Consciousness

Question 1

What makes up consciousness?

Answer 1

Cerebral cortex and the reticular formation

Positive feedback loop connects the two

Question 2

Briefly describe the reticular formation (include inputs and outputs)

Answer 2

Specialised interneurones in the brainstem 
Input:
Sensory system 
Cortex
Output:
Thalamus (sensory gating)
Hypothalamus
Basal forebrain nuclei
Spinal cord (muscle tone)- think muscle paralysis in REM sleep

Question 3

Briefly describe the reticular activating system

Answer 3

Important in arousal
Mainly ascending neurones to the cortex to stimulate the cortex
Part of the positive feedback loop

Question 4

What 3 domains does the GCS examine?

Answer 4

Eye opening
Motor response
Verbal response

Question 5

What methods can be used to assess consciousness

Answer 5

Glasgow coma scale

Electroencephalogram (EEG)

Question 6

Briefly describe some features of the different stages of sleep on an EEG

Answer 6

REM:
Identical to EEG when awake- associated with dreaming
Stage 1:
Theta waves
Stage 2/3:
Sleep spindle- spikes of thalamus activity
K complex- prelude to delta waves
Stage 4:
Delta waves- slow, synchronous waves with high amplitude

Question 7

Briefly describe the neural mechanism of sleep

Answer 7

Deactivating reticular activating system.
Inhibits thalamus
Inhibits positive feedback between RAS and cortex by removing sensory inputs
Inhibits cortex

Question 8

Briefly describe what happens during REM sleep

Answer 8

Muscle tone is lost due to descending LMN inhibition by glycinergic fibres- prevents sleepwalking etc
Eye movements and CN functions are preserved e.g. grinding teeth (nocturnal bruxism)
Autonomic effects- erection and loss of thermoregulation

Question 9

Briefly describe the function of sleep

Answer 9

Bodily repair
Memory consolidation
Clearance of extra cellular debris by opening of passages in the glymphatic system- may explain association between dementia and lack of sleep

Question 10

List some disorders of sleep

Answer 10

Insomnia
Narcolepsy
Sleep apnoea

Question 11

Briefly describe some disorders of consciousness and their eeg pattern

(Brain death, coma, pvs, locked in syndrome)

Answer 11

Brain death- cortical and brainstem damage. Flat EEG.
Coma- cortical and brainstem damage with disordered EEG.
-Unarousable and unresponsive to meaningful stimuli
-No sleep wake cycle detected
PVS- cortical damage with disordered EEG.
-Some spontaneous eye opening
-May localise to stimuli via brainstem
-Sleep wake cycle detectable
Locked in syndrome
-Basilar/pontine artery occlusion
-Cortex is disengaged from the rest of the body
-Eye movements preserved
-All somatic functions lost from pons down