Wakefulness & Sleep Flashcards
what is an endogenous rhythm?
internal mechanisms that operate on an approximately 24 hour cycle
What two measures are circadian rhythms assessed by?
Physiological and Behavioural
What is the infradian rhythm? name an example
Biological rhythm lasting over 24 hours e.g a menstrual cycle (approx. 28 days)
What is a circannual rhythm?- give example
Biological rhythm that lasts over a year- e.g. hibernation or SAD
What is ultradian rhythm? give example
A rhythm that lasts shorter than a cicardian rhythm- e.g. hunger fluctuations
3 types of endogenous biological rhythms discussed in chapter
circannual
ultradian
infradian
what evidence indicates that humans have an internal biological clock?
people who have lived in an environment without light-dark scedhule much different from 24 hours fail to follow that schedule and instead become wakeful and sleepy on an approx. 24 hour basis
What is stimulus Zeitgeber?
a stimulus that rests the circadian rhythm
What is the primary Zeitberger for humans? Name some secondary ones as well
Sunlight- primary
secondary- exercise and social interaction
Why does jet lag occur?
A mismatch between internal circadian clock and external time
What is it to phase-delay sleep?
To delay sleep- go to sleep a little later than what we are used to
What is it called when we sleep earlier and awaken earlier? Opposite of phase-delay
Phase-advance
People in big cities surrounded by bright lights are more likely to stay up late than people in rural areas. T/F?
T
What is the concept developed by Richer that says the brain generates its own rhythms?
Biological clock
How to blind people maintain a circadian rhythm?
Meal times, noise, temperature, activity, etc.
What is the main driver of rhythms for sleep and body temperature?
suprachiasmatic nucleus (scn)
where can you find the scn?
it is a part of the hypothalamus- above the optic chiasm
What happens if you damage the SCN?
the body’s rhythm becomes erratic
an isolated SCN cell can maintain a circadian rhythm although _______.
interactions among cells sharpen the accuracy of the rhythm
Which gland does the SCN influence?
the pineal gland, which then produces melatonin
What evidence strongly indicates that the SCN produces the circadian rhythm itself?
SCN cells produce a circadian rhythm of activity even if they are kept in a cell culture isolates from the rest of the body.
What is the retinohypothalamic path?
A small branch of the optic nerve
consisting of a special path of ganglion cells that extend from the retina to the SCN.
What is special about the retinohypothalamic ganglion cells?
They have their own photopigment- melanopsin that don’t require input from rods & cones
People who are blind because of cortical damage can still synchronise their circadian rhythm, why?
if the retina is intact, melanopsin-containing ganglion cells can still send messaged to the SCN, resetting its rhythm.
Proteins & the SCN- explain the mechanism (4 steps)
- SCN makes two proteins called CLOCK & CYCLE from DNA, RNA with help from ribosomes
- CLOCK & CYCLE bind to DNA in the nucleus of SCN cells to transcribe the proteins: PER & TIM.
- PER & TIM proteins inhibit the expression of CLOCK & CYCLE genes (stop from making more PER & TIM)
- PER & TIM proteins are slowly broken down by an enzyme to ensure that the loop can begin again & we can synthesise CLOCK & CYCLE.
at night PER & TIM concentrations are at their ______.
highest
How do the SCN & pineal gland work together?
The SCN controls the pineal gland to release melatonin
Where can I find the pineal gland?
posterior to the thalamus
What does melatonin do?
increase sleepiness & drowsiness in diurnal (humans)
nocturanal- opposite
What is a circadian rhythm?
internally generated rhythms of activity and sleep lasting approx 24 hrs
Workers on submarines work 6 hours, relax 6 hours and sleep 6 hours. After weeks on this schedule what happens to circadian rhythm?
it produces a rhythm intermediate between 18-24 hrs
why do people in Antarctica during the winter find it difficult to work together?
their circadian rhythms drift out of phase with one another
If you want to get sleep on time, what should you avoid?
Short-wavelength light late in the evening
What are the four stages of sleep?
stage 1, stage 2, slow wave & REM/ paradoxical
what is characteristic of stage 1 sleep?
irregular, jagged, low voltage waves
what is characteristic of stage 2 sleep?
K-complexes & sleep spindles
What are k-complexes?
a sharp wave associated with a temporary inhibition of neuronal firing
What is a sleep spindle?
a burst of 12-14 Hz waves for at least half a second resulting from oscillating reactions between cells in the thalamus & cortex
Sleep spindles (increase/ decrease) ______ in number after new learning.
increase
Sleep spindles represent activity related to the ______ of memory.
consolidation
what is characteristic of slow wave sleep?
heart-rate, breathing rate & brain activity decrease. Slow, large amplitude waves become more common.
Within slow wave sleep- what are the differences between stage 3 & 4
stg 3- fewer slow waves
stg 4- more slow waves
What do slow waves indicate about neuronal activity?
That it is highly synchronised
Why is REM sleep known as paradoxical sleep?
both deep sleep and light sleep.
Deep sleep: postural muscles of the body are more relaxed than any other stage.
light sleep: EEG waves are irregular, low-voltage & fast
How long does a sleep cycle usually last?
90 minutes
During which part of a night’s sleep is REM most common?
Towards the end
How does a cut through the midbrain decrease arousal?
by damaging the reticular formation
what is the pontomesebcephalon?
a part of the reticular formation that contributes to cortical arousal.
How do the reticular formation & pntomesencephalon determine arousal?
regulate potassium and other ions that support arousal.
what is the locus coeruleus?
dark blue place
small structure in the pons, emits bursts of impulses in response to meaningful events
release norepinephrine throughout the cortex
increases activity of most active neurons and decreases activity of less active ones
Where is histamine released?
hypothalamus
What is orexin
peptide neurotransmitter
in lateral and posterior hypothalamus
promote wakefulness and activity
necessary for staying awake
What does acetylcholine do?
Stimulates basal forebrain cells to promote wakefulness
During sleep, neurons in the thalamus become (hyper/hypo) polarised
hyperpolarised, decreases their readiness to respond to stimuli
Which inhibitory neurotransmitter is important for sleep?
GABA
What happens when GABA inhibits information?
interferes with the spread of information from one neuron to the other and therefore one part of the brain to the other.
when stimulation doesnt spread through the brain you dont become conscious of it
What would happen to sleeping and waking if you took a drug that blocked GABA?
You would remain awake or at least somewhat conscious
Activity _____ (increases/ decreases) in pons during REM sleep?
increases
Activity _____ (increases/ decreases) in the limbic system during REM sleep
increases
Activity _____ (increases/ decreases) in the primary visual cortex, dorsolateral prefrontal cortex during REM sleep
decreases
REM sleep is associated with distinctive patterns of high-amplitude electrical potentials known as ______
PGO waves
Types of sleep apnea:
obstructive- relaxation of the chest, diaphragm and throat
central- malfunctioning of breathing reflex response mediated by brain stem structures
Symptoms of nacrolepsy (4)
- attacks of sleepiness
- cataplexy
- sleep paralysis
- hynagogic halluncinations
How do nacrolepsy & orexin connect?
people with nacrolepsy lack the hypothalamic cells that produce and release orexin.
Periodic Limb movement disorder
Repeated involuntary movements of the legs & sometimes arms during sleep.
REM behaviour disorder
act out their dreams
Functions of sleep
- energy conservation
- body restoration
- memory consolidation
What are the two biological theories on dreaming?
- activation-synthesis
- clinico-anatomical hypothesis
What does the activation synthesis hypothesis state?
dreams begin with spontaneous activity in the pons which activates many parts of the cortex
the cortex synthesises a story from the pattern if activation
What is the reticular formation?
A structure that extends from the medulla to the forebrain. Some axons go towards the brain and others toward the spinal cord- regulates arousal
