Sleep Physiology Flashcards
What is sleep?
A behavioral state characterized by decreased awareness of external environment, decreased reactivity to stimuli, but with the capability to return rapidly to wakefulness.
Why do we sleep?
For learning, brain development, repair, maintenance, energy preservation, to keep out of trouble
What are the effects of sleep deprivation?
mortality, lower cognition, irritability, impaired immune system, increase risk of heart disease, risk of type 2 diabetes, risk of obesity
What happens to breathing during sleep?
lose input from higher brain centres, lose wakefulness drive to breathe, lose input of emotional stimuli, down regulate input from muscle and joints, down regulate input from pain receptors, down regulate input from stretch receptors, reduced upper airway tone increases resistance - become dependent on chemoceptors for drive
What happens to minute ventilation during sleep?
Decreases
What happens to CO2 during sleep?
Increases
What are the stages of sleep?
Stage 1-4 slow wave sleep and REM sleep
How long is a sleep cycle?
90-120 minutes
How many sleep cycles per night?
4-6
How does sleep change with age?
Infants have more REM sleep, amount of sleep in total decreases with age, amount of deep sleep decreases with age
How is sleep regulated?
Homeostatic sleep mechanisms and circadian rhythm
How is sleep generated?
There are activating systems in the brain for maintaing wakefulness and a nucleus (the VLPO) for generating sleep rhythms. These two systems are mutually inhibitory. Orrexin acts as a stabiliser between the two. If it reaches a point where the accumulation of adenosine in the basal forebrain is sufficient to stimulate the VLPO then VLPO activity becomes high enough that the system flips into sleep and inhibits the activating system. With the loss of adenosine during sleep you will ‘flip’ back into wakefulness.
