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Nervous System And Neuropsychiatry > Session 8 L2: Consciousness > Flashcards

Session 8 L2: Consciousness Flashcards

1
Q

What is arousal?

A

The emotional state associated with some kind of goal or avoidance of something noxious. Regulated by inputs from sensory system and cortex

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2
Q

What is consciousness?

A

-Related to awareness of both external environment and internal states.

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3
Q

What is the requirement of consciousness?

A
  • Cerebral cortex

- Reticular formation.

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4
Q

How does the cerebral cortex affect consciousness?

A
  • The site where conscious thoughts arise

- Receives many inputs, including from the reticular formation

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5
Q

How does the reticular formation affect consciousness?

A

-Circuitry to keep cortex awake, particularly the reticular activating system in the brain stem

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6
Q

What is the reticular formation?

A
  • A population of specialised interneurons in the brainstem. It is a diffuse network of grey matter and is poorly defined. Lives in all 3 divisions of the brainstem
  • Receives many inputs, including from the cortex and sensory systems
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7
Q

How are the cortex and reticular formation associated?

A
  • Cortex and reticular formation are connected by reciprocal excitatory projections, forming a positive feedback loop
  • Binary outcome of sleep/awake
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8
Q

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

A

-Occurs via three major relay nuclei

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9
Q

What are the types of projections from the reticular formation?

A

Cholinergic Projections (excitatory)

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10
Q

Which three major relay nuclei do reticular formation send fibres by?

A
  • Thalamus sends excitatory glutamatergic fibres to the cortex (sensory gating)
  • Hypothalamus sends excitatory histaminergic fibres to the cortex (think sedative side-effects of seating antihistamines)
  • Basal forebrain nuclei sends excitatory cholinergic fibres to cortex (think sedative side effect of sedating anticholinergics)
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11
Q

What other fibres are sent by the reticular formation?

A

-Projections sent down the cord, responsible for mainting muscle tone

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12
Q

What is used to assess cortical function?

A
  • EEG

- Glasgow Coma Scale

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13
Q

What is an EEG?

A
  • Measures combined activity of thousands of neurones in a given part of cortex to very high temporal resolution but low spatial resolution
  • Neurones in the brain tend to fire synchronously when deprived of sensory input
  • Good for detecting neuronal synchrony
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14
Q

What are the responses tested in the Glasgow Coma Scale?

A
  • Eye opening response
  • Verbal response
  • Motor response
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15
Q

What are the function of sleep?

A
  • Energy conservation and bodily repair
  • Memory consolidation
  • Clearance of extracellular debris
  • Resetting of the CNS
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16
Q

How many stages do you pass through in sleep?

A
  • Typically pass through around 6 cycles of sleep per night
  • 4 major stages + rapid eyes movement
  • As you progress from Stage 1 to Stage 4, amplitude increases and frequency decreases
17
Q

What are the stages of Sleep?

A

Awake with eyes open - Beta waves (50Hz). Irregular

Awake with eyes closed - Alpha waves(10Hz). Regular

Stage 1 - Background of alpha waves + interspersed theta waves (5Hz)

Stage 2/3 - Background of theta waves with interspersed sleep spindles and k-complexes

Stage 4 - Delta waves (1Hz). Regular

REM sleep - EEG similar to beta waves. Dreaming occurs here

18
Q

What are Sleep spindles and K complexes seen in stage 2/3?

A
  • K complexes represent the emergence of the intrinsic rate of the cortex
  • Sleep spindles are high frequency burst arising from the thalamus
19
Q

What are the mechanisms of the sleep?

A
  • Complex
  • Deactivation of the reticular activating system and hence the cortex and inhibiting the thalamus.
  • Positive feedback loop between RAS and cortex is inhibited, leading to decreased cortical activity
  • Inhibition of the positive feedback loop by removal of sensory inputs (fewer positive influences on positive feedback loop).
20
Q

How is REM sleep initiated?

A

-Initiated by neurones in the pons

21
Q

Why is the person difficult to rouse in REM sleep?

A

-Although EEG activity is similar to that seen during arousal, there is strong inhibition of the thalamus

22
Q

Why is Muscle Tone affect in the body in REM sleep?

A

-Muscle tone in most of the body is lost due to descending inhibition of LMNs by glycinergic fibres arising from the reticular formation and running down the reticulospinal tracts

23
Q

What are autonomic effect in REM sleep?

A
  • Penile erection seen

- Loss of thermoregulation

24
Q

What is important about REM sleep?

A

-REM sleep is essential for life. Long deprivation leads to death

25
Q

Describe cranial nerve function during REM sleep?

A

-Eye movement and some other cranial nerve functions are preserved

26
Q

What are some sleep disorders?

A
  • Insomnia
  • Narcolepsy
  • Sleep apnoea
27
Q

What is insomnia?

A
  • Inability to sleep

- Due to psychological or psychiatric disorder (depression and anxiousness) as opposed to ‘primary insomnia’

28
Q

What is narcolepsy?

A
  • Rare disorder
  • Some cases are caused by mutations in orexin gene affecting neurotransmission. Positive loop feedback can’t work. Orexin is a peptide transmitter involved in sleep
  • Caused by neurotransmission. Can’t keep the positive loop feedback working. (look at orexin)
  • Inability to keep wakefulness
29
Q

What cause sleep apnoea?

A
  • Common condition. Affects men and often caused by excess neck fat leading to compression of airways during sleep and frequent waking
  • Obstruction of structures in the neck causing a loss of sleep due to hypoxia.
  • Causes excessive daytime sleepiness
30
Q

What are some contains of disordered consciousness?

A
  • Brain death
  • Coma
  • PVS
  • Locked in syndrome
31
Q

What is a coma?

A

Widespread brainstem and cortical damage, with various (disordered) EEG patterns detectable. Unarousable and unresponsive to psychologically meaningful stimuli. No sleep-wake cycle detectable

32
Q

What is PVS?

A

Widespread cortical damage, with various (disordered) EEG patterns detectable. Like coma but with some spontaneous eye opening. Can even localise to stimuli via brainstem reflexes. Sleep-wake cycle detectable

33
Q

What is Locked In Syndrome?

A

Can be caused by basilar/pontine artery occlusion. Eye movements can be preserved, but all other somatic motor functions lost from the pons down.

Nervous System And Neuropsychiatry (20 decks)

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