The Brainstem, Arousal and Sleep Flashcards

1
Q

What does the reticular formation do?

A
Sleep regulation
Motor control
Cardio/Respiratory control
Autonomic functions
Motivation and reward
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2
Q

Where is the reticular formation found?

A

In the brainstem, the pons

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3
Q

What is the ascending reticular activating system?

A

Formed by projections of the RF
Specific effects throughout the CNS to raise levels of consciousness
Filters incoming signals (LSD knock this out giving overwhelming senses)
Inhibited by hypothalamic sleep centres

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4
Q

How does the neuronal circuit work to keep us awake?

A

The brainstem send two projections to the thalamus,
One to activate the thalamus (ACh)
One to inactivate an inhibitory interneuron

So when awake or in paradoxical sleep, the brainstem is sensitising the thalamus to sensory signals and inhibiting the ‘off’ switch

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5
Q

What is an EEG?

A

Electroencephalography

Algebraic sum of the electrical activity (both excitatory and inhibitory) of neurones, from scalp

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6
Q

How do you interpret an EEG?

A

When eyes are shut, it is synchronised, the waves are low frequency and high amplitude
When eyes are open, it is desynchronised, the waves are high frequency and low amplitude

This is because when there are lots of signals they cancel each other out creating a low amplitude

Alpha waves - 8-13Hz (50muV), (mainly occipital) awake, quiet, eyes shut

Beta >14Hz, (parietal and frontal lobes) awake + eyes open

Theta 4-7Hz, (parietal and temporal lobes) Children, concentrating or meditating adults

Delta

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7
Q

What does consciousness require?

A

Requires adequate function of both the cerebral cortex and RAS

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8
Q

What is a coma?

A

A state of unconsciousness from which the person cannot be roused using pain, sound, light. Patient does not initiate any voluntary movement

Causes: intoxication, metabolic, neurological, trauma

Evaluation: GCS, Scans, blood work, EEG

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9
Q

Why do wee need sleep?

A

CNS resetting/clearance
Memory
Homeostasis (reduced sleep switches on ‘bad’ genes)

(Energy conservation - discredited, don’t save that much)

Might be a glymphatic system that is washed down with CSF

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10
Q

How is sleep controlled?

A

Reticular Formation
Hypothalamus
(Inhibits RF to promote sleep)

Biological clocks

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11
Q

What are the different sleep states?

A
Non REM
Slow wave sleep
'active body, inactive brain'
Sleepwalking
4 stages

REM
Rapid eye movement
‘active brain, inactive body’
EEG as if awake (paradoxical)

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12
Q

How does someone going to sleep look like on an EEG?

A

Alpha waves (awake)

Sleep
Stage 1 - Theta waves
Stage 2 - decreasing amplitude
Stage 3 - decreasing amplitude with some k complexes
(High amplitude peaks)
Stage 4 - Delta waves - Thalamocortical oscillations

REM - paradoxical - similar to awake

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13
Q

What functions occur during non-REM sleep?

A
Restorative - 'neurological rest'
Neuroendocrine - 90% are released
Decreased:
- Cerebral blood flow
- O2 consumption
- Body temperature
- BP
- Respiratory

Hence BMR reduced

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14
Q

What happens during REM sleep?

A
EEG waves spread from pons to thalamus then occipital lobe
Dreaming
Difficult to disturb
Irregular heart rate and respiratory rate
Increased BMR
Descending inhibition of motorneurones
Penile erection
Reduced by alcohol
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15
Q

What is the pharmacology of sleep?

A

During waking

  • 5-HT/NA constantly active
  • ACh neurones active during a novel input

Non-REM sleep

  • 5-HT and NA active
  • ACh inactive

REM

  • 5-HT inactive, NA inactive
  • ACh fully active

Coming out of REM
- Increase NA activity

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16
Q

What are some sleep disorders?

A
Insomnia
Parasomnia
- Sleep paralysis
Hypersomnia
- Daytime sleepiness
- Narcolepsy
- Obstructive sleep apnoea
17
Q

What happens in obstructive sleep apnoea?

A

Loss of tone of upper resp tract muscles, e.g. palatal muscles
Closure of airways, reducing PO2 arterial
Snoring, wakefulness