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PSC3008 > lecture 25 - anya hurlbert > Flashcards

lecture 25 - anya hurlbert Flashcards

1
Q

what is sleep

A

readily reversible state of diminished responsiveness to and interaction with the environment

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2
Q

how is it different to coma or general anaesthesia

A

coma or general anaesthesia are not readily reversible

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3
Q

the drive to sleep is governed by…

A

circadian rhythm
sleep pressure

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4
Q

circadian drive is high in the morning and starts to fall towards evening (the drive to stay awake) whereas…

A

the sleep drive builds up during the day and becomes higher and higher

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5
Q

what is building up during the day

A

adenosine

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6
Q

adenosine is part of…

A

ATP

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7
Q

adaptational purposes of sleep

A

hides organism when vulnerable
conserves energy

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8
Q

regulatory purposes of sleep

A

thermoregulation (cooling of the brain)
metabolism regulation

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9
Q

restorative purposes of sleep

A

emotions
mental health
growth (increased protein and RNA synthesis)
immune system
cognition
consolidation of learning and memory

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10
Q

consolidation of learning and memory

A
  • slow wave sleep transfers learning from hippocampus to cortex
  • REM sleep consolidated memories in cortex
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11
Q

medial temporal cortex neurons in rats fire most actively at night
this is involved in…

A

consolidation of memories

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12
Q

during sleep protein synthesis increases

A

this strengthens synapses
as proteins are being made that make synaptic changes permanent

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13
Q

behavioural evidence

A

learning occurs more effectively after a good nights sleep

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14
Q

stages of sleep
REM sleep:

A
  • rapid eye movement (25% of total sleep time)
  • duration increases through night
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15
Q

non REM sleep

A
  • 75% of total sleep time
  • stage 1 (few minutes, lightest sleep)
  • stage 2 (5-15 minutes, deeper)
  • stage 3 (up to 30 mins, absent towards morning)
  • stage 4 (up to 40 mins, deepest sleep)
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16
Q

measuring brain rhythms with EEG (electroencephalography)

A

EEG measures synchronised electrical activity of neurones in the brain (primarily pyramidal cell neurones)
EEG record is characterised by amplitude and frequency
recorded from scalp electrodes, only thing that gets up to the electrodes that are sitting on the brain is activity that’s strong enough to make it through different media (that will be activity that represents synchronised activity of many thousands of neurones)

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17
Q

in the awake state what is observed on an EEG

A

brain waves of very small amplitude and mostly irregular high frequency (called beta rhythms)

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18
Q

when are alpha rhythms seen

A

when you’re awake but your eyes are closed and you’re relaxing
they are more regular and have higher amplitude

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19
Q

awake, eyes closed

A

alpha, 8-12 Hz, low voltage

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20
Q

REM sleep

A

beta, 14-150 Hz, low voltage

21
Q

stage 1: falling asleep, lightest sleep

A

theta, 4-7 Hz, high voltage

22
Q

stage 2: deeper sleep

A

theta, K complexes (high amplitude, sharp from cortex) and spindles (bursts of 8-14Hz oscillations, from thalamus)

23
Q

stage 3 and 4: deepest sleep

A

delta, 1-4 Hz, high voltage

24
Q

EOG (eye movement)
non-REM:

A

no eye movements at all

25
Q

REM:

A

look like eye movements in awake state

26
Q

sensations

A

awake - vivid, externally generated
non-REM - dull, absent
REM - vivid, internally generated (dreams)

27
Q

thoughts

A

awake - logical, progressive
non-REM - logical, perseverative (round and round)
REM - illogical, bizarre

28
Q

movement

A

awake - continuous, voluntary
non-REM - episodic, involuntary
REM - inhibited: none except eye movements

29
Q

alternation between what two different neurotransmitter systems governs the change in brain rhythms

A

ascending reticular activating systems (RAS) and the pontine reticular formation (PRF)

30
Q

RAS

A

set of noradrenergic neurons in the locus coeruleus
and serotonergic neurons in the raphe nucleus

31
Q

alternate in activity with

A

cholinergic neurones in the pons and the basal forebrain

32
Q

these two different NT systems project to the…

A

thalamus (gateway to the cortex)

33
Q

neuromodulatory systems

A

core system consists of small number of neurons each contacting more that 100,000 neurons spread widely across the brain
most neurones arise from the central core of the brain
synapses release neurotransmitter into extracellular fluid so that transmitter can diffuse to many neurons not just across synaptic cleft
systems use NE, 5HT, ACh, DA (all activate metabotropic receptors)
modular activity of neurons making them more or less excitable or synchronous

34
Q

the NE diffuse modulatory system.

A

arises from locus coeruleus cluster of cells in the pons
send outputs to multiple areas in the brain
regulates attention, arousal, sleep-wake cycle

35
Q

the 5HT diffuse modulatory system

A

arises from raphe nuclei (various clusters running down the brainstem)
projects all around the brain
regulates attention, arousal, sleep-wake cycle

36
Q

the ACh diffuse modulatory system

A

regulate wakefulness
arises from the pontomesencephalotegmental complex (dont need to remember) in the brainstem

37
Q

the activity of the neurones in the clusters in the pons oscillates at the same time as…

A

REM and non-REM stages

38
Q

as REM sleep end, activity ________ in NE neurones and 5HT neurones and then ______ as non REM sleep begins

A

increases
decreases

39
Q

as REM sleep enters, activity _____ in ACh neurones in the pons

A

increases

40
Q

the cholinergic neurones block…

A

the thalamus from setting up slow wave sleep
by blocking burst mode of thalamic relay cells

41
Q

when signals come through the thalamus, the thalamus can either be in transmission mode where a the signal is passed to the cortex (awake or REM).
or can be in burst mode and sends little bursts of AP separated by long interval which creates a low frequency brain wave.
the ACh will block that burst mode and enable it to be in transmission mode and makes the brain look like its awake, any signal that comes up from the thalamus to the brain are perceived as real stimuli even if they’re internally generated

A
42
Q

the biological clock is located in the…

A

suprachiasmatic nucleus of the hypothalamus (SCN)
receives direct input from retina for adapting to dark/light cycles

43
Q

this then regulates the timing of which hormone

A

melatonin released from the pineal gland which in turn feeds back to SCN to reduce its activity

44
Q

melanopsin containing intrinsically photosensitive retinal ganglion cells (ipRGCs)

A

they respond directly to light through their pigments in their membranes
the pigments are most sensitive to short wavelength light (blue light, 480nm)
project to SCN

45
Q

exposure to 2 hours of 480nm light (blue) at night time suppresses melatonin and sleepiness more than exposure to 550 light (green) or darkness

A
46
Q

the SCN is periodic in its firing

A

it contains clock genes that determines its periodicity

47
Q

during sleep the hippocampus and the cortex replay events that happened during the day.
hippocampus generates sharp waves and ripples, similar to cortical K complexes

A
48
Q

the active system consolidation hypothesis

A

during non REM reactivation and redistribution of hippocampus dependent memories to neocortical sites (coordinated by slow oscillations, spindles and ripples)
synaptic consolidation of memories in cortex, via local increases in plasticity related immediate early gene activity, during REM

49
Q
A

PSC3008 (28 decks)

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