Sleep (L5)

Question 1

What is meant by…

• Circannual
• Circadian

Answer 1

Circannual - about a year

Circadian - about a day

Question 2

Rhythms

Answer 2

• Endogenously generated but can be modulated by external cues (zeitgebers)
• Patterns of brain activity, hormone production and cell regeneration

Question 3

Human biological clock

Answer 3

• Discovered by Carl Richter
  1. Waking signals: Neurons in the upper pons produce Ach which activates the thalamus then the cerebral cortex
  2. Brain tires: As ATP breaks down, adenosine builds up and triggers neuron activity in the ventrolateral preoptic nucleus
  3. Suprachiasmatic nucleus acts as the brain’s clock
  4. VLPO neurons release GABA and galanin which inhibit the ascending arousal system in the hypothalamus and pons

Question 4

Suprachiasmatic nucleus (SCN)

Answer 4

• Part of the hypothalamus
• Main control centre of circadian rhythms
• Controlled by signals from the retina in the day and by melatonin from the pineal gland at night

Question 5

Stages of sleep

Answer 5

• Measured using polysomnography (EEG and eye tracking)
• 3 stages of non-REM and 1 stage of REM
• 90 min cycle
• Human sleep cycle is 25.1 hours

Question 6

NREM stage 1

Answer 6

• Light sleep
• Theta waves
• Fleeting thoughts
• Eyes move slowly
• Reduced muscle activity

Question 7

Awake

Answer 7

• Beta waves

- Alpha waves when drowsy

Question 8

NREM stage 2

Answer 8

• Light sleep
• Theta waves
• Sleep spindles (0.5s bursts of 10-16Hz waves)
• K-complexes (sharp negative then smaller positive wave)

Question 9

NREM stage 3

Answer 9

• Deep sleep
• Delta waves
• Heart, breathing rate and temp decrease
• Reduced brain activity and muscle tone

Question 10

REM sleep

Answer 10

• Rapid eye movement
• Heart rate and blood pressure increases
• Proportion increases during the night
• Paradoxical sleep
• Partial muscle paralysis

Question 11

What 3 vital bodily functions does sleep deprivation affect?

Answer 11

1. Thermoregulation
2. Immune system
3. Metabolism
   - Associated with decreased attention and working memory

Question 12

Insomnia

Answer 12

• Inadequate sleep caused by noise, stress, pain, diet, medication, etc.
• May be due to shifts in circadian rhythms

Question 13

Sleep apnea

Answer 13

• Inability to breathe during sleep
• Symptoms include sleepiness during the day, impaired attention and depression
• Therapies involve weight loss, drugs or sleep

Question 14

Narcoplepsy

Answer 14

• Frequent unexpected periods of sleepiness during the day
• REM sleep intruding into wakefulness
• Caused by lack of the hypothalamic cells that produce and release orexin
• Treated with stimulant drugs such as Ritalin

Question 15

Periodic limb movement disorder

Answer 15

Repeated involuntary limb movements that can cause insomnia

Question 16

REM behaviour disorder

Answer 16

Movement during REM period apparently acting out their dreams

Question 17

Night terrors

Answer 17

An abrupt, anxious awakening from NREM sleep

Question 18

Sleepwalking

Answer 18

Usually occurs during stages 3/4

Question 19

What are the functions of sleep?

Answer 19

• Energy conservation (eg. animals increase sleep during hibernation)
• Memory consolidation

Question 20

What is the effect of depriving people of…

• NREM sleep
• REM sleep

Answer 20

NREM sleep: impaired verbal learning, fatigue, hypersensitivity to muscle and bone pain
REM sleep: memory problems, excessive aggression

Question 21

Consiousness

Answer 21

• Sleep is a state of unconsciousness
• Dreams are an altered state of consciousness
• Pre-sleep consciousness is called the hypnagogic state
• Post-sleep consciousness is called the hypnopompic state

Question 22

Sleeping pills

Answer 22

• Usually benzodiazepines
• People become dependent and tolerant
• Reduce the proportion of time spent in REM sleep

Question 23

Sleep paralysis

Answer 23

• Experience of waking up unable to move

Question 24

Dream theories

Answer 24

• Freud proposed that dreams represent unacceptable wishes (supressed thought)
• Hobson + McCarley suggested that dreams are produced when the mind attempts to make sense of random neural activity during sleep

Question 25

What occurs in the brain during dreaming?

Answer 25

• Amygdala is activated (associated with emotion)
• Visual association cortex is activated
• Motor cortex is activated (spinal neurons inhibit this expression)
• Prefrontal cortex is deactivated (lack of planning)

Question 26

Lucid dreaming

Answer 26

The awareness of dreaming during the dream