Sleep & Dreaming

NREM sleep

Non-rapid eye movement sleep

• Sleep Stages 1-4 are NREM

Sleep Cycle

Nightly pattern of deep sleep, light sleep and dreaming.

• Lasts 90 mins.

• In 1 night: 5 cycles of the 4 stages + 1 REM stage for every cycle.

• As the cycles progress, REM sleep gets longer and there is less deep sleep from the NREM stages.

Stage 1

• Light sleep: Easy to be woken up

• Muscles are less active

• Eye movements are slow and you may twitch suddenly

• Experience Alpha and Theta brainwaves

Alpha vs Theta

Alpha - You are awake but very relaxed and calm

Theta - Transitional period between being awake and asleep

Stage 2

• Sleep

• Brainwaves are slower

• Eye movements stop

• Occasional burst of brain activity (spindles)

• Body temperature ⬇ Heart rate ⬇

  
  

Stage 3

• Deep sleep

• There are mostly delta brainwaves (slowest form) but there can also be some faster ones (theta)

Stage 4

• Deep sleep

• Almost all waves are delta waves

• Very hard to wake you up (when woken you may feel disoriented)

• No eye movements

• May experience sleepwalking or night terrors

REM sleep

Part of the sleep cycle with rapid eye movements caused by the eyes moving a lot behind the eyelids when dreaming occurs.

What happens during REM sleep?

• Incoming sense information is blocked (sensory blockade)

• Starts with signals in the pons which shuts of neurons in the spinal chord and prevent us from moving.

• Fast and shallow breathing

• Eyes jerking

• Muscles paralysed

• Heart rate ⬆ Blood pressure ⬆

• Dreaming occurs

Sensory blockade

In REM sleep, all incoming sensory information is blocked.

Neurons

A nerve cell that transmits information.

Movement Inhibition

When movement is prevented in REM sleep.

How many hours of sleep does an adult need?

7-8 hours

How many hours of sleep does a teenager need?

About 9 hours

Importance of Sleep

• Essential for survival.

• Allows neurons to be repaired.

• Prevents the breakdown of proteins in the body.

• Strengthens neurosynaptic traces that allow us to retrieve memories.

Sleep deprivation

Not having enough sleep. This affects physical and brain functioning.

Circadian Rythm

Human body rythms that have a daily cycle (Happen once every 24 hours)

• Controlled by SCN.

• Includes sleep wake cycle

Ultradian Rythm

Rythms that occur in periods less than 24 hours. (Happen more than once every 24 hours)

Body Temperature and the Sleep-Wake Cycle

Body temperature: ⬆ When we need to wake up ⬇ When we need to fall asleep or in the afternoon

What can interfere with the sleep-wake cycle? (exogenous pacemakers)

• Jetlag

• Shiftwork

Superchaismatic Nuclei

• Small part of the brain that controls our body’s internal clock (circadian rythms)

• Controlled by both internal and external factors