN neurons keep time, but many neural circuits regulate what
arousal
what signaling molecules below are found in neurons that show increased activity during periods of arousal, alertness, and wakefulness and decreased activity during slow-wave sleep
Acetylcholine (throughout the brain)
– Norepinephrine (locus coeruleus in the hindbrain) – Serotonin (raphe nuclei in the hindbrain)
– Histamine (hypothalamus)
– Orexin (hypothalamus)
Norepinephrine neuron activity tends to do what
to positively correlate with focus and attention
Serotonin (5-HT) neuron activity positively correlates with what
positively correlates with cortical arousal (as measured by EEG), and drugs that increase serotonin signaling tend to suppress aspects of REM sleep (without affecting memory).
where are Histamine neurons located
in the hypothalamus
Histamine neurons located in the hypothalamus exhibit activity when
high activity during waking and low activity during sleep
Histamine receptor blockers (antihistamines) do what to sleep
increase sleep
Orexin neurons (hypocretin neurons) located where
in the hypothalamus
Orexin neurons (hypocretin neurons) located in the hypothalamus are active when
Orexin neurons (hypocretin neurons) located in the hypothalamus fire at a high rate during awake and alert states, but fire at a low rate during sleep
The most common form of narcolepsy is caused by what
a lack of orexin signaling in the brain.
Neurons in the ventral lateral preoptic area (vlPOA) of the hypothalamus promote what
sleep
Neurons in the ventral lateral preoptic area (vlPOA) of the hypothalamus promote sleep. Electrical stimulation does what
causes drowsiness and sometimes immediate sleep.
Lesions of the preoptic area do what
suppress sleep and cause insomnia.
Neurons in the ventral lateral preoptic area (vlPOA) of the hypothalamus promote sleep. Electrical stimulation causes drowsiness and sometimes immediate sleep.
▪ Lesions of the preoptic area suppress sleep and cause insomnia.
▪ These neurons inhibit wake-promoting neurons, such as what
histamine, serotonin, and norepinephrine neurons.
explain The Sleep/Wake Flip-Flop Circuit
The vlPOA receives inhibitory inputs from the same regions it inhibits.
Reciprocal inhibition characterises a flip-flop circuit which assumes an ON or OFF state.
▪ In the ON state, the arousal system (wake-promoting region) is active and the sleep-promoting region in the vlPOA is inhibited (animal is awake).
▪ In the OFF state, the sleep-promoting
region in the vlPOA is active and wake- promoting regions of the arousal system is inhibited (animal is asleep).
▪ Neurons in both regions cannot be active at the same time and the switch from one state to another is fast; either asleep or awake.
what is The Sleep Molecule Hypothesis
Adenosine Version
A prominent hypothesis is that, in addition to SCN timekeeping, there is a build of certain molecules in the brain during waking hours that promote tiredness and sleep. These molecules would be cleared from the brain during sleep
A prominent hypothesis is that, in addition to SCN timekeeping, there is a build of certain molecules in the brain during waking hours that promote tiredness and sleep. These molecules would be cleared from the brain during sleep.
• A specific molecule that has received lots of attention is adenosine, what is this
a metabolite of brain activity (ATP).
The concentration of adenosine in the brain is active when
The concentration of adenosine in the brain increases during waking, accumulates even more with sleep deprivation, and decreases rapidly during sleep, even during only brief intrusions of sleep.
the duration and depth of sleep appear to be profoundly modulated by what (in the sleep molecule hypotheses)
concentrations of adenosine
give a summary of The Sleep Molecule Hypothesis
Adenosine Version
A prominent hypothesis is that, in addition to SCN timekeeping, there is a build of certain molecules in the brain during waking hours that promote tiredness and sleep. These molecules would be cleared from the brain during sleep.
• A specific molecule that has received lots of attention is adenosine, a metabolite of brain activity (ATP).
• The concentration of adenosine in the brain increases during waking, accumulates even more with sleep deprivation, and decreases rapidly during sleep, even during only brief intrusions of sleep.
• Moreover, the duration and depth of sleep appear to be profoundly modulated by concentrations of adenosine.
• Maybe adenosine serves as a sleep-inducing molecule that underlies the homeostatic drive for sleep.
Adenosine receptor are expressed by many different types of neurons throughout the brain. Adenosine receptor activity has been found to excite neurons in the vlPOA and inhibit acetylcholine (ACh) neurons throughout different areas of the forebrain and hindbrain. (ACh neurons fire a lot during waking hours, but not much during deep sleep.)
• So the idea is that during waking hours adenosine levels rise extracellularly. High adenosine concentrations promote vlPOA neuron activity and inhibit ACh neuron activity. Through these mechanisms adenosine may reduce arousal and promote sleep.
• During sleep, extracellular adenosine is cleared away. As adenosine receptor activity falls, vlPOA neurons eventually stop firing and ACh neurons start firing.
Caffeine, which promotes arousal, is what
an adenosine receptor antagonist
Adenosine receptor are expressed by many different types of neurons throughout the brain. Adenosine receptor activity has been found to excite neurons in the vlPOA and inhibit acetylcholine (ACh) neurons throughout different areas of the forebrain and hindbrain… what does this mean
(The Sleep Molecule Hypothesis (Adenosine Version))
ACh neurons fire a lot during waking hours, but not much during deep sleep
So the idea is that during waking hours adenosine levels rise extracellularly. High adenosine concentrations promote vlPOA neuron activity and inhibit ACh neuron activity. Through these mechanisms adenosine may do what
reduce arousal and promote sleep.
During sleep, what happens to extracellular adenosine
The Sleep Molecule Hypothesis (Adenosine Version)
cleared away. As adenosine receptor activity falls, vlPOA neurons eventually stop firing and ACh neurons start firing.
what is Orexin
(also known as hypocretin) is a peptide produced by neurons in the hypothalamus
Orexin neuron activity does what
promotes wakefulness. Motivation to remain awake activates orexin neurons.
basically, when sitting and doing nothing/very bored, the body may want to sleep but this peptide sends sig all such as hunger to remind the body to stay awake because it is not time to sleep
what is Narcolepsy
Sleep disorder characterized by periods of excessive daytime sleepiness and irresistible urges to sleep as well as other symptoms described below. It is a hereditary autoimmune disorder.
For most with narcoleptics, the disease is caused by what
the death (degeneration) of orexin neurons in the hypothalamus. During adolescence the immune system attacks these neurons and symptoms of narcolepsy begin.
what is Cataplexy
complete paralysis that occurs during waking, typically precipitated by strong emotional reactions or sudden physical effort (e.g. laughter, anger, excitability).
what is Sleep paralysis
REM-associated paralysis occurring just before person falls asleep
Sleep paralysis – REM-associated paralysis occurring just before person falls asleep. Often accompanied with what symptom
Hypnagogic hallucination
what is Hypnagogic hallucination
vivid dreams that occur just before a person falls asleep; accompanied by sleep paralysis
