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Clinical neuroscience > Consciousness > Flashcards

Consciousness Flashcards

1
Q

What is consciousness?

A
  • Related to awareness of external and internal states
  • Arousal is a related concept which is associated with goal-seeking behaviour and avoidance of noxious stimuli
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2
Q

Which two neural components are required for consciousness?

A
  • Cerebral cortex
  • Reticular formation
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3
Q

What is the function of the cerebral cortex in consciousness?

A
  • The site where conscious thoughts arise
  • Receives many inputs, including from the reticular formation
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4
Q

What is the function of the reticular formation in consciousness?

A
  • This is the circuitry that keeps the cortex awake
  • Receives many inputs from the cortex and sensory systems
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5
Q

How do the cortex and reticular formation work together?

A
  • Connected by reciprocal excitatory projections, forming a positive feedback loop
  • Positive feedback loops are seen where there is a binary outcome
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6
Q

What are the outputs from the reticular formation to the cortex?

A
  • Occurs via three major relay nuclei
  • Reticular formation sends cholinergic (excitatory) projections to these relays
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7
Q

What are the different major relay nuclei of the reticular formation?

A
  • Basal forebrain nuclei
  • Hypothalamus
  • Thalamus
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8
Q

What do the basal forebrain nuclei do?

A
  • Send excitatory cholinergic fibres to cortex
  • Think sedative side effects of anticholinergics
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9
Q

What does the hypothalamus do?

A
  • Send excitatory histaminergic fibres to the cortex
  • Think sedative side effects of antihistamines
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10
Q

What does the thalamus do?

A
  • Sends excitatory glutamatergic fibres to the cortex
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11
Q

What is the motor function of the reticular formation?

A
  • Sends projections down the cord, responsible for maintaining muscle tone
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12
Q

How is consciousness clinically assessed?

A
  • GCS
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13
Q

What are the components of the GCS?

A
  • Eye opening
  • Motor response
  • Verbal response
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14
Q

How is eye opening assessed in the GCS?

A
  • Spontaneous eye opening suggests normal cortical and brainstem function
  • Response to speech suggests slightly diminished cortical function but still functioning brainstem
  • Response to pain suggests impaired cortical function but brainstem preserved so that reflex opening can occur
  • No response suggests severe damage to brainstem +/- cortex
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15
Q

How is motor response assessed in the GCS?

A
  • Obeys commands (6)
  • Localises to stimuli (5)
  • Withdraws to pain (4)
  • Flexor response to pain (3)
  • Extensor response to pain suggests a lesion below the red nuclei (not physiological at all)
  • No response to pain suggests severe damage to brainstem +/- cortex
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16
Q

What does a patient obeying a motor command suggest?

A
  • Normal function with working connections from auditory system to brainstem/cord
17
Q

What does a patient localising to stimuli suggest?

A
  • Diminished higher cortical function but still connections working from sensory to motor cortex
18
Q

What does a patient withdrawing to pain suggest?

A
  • There is still a physiological reflex response to stimuli
19
Q

What does a patient flexing in response to pain suggest?

A
  • Suggests a lesion above the level of the red nuclei (semi-physiological)
20
Q

What does a patient extending in response to pain suggest?

A
  • Severe damage to the brainstem +/- cortex
21
Q

How is verbal response assessed by the GCS?

A
  • Oriented in time/place (5) - normal cortical function
  • Confused conversation (4) - diminished higher cortical function but language centres are still functioning adequately
  • Inappropriate words (3) - language centres have been damaged
  • Incomprehensible sounds (2) - cortical damage with brainstem mediated groans
  • No response (1) - severe damage to brainstem +/- cortex
22
Q

What does the electroencephalogram measure?

A
  • The combined activity of thousands of neurones in a particular region of the cortex
  • High temporal resolution, low spatial resolution
23
Q

What is the electroencephalogram good for?

A
  • Detecting neuronal synchrony and evidence of normal cerebral function
24
Q

What is neuronal synchrony?

A
  • A phenomenon which occurs commonly in the brain during both physiological and pathological processes such as sleep and epilepsy
25
Q

What are the functions of sleep?

A
  • Generally unknown
  • Energy conservation/repair
  • Memory consolidation
  • Clearance of extracellular debris
  • Resetting of the CNS
26
Q

How many sleep cycles do we typically pass through each night?

A
  • 6
27
Q

What are the stages of sleep?

A
  • 4 major stages and REM sleep
28
Q

What happens on an EEG when a person is awake with their eyes open?

A
  • Beta waves - irregular, 50 Hz
29
Q

What happens on an EEG when a person is awake with their eyes closed?

A
  • Alpha waves - regular, 10 Hz
30
Q

What happens on an EEG when a person is in stage 1 sleep?

A
  • Background of alpha and interspersed theta waves
  • At around 5 Hz
31
Q

What happens on an EEG when a person is in stage 2/3 sleep?

A
  • Background of theta and interspersed sleep spindles and k-complexes
32
Q

What are sleep spindles?

A
  • High frequency bursts arising from the thalamus
33
Q

What are k complexes?

A
  • Represent the emergence of the intrinsic rate of the cortex
34
Q

What happens on an EEG when a person is in stage 4 sleep?

A
  • Delta waves - regular 1 Hz
  • Related to k-complexes seen in stages 2/3
35
Q

What happens on an EEG when a person is in REM sleep?

A
  • Initiated by neurones in the pons
  • EEG is similar to when person is awake with eyes open
36
Q

What happens to the body during REM sleep?

A
  • Difficult to rouse due to strong thalamic inhibition
  • Decreased muscle tone due to glycinergic inhibition of LMNs
  • Eye movements and some other cranial nerve functions can be preserved
  • Autonomic effects are seen
  • Essential for life
37
Q

What are some different types of sleep disorder?

A
  • Insomnia - commonly caused by underlying psychiatric disorder as opposed to primary insomnia
  • Narcolepsy - rare disorder
  • Sleep apnoea - causes excessive daytime sleepiness
38
Q

What causes narcolepsy?

A
  • Some cases are caused by mutations in the orexin gene
  • Orexin is a peptide
39
Q

What causes sleep apnoea?

A
  • Excess neck fat leading to compression of airways during sleep and frequent waking

Clinical neuroscience (19 decks)

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