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18. Nervous System > 10. Reticular Formation > Flashcards

10. Reticular Formation Flashcards

1
Q

What is arousal?

A

Emotional state associated with some kind of goal or avoidance of something noxious.

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2
Q

What is consciousness?

A

Hard to define but to do with awareness of external world and internal states.

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3
Q

What two structures are needed for consciousness?

A

Cerebral cortex and reticular formation.

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4
Q

What is the reticular formation?

A

A population of specialised interneurones in the brainstem.

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5
Q

What are the inputs to the reticular formation that regulate arousal?

A

Sensory system, cortex.

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6
Q

What are the outputs from the reticular formation?

A

Thalamus, hypothalamus, basal forebrain nuclei, spinal cord.

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7
Q

Which part of the reticular formation is devoted to arousal?

A

Reticular activating system.

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8
Q

What is the feedback loop involved in arousal?

A

Positive - reticular activating system has stimulatory effect on cortex which stimulates RAS and so on.

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9
Q

Explain the effect the RAS has on the thalamus and thereafter.

A

ACh neurone acts on thalamus, then glutamate neurone acts on cortex.

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10
Q

Explain the effect the RAS has on the hypothalamus and thereafter.

A

ACh neurone acts on hypothalamus and histamine neurone acts on cerebral.

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11
Q

Why can antihistamines cause drowsiness?

A

They block the outflow from hypothalamus acting to stimulate the cortex.

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12
Q

Explain the effect the RAS has on the basal forebrain nuclei.

A

ACh neurone acts on basal forebrain nuclei and ACh neurones stimulate cortex.

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13
Q

Why can antimuscarinics cause drowsiness?

A

They block the outflow from the basal forebrain nuclei acting to stimulate the cortex.

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14
Q

How can consciousness be assessed?

A

Using the Glasgow Coma Scale (GCS) or electroencephalogram (EEG).

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15
Q

What are the things assessed in the GCS?

A

Eye opening, motor response, and verbal response.

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16
Q

What does an EEG measure?

A

Combined activity of thousands of neurones in a given part of the cortex to a very high temporal resolution.

17
Q

What is the baseline firing of neurones in the brain?

A

Synchronous if undisturbed.

18
Q

What is the EEG in wakefulness?

A

B waves, irregular due to interruption from sensory input, frequency 50Hz

19
Q

What is the EEG with eyes closed?

A

a wave, regular as deprived of some sensory input, frequency 10Hz.

20
Q

What is the EEG in stage 1 sleep?

A

Background of a waves with some theta waves, frequency 5Hz.

21
Q

What is the EEG in stage 2/3 sleep?

A

Background of theta waves with sleep spindles (thalamus tries waking cortex, high frequency) and K complex (cortex tends to intrinsic rate with all inputs removed, high amplitude).

22
Q

What is the EEG in stage 4 sleep?

A

Delta waves as all inputs removed, frequency 1Hz.

23
Q

What is the EEG in REM sleep?

A

B waves like wakefulness as cortex has input from dreams, frequency 50Hz.

24
Q

How is muscle tone lost in REM sleep?

A

Descending inhibition of LMNs by glycinergic fibres from reticular formation and running down from reticulospinal tracts.

25
Q

What actions are preserved in REM sleep?

A

Eye movements and some other cranial nerve functions, autonomic effects are seen (penile erection, loss of thermoregulation).

26
Q

What are the functions of sleep?

A

Enigmatic (mystery!), energy conservation and bodily repair?, memory consolidation?, clearance of extracellular debris?, resetting of the CNS?.

27
Q

What are some disorders of sleep?

A

Insomnia, narcolepsy, sleep apnoea.

28
Q

What is insomnia linked to?

A

Mental health, so may not be a problem with neurology.

29
Q

What could narcolepsy be due to?

A

Loss of transmission between eyes and hypothalamus.

30
Q

What could sleep apnoea be due to?

A

Fat necks compress airways in the night causing hypoxia and waking up in night -> excessive daytime sleepiness.

31
Q

What are some disorders of consciousness?

A

Brain death, coma, PVS (persistent vegetative state), locked in syndrome.

32
Q

What is brain death?

A

Widespread cortical and brainstem damage with flat EEG.

33
Q

What is a coma?

A

Widespread brainstem and cortical damage with various disordered EEG patterns. Unarousable and unresponsive to stimuli, no sleep-wake cycle.

34
Q

What is PVS?

A

Widespread cortical damage with various disordered EEG patterns. Some spontaneous eye opening and possible brainstem reflexes, sleep-wake cycle detectable.

35
Q

What can cause locked in syndrome?

A

Basilar/pontine artery occlusions so corticospinal tract destroyed.

36
Q

What is locked in syndrome?

A

Some eye movements preserved but other somatic motor functions lost from pons down.

18. Nervous System (17 decks)

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