Consciousness

Question 1

Define consciousness

Answer 1

awareness of external environment and internal state

Question 2

what is arousal ?

Answer 2

associated with goal - seeking behaviour and avoidance of noxious stimuli

Question 3

what 2 neural components are needed to be connected for consciousness?

Answer 3

Cerebral cortex

reticular formation

Question 4

what does the cerebral cortex do in consciousness?

Answer 4

site where conscious thoughts arise

 Receives many inputs, including from the reticular formation

Question 5

what does the reticular formation do in consciousness?

Answer 5

– the circuitry that keeps the cortex ‘awake’

 Receives many inputs, including from the cortex and sensory systems

Question 6

describe the nature of the connection of the reticular formation and cerebral cortex ?

Answer 6

reciprocal excitatory
projections, forming a positive feedback loop
due to binary outcomes e.g. sleep/awake

Question 7

what 3 outputs does the reticular formation send out to cortex ?
what about the 4th one?

Answer 7

Basal forebrain nuclei via excitatory cholinergic fibres
hypothalamus via excitatory histaminergic fibres
thalamus via excitatory glutamatergic fibres

projections down cord for muscle tone

Question 8

what 3 components of the GCS are used to asses consciousness?

Answer 8

Eye opening (4)
Motor response (6)
• Verbal response (5)

Question 9

when should you get a senior after GCS assessment ?

Answer 9

A sustained (that is, for at least 30 minutes) drop of one point in GCS level

Question 10

what does an EEG do ?

Answer 10

Measures the combined activity of thousands of neurones in a particular
region of cortex to a very high temporal resolution but low spatial

Question 11

what happens when the brain is deprived of sensory inout ?

can you give a physiological and pathological example ?

Answer 11

Neuronal synchrony

Sleep and epilepsy

Question 12

what are the theories on why we need sleep ?

Answer 12

Energy conservation / repair
Memory consolidation
clearance of extracellular debris?
“Resetting’ of the CNS

Question 13

how many cycle so sleep per night on avg do we go through ?

Answer 13

6 cycles of sleep per night

Question 14

what are the stages of sleep ?

describe the EEG pattern

Answer 14

stage 1 sleep  = Awake with eyes closed
Alpha waves – regular, 10Hz
stage 2/3 = Background of theta + interspersed sleep spindles and
k-complexes
stage 4 = Delta waves – regular, 1Hz
REM = similar to beta waves

Question 15

what do K complexes represent ?

what about Sleep spindles ?

Answer 15

Sleep spindles are high frequency bursts arising
from the thalamus
K-complexes represent the emergence of the
‘intrinsic rate’ of the cortex

Question 16

What kind of EEG in seen in normal awake consciousness ?

Answer 16

Beta waves – irregular, 50Hz

Question 17

why is beta waves seen in REM sleep ?

Answer 17

similar to awake consciousness as dreaming is occuring

Question 18

describe the neural mechanism of Non-REM sleep

Answer 18

Deactivation of the reticular activating system (and hence cortex)
inhibition of the thalamus.
facilitated by removal of sensory inputs (fewer
positive influences on positive feedback loop)

Question 19

describe the neural mechanism of REM sleep

Answer 19

Initiated by neurones in the pons- active process
difficult
to rouse due to strong thalamic inhibition

Essential for life – long term deprivation leads to death

Question 20

what can be seen during REM sleep ?

Answer 20

Decreased muscle tone due to glycinergic inhibition of lower motor
neurones
Eye movements and some other cranial nerve functions can be
preserved
Autonomic effects are seen

Question 21

What can cause insomnia ?

Answer 21

underlying psychiatric disorder as

opposed to ‘primary’ insomnia

Question 22

what can cause narcolepsy ?

Answer 22

mutations in the orexin gene.

Orexin is a peptide transmitter involved in sleep

Question 23

what can cause sleep apnoea ?

Answer 23

excess neck fat leading to
compression of airways during sleep and frequent waking
• Causes excessive daytime sleepiness

Question 24

what are the features of a coma ?

Answer 24

widespread brainstem/ cortical damage
EEG disordered with no sleep wake cycle
unresponsive

Question 25

what are the features of a PVS?

Answer 25

Widespread cortical damage with disordered EEG
some spontaneous eye opening and responsed to stimuli via brainstem reflexes
sleep/cycle detectable

Question 26

what are the features of Locked in syndrome ?

Answer 26

caused by basilar / pontine artery occlusion

eye movements preserved but all other somatic motor function lost form pons down