Ch. 8- Wakefulness and Sleep Flashcards
endogenous circannual rhythm and
endogenous circadian rhythm
endogenous: coming from inside the animal/ not necessarily triggered by outside stimuli
circannual: yearly (birds flying north)
circadian: daily
processes that follow the circadian rhythm in humans
sleep, body temperature, mood, hormones, and much more
zeitgeber
stimuli that help setting and resetting the biological clock. Light is the important one for humans, other factors like activity, or food intake play a minor role. Lack of or problematic zeitgeber (e.g. in Antarctica) can lead to bad sleep and feeling unrested
jet lag
disruption of circadian rhythms due to crossing time zones. Jet lag is stressful –> more cortisol –> long term repeated jet lag damages the hippocampus
shift work
people often cannot adjust to working in the night
To improve adjustment the sleeping room must be very dark and the work place must have bright blueish light
morning and evening types
the body temperature rhythm differs for people, some have their peek of activity in the midday, some have it later in the afternoon
middle of sleep at different ages
the middle of sleep gets later and later until age 20, from which it starts to get earlier and earlier again
social jet lag
teenagers that are evening types suffer under the early times school starts and get worse grades than pupils with comparable IQ
the biological clock
the biological clock is endogene and works even when a person is deprived of light, food, has brain damages, takes drugs etc. It is quite robust. It slowly gets out of phase though when people do not get any indication of the day time
main brain structure for rhythms of sleep and body temperature
Add to dictionary nucleus (SCN)
properties of suprachiasmatic nucleus
lies just above the optic chiasm, works independent of the rest of the body,
how does light influence the SCN
there are special ganglion cell at the eye, which slowly respond to light, and transmit the average light intensity right into the SCN. These ganglion cells even work with little information, for example for nearly blind people
what are PER and TIM, and how do they work
They are proteins which promote sleep. Their production follows a negative feedback loop. Concentration is low in the morning, so they get produced. We (or flies actually) have the most of them in the night. A lot of PER and TIM sends messages to stop producing them. Therefore, the PER and TIM levels lower towards the morning. Light activates chemical to destroy these proteins
melatonin
is a hormone that promotes sleep and thereby also influence circadian rhythms. It get released by the pineal gland, which in turn is controlled by the SCN
distinction sleep and coma
sleep: actively produced by the brain, characterized by decreased responsibility to stimuli, but a loud noise still can wake people up
coma: extended period of unconsciousness caused by head trauma or the like. People cannot be woken up with a loud noise. Usually leads to death or recovery within
vegetative state
alternate between sleep and moderate arousal, but never with awareness of surroundings or purposeful behavior. Can last a long time
minimally conscious state
occasional brief periods of purposeful actions and limited amounts of speech and comprehension. Can last a long time
brain death
no sign of brain activity or response to stimuli, for 24 hours
EEG measurements
the eeg measures activity when most cells do the same thing, so no slight or small regional variations
polysomnography
a combination of eeg and eye movements
alpha waves
characteristic of relaxation, not of full wakefulness, frequency of 8 to 12 per second
sleep spindle
12 to 14 hz waves during a birst that lasts at least half a second, results out of interactions between thalamus and cortex
k-complex
a sharp wave associated with temporary inhibition of neuronal firing
stage 1 sleep
irregular, jagged low voltage waves
stage 2 sleep
characterized by sleep spindles and k-complexes
sleep stage 3 and 4, aka slow-wave sleep
activity decreases, slow high voltage (amplitude) waves become more common. highly synchronized neuronal activity
paradoxical sleep
the same as rem sleep. was called this way because animals seemed highly relaxed (muscles) but active (brain) at the same time. We do not call rem sleep “deep” or “light” because of this, because this categorization would be misleading
non-rem sleep (NREM)
exactly that, just wanted to mention it
sleep cycle
stage 2 –> 3 –> 4 –> 3 –> 2 –> rem repeat
early in the night longer 4 and 3, later longer rem
rem and dreams
rem seems to have more visual and intense dreams, but dreams can occur outside rem too
–> they are not the same
reticular formation
damaging this formation decreases brain arousal
it is located in the midbrain, and has axons down the spinal cord and up to the brain
a cut through this structure puts animals into days of sleep with only short periods awake
pontomesencephalon
part of the reticular formation
input: sensory information + spontaneous activity on its own
output: hypothalamus, thalamus, basal forebrain
maintains arousal during wakefulness
stimulation wakes sleeping animals up
locus coeruleus
small structure in the pons that increases attention
inactive during sleep
sends bursts of norepinephrine to emotional meaningful events
it increases activity of most active neurons and decreases activity of least active ones
enhanced attention to important information and enhanced memory
histamine
neurotransmitter, has an excitatory effect that increases arousal
released by the hypothalamus
orexin or hypocretin (same thing)
peptide neurotransmitter, necessary for staying awake
not necessary for waking up
released by the hypothalamus
basal forebrain
anterior dorsal to the hypothalamus
has axons that provide acetylcholine through the cerebral cortex and thalamus exiting it, but can also release gaba, inhibiting them
acetylcholine
tends to be excitatory, not released during slow-wave sleep, sharpens attention during wakefulness
how do we stay unconscious during sleep?
thalamus becomes hyperpolarized, decreasing its “information relay” function
GABA is released throughout the brain, which interferes with the spread of information from one neuron to the other
connections between brain areas become weaker
when stimulation does not spread, you don’t become conscious of it
explain sleep walking and lucid dreams
sleep can occur in parts of the brain but not in others.
sleep walkers for example are awake in the motor cortex and some other areas, lucid dreaming works similarly
the pons in rem
the pons makes sure that you do not move during rem sleep (except for eye and facial muscles). If you awake while the pons is still in rem, it is a very unpleasant experience
PGO-waves
Pons-geniculate-occipital. The geniculate is a nucleus in the thalamus. This wave occurs during REM and moves from P to G to O.
important neurotransmitters for rem sleep
it depends on the relationship between serotonin and acetylcholine. stimulating acetylcholine synapses moves people into rem quicker. Note: acetylcholine is important for both wakefulness and rem. Serotonin and norepinephrine interrupt rem sleep
insomnia
inadequate sleep. most adults need 7 1/2 to 8 hours. Reasons can be nearly anything. Most interesting one: circadian body temperature rhythm can be phase delayed (to actual sleeping times) –> problems falling asleep; or it can be phase advanced –> problems staying asleep
sleep apnea
impaired ability to breathe while sleeping. Causes them to awake in the nights, which leads to impaired attention, depression (a common symptom of sleep problems in general), even loss of neurons. Comes from genetics, hormones, obesity, old-age. Is treated through diet, no alc, surgery, or a breathing mask
symptoms narcolepsy
1 in a 1000 people, has a genetic component.
- attacks of sleepiness during the day
- occasional cataplexy, an attack of muscle weakness triggered by strong emotions
- frequent sleep paralysis
- Hypnagogic hallucinations, dreams that cannot be distinguished from reality, at the onset of sleep
causes narcolepsy
lack of hypothalamic cells that produce and release orexin –> less orexin (which is important for maintaining wakefulness) –> frequent alternations between wakefulness and sleep
-the lack of hypothalamic cells might be due to an autoimmune reaction, where the immune system destroys theses cells
periodic limb movement disorder
involuntary movement of the limbs during sleep. Middle aged people mostly, kick once every 20-30 seconds during nrem
rem behavior disorders
moving vigorously during rem, acting out the dream. Often injure themselves or others. GABA not working properly might be the explanation
night terrors
intense anxiety from which a person awakens screaming in terror. A night terror is more severe than a nightmare, which is simply an unpleasant dream. Night terrors occur during NREM sleep and are more common in children than adults. Dream content, if any, is usually simple, such as a single image
sleep walking
Sleepwalking runs in families and occurs mostly in children. Most people who sleepwalk, and many of their relatives, have one or more additional sleep difficulties such as chronic snoring, disordered sleep breathing, bed-wetting, and night terrors. The causes of sleepwalking are not well understood, but it is more common when people are sleep deprived or under unusual stress. It is most common during slow-wave sleep early in the night and usually not accompanied by dreaming. usually harmless, but not always. Parts of the brain are asleep while others are awake. not dangerous to wake them up
sexsomnia
An analogous condition is sleep sex or “sexsomnia,” in
which sleeping people engage in sexual behavior, either with a partner or by masturbation, and do not remember it afterward. Sexsomnia poses a threat to romances and marriages
sleeps original function
to save energy. There are times where we can work efficiently and times where we cant, and when we cant we should conserver our energy (night for example). The decrease in body temperature saves energy. In that sense, sleep can be compared to hibernation
hibernation
body functions get shut down as much as possible. it retards the aging process
species differences in sleep
deep sea fish appear to never sleep. Other animals might have special times in their lives, migrating birds or dolphins after giving birth, where their need for sleep greatly decreases or vanishes completely. Overall we can say that the amount of sleep an animals gets seems to fit in well with the animals need to conserve energy. animals that must spend their whole day grazing sleep less than animals that can fill their nutritional needs in a short hunt.
sleeps influence on memory
sleep helps retrieve memories, it helps consolidating new memories, it helps reanalyzing memories
how does sleep improve memory
in sleep, fast activity in the hippocampus that resembles the activity during learning. The brain replays its daily experiences but with no clear pattern, so the role of hippocampal activity is not really clear. The brain also weakens less appropriate (less used synapses) during sleep, thereby emphasizing the synapses that do get used during wakefulness. Sleep spindles seem to contribute too. They also correlate highly (0.7) with IQ
