Sleep Flashcards
What is sleep? What does sleep do?
Animal behaviour defined by characteristics:
Stereotypical posture (species specific)
Minimal movement
Reduced response to external stimuli
Reversable with stimuli
Unknown but suggested purposes (with faults)
Recovery - increased activity doesn’t trigger more
Energy conservation - only 10% in BMR, same occurs while lying down
Predator avoidance - sleep is complex plus this seems counterintuitive
Brain function - memory etc
What three techniques are used to monitor activity during sleep?
Electroencephalography (EEG)
Electromyography (EMG)
Electrooculography (EOG)
Describe the EEG and EMG activity in wakefulness.
EEG – fast brain rhythm – beta waves (~30 Hz)
EMG – reasonable amount of muscle tone because you are maintaining posture and ready for action
Describe the EEG, EMG and EOG activity in non-REM sleep.
Stage 1+2 (Light sleep)
EEG – theta (4-8 Hz) waves – gradually becoming more and more drowsy
EOG – NO eye movements
EMG – muscle activity reduced considerably
Stage 3+4 (Very deep sleep)
EEG - Delta activity (< 4 Hz)
EOG – minimal eye movement
EMG – continued relaxation of muscles
Describe the EEG, EMG and EOG activity in REM sleep.
EEG – brain shifts abruptly back to fast rhythm (similar to wakefulness)
EOG – rapid eye movement
EMG – muscle activity at its lowest – subject is basically paralysed
How long is a normal sleep cycle?
1-1.5 hours
Compare the relative amounts of NREM and REM sleep in a sleep cycle at the start of a night’s sleep and at the end.
Start of the night – more NREM sleep End of the night – more REM sleep
Describe how heart rate and respiratory rate change during sleep.
SLOW during NREM
FAST during REM sleep
Which system is responsible for maintaining consciousness?
Reticular activating system
Either via direct connections or via indirect connections through the intralaminar nuclei of the thalamus
What are the two important nuclei in the hypothalamus that are responsible for influencing the reticular activating system and, hence, regulating the sleep-wake cycle?
Hypothalamus - Lateral nucleus promotes wakefullness via Orexin/hypocretin
Ventrolateral preoptic nucleus (hypothalamus) promotes sleep
Describe the circadian synchronisation of the sleep-wake cycle.
The suprachiasmatic nucleus is responsible for synchronising the sleep-wake cycle with falling light level
It receives an input from the retina (not from the usual photogenic cells) and as light level falls the suprachiasmatic nucleus becomes more active
Describe the effect of the suprachiasmatic nucleus on the nuclei within the hypothalamus.
Falling light level –> increased activity of suprachiasmatic nucleus This leads to activation of ventrolateral preoptic nucleus and inhibition of lateral hypothalamus so you become sleepier
What other important projection does the suprachiasmatic nucleus have and what is the importance of this projection?
Projection to the pineal gland Increase in suprachiasmatic nucleus activity leads to activation of pineal gland so that it releases melatonin Melatonin adjusts various physiological processes in the body that fit with sleep
What are some consequences of sleep deprivation
Physchiatric
- Irritable
- Stressed
- Mood fluctuation
- Depression
- Impulsivity
- Hallucinations
Neurological
- Impaired attention, memory, executive function
- Risk of errors/accidents
- Maybe neurodegeneration?
Somatic
- Glucose intolerance
- Reduced Leptin - higher appetite
- Impaired immunity
- Increased CVS and cancer risk
- Death
Describe three ways in which sleep is regulated after sleep deprivation.
Reduced latency of sleep onset (fall asleep faster) Increased NREM sleep (sleep for longer) Increased REM sleep (after selective REM sleep deprivation)
