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Clinical Neuroscience > Reticular Formation and Conciousness > Flashcards

Reticular Formation and Conciousness Flashcards

1
Q

Define arousal

A

The emotional state associated with some kind of goal or avoidance of something noxious

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2
Q

Define conciousness

A

Difficult to define but something to do with awareness of both the external world and internal states

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3
Q

What two areas of the brain make up conciousness?

A

Cerebral cortex + reticular formation

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4
Q

What is the reticular formation?

A

A diffuse networks of neurones running the full legnth of the brainstem

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5
Q

Which 3 areas of the brain does the reticular formation project onto?

A
  • Basal forebrain nuclei
  • Hypothalamus
  • Thalamus
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6
Q

What are the effects of stimulation by the reticular formation of the basal forebrain nuclei, hypothalamus and thalamus on the cerebral cortex?

A

Basal forebrain nuclei - realeases ACh → excitatory to the cerebral cortex

Hypothalamus - releases Histamine to cerebral cortex → drowsiness

Thalamus - releases Glutamate → excitatory to cerebral cortex

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7
Q

What inputs to the reticular formation regulate the level of arousal?

A
  • Sensory system
  • Cortex
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8
Q

What aspects are assessed in assessing conciousness in the Glasgow Coma Scale?

A
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9
Q

What does an EEG measure?

A

Electroencephalogram

Measure the combined activity of thousands of neurones in a given part of the cortex to a very high temporal resolution (but poor spatial resolution)

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10
Q

How many cycles of sleep do you go through in a night?

A

Typically 6 rounds of sleep

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11
Q

What are the different stages of sleep

A

Stage 1 -4 gets progressively deeper

Stage 4 rapidly switches to REM

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12
Q

What type of waves are shown on an EEG when awake?

A

Beta waves

50 Hz - irregular pattern

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13
Q

What waves are seen on the EEG when the eyes are closed/ stage 1 sleep?

A

Alpha waves

10 Hz

reduced sensory input

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14
Q

What do you see on the EEG in stage 2/3 of sleep

A

Backgrounnd of alpha wabes with occasion spindles (thalamus burst) and K complexes

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15
Q

What is seen on the EEG during stage 4/ deep sleep

A

Delta waves

High amplitude, low frequency

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16
Q

Explain the neural mechanism of sleep

A
  • Deactivation of the reticular activating system inhibits the thalamus
  • Positive feedback loop between RAS and cortex is inhibited → decreased cortical activity
  • Removed sensory inputs
17
Q

Explain what happens in REM sleep

A
  • Initiated by groups of neurones in the pons
  • EEG acitivty beta waves (similar to arousal) but thalamus is strongly inhibited
  • Most of the muscle tone of the body is lost due to descending inhibition of lower motor neurones by glycinergic fibres (from the reticular formation)
  • Eye movements preserved
  • See autonomic effects: penile erection, loss of thermoregulation
18
Q

What are the functions of sleep?

A

Not fully understood:

  1. Energy conservation and bodily repair
  2. Memory consolidation
  3. Clearance of extracellular debris
  4. Resetting of CNS
19
Q

What is insomnia?

A

Inability to sleep

Often a manifestation of some other psychiatric cause

20
Q

What is narcolepsy?

A

Suddently falling asleep at innapropriate times

rare thought to be due to orexin gene

21
Q

What is sleep apnoea?

A

Periods of stopping sleeping / shallow breathing during sleep

22
Q

What are risk factors for sleep apnoea

A
  • Overweight
  • Older
  • Main
  • Thicker neck
  • Smoker
  • Nasal Congestion
23
Q

What happens in brain death, what do you see on the EEG?

A

Widespread cortical and brainstem damage

EEG completely flat

24
Q

What is a coma?

A

Widespread brainstem and cortical damage with various patterns on the EEG

Unarousable and unresponsive to psycholical stimuli

No sleep- wake cycle detectable

25
Q

What is persistant vegetative state?

A

Widespread cortical damage with various disordered EEG patterns

Similar to coma but some spontaneous eye opening

Sleep wake cycle detectable

26
Q

What is locked in syndrome?

A

Basilar/ pontine artery occlusion

Eye movement can be preserved but all other somatic motor fnctions are lost from the pons down

Clinical Neuroscience (18 decks)

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