Sleep Flashcards
What does an EEG measure?
→ The combined activity of a large number of similarly orientated neurons
What does an EEG require?
→ synchronous activity across groups of cells
What does the amplitude of an EEG signal depend on?
→ how synchronous the activity of the neurons are
What is a large summed signal caused by?
→ tiny signals summed up to generate a large surface signal
What is a small summed signal caused by?
→ the same amount of excitation as a large signal
→ but at irregular intervals
What do EEG rhythms correlate with?
→ States of behaviours
What is high frequency and low amplitude associated with?
→ Alertness and wake
What is low frequency and high amplitude associated with?
→ Non dreaming sleep or coma
What are the two theories of how rhythms are generated during sleep?
→ There is a pacemaker that acts as a conductor (conductor telling everyone to clap)
→ mutual excitation and inhibition and neurons sync to what other neurons are doing (people clapping at random and syncing to each other)
What is theorised to be the pacemaker in the brain and why?
→ Thalamus
→ thalamic nuclei communicate with every cortical brain structure
Describe the hypothesis for slow frequency and high amplitude rhythms during sleep?
→ Thalamus acts as a gatekeeper it stops information getting to the brain during sleep
(like a spinning arm in an obstacle course)
Describe the hypothesis for fast frequency and low amplitude rhythms during wakefulness
→ the brain is attention grabbing to bind together regions needed for task execution
What is sensation like in non REM sleep?
→ dull or absent
What is thought like in non REM sleep?
→ logical
→ repetitive
What is movement like in non REM sleep
→ occasional
→ involuntary
What is sensation like in REM sleep?
→ vivid
→ internally generated
What is thought like in REM sleep?
→ vivid
→ illogical
→ bizarre
What is movement like in REM sleep?
→ muscle paralysis
→ movement commanded by the brain but not carried out
What is temperature, heart rate, breathing and energy consumption like in non REM sleep?
→ Decreased temperature
→ decreased heart rate
→ decreased breathing
→ decreased brain energy consumption
What is temperature, heart rate, breathing and energy consumption like in REM sleep?
→ very low temperature
→ increased heart rate
→ increased breathing
→ very high brain energy consumption
What kind of sleep do you begin with?
→ non REM sleep
When do sleep cycles repeat?
→ every 90 minutes
How many minutes of non REM do you need to progress into REM?
→ 30 minutes
Why do we sleep?
→ getting rest -cognitive performance is increased after sleeping
→ adaptation to protect themselves and conserve energy
When you are awake what neurotransmitters are secreted and from where and what do they do?
→ ACh and orexin
→ basal forebrain and hypothalamus
→ increase excitatory activity and decrease synchronous firing
When you fall asleep what drives neural activity?
→ thalamus
What receptor activation promotes sleepiness?
→ adenosine
What does adenosine receptor activation cause?
→ Decrease heart and respiratory rate
→ smooth muscle tone decrease
What are adenosine levels like during the day and night?
→ day - increasing
→ night - rapidly drop
What stimulates adenosine release?
→ nitric oxide
What other factors contribute to sleepiness?
→ inflammatory factors
What is melatonin and when is it secreted?
→ compound that increases when there is a reduction in light
What is body temperature like during the day and night?
→ high during the day
→ decreases at night
What hormone increases at night?
→ Growth hormone
What is cortisol like during the day and night?
→ Cortisol decreases during the day then increases before wakefulness
What are zeitgebers?
→ environmental cues such as the sun
What is the natural sleep cycle with no cues?
→ 24-25 hours
Where is the suprachiasmatic nucleus?
→ Located between the optic chiasm at the base of the hypothalamus
What does the suprachiasmatic nucleus do?
→ provides a circadian rhythm
What happens when the suprachiasmatic nucleus is inhibited?
→ The cycles are irregular
Describe how melatonin is inhibited?
→ Ganglion cells have a protein that is reactive to light
→ melanopsin ganglion cells transmit the activation to the suprachiasmatic nucleus
→ this inhibits the pineal gland
→pineal gland is reponsible for the production of melatonin
Describe how melatonin is produced
→ no activation of melanopsin at night
→ SCN is not activated
→ pineal gland is not inhibited
→ produces melatonin
