S8.1 - Consciousness

Question 1

what are the two key components that determine consciousness ?

explain consciousness

Answer 1

Consciousness requires two neural components to be functioning normally, andconnected to each other

Cerebral cortex – the site where conscious thoughts arise
Receives many inputs, including from the reticular formation

Reticular formation (particularly the reticular activating system in the brainstem) – the circuitry that keeps the cortex ‘awake’
Cortex and reticular formation are connected by reciprocal excitatory projections, forming a positive feedback loop

Question 2

how do we asses consciousness ?

Answer 2

the glasgow coma scale (GCS)

read over this from the lecture, understand the steps

Question 3

how do we asses consciousness

Answer 3

and EEG - electroenchephalogram

Question 4

what three nuclei travel from reticular formation to the cortex ?

Answer 4

Occurs via three major relay nuclei

Reticular formation sends cholinergic (excitatory) projections to these relays

Basal forebrain nuclei send excitatory cholinergic fibres to cortex (think sedative side effects of anticholinergics)

The hypothalamus sends excitatory histaminergic fibres to the cortex (think sedative side-effects of sedating antihistamines)

The thalamus sends excitatory glutamatergic fibres to the cortex

The reticular formation also sends projections down the cord, responsible formaintaining muscle tone

Question 5

outline the 5 stages of sleep, what is seen on an EEG?

what waves are seen ?

look at lecture after trying to explain

Answer 5

do it

Question 6

what is REM sleep ?

Answer 6

REM sleep
Initiated by neurones in the pons (i.e. initiation appears to be an active process)

Similar EEG to when awake with eyes open (beta waves), but difficult to rouse due to strong thalamic inhibition

Decreased muscle tone due to glycinergic inhibition of lower motor neurones

Eye movements and some other cranial nerve functions can be
preserved (e.g. teeth grinding)

Autonomic effects are seen (e.g. penile erection, loss of thermoregulation)

Essential for life – long term deprivation leads to death

Question 7

what are

insomnia

narcolepsy

sleep apnoea

Answer 7

Sleep disorders

Insomnia
• Commonly caused by underlying psychiatric disorder as opposed to ‘primary’ insomnia - such as anxiety or depression

Narcolepsy
• Rare disorder
• Some cases are caused by mutations in the orexin gene. or loss of orexin center
Orexin is a peptide transmitter involved in sleep

Sleep apnoea
• Common condition, often caused by excess neck fat leading to compression of airways during sleep and frequent waking - hence very tired people
• Causes excessive daytime sleepiness