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SO-Nervous System > Reticular Formation > Flashcards

Reticular Formation Flashcards

1
Q

What is arousal?

A

The emotional state associated with some kind of goal or avoidance of something noxious

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2
Q

What is consciousness?

A

Difficult to determine, something to do with ‘awareness’ of both external world and internal states

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3
Q

What parts of the brain are required for consciousness?

A
  • Cerebral cortex
  • 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 inputs to the reticular system regulate the level of arousal?

A
  • Inputs from sensory system
  • Inputs from cortex
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6
Q

What are the widespread outputs from the reticular formation?

A
  • Thalamus
  • Hypothalamus
  • Basal forebrain
  • Spinal cord
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7
Q

What is the part of the reticular formation that is devoted to arousal?

A

The reticular activating system

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8
Q

Where is the reticular formation found?

A

In the brainstem

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9
Q

What does the reticular formation consist of?

A

Diffuse population of interneurones

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10
Q

What are the major inputs to the reticular system?

A
  • Sensory system
  • Cerebral cortex
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11
Q

Describe the relationship between the reticular activating system and the cerebral cortex?

A

The cerebral cortex sends excitatory projections to the reticular formation, and the reticular formation activates the cortex - mutual excitation produces a positive feedback loop

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12
Q

What is the importance of the positive feedback loop produced between the cerebral cortex and the reticular activating formation?

A

It produces an all or nothing phenomenon which is required to maintain the awake state

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13
Q

Give two methods of assessing consciousness

A
  • The glasgow coma scale
  • EEG
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14
Q

What does the EEG measure?

A

Combined activity of thousands of neurones in a given part of the cortex

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15
Q

Describe the resolution of the EEG

A
  • Very high temporal resolution
  • Very poor spatial resolution
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16
Q

What do neurones in the brain tend to do when deprived of sensory input?

A

Fire synchonously

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17
Q

What happens to the EEG during sleep?

A

You typically pass through 6 stages of sleep, progressing from an awake state through to stage 4, and then periodically going from stage 4 rapidly up into REM sleep

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18
Q

What does the EEG show going down to the first 4 stages of sleep?

A

Decreasing frequency and increasing amplitude, as neuronal populations in the cortex become synchronous

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19
Q

Describe the brainwaves in an awake person

A
  • ß-waves at about 50Hz
  • Irregular
20
Q

Why are the brainwaves in an awake person irregular?

A

Because you are processing sensory input

21
Q

Describe the brain waves of a person with their eyes closed

A
  • Alpha waves, at about 10Hz frequency
  • More regular
22
Q

What happens with increasing synchronicity amongst neurones?

A

Increased amplitude

23
Q

Describe the brainwaves in stage 1 sleep

A

Background of alpha waves with occasional low frequency θ waves at about 5Hz

24
Q

Describe the brainwaves in stage 2/3 sleep

A

Background of θ, but ocassional bursts of activity called sleep spindles. Occassionally get very big waves called K complexes

25
Q

What are sleep spindles?

A

Attempt by the thalamus to wake the cortex - K complex is the cortex trying to go back to the intrinsic rate

26
Q

Describe the brainwaves in stage 4 of sleep

A

Just see delta waves at a frequency of 1 per second, as cortex is now acting independantly of reticular formation

27
Q

What is the neural mechanism of sleep?

A

Complex, but is basically about ‘deactivating’ the reticular activating system, and hence teh cortex, and inhibiting the thalamus

28
Q

What happens to the positive feedback loop between the reticular activating system and the thalamus in sleep?

A

It is inhibited, leading to decreased cortical activity

29
Q

What is inhibition of the positive feedback loop between the reticular activating system and the cortex assisted by?

A

Removal of sensory inputs

30
Q

What is REM sleep initiated by?

A

Groups of neurones in the pons

31
Q

Describe the EEG activity in REM sleep

A

SImilar to that seen during arousal, with beta waves

32
Q

Why is the person difficult to rouse in REM sleep?

A

Due to strong inhibition of the thalamus

33
Q

What happens to muscle tone in most of the body during REM sleep?

A

It is lost due to descending inhibition of LMNs by glycinergic fibres arising from the reticular formation, and running down the reticulospinal tracts

34
Q

What functions are preserved during REM sleep?

A

Eye movements and some other cranial nerve functions

35
Q

What autonomic effects are seen during REM sleep?

A
  • Penile erection
  • Loss of thermoregulation
36
Q

How is penile erection during REM sleep clinically useful?

A

Good for determining if physiological or psychological impotence

37
Q

Give three examples of disorders of sleep

A
  • Insomnia
  • Nacrolepsy
  • Sleep apnoea
38
Q

What are the common causes of insomnia?

A

Anxiety and mental health

Rarely neurological

39
Q

Give four examples of disorders of consciousness

A
  • Brain death
  • Coma
  • Persistent vegetative state
  • Locked in syndrome
40
Q

What is brain death?

A

Widespread cortical and braimstem damage

41
Q

What is shown on the EEG in brain death?

A

Flatline

42
Q

What is a coma?

A

Widespread brainstem and cortical damage, with various (disordered) EEG patterns detectable. Unarousable and unresponsive to psychologically meaningful stimuli.

43
Q

Is a sleep-wake cycle detectable in coma?

A

No

44
Q

How does persistant vegetative state differ from a coma?

A
  • Some spontaneous eye opening
  • Can localise stimuli via brainstem reflexes
  • Sleep-wake cycle detectable
45
Q

What can locked in syndrome be caused by?

A

Basilar/pontine artery occlsuion

46
Q

What happens to motor functions in locked in syndrome?

A

Eye movements can be preserved, but all other somatic motor functions are lost from the pons down

SO-Nervous System (18 decks)

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