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MD4001 Physiology > Sleep, Wakefullness and the ECG > Flashcards

Sleep, Wakefullness and the ECG Flashcards

1
Q

What are the three states of consciousness

A

wakefullness

core consciousnes- wakefullness plus emotional responses, simple memory

extended consciousness- all of the above plus self awareness, autobiographical memory, language and creativity

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2
Q

are brain neurones active during sleep

A

yes but have a different activity

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3
Q

what are the two main phases of sleep

A

REM and non REM/ slow wave or deep sleep

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4
Q

what signals can be picked up from the EEG

A

post synaptic activity of synchronised dendritic activity but not individual neurons

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5
Q

what determines the size of the peak on the EEG

A

the number of neurons that are synchronised

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6
Q

what causes neurons to synchronise

A

neuronal interconnections or by pacemaker

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7
Q

describe how EEGs are performed

A

electrodes are arranged in 19 pairs on the surface of the head

comparison between pairs of electrodes provides a pictures of neuronal activity in areas of the brain

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8
Q

what happens during stage one sleep

A

slow rolling eye movements, theta waves

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9
Q

what happens during stage 2

A

K complexes and sleep spindles, no eye movements, body movement remains possible

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10
Q

what happens during stage 3 sleep

A

slow frewuency delta waves

harder to rouse

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11
Q

what happens in stage 4 sleep

A

deepest sleep hardest to rouse
heart rate and blood pressure lower

synchronised firing of large groups of neurons

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12
Q

what happens in REM sleep

A

fast beta waves and REM, easier to rouse than in stage 4

dreaming and low muscle tone

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13
Q

how long does it take to get from drowsy to deep sleep

A

one hour

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14
Q

describe sleep cycles throughout the night

A

stage 4 is only reached in the initial cycles, thereafter the deepest sleep atained is stage 3

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15
Q

what are the characteristics of REM sleep

A

increase in heart rate, neural activity, respiration and oxygen consumption, erection

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16
Q

what are the subtypes of alpha waves

A

visual cortex (classic)
sensory motor cortex (mu)
auditory( kappa)

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17
Q

what is the function of slow waves

A

thought to be involved with inhibiting sections of the relevant cortex

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18
Q

during what stage of sleep is the body paralysed, and body temperature drops

A

REM

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19
Q

what is the reticular formation

A

a diffuse collection of at least 100 neuromodulatory neurones spanning all three divisions of the brainstem

pathways in the brainstem connecting the spinal cord, cerebrum, and cerebellum, and mediating the overall level of consciousness.

it is not homogenous and has diverse functions

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20
Q

what are the functions of the reticular formation

A

posture, respiration, sleep, heart rate

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21
Q

where does the reticular formation project to

A

the thalamus, hypothalamus, brainstem nuclei, cerebellum, spinal cord and cerebral cortex

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22
Q

what does the reticular formation recieve input from

A

cerebra, visual and auditory systems, sensory spinal systems, cerebellum, certain brainstem nuclei

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23
Q

what structure is required for consciousness

A

release of neurotransmitters from neurones of the reticular formation (norepinephrin, serotonin, acetylcholine)

24
Q

what neurotransmitters are required for consciousness

A

norepinephrin, serotonin, acetylcholine

25
Q

what structure modulates arousal in the cerebral cortex

A

thalamus

26
Q

what inputs go to the thalamus

A 
midbrain reticular formation
vestibulocochlear nuclei
spinal nucleus 5
spinoreticular pathway 
nucleus basalis 
thalamus
27
Q

how can excitability of the thalamus be controlled

A

reticular formation

28
Q

what is the effect of lesions to the thalamus on the eeg

A

most synchronous eeg waves are abolished

29
Q

what stimulates stage 4 sleep

A

rhythmic stimulation of the thalamus induces stage 4 sleep

30
Q

how can EEG wave types can be changed

A

activation of the reticular formation and so the thalamus- increasing stimulation of the thalamus increases alertness

31
Q

what 3 structures are most concerned with wakefulness and are interconnected

A

thalamus, reticular formation, cerebral cortex

32
Q

describe the effect of excitation on the reticular formation

A

depolarisation of the thalamus causes non rhythmic output to the cortex

this causes increase arousal (alpha and beta waves)

33
Q

describe the effect of inhibition to the reticular formation

A

this causes hyperpolarisation of the thalamus which causes rhythmic output to the cortex

this causes slow EEG waves in the cerebral cortex so deeper sleep

34
Q

how is deeper sleep achieved

A

inhibition of the reticular formation

35
Q

what is non rem sleep characterised by

A

slow synchronised cortex waves, caused by a hyperpolarised thalamus and decreased activity in the arousal centres of the reticulum

36
Q

what causes sleep spindles and K complexes (stage 2)

A

inherent rhythmicity of thalamic neurons as they hyperpolarise due to reduced ascending reticular formation input

37
Q

describe the effect as thalamic cells hyperpolarise further

A

they develop slow wave rhythmicty due to thalamic interconnections which blocks ascending sensory input this rhythmicity is transmitted to the cortex and the waves become synchronised

38
Q

what does the locus coeruleus block during rem sleep

A

descending motor output

39
Q

describe the oxygen consumption of the brain during rem sleep

A

uses more than awake and engaged in a complex problem

40
Q

what does the midbrain reticular formation do during rem

A

excites the thalamus and provides descending inhibitory stimuli to the motor pathways

41
Q

describe the passage from wakefullness to sleep

A

midbrain reticulum projects cholinergic excitation onto the thalamus
pathway is on except for NREM sleep

direct cortical excitation is quiescent during REM sleep (lesions cause coma)

42
Q

what is the ventrolateral pre optic nuceus

A

the centre of NREM sleep promotion

it has inhibitory projections to all the major arousal centres and is active during sleep

43
Q

what structures inhibit the ventrolateral pre optic nucleus

A

arousal centres

44
Q

what are orexinergic neurons

A

normally acitve during wakefullness (lateral hypothalamus)

they project to the cerebra, the arousal nuclei and the VLPO

this causes indirect inhibition of the VLPO via reciprocal inhibition pathways

45
Q

what hormone is pivotal in sleep awake switch circuitry

A

orexin

46
Q

what happens when orexin is released

A

stimulates arousal centres and so causes inhibition of the VPLO

shifts the balance towards wakefulness

47
Q

what happens when the VPLO fires

A

inhibits orexinergic neurons and the arousal centres

this causes sleep

48
Q

where is the suprachiasmatic nucleus located

A

hypothalamus

49
Q

what does the suprachiasmitic nucleus control

A

circadian cycles, physiolical and behavioural rhythms including sleep wake cycle

50
Q

what resets the SCN clock

A

zeitgebers (time givers) e.g. the light/ dark cycle

51
Q

what do receptors in the retina contain

A

melanopsin which reacts to light and resets the clock gene

52
Q

what are the two forms of permanent insomnia

A

rare inherited neurodegenerative process affecting the thalamus and the rostral hypogenic sleep centres

stroke resulting in blockade of the basilar artery causing locked in sydrome, if this includes the loss of the pontine hypogenic centre the result can include insomnia

53
Q

what causes narcolepsy

A

loss of orexinergic neurons in the lateral hypothalamus

inherited autoimmune

54
Q

what are the symptoms of narcolepsy

A

repeatedly falling asleep during the day

limb weakness during emotional episodes (cataplexy)

night time or morning wakening accompanied by muscular paralysis

vivid dream recollection

caused by pontine influence of muscle tone during REM

55
Q

What is the term for sleep walking

A

somnambulance

56
Q

what is REM sleep behaviour disorder

A

n the descending pontine reticular
formation fails to properly immobilise the body. Characterised
by rapid/violent movement and behaviour

57
Q

what is somnambulance

A

during non-REM sleep. Often the
same as REM sleep behaviour disorder but there is no memory
of the dreams enacted. Occurs in NREM sleep which is why
there is no memory, and happens when the midbrain reticular
formation fails to paralyse the body

MD4001 Physiology (19 decks)

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