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Neurophysiology & Human Behaviour > Arousal & sleep > Flashcards

Arousal & sleep Flashcards

1
Q

What are the different types of dendritic structures found in the reticular formation?

A
  1. Isodendritic: Dendrites radiate in uniform directions over large distances (diffuse), usually perpendicular to the axis of the brainstem. This is the most common form of dendrite arrangement.
  2. Allodendritic: More specialised dendritic radiations in a smaller area.
  3. Idiodendritic: Dendrites are located within very small and specialised nuclei within the brainstem.
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2
Q

What are the longitudinal zones of the reticular formation?

A
  • Raphe: Close to the midline
  • Medial zone: Contains many large neurones with long descending axons involved in motor control
  • Lateral zone: Contains smaller neurones with short ascending axons involved in sensory-related tasks
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3
Q

What are the functions of the reticular formation?

A
  1. Ascending projection: Involved in regulation of levels of activity in the brain (such as those involved in sleep, attention, arousal…)
  2. Descending projections: Involved in stereotyped motor activities (such as swallowing, chewing, vomiting, sneezing, eye movements…) as well as control of basic involuntary actions (such as breathing and cardiovascular control)
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4
Q

What are the rostral continuations of the reticular formation?

A

Lateral hypothalamus and subthalamic regions

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5
Q

What are the caudal continuations of the reticular formation?

A

Intermediate grey of the spinal cord

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6
Q

What are the projections of the reticular formation into the cortex?

A
  1. Direct: Via medial forebrain bundle (through lateral hypothalamus)
  2. Indirect: Via intralaminar nuclei of thalamus
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7
Q

What are the different neurotransmitters used by the cortical projecting RF neurones?

A
  1. NA
  2. 5-HT
  3. DA
  4. ACh
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8
Q

What are the origins and functions of NA neurones from RF?

A

Origins: Locus ceruleus

Functions: Increases general cortical responses to sensory stimuli, increasing cortical signal-to-noise ratio

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9
Q

What are the origins and functions of the DA neurones from RF?

A

Origins: Ventral tegumental area, substantia nigra

Functions:

  • Projections into ventral striatum: Mediates appetitive motivated behaviours
  • Projections into dorsal striatum: Mediates gating of motor activity and thus consummatory behaviours
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10
Q

What are the origins and functions of the 5-HT neurones from RF?

A

Origins: Raphe nucleus

Functions: May be involved in gating and inhibition of impulsive responses to sensory stimuli

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11
Q

What conditions are related to defects in the 5-HT system?

A

Obsessive compulsive disorders

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12
Q

What are the origins and functions of the ACh neurones from RF?

A

Origins: Various (inc. substantia innominata)

Functions:

  • Forebrain projections: Learning and memory
  • Thalamus: Gating sensory information access to the cortex
  • Peduncopontine projections: Sleep
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13
Q

What are electroencephalograms (EEGs)?

A

Measurements are taken as electrical activity from the scalp, usually as a result of summation of slow changes in membrane potentials (e.g. EPSPs, IPSPs) in cortical neurones.

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14
Q

What is the general relationship between cortical activity and EEG?

A

Lower activity → Higher amplitude EEGs

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15
Q

What are the types of EEG waveforms?

A
  1. Delta (<4 Hz)
  2. Theta (4-7 Hz)
  3. Alpha (8-15 Hz)
  4. Beta (16-31 Hz)
  5. Gamma (>32 Hz)
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16
Q

What types of activities are associated with delta waves?

A
  • Slow-wave (deep) sleep – adult
  • Babies
17
Q

What types of activities are associated with theta waves?

A
  • Young children
  • Drowsiness (adults)
  • Inhibition of responses
18
Q

What types of activities are associated with alpha waves?

A
  • Relaxation
  • Resting (closing eyes)
19
Q

What types of activities are associated with beta waves?

A
  • High frequency, low amplitude
  • Thinking/focus
  • Anxiety
  • Stress
20
Q

What types of activities are associated with gamma waves?

A
  • Integration of sensory modalities
  • Memorisation tasks
21
Q

What are the stages of non-REM sleep?

A
  1. Stage 1 (Drowsy period): Falling asleep, whereby the high frequency, low amplitude waves of the awake state give way to lower frequency, higher amplitude waves. This stage is characterised by theta waves.
  2. Stage 2 (Light sleep): Further decrease in frequency of synchronised brain activity, with occasional high frequency spikes.
  3. Stage 3 (Moderate-deep sleep): Further decrease in frequency and increase in amplitude of waves.
  4. Stage 4 (deep sleep): Stage of sleep with the lowest frequency and highest amplitude of synchronised activity waves known as delta waves.
22
Q

What is the general pattern of change in EEGs as one descends from wakefullness into deep sleep?

A
  1. ↑ Amplitude
  2. ↓ Frequency
23
Q

What are the physiological changes that occur during non-REM sleep?

A
  1. Decreased muscle tone
  2. Decreased heart rate
  3. Decreased breathing rate
  4. Decreased blood pressure
  5. Decreased metabolic rate
24
Q

What are the physiological changes that occur during REM sleep?

A
  1. Increased blood pressure
  2. Increased heart rate
  3. Increased metabolic rate
  4. Rapid eye movements
25
Q

What is the general shape of the sleep cycle?

A
  • 90 minute cycles alternating between REM and non-REM sleep
  • Progressively shallower sleep as the sleep cycle continues
26
Q

What are the possible functions of sleep?

A
  1. Restoration of physiological/neurological function
  2. Brain development (children)
  3. Memory consolidation
27
Q

What are the neural changes that occur during wake → non-REM sleep transition?

A
  • ↓ ACh (peduncopontine)
  • ↓ NA
  • ↓ 5-HT
28
Q

What are the neural changes that occur during the non-REM sleep → REM sleep transition?

A
  • ↑ ACh (peduncopontine)
  • ↓ NA
  • ↓ 5-HT
29
Q

What are the changes in the cortex that occur in sleep?

A
  • Non-REM: Cortical activity depressed so that there are no cognitive processes present
  • REM: Cortical activity analogous to wakeful state and cognitive processes are present but sensory inputs and outputs are inhibited (i.e. cortex disconnected from outside world)
30
Q

What is the flip-flop model for control of sleep-wakefulness?

A
  • There is mutual inhibition between the ventrolateral preoptic area (VLPA) that promotes sleep and the RF arousal systems (e.g. NA, 5-HT…) that promote wakefulness.
  • Balance between inhibition of these 2 components determine whether individual is asleep or awake.
  • External systems alter this balance and thus together control sleep-wakefulness.
31
Q

What is narcolepsy?

A

Frequent, sudden attacks of REM sleep during day for a few minutes. This may be accompanied by cataplexy (loss of motor control).

32
Q

What is narcolepsy possibly caused by?

A

Mutations in orexin gene

33
Q

What is the relationship between feeding and sleep?

A
  • Hunger inhibits sleep while satiety promotes sleep
  • Due to high [orexin] during hunger and low [orexin] during satiety
34
Q

Which part of the brain is resposible for circadian rhythms?

A

Suprachiasmatic nucleus (hypothalamus)

35
Q

What is the main mechanism by which circadian rhythms are synchronised to the day-night cycle?

A

Blue light (zeitgeber) detected by melanopsin in ipRGCs

36
Q

What is a pathway by which circadian rhythms may be used to control sleep?

A

SCN → Dorsomedial nucleus (DMN) of hypothalamus → VLPA hypothalamus (promotes sleep)

Neurophysiology & Human Behaviour (20 decks)

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