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PHYS - NEURO > 10. SLEEP > Flashcards

10. SLEEP Flashcards

1
Q

What are brain rhythms?

A
  • Brain rhythms are distinct patterns of neuronal activity that are associated with arousal, sleep state & specific behaviours
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2
Q

How can brain rhythms be measured?

A
  • Brain rhythms can be measured with EEGs
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3
Q

What is an EEG?

A
  • Electroencephalogram measures electrical activity produced by the brain
  • EEG involves placing non-invasive electrodes onto the scalp
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4
Q

What produces EEG signals?

A

The combined activity of large groups of similarly orientated neurones produces EEG signals
- Requires synchronous activity to produce summed action potential EEG signals

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5
Q

What are the two main categories of brain waves?

A
  1. HIGH AMPLITUDE, LOW FREQUENCY = Wakefulness & Alertness

2. LOW AMPLITUDE, HIGH FREQUENCY = Non-dreaming sleep

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6
Q

What are the four types of brain waves?

A
  1. Beta
  2. Alpha
  3. Theta
  4. Delta
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7
Q

What are the characteristics of beta waves?

A
  • Beta waves have a high frequency & low amplitude
  • 14 -30 Hz
  • Awake with mental activity
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8
Q

What are the characteristics of alpha waves?

A
  • Alpha waves have a high frequency & low amplitude
  • 8 -13 Hz
  • Awake & resting
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9
Q

What are the characteristics of theta waves?

A
  • Low frequency, high amplitude
  • 4- 7 Hz
  • Sleeping
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10
Q

What are the characteristics of delta waves?

A
  • Low frequency, low amplitude
  • < 4Hz
  • Deep sleep
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11
Q

What are the two ways to generate synchronous brain rhythms?

A
  • Synchronous brain rhythms can be generated with:
    1. PACEMAKER
    2. COLLECTIVE BEHAVIOUR
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12
Q

What is the pacemaker of the brain?

A
  • Thalamus
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13
Q

How does the thalamus generate synchronous activity?

A
  • A small group of central thalamic neurones can influence a large group of cortical neurones
  • The thalamic neurones project into the cerebral cortex
  • Synaptic connection between the excitatory & inhibitory thalamic neurones, forces each individual neurone to follow the rhythm
  • These co-ordinated rhythms will then be passed on to the cortex
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14
Q

Describe the collective behaviour of cortical neurones to produce synchronous brain rhythms?

A
  • In some regions of the cerebral cortex, the rhythms rely on collective interactions of the cortical neurones
  • Co-ordinated patterns of synchronous activity are produced due to the interconnections between cortical neurones
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15
Q

Define sleep

A
  • Sleep is a reversible state of reduced responsiveness or decreased interaction with the environment
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16
Q

What are the characteristics of the brain rhythm for wakefulness?

A
  • High frequency, low amplitude
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17
Q

Describe sensation, thought & movement for wakelfulness?

A
  • SENSATION = vivid, externally generated
  • THOUGHT - Logical progressive
  • MOVEMEMENT - Continuous, voluntary
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18
Q

What are the two types of sleep?

A
  1. NON-REM SLEEP

2. REM SLEEP

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19
Q

What is non-REM sleep?

A
  • In NON-REM sleep, the body is capable of involuntary movement. Sleeping is rarely accompanied by vivid dreams
20
Q

What is the brain rhythm for NON-REM sleep?

A
  • Low frequency, high amplitude
21
Q

What happens to thought, sensation & movement during NON-REM sleep?

A
  • SENSATION - Dull/absent
  • THOUGHT - Logical, repetitive
  • MOVEMENT - occasional, involuntary
22
Q

What is REM sleep?

A
  • REM sleep is a state of muscle paralysis (immobilised) accompanied by vivid dreams
23
Q

What is the brain rhythm for REM sleep?

A
  • REM sleep has high frequency, low amplitude brain waves
24
Q

What happens to thought, sensation & movement during REM sleep?

A
  • SENSATION = vivid, internally generated
  • THOUGHT = bizarre, illogical
  • MOVEMENT - muscle paralysis
25
Q

What happens to temperature in non-REM & REM sleep?

A
  • Core body temperature drops for both REM & NON-REM sleep

- But temperature drops more in REM sleep

26
Q

What happens to heart rate & breathing in non-REM & REM sleep?

A
  • Heart rate & breathing rate both decrease in REM & NON-REM sleep
  • But heart rate & breathing rate is much lower for NON-REM sleep
  • Heart rate & breathing are irregular during REM sleep
27
Q

What happens to brain oxygen/energy consumption during REM/NON-REM sleep?

A
  • During NON-REM sleep - brain energy consumption decreases

- But during REM sleep, brain energy consumption increases, which is balanced by the drop in muscle movement (paralysis)

28
Q

Describe the characteristics of a sleep cycle?

A
  • Sleep begins with non-REM sleep &gradually progresses into REM sleep.
    There are four stages of sleep, where it cycles between REM sleep and non-REM sleep
  • ## The sleep stages are then cycled, repeating every 90 minutes
29
Q

What are the two proposed theories for the function of sleep?

A
  1. RESTORATION - restore & recover to prepare for next day

2. ADAPTATION - Sleep is a way to conserve energy & protect us

30
Q

What happens to brain stem activity during wakefulness?

A
  • During wakefulness, there’s increased brain stem activity
  • Increased firing of brain stem neurones, to produce neurotransmitters that promote wakefulness
  • These neurones project to the thalamus & cortex
  • Effect of brain stem neurone is inhibitory, supressing thalamus & cortex
31
Q

What happens to brain stem activity during sleep?

A
  • During sleep, there’s decreased brain stem activity
  • Decreased firing from the brain stem, reduces the inhibitory output on thalamus & cortex
  • Thalamus is no longer suppressed
  • Both thalamus & cortex are active
  • But the rhythmic firing of the thalamus blocks the flow of sensory information into the cerebral cortex during sleep
32
Q

Which area of the brain is associated with dreaming and is active during sleep?

A
  • The pons is active during sleep & is thought to be associated with dreaming
  • There’s increased firing if cholinergic neurone sin the pons, which is associated with dreaming
  • Activates areas of cerebral cortex which are involved in eliciting emotions & memories
33
Q

What are 4 sleep promoting factors?

A
  1. ADENOSINE
  2. NITRIC OXIDE
  3. INFLAMMATORY MEDIATORS
  4. MELATONIN
34
Q

What is adenosine?

A
  • Adenosine the building block for ATP

- It accumulates throughout the day

35
Q

How does adenosine promote sleep?

A
  • Adenosine binds to it’s receptor to cause decreased heart rate, respiratory rate & decreased contraction of smooth muscle. Overall, reducing blood pressure
  • Adenosine also has an inhibitory effect on neurotransmitters that promote wakefulness such as acetylcholine, serotonin etc.
  • Adenosine is highest in the late evening to induce sleep & begins to fall during sleep
36
Q

What can adenosine antagonists do?

A
  • Adenosine antagonists can bind to the adenosine receptor to promote wakefulness as it prevents the induction of sleep
  • Caffeine is a adenosine antagonist
37
Q

What is nitric oxide?

A
  • Nitric oxide is a potent vasodilator, which dilate blood vessels causing a drop in blood pressure
38
Q

How can nitric oxide promote sleep?

A
  • Nitric oxide decreases blood pressure
  • Nitric oxide also stimulates adenosine release
  • Adenosine stimulates sleep, by blocking the neurones that produce neurotransmitters involved in wakefulness
39
Q

How can inflammatory mediators promote sleep?

A
  • Inflammatory mediators can be released during infection

- Interleukin 1 can promote sleepiness

40
Q

Where is melatonin released from?

A
  • Melatonin is a hormone released by the pineal gland
41
Q

How does melatonin promote sleep?

A
  • Melatonin levels rise in the late evening & peak in the early hours of the morning (e.g 1AM).
  • Melatonin levels fall just before we wake
  • Melatonin is involved in initiating & maintaining sleep
42
Q

What is a circadian rhythm?

A
  • A circadian rhythm refers to any period of rhythm within 24 hours
  • E.g sleep/wake
43
Q

What are zeitgebers?

A
  • Zeitgebers are environmental time cues such as temperature, light, humidity
44
Q

What is the suprachiasmatic nucleus?

A
  • SCN is a small nucleus in the hypothalamus which receives input from retinal innervation
  • The SCN synchronises the circadian rhythm with the daily light/dark cycle
45
Q

What happens in the absence of the SCN or cues?

A
  • In the absence of cues, the SCN is still able to regulate circadian rhythms
  • If the SCN is inhibited, sleep can still be coordinated with light/dark cycles
46
Q

How does the SCN regulate the rhythmicity of circadian rhythms?

A
  • SCN clock genes produce a protein
  • This protein feeds back to the SCN to inhibit production of the protein by decreasing gene expression
  • Negative feedback of protein
  • Light information form retina resets SCN neurones
  • Each individual SCN neurone is a biological clock
  • SCN has control over circadian clocks in our body e.g stomach, liver

PHYS - NEURO (18 decks)

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