Lecture 11

Question 1

Sleep research is conducted where

Answer 1

in a sleep laboratory.

Question 2

Electrodes placed around the eyes monitor eye movements recorded aswhat

Answer 2

an electro- oculogram (EOG).

Question 3

Electrodes are also attached to the subjects chin to record muscle activity recorded as what

Answer 3

an electromyogram (EMG).

Question 4

Electrodes are attached to the subjects scalp to record electrical activity of the brain. The amplifier records a what

Answer 4

electroencephalogram (EEG).

Question 5

what are the stages of sleep

Answer 5

awake
REM
non-rem stage 1
non-rem stage 2
non-rem stage 3 (formerly stage 3&4)

Question 6

what is the characteristics with regard to the wavelengths during stage 4 vs awake

Answer 6

stage 4– low frequency, high amplitudes

awake– low amplitudes, high frequency

Question 7

what is Slow-wave sleep

Answer 7

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.

Question 8

what is Rapid eye movement (REM) sleep

Answer 8

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.

Question 9

what are the EEG SIGNALS DURING SLEEP

Answer 9

beta activity
alpha activity
theta activity
delta activity

Question 10

what is Beta activity,

Answer 10

13–30 Hz; typical of an aroused state. It reflects desynchronous neural activity (high frequency, low amplitude oscillations)

Question 11

what is Alpha activity,

Answer 11

8–12 Hz; typical of awake person in a state of relaxation

Question 12

what is Theta activity,

Answer 12

3.5–7.5 Hz; appears intermittently when people are drowsy, and is prominent during early stages of slow-wave sleep

Question 13

what is Delta activity;

Answer 13

<4 Hz; occurs during deepest stages of slow-wave sleep; reflects synchronized low frequency, large amplitude brain activity

Question 14

Starting after about 10 minutes of sleep, EEG recordings of humans include a mixture of what

Answer 14

sleep spindles and K complexes.

Question 15

what are Sleep spindles

Answer 15

short bursts of desynchronized activity (12-14 Hz) which occur between 2-5 times a minute during sleep stages 1-4.

Question 16

what are K complexes

Answer 16

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.

Question 17

what happens to muscles in REM sleep

Answer 17

they go limp

Question 18

If you don’t sleep what happens

Answer 18

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

Question 19

can lack of sleep cause death

Answer 19

yes

Question 20

how do Dolphin sleep

Answer 20

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

Question 21

do all animals sleep

Answer 21

it appears so

Question 22

give an example of large developmental differences within species

Answer 22

50% of human infant sleep is REM sleep

• 25% of human adult sleep is REM sleep

Question 23

There are even larger differences between species in what sense

Answer 23

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.

Question 24

what is the correlations between sleep and body weight

Answer 24

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

Question 25

what is the correlation between metabolic rate and body weight

Answer 25

While overall metabolic rate increases as mass increases, metabolic rate per pound (or per cell) decreases as mass increases.

Question 26

what is the correlation between metabolic rate and sleep

Answer 26

↑ 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.

Question 27

• Why do all these correlations exist?

Answer 27

* 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

Question 28

what are the main theories of why animals sleep

Answer 28

energy conservation brain processing restoration of some kind

Question 29

explain the energy conservation theory

Answer 29

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).

Question 30

what is the problems with the energy conservation theory

Answer 30

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).

Question 31

explain the Brain Processing theory

Answer 31

(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)

Question 32

explain the theory about Restoration of some kind

Answer 32

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

Question 33

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

Answer 33

the diffusion of cerebrospinal fluid into the brain, which results in increased clearance of waste products.

Question 34

It seems that sleep-wake cycles regulate the volume of interstitial space. Why do big animals sleep less than small animals?

Answer 34

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.

Question 35

explain the The Glymphatic System

Answer 35

``` 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. ```

Question 36

The clearance of proteins and waste products from the brain occurs when

Answer 36

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.)

Question 37

Evolutionarily, we didn’t we just evolve bigger brains that allowed for CSF diffusion all the time?

Answer 37

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

Question 38

what is circadian rhythm

Answer 38

The daily change in behaviour and physiological processes that follows a cycle of approximately 24 hours is known as a circadian rhythm

Question 39

Circadian rhythms are controlled by what

Answer 39

internal biological clocks. Regular daily variation in light levels keeps the clock adjusted to 24 hours.

Question 40

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

Answer 40

the rat’s activity cycle changes as well - the body adapts to this change

Question 41

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

Answer 41

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.

Question 42

where is the suprachiasmatic nucleus (SCN)

Answer 42

hypothalamus

Question 43

The suprachiasmatic nucleus (SCN) of the hypothalamus regulates what

Answer 43

sleep-cycles cycles. It receives a direct input from the retina

Question 44

Lesioning the SCN does what

Answer 44

dramatically alters circadian rhythms (such as sleep-wake cycles and hormone secretions).

Question 45

SCN lesions alter what

Answer 45

the length and timing of sleep-wake cycles, but they do not change the total amount of time that animals spend asleep

Question 46

What makes SCN neurons 􏰀tick􏰁?

Answer 46

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.

Question 47

what is Advanced sleep phase syndrome

Answer 47

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)

Question 48

what is Delayed sleep phase syndrome

Answer 48

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)

Question 49

SCN neurons keep time, but many neural circuits regulate what

Answer 49

arousal

Question 50

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

Answer 50

Acetylcholine (throughout the brain) – Norepinephrine (locus coeruleus in the hindbrain) – Serotonin (raphe nuclei in the hindbrain) – Histamine (hypothalamus) – Orexin (hypothalamus)

Question 51

Norepinephrine neuron activity tends to do what

Answer 51

to positively correlate with focus and attention

Question 52

Serotonin (5-HT) neuron activity positively correlates with what

Answer 52

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).

Question 53

where are Histamine neurons located

Answer 53

in the hypothalamus

Question 54

Histamine neurons located in the hypothalamus exhibit activity when

Answer 54

high activity during waking and low activity during sleep

Question 55

Histamine receptor blockers (antihistamines) do what to sleep

Answer 55

increase sleep

Question 56

Orexin neurons (hypocretin neurons) located where

Answer 56

in the hypothalamus

Question 57

Orexin neurons (hypocretin neurons) located in the hypothalamus are active when

Answer 57

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

Question 58

The most common form of narcolepsy is caused by what

Answer 58

a lack of orexin signaling in the brain.

Question 59

Neurons in the ventral lateral preoptic area (vlPOA) of the hypothalamus promote what

Answer 59

sleep

Question 60

Neurons in the ventral lateral preoptic area (vlPOA) of the hypothalamus promote sleep. Electrical stimulation does what

Answer 60

causes drowsiness and sometimes immediate sleep.

Question 61

Lesions of the preoptic area do what

Answer 61

suppress sleep and cause insomnia.

Question 62

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

Answer 62

histamine, serotonin, and norepinephrine neurons.

Question 63

explain The Sleep/Wake Flip-Flop Circuit

Answer 63

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.

Question 64

what is The Sleep Molecule Hypothesis | Adenosine Version

Answer 64

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

Question 65

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

Answer 65

a metabolite of brain activity (ATP).

Question 66

The concentration of adenosine in the brain is active when

Answer 66

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.

Question 67

the duration and depth of sleep appear to be profoundly modulated by what (in the sleep molecule hypotheses)

Answer 67

concentrations of adenosine

Question 68

give a summary of The Sleep Molecule Hypothesis | Adenosine Version

Answer 68

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.

Question 69

Caffeine, which promotes arousal, is what

Answer 69

an adenosine receptor antagonist

Question 70

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))

Answer 70

ACh neurons fire a lot during waking hours, but not much during deep sleep

Question 71

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

Answer 71

reduce arousal and promote sleep.

Question 72

During sleep, what happens to extracellular adenosine | The Sleep Molecule Hypothesis (Adenosine Version)

Answer 72

cleared away. As adenosine receptor activity falls, vlPOA neurons eventually stop firing and ACh neurons start firing.

Question 73

what is Orexin

Answer 73

(also known as hypocretin) is a peptide produced by neurons in the hypothalamus

Question 74

Orexin neuron activity does what

Answer 74

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

Question 75

what is Narcolepsy

Answer 75

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.

Question 76

For most with narcoleptics, the disease is caused by what

Answer 76

the death (degeneration) of orexin neurons in the hypothalamus. During adolescence the immune system attacks these neurons and symptoms of narcolepsy begin.

Question 77

what is Cataplexy

Answer 77

complete paralysis that occurs during waking, typically precipitated by strong emotional reactions or sudden physical effort (e.g. laughter, anger, excitability).

Question 78

what is Sleep paralysis

Answer 78

REM-associated paralysis occurring just before person falls asleep

Question 79

Sleep paralysis – REM-associated paralysis occurring just before person falls asleep. Often accompanied with what symptom

Answer 79

Hypnagogic hallucination

Question 80

what is Hypnagogic hallucination

Answer 80

vivid dreams that occur just before a person falls asleep; accompanied by sleep paralysis