Lecture 12: Sleep & Pheromones Flashcards
Pheromones
molecules released by one animal to signal something to another member of the same species
how are behavioural responses to pheromones developed?
Behavioural responses to pheromones are largely innate
what are pheromones used for?
- attract or repel other members of the same species
- signal attractiveness and sexual receptivity
- mark a path to follow (as seen in ants)
- signal danger
do pheromones exist in humans?
no
Vomeronasal organ
Processes pheromones. Activated by sniffing of the mouth/actogenital region
main olfactory bulb and the olfactory epithelium
process regular odours
how are pheromones detected?
metabotropic vomeronasal receptors
what animals don’t have functional vomeronasal organs?
birds, apes, humans
how are pheromones usually released?
in urine
Female-to-male pheromone signalling
Male mice with functional vomeronasal systems will only attempt to mate with female mice that are in heat.
what type of pheromone signalling is most powerful?
female-to-male
Male-to-female pheromone effects
Females prefer males that have healthy testosterone levels because of testosterone-induced male sex pheromone signalling
Lee-boot effect
When female mice are housed together (without any male urine present), their estrous cycles slow down and eventually stop
whitten effect
Pheromones in the urine of male mice can trigger synchronous estrus cycles in groups of female mice
estrus cycle
not characterized by bleeding, is signalling broadly to other members of the species. Occurs every 4-5 days in mice
Vandenbergh Effect
Earlier onset of puberty seen in female animals that are housed with males
bruce effect
The tendency for female rodents to terminate their pregnancies following exposure to the scent of an unfamiliar male
Electroencephalogram (EEG)
Measures brain activity by attaching electrodes to the scalp
Electromyogram (EMG)
Measures muscle activity by attaching electrodes to the chin
Electrooculogram (EOG)
Measures eye movement by placing electrodes near the eyes
beta activity
Typical of an aroused state. It reflects asynchronous neural activity. High frequency, low amplitude oscillations.
frequency of beta activity
12-30 Hz
alpha activity
Typical of an awake person in a state of relaxation.
frequency of alpha activity
8-12 Hz
theta activity
Appears intermittently when people are drowsy and is prominent during early stages of sleep (stages 1-2)
theta activity frequency
4-8 Hz
Delta activity
Occurs during deepest stages of slow-wave sleep; reflects synchronized low frequency, large amplitude brain activity (stage 3-4)
delta activity frequency
< 4Hz
REM sleep
associated with desynchronized EEG activity (theta and beta activity), rapid eye movements, dreaming, and muscle paralysis; muscles are inactive apart from occasional twitches.
what happens to blood flow and oxygen consumption during rem sleep?
Central blood flow and oxygen consumption increase
what happens after rem sleep
Partial awakening with body movements after REM sleep
slow-wave sleep
stage 3/4 non-REM sleep (also known as deep sleep) corresponds to large amplitude, low-frequency oscillations of brain activity as measured with EEG. This pattern of neural activity reflects synchronized bursts of action potentials in large collections of neurons.
what happens to muscles during rem sleep?
they go limp
what happens to an experimental rat after 2-3 weeks of sleep deprivation?
loses control of temperature regulation (starts running hot), and metabolic processes and body weight plummets
what happens to an experimental rat after 3-4 weeks of sleep deprivation?
it dies
what happens when people don’t sleep
- delayed reaction times and poor judgements
- increases in stress hormones, mood swings, and impulsive behaviour
- worse learning and memory
- hungrier
- increase your propensity for weight gain, migraines, hallucinations, dementia, seizures, and death
- Sleep debt is created
- microsleep
- lack of sleep often precedes mental illnesses
microsleep
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 cycles of dolphins
Dolphins’ sleep alternates between the two cerebral hemispheres so that they can maintain vigilance during sleep
sleep debt in dolphins
created in one hemisphere
rem sleep in adults vs infants
50% of human infant sleep is REM sleep
35% of human adult sleep is REM sleep
differences in rem sleep between species
Amount of sleep
Ratio of REM to non-REM sleep
Length of sleep cycles (average time between two REM events)
rem sleep in predators and prey
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
weight and sleep
The amount of time a species sleeps each day is inversely correlated with weight
metabolic rate and sleep
While overall metabolic rate increases as mass increases, metabolic rate per pound decreases as mass increases
↑ body mass, ↑ brain mass, ↑ overall metabolic rate
↓ metabolic rate per kg (or per cell), ↓ heart rate, ↑ life span, ↓ total sleep time, ↑ length of sleep cycles
economies of scale hypothesis
when things get bigger, their costs per output get cheaper. Large animals benefit from this, so each cell doesn’t have to work as hard to maintain its temperature
why do animals sleep (theories)
- to recover from exertion
- brain processing
- waste removal
- optimizing brain function
blood pressure and heart rate during sleep
There is a reduction in blood pressure and heart rate when people sleep
when do synaptic modifications occur?
occur during sleep
slow wave sleep and memory
The amount of slow-wave sleep people get is correlated with improvements in declarative memory
rem sleep and memory
The amount of REM sleep people get is correlated with improvements in procedural memory
information processing and sleep
During sleep, the brain appears to be actively processing information and transferring it between different areas both within cells (through gene transcription) and between cells (through network oscillations)
how does information processing occur between different areas of cells?
gene transcription
how does information processing occur between different cells?
network oscillations
protein concentration in the brain
The concentration of many proteins in the brain increases across periods of wakefulness and decreases across periods of sleep
when does protein clearance occur?
The clearance of proteins and waste products from the brain is almost nonexistent during wakefulness but is high during sleep.
glial cells and sleep
Glial cells (astrocytes) shrink in size when people sleep, increasing the volume of extracellular fluid and promoting the diffusion of CSF
why do scientists think big animals sleep less?
because waste clearance benefits from economies of scale
what causes signalling molecules in the brain to act
diffusion
what does regulatory control do
regulate diffusion
brain function hypothesis
Sleep may have evolved to ensure optimal brain function most of the day becausehere may have been evolutionary pressure to control and contain diffusion within the brain to such an extent that waste products can now not be effectively cleared while the brain is functioning
cerebrospinal fluid
a clear colourless fluid that is continually being made in brain ventricles
glympathic system
CSF circulates the brain and diffuses interstitial space, thus becoming the extracellular solution that surrounds neurons
As CSF moves through the interstitial space, it clears waste products away before exiting into blood vessels
when does waste clearance occur?
The clearance of waste from the brain may be minimal during waking hours but high during sleep
lymphatic system
clears away cellular waste in the PNS
what types of animals are better at clearing away waste?
Bigger animals
circaidan rhythms
The daily change of behaviour and physiological processes that follow a cycle of approximately 24 hours
what controls circadian rhythms?
internal biological clocks
what happens if we shift the circadian rhythms of mice?
the rat’s activity cycle changes as well–the body adapts to this chan
the function of the Suprachiasmatic Nucleus (SCN)
Regulates sleep-wake cycles by receiving direct input from the retina
where is the suprachiasmatic nucleus located?
in the hypothalamus
SCN lesions
dramatically alters circadian rhythms such as sleep-wake cycles and hormone secretions
t or f: SCN lesions change the total amount of time that animals spend asleep
false
maintenance of circadian rhythms
maintained via the production of several genes and two interlocking feedback loops. When the expression of one protein gets high enough, it inhibits its own production and promotes the expression of a different protein
Advanced sleep phase syndrome
a mutation of the per2 gene that causes a 4-hour advance in the biological clock and results in a strong desire to go to sleep at 7 pm and wake up at 4 am
Delayed sleep phase syndrome
a mutation of the per3 gene that causes a 4-hour delay in the biological clock and results in a strong desire to go to sleep at 2 am and wake up at 11 am
adenosine levels
rise in the brain during waking hours and accumulate with sleep deprivation. Levels fall rapidly in the brain during sleep, even during brief periods of sleep
how are drowsiness and the duration and depth of sleep modulated?
adenosine receptor signalling
caffeine is a
adenosine receptor antagonist
Signalling molecules released by neurons that show increased activity during periods of arousal and decreased activity during slow-wave sleep
serotonin, Norepinephrine, Acetylcholine, Orexin, Histamine
where are serotonin signalling molecules released?
raphe nuclei in the hindbrain
where are norepinephrine signalling molecules released?
locus coeruleus in the hindbrain
where are acetylcholine signalling molecules released?
throughout the brain
where are orexin signalling molecules released?
hypothalamus
where are histamine signalling molecules released
hypothalamus
serotonin and arousal
Positively correlates with cortical arousal
serotonin signalling and rem sleep
Drugs that increase serotonin signalling tend to suppress aspects of REM sleep without affecting memory
norepinephrine and attention
Positively correlates with focus and attention
what is orexin
Neuropeptide released by neurons in the hypothalamus
what is histamine
Neuropeptide released by neurons in the hypothalamus
histamine signalling and arousal
Histamine receptor blockers (antihistamines) often cause drowsiness
ventral lateral preoptic area (vlPOA)
area of the hypothalamus
vIPOA neuron
promote sleep by inhibiting wake-promoting neurons
electrical stimulation of vIPOA neurons
causes drowsiness and sometimes immediate sleep
lesions of vIPOA
suppress sleep and cause insomnia
sleep-wake flip-flop circuit
both regions cannot be active at the same time and the switch from one state to another is fast
The animal is awake when the arousal, wake-promoting system is more active than the vlPOA neurons
The animal is asleep when vlPOA neurons are more active than the wake-promoting arousal system
where are adenosine receptors located
on many neurons throughout the brain
when is extracellular adenosine most concentrated?
Extracellular adenosine builds up during the day
how are vIPOA neurons activated
by adenosine signalling
effect of adenosine on acetylcholine
inhibited by adenosine signalling
orexin
a peptide produced by neurons in the lateral hypothalamus (LH). Promotes wakefulness
how are orexin neurons activated?
Motivation to remain awake
narcolepsy and orexin
Most forms of narcolepsy are associated with the absence of orexin neurons
t or f: SCN neuron activity can mask the influence of adenosine signalling during the day
t
narcolepsy
A rare autoimmune sleep disorder characterized by periods of excessive daytime sleepiness and irresistible urges to sleep
what causes narcolepsy
Related to the death of orexin neurons in the hypothalamus. They seem to be attacked by the person’s own immune system
when does narcolepsy begin
Usually begins during adolescence or young adulthood while the immune system is fighting the flu
two other symptoms of narcolepsy
sleep paralysis and cataplexy
sleep paralysis
when REM-associated paralysis occurs just before a person falls asleep or just after they wake up. It is often accompanied by vivid, dream-like hallucinations
cataplexy
when complete muscle paralysis suddenly occurs when someone is awake. It is typically precipitated by strong emotional reactions or sudden physical effort (e.g., laughter, anger, excitability)
insomnia
Characterized as difficulty falling asleep after going to bed or after awakening during the night
what % of people are affected by insomnia
approximately 25% of the population occasionally and 9% regularly
Fatal Familial Insomnia & Sporadic Fatal Insomnia
involves progressively worsening insomnia, which leads to hallucinations, delirium, and confusional states
how does fatal familial insomnia develop
Typically inherited but can also develop spontaneously
how is fatal familial insomnia cured
no known cure
survival span of someone with fatal familial insomnia
18 months
what part of the night has more rem sleep`
2nd half`
non-rem parasomnias examples
sleepwalking, sleep-talking, sleep-groaning, sleep-crying, sleep-eating, sleep-masturbating, sleep-teeth grinding
when do non-rem parasomnias occur?
Can be caused by certain medications or medical conditions. Some of these conditions tend to be more prevalent in children
sleep terrors
overwhelming feelings of terror upon waking
May include panic and screaming and bodily harm caused by rash actions
who is most at risk for sleep terrors?
people with PTSD
children with sleep terrors
usually have no recollection of these events
rem sleep behaviour disorder
neurological disorder in which the person does not become paralyzed during REM sleep and thus act out dreams
who is most at risk for rem sleep behaviour disorder
people with more common neurodegenerative disorders such as Parkinson’s
paradoxical sleep
another word for rem sleep because its wavelengths are similar to when we’re awake
effect of light on circadian rhythms
light helps to keep the biological clock timed to 24 hours
flip flop OFF
vlPOA is active & it inhibits the arousal system. The animal is asleep
flip flop ON
Arousal system is active & it inhibits vlPOA. The animal is awake
what does acetylcholine do to the flip-flop?
inhibits adenosine signalling, turning the flip-flop OFF
rem flip flop OFF
VIPAG is active and it inhibits the SLF. The animal is not in REM
rem flip flop ON
SLD is active and it inhibits VIPAG. The animal is in REM.
what sleep stage is associated with narcolepsy?
rem sleep
what sleep stage is associated with sleepwalking, talking, eating, and night terrors
slow wave sleep
what happens to the VNO during fetal development
it shrivels up and is no longer functional
examples of pheromones in humans
Synchronization of menstrual cycles with females who spend time together
Females that spend time with males have shorter cycles
what is the problem with the exertion sleep hypothesis?
No clear correlation between exertion and sleep
what do neurons using orexin do to the flip-flop?
keep it on
SLD
sublateral dorsal nucleus of the thalamus
vlPAG
ventrolateral periaqueductal grey
Accessory olfactory bulbs
Necessary for the effects of pheromones
