Sleep

Question 1

What is the behavioural criteria of sleep and how can it be monitored

Answer 1

Stereotypic posture, minimal movement, reduced responsiveness to external stimuli, reversible with stimulation

Sleep can be monitored via EEG (electroencephalogram), EOG (electrooculogram) and EMG (electromyogram). They monitor brain activity, eye movement and muscle tone (jaw).

Question 2

Explain the stages of sleep

Answer 2

Awake - EEG is active with fast rhythm, EOG is moderately moving and EMG is moving

1. Stages 1 and 2 (REM): no eye movement (EOG no movement) less and slower EEG and EMG.
2. Stages 3 and 4 (NREM): EEG is slowest, eye movement speeds up, and EMG slows down
3. Stage 5 (REM): eye movement very quick, brain activity is similar to when awake but muscle tone is zero baseline (EMG)

A single sleep cycle is around 90 minutes, you have multiple sleep cycles periodically during the night

Question 3

Explain the control of sleep

Answer 3

1. RAS - starts in the brain stem and projects upwards to control consciousness
2. Lateral hypothalamus - promotes wakefulness - neurotransmitter (one in and hypocretin) (condition of too much sleep is low hypocretin)
3. Ventrolateral pre-optic nucleus - promotes sleep and thus negative effect on consciousness
4. Suprachiasmatic nucleus - synchronises sleep with falling light level, tracks level of light via melatonin (jet lag) .

Question 4

Describe the effect of sleep deprivation

Answer 4

Psychiatric: sleepiness, irritability, stress, mood fluctuations, depression, impulsivity

Neurological: impaired attention, memory, executive function, risk of errors and accidents, neurodegeneration

Somatic: glucose intolerance, increased appetite, reduced Leptin, impaired immunity, increased risk of cancer and death

After loss of sleep the RAS tries to regulate via reduced latency to sleep, increase of slow wave NREM, and increase REM sleep.

Question 5

Explain how dreams work

Answer 5

Occur in NREM and REM (mostly), can be more easily recalled from REM sleep, brain activity in limbic system is higher than in frontal lobe (more emotions than logic)

Function of dreams is a safety valve for antisocial behaviour, disposal of unwanted emotions and memory consolidation. ,

Question 6

Explain three sleep disorders

Answer 6

1. Insomnia: high prevalence, causes may be psychological eg sleep apnoea, chronic pain, brain dysfunction eg depression and treatment includes: sleep hygiene, hypnotics, sleep CBT
2. Hypersomia: poor quality of sleep at night. Due to obstructive sleep apnoea, restless leg syndrome, medication, nocturnal pain, narcolepsy, post traumatic brain injury
3. Narcolepsy: falling asleep repeatedly during the day because of poor quality of sleep during the night, also due to cataplexy, dysfunction of control of REM sleep and orexin/hypocretin deficiency