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Nervous System > EEG, Sleep and Circadian Rhythms > Flashcards

EEG, Sleep and Circadian Rhythms Flashcards

1
Q

where do the active inhibitory processes that causes the brain to sleep originate from?

A

in the pons

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2
Q

what area is closely associated with controlling the state of consciousness?

A

Reticular Formation of the brain stem

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3
Q

what type of drugs inhibit sleep?

A

drugs that block serotonin formation

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4
Q

where are suprachiasmatic nuclei (SCN) found?

A

in the hypothalmus

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5
Q

what is evidence show that SCN has a role in sleep?

A

Electrical stimulation of the SCN can promote sleep and damage to the SCN disrupts the sleep-wake cycle

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6
Q

what excitatory neurotransmitter does the hypothalamus release that is required for wakefulness?

A

orexin (aka hypocretin)

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7
Q

what does defective orexin signalling cause?

A

narcolepsy; individual will suddenly fall asleep, sometimes even when talking.

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8
Q

describe the positive feedback that allows sustained wakefulness?

A

Excitatory neurons are released from inhibition from Sleep Centres in Reticular Formation.
Stimulate excitatory pathways (both the CNS and PNS)
this loop carries on

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9
Q

what occurs when these active cell become fatigued and excitatory signals fade?

A

inhibitory, peptide signals from the Sleep Centres in the Reticular Formation likely take over and rapidly inhibit the weakening excitatory signals leading to rapid progression into the sleep state

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10
Q

what does assessing level of consciousness in an awake person involve?

A
  • Look at their behaviour, general alertness etc

- Record patterns of brain activity using ElectroEncepheloGram (EEG)

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11
Q

what are EEG waves analysed by?

A

Amplitude: the size of the wave (ranges from 0-200 µV)
Frequency: number of waves per second (ranges from 1-50+)

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12
Q

does the EEG frequency increase or decrease when asleep vs awake

A

In general frequency increases with neuronal excitation so higher frequency when awake, and higher still when focused

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13
Q

what is EEG characterised by when in a relaxed awake state?

A

high frequency, high amplitude waves termed alpha waves.

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14
Q

what is EEG characterised by when in an alert awake state?

A

even higher frequency, low amplitude asynchronous waves termed beta waves

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15
Q

why is the amplitude lower during the alert awake phase?

A

increase in activity is asynchronous as brain is doing so many things at once, and opposing polarities of the signals cancel each other out and do not get recorded on EEG.

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16
Q

what are theta waves characterised by?

A

low frequency waves which can vary enormously in amplitude.

common during emotional stress

17
Q

what are delta waves characterised by?

A

very low frequency but high amplitude. They occur in deep sleep

18
Q

describe the 1st stage of sleep

A

Slow wave, non-REM, S-sleep. Slow eye movements. Light sleep. Easily roused. High amplitude, low frequency theta waves

19
Q

describe the 2nd stage of sleep

A

Eye movements stop. Frequency slows further but EEG shows bursts of rapid waves called “sleep spindles” (clusters of rhythmic waves, ~12-14Hz)

20
Q

describe the 3rd stage of sleep

A

High amplitude, very slow (2Hz) delta waves interspersed with short episodes of faster waves, spindle activity declines.

21
Q

describe the 4th stage of sleep

A

exclusively delta waves.

22
Q

describe the REM stage of sleep

A

during which there are rapid eye movements. Aka paradoxical sleep. Dreams occur during REM sleep. 25% of sleep is REM.

23
Q

which stages are known as the deep sleep?

A

stages 3 and 4

Sleep walking/talking occurs during these

24
Q

what characterises stages 1-4?

A

slow wave sleep

25
Q

what characterises REM sleep?

A

fast waves, eerily similar to those of the awake state

26
Q

what are the Physiological Characteristics of Deep, Slow Wave Sleep?

A

occurs in the first hours of sleep
Most restful type of sleep.
Associated with decreased vascular tone (and therefore BP), respiratory and basal metabolic rate (hence drop in BT).
Dreams may occur but are rarely remembered.

27
Q

what are the Physiological Characteristics of REM Sleep?

A

Lasts 5-30mins every 90mins
Dreams mostly occur here
Eye muscles show bursts of rapid activity.
Profound inhibition of all other skeletal muscles
HR/RR become irregular and brain metabolism increases
difficult to arouse an individual from REM sleep

28
Q

what drugs increase time spent in REM sleep?

A

Anticholinesterases

29
Q

what do Sleep deprived subjects demonstrate, without exception?

A 
Impairment of cognitive function
Impairment of physical performance
Sluggishness
Irritability
(Psychosis)
30
Q

what does sleep support?

A 
Neuronal plasticity
Learning and memory
Cognition
Clearance of waste products from CNS
Conservation of whole body energy 
Immune function (reason sleep increases when ill?)
31
Q

what is the definition of insomnia?

A

“chronic inability to obtain the necessary amount or quality of sleep to maintain adequate daytime behaviour”, very subjective, very common
chronic vs temporary
associated with PTSD

32
Q

what are problems with hypnotic drugs?

A

can depress REM sleep
addictive
cause many problems on withdrawal
should not be given chronically.

33
Q

what is the definition of night terrors?

A

occur in deep, delta sleep and are common in children 3-8 years, typically occurring early in the night. Children thrash and scream and may sit or stand up with their eyes open but are not properly awake and often fail to recognise their parents. The child does not remember the episode on waking the following morning.

34
Q

what is the definition of Somnambulism (Sleep-walking)?

A

occurs exclusively in non-REM sleep, mainly in Stage 4 sleep and is more common in children and young adults
Somnambulists walk with their eyes open, can see and will avoid objects, can carry out reasonably complex task such as prepare food and will often obey instructions but have no recall of the episode when woken.

35
Q

what is the definition of Narcolepsy?

A

Patients enter directly into REM sleep with little warning. Effectively symptoms could be interpreted as intrusion of REM sleep characteristics onto the waking state. Very dangerous because of accident risk if e.g. driving.

36
Q

sleep is part of the circadian rhythm, what does this mean?

A

biological systems show oscillations with a 24 hour period.

37
Q

where is the “master-clock” located?

A

suprachiasmatic nucleus (SCN) of the hypothalamus, lying just above the optic chiasma.

38
Q

describe the neurones of the “master-clock’

A

These neurons have an inherent 24 hour cycle which is entrained by external cues such as light/dark cycles

Nervous System (37 decks)

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