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sleep Flashcards

1
Q

how do we measure brain rhythmicity?

A

an electroencephalogram (EEG)

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2
Q

what does an electroencephalogram (EEG) involve?

A

non invasive electrodes placed on standard positions on the head and connected to amplifiers and a recording device

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3
Q

what are electroencephalogram (EEG)’s used for?

A

diagnose certain neurological disorders

e.g. seizures in epilepsy

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4
Q

what does an electroencephalogram (EEG) measure?

A

the combined activity of a large number (1000s) of similarly orientated neurons

  • summed post-synaptic activity
  • requires synchronous activity across groups of cells
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5
Q

what does the amplitude of an EEG signal depend on?

A

how synchronous the activity of the neurons is

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6
Q

what happens when a group of cells is excited?

A

the tiny signals sum to generate a large surface signal

-the same amount of excitation can occur, but at irregular intervals, resulting in a small summed signal

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7
Q

what do EEG rhythms correlate with and how are they categorised?

A
  • correlate with states of behaviours

- categorised by their frequency range

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8
Q

alertness and waking has what EEG rhythm?

A

high-frequency low-amplitude

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9
Q

non-dreaming sleep or coma has what EEG rhythm?

A

low-frequency high-amplitude

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10
Q

2 ways synchronous brain rhythms are generated?

A

pacemaker
-synchronous rhythms led by a central clock/pacemaker (e.g. thalamus)

collective behaviour
-synchronous rhythms arise from the collective behaviour of cortical neurons themselves

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11
Q

how can the thalamus act?

A

as a pacemaker

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12
Q

pacemaker behaviour, how is each individual thalamic neuron forced to conform to the rhythm of the group?

A

synaptic connections between excitatory and inhibitory thalamic neurons

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13
Q

the thalamus passes coordinated rhythms onto where?

A

the cortex by thalamocortical axons

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14
Q

a relatively small group of centralised thalamic cells can do what?

A

can compel a much larger group of cortical cells

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15
Q

with collective behaviour, how does synchronous coordinated activity happen in the neurones?

A

excitatory and inhibitory interconnections of neurons

-can remain localised or spread to larger regions of the cortex

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16
Q

name the 3 functional states of the brain

A
  • Wakefulness
  • non-REM sleep
  • REM sleep
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17
Q

describe non-REM sleep

A

body capable of involuntary movement, rarely accompanied by vivid, detailed dreams

  • “Idling brain in a moveable body”
  • low frequency high amplitude
  • occasional voluntary movement
  • logical repetitive thoughts
18
Q

describe REM sleep

A

body immobilised, accompanied by vivid, detailed dreams

  • “An active, hallucinating brain in a paralysed body”
  • Low-amplitude, high frequency - just like when awake
  • vivid bizarre thoughts
  • muscle paralysis
19
Q

explain what happens to temperature, heart, rate, breathing during non-REM and REM sleep

A

temperature, heart rate and breathing all decrease

  • temp decreases more in REM sleep
  • HR and breathing decrease more in non-REM sleep
20
Q

brain energy consumption in REM vs non-REM sleep

A

brain energy consumption decreases in non-REM sleep

INCREASES massively in REM sleep

21
Q

what does each night begin with and what happens as night progresses?

A
  • each night begins with a period of non-REM sleep

- as night progresses, there is a shift from non-REM to REM sleep

22
Q

how often are sleep cycles repeated throughout the night?

A

every 90 minutes

23
Q

purpose of sleep?

A
  • restoration and adaptation
  • sleep means we can rest and recover
  • sleep means we can protect ourselves and conserve energy
24
Q

what happens during wakefulness?

A

there is an increase in brainstem activity, and several sets of neurones in increase their rate of firing in anticipation of waking to enhance the wake state
-ACh, 5-HT, NA and histamine

25
Q

in waking where do the ACh, 5-HT, NA and histamine synapse to?

A

synapse directly to brain regions including the thalamus and cerebral cortex

26
Q

the increase in excitatory activity upon waking has what effect?

A

suppresses rhythmic forms of firing in the thalamus and cortex present during sleep

27
Q

during sleep, what happens to brain stem activity?

A

decreases

-rhythmic firing from thalamus blocks the flow of sensory information up to the cortex

28
Q

what happens to several sets of neurones during sleep?

A

decrease their rate of firing

-Ach, 5-HT, NA

29
Q

cholinergic neurons in the pons…

A

…..increase their rate of firing to induce REM sleep

30
Q

other sleep promoting factors?

A
  • adenosine
  • nitric oxide
  • inflammatory factors
  • melatonin
31
Q

role of adenosine in sleep?

A
  • DNA, RNA, ATP building block

- adenosine receptor activation decreases HR, SM tone and respiratory rate - decrease in BP

32
Q

what do adenosine receptor antagonists, like caffeine, promote?

A

promote wakefulness

33
Q

role of nitric oxide in sleep?

A
  • a potent vasodilator
  • decreases SM tone - decrease BP
  • stimulates adenosine release
34
Q

role of inflammatory factors in sleep?

A
  • consequence of infection
  • cytokines (e.g. interleukin-1) stimulates the immune system to fight infections
  • Interleukin-1 levels promote non-REM sleep
35
Q

role of melatonin in sleep?

A
  • secreted by the pineal body at night, induces sleep
  • over-the-counter medication for symptoms of jet-lag
  • initiates and maintains sleep – unclear role in natural sleep wake cycle
36
Q

circadian rhythms

A

daily cycles of daylight and darkness

-based on 24hr clock

37
Q

what is the suprachiasmatic nucleus (SCN)?

A
  • small hypothalamic nucleus innervated by the retina

- synchronises circadian rhythms with the daily light-dark cycle

38
Q

if the SCN is inhibited does it abolish sleep?

A

no

39
Q

is the SCN stimulated by rods and cones?

A

no, specialised photoreceptor cells expressing the photopigment melanopsin

40
Q

how are photoreceptors expressing melanopsin affected by light and where do they project to?

A
  • slowly excited by light, detect changes in luminosity

- project directly to SCN, inhibiting the melatonin production by the pineal gland

Neuro (21 decks)

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