Wk 8 - Sleep

Question 1

What are three ways to measure physiological changes during sleep?

Answer 1

• Electroencephalogram (EEG) = Brain waves. Uses electrodes placed on the scalp to measure electrical activity from the brain.
• Electrooculogram (EOG) = Eye movements
• Electromyogram (EMG) = Muscle tension

Question 2

What are the two basic changes of sleep?

Answer 2

• REM and NREM

Question 3

What are the characteristics of REM sleep

Answer 3

• (All in comparison to NREM)
• Called “paradoxical sleep” because EEG signals are similar to that of waking.
• Brain activity increases in motor and sensory areas.
• Blood pressure (up to 30%) and heart rate increase
• Blood flow to the brain increases by 50-200%
• Respiration increases and varies. Coughing suppressed.
• Body temperature stops being regulated. The temp moves towards that of the surrounding environment. No shivering or sweating.

Question 4

What are the characteristics of NREM sleep?

Answer 4

(All in comparison to when awake)
- Brain activity decreases
- Heart rate slows and blood pressure lowers.
- Blood flow to the brain does not change
- Respiration decreases
- Body temperature is regulated at a lower set point than wakefulness. I.e Shivering will not start until a lower than normal temperature is reached.

Question 5

How many stages of sleep are there and which are REM and NREM? How many cycles per night?

Answer 5

• 4 stages of sleep
• Stages 1-3 are NREM sleep

-Stage 4 is REM sleep.

• A complete cycle through all these stages takes around 90-110 minutes.
• 4 to 5 cycles every night

Question 6

What brain waves are found between alert wakefulness and stage 4 sleep?

Answer 6

• In alert wakefulness: beta waves
• Just before sleep: Alpha waves
• Stage 1: Theta waves
• Stage 2: K Complex waves

Stage 3: Delta waves

Stage 4: (REM) Theta, Beta and Gamma

Question 7

Analyse these EEG signals during the sleep cycle

Answer 7

Question 8

Visualise sleep stages and quantity of cycles across a typical nights sleep

Answer 8

• The cycle begins every 80-110 minutes
• Peeps have around 4-6 cycles every night.

The amount of sleep we get decreases as we age. The REM sleep stages making up a smaller and smaller amount.

Question 9

What controls the circadian sleep cycle and where is it located?

Answer 9

• The suprachiasmatic nucleus (SCN)
• Located in the hypothalamus (Forebrain > Diencephalon > Hypothalamus)

Question 10

What dictates the circadian sleep cycle?

Answer 10

• It is dictated by the light-dark cycle from the retinohypothalamic tract
• When the retinohypothalamic tract is sectioned (cut) it prevents light-dark regulation of the circadian rhythms. When the optic tract is sectioned this does not affect it.

Question 11

What are the neural systems involved in sleep and their functions

Answer 11

• Basal Forebrain (in ventral lobe): For NREM/slow wave sleep
• Pons (some regions): For triggering REM sleep and muscle atonia.
• Reticular Formation: for waking brain from sleep.
• Hypothalamus: for transitioning between the different systems above.

Question 12

What are the proposed functions of sleep?

Answer 12

Restoration and recovery of bodily systems?
Energy conservation?
Memory consolidation?
Protection from predation?
Brain development?

Question 13

Think of some sleep disorders

Answer 13

Insomnia
Sleep Apnoea
Somnabulism
Night terrors
REM sleep behaviour disorder
Narcolepsy

Question 14

What is significant about brain activity in stage 2 sleep. What occurs.

Answer 14

In stage 2 sleep two things happen:

• First a sleep spindle fires which is a low level cluster of signals. Thought to play a role in brain plasticity and the learning and integration of new memories.
• Then a K Complex signal fires. This is thought to suppress cortical arousal and aids in sleep based memory consolidation.

sleep a sleep spindle happens where there