Sleep Psychology

Why do we develop evolved behaviours?

We assume the behaviour provides benefit over those who do not elicit said behaviour

Definition of sleep

A period of inactivity during the darkest hours of the day

What four actions must early humans have done?

Hunt, forage, reproduce and survive from predators

Why sleep in the darkest hours?

The darkest hours would’ve made it difficult for humans to hunt and forage while making us more susceptible to predators with superior eyesight

Why is it better to be sedentary when asleep?

Saves calories

What other “communal benefits” does sleeping provide?

Communal behaviours such as sleeping together could’ve let to increased chances of reproduction

List the evolutionary reasons for sleeping

• Provides benefits over those who dont

• Human need to hunt, forage, reproduce and survive from predators

• Dark hours make It difficult to forage and hunt plus give an advantage to predators with superior eyesight

• Communal sleep may encourage reproduction

What/why does our body carry out necessary functions?

• To remove biological waste

• Produce hormones and neurotransmitters

• Repair tissues

What chemicals does our body clear out during our sleep and why?

Chemicals like beta-amyloid and adenosine build in the brain, and the brain has time to clear it out during sleep, ensuring the brain can function at optimal level

Explain circadian rhythm

Timing for sleep is regulated by a circadian rhythm, our internal body clock which regulates the melatonin enabling us to sleep.

Break down sleep

• 1.5hr cycles

• 4-6 cycles per sleep

• REM and non-REM

Explain NREM-1

• Lightest sleep

• First stage

• 1-7 mins (max 10)

• Decreased heart rate and eye movement

• Relaxed muscles (occasional twitches)

• Only occurs once during entire sleep

• Producing alpha waves before producing theta waves

NREM2

• Light sleep

• 10-25 mins

• Heart rate continues decreasing

• Eye movement stops

• Increased muscle relaxation (still occasional twitches)

• Increases in duration in following cycles

• Theta waves

NREM 3

• Deep sleep

• 20-40 mins decreasing in subsequent cycles (may not even occur eventually)

• Minimal eyemoment

• Muscles at peak relaxation

• Heart rate further decreased

• Human growth hormones released

REM Sleep

• 10-60 mins long increasing in subsequent cycles

• more REM in childhood

• Heart rate matches waking heart rate

• Eye moves rapidly but vision isnt transmitted to brain

• Muscles either than those aiding in breathing or eyemovement are paralysed

• Dreams occur

• Brain is almost as active as when awake with Beta waves