EEG, Sleep and Circadian Rhythm

Question 1

Where is it suspected that the active inhibitory processes that lead to sleep originate?

Answer 1

• In the reticular formation of the pons
• If the brainstem is destroyed at the mid pons, the brain loses the ability to sleep. Probably originates from below this level

Question 2

How is release of melatonin controlled by the hypothalamus?

Answer 2

• The suprachiasmatic nuclei (SCN) of the hypothalamus inhibits the pineal gland when exposed to light, and therefore inhibits melatonin release
• Darkness corresponds to decreased SCN activity and therefore increased melatonin release by the pineal

Question 3

Where is melatonin made and released from?

Answer 3

The pineal gland

Question 4

Which hormone facilitates SCN inhibition of the pineal gland?

Answer 4

• Orexin (released by hypothalamus during bright hours)

- AKA hypocretin

Question 5

What is narcolepsy?

Answer 5

The condition of being unable to regulate sleep appropriately

• The narcoleptic patient will fall asleep at inappropriate times and often have daytime drowsiness
• Usually due to inadequate orexin (hypocretin) production

Question 6

Likely reason that serotonin is necessary for sleep induction?

Answer 6

• Serotonin is a precursor to melatonin in melatonin production
• Serotonin Selective Reuptake Inhibitors can treat sleep disruption, act to increase serotonin levels in synapse

Question 7

What does EEG stand for? What is it used to record?

Answer 7

• Electroencephalogram

- Records electrical activity in the brain

Question 8

Main characteristics of an EEG wave?

Answer 8

• Amplitude

- Frequency (increases with neuronal excitation)

Question 9

What are the four main types of EEG waves?

Answer 9

• Alpha
• Beta
• Theta
• Delta

Question 10

In a relaxed, awake state what sort of EEG waves are seen?

Answer 10

Alpha waves

• High frequency, high amplitude

Question 11

In an alert, awake state what sort of EEG waves are seen?

Answer 11

Beta waves

• High frequency, low amplitude waves.
• Waves are asynchronous because brain is doing so much at once that opposing polarities of signals cancel eachother out and are not recorded

Question 12

Which waves are common in children and during times of emotional stress/frustration?

Answer 12

• Theta waves

- Low frequency, varying amplitude

Question 13

Which waves only occur during sleep?

Answer 13

Delta waves

• Low frequency and high amplitude

Question 14

5 stages of sleep and brief description of each?

Answer 14

• Stage 1: low frequency theta waves, light sleep.
• Stage 2: eye movements stop, slower frequency. Clusters of rhythmic waves (sleep spindles) on EEG
• Stage 3: high amplitude, v slow delta waves. Sleep spindle activity declines
• Stage 4: Exclusively delta waves (stage 3&4 known as deep sleep, hard to rouse from)
• REM sleep: rapid eye movements, dreams occur here

Question 15

How does amplitude vary with sleep stages?

Answer 15

Larger amplitudes associated with deeper sleep

Question 16

How does REM sleep look on an EEG?

Answer 16

Fast waves, quite similar to the awake state

• Desynchronized, high frequency, low amplitude

Question 17

What is the most restful type of sleep and when does it occur?

Answer 17

Deep sleep

Occurs in the first hours of sleep, associated with drop in vascular tone (BP) and metabolic rate

Question 18

After the initial S-wave sleep of stages 3 and 4 what occurs?

Answer 18

A gradual awakening towards stage 1, but not the initial stage 1 - instead REM sleep

Question 19

Characteristics of REM sleep?

Answer 19

• Dreams occur
• Eye muscles move rapidly, pons inhibits other skeletal muscles
• HR/RR become irregular, brain metabolism increases
• Difficult to arouse an individual from REM sleep
• Whenever deprived of REM sleep there is a catch up period during next sleep

Question 20

What behaviours do sleep deprived subjects demonstrate?

Answer 20

• Impaired cognitive function
• Impaired physical performance
• Sluggishness
• Irritability

Question 21

What are some of the important functions sleep supports?

Answer 21

• Neuronal plasticity
• Learning and memory
• Cognition
• Clearance of waste products from CNS
• Conservation of whole body energy
• Immune function

Question 22

How does sleep change as an individual ages?

Answer 22

• Total sleep time declines drastically over a lifetime

- REM sleep percentage also decreases (from about 50% in infant, to 25% in an adult, may be absent in elderly)

Question 23

5 common sleep disorders?

Answer 23

1. Insomnia
2. Nightmares
3. Night terrors
4. Somnambulism
5. Narcolepsy

Question 24

How is insomnia defined? What are the two types?

Answer 24

• Chronic inability to obtain the necessary amount of quality sleep to maintain daytime behaviour

1. Chronic - usually no identifiable cause
2. Temporary - in response to pain etc. Usually short lived

Question 25

Which individuals tend to experience night terrors?

How are they different to nightmares?

Answer 25

• Children age 3-8
• Nightmare is visual, waking stops it and individual remembers the dream. Night terrors may cause individual to react physically, not remembered the following morning

Question 26

What is somnambulism? Characteristics of the disorder?

Answer 26

• Sleep walking

- Individual often walks with eyes open and can carry out certain tasks, no recollection of episode the next morning