10 - Sleep and Wake Cycle Flashcards
the change from sleep to wakefulness is mediated by what?
reticular activiating mechanism
the biological clock detects what?
decreases in light levels as night approaches
what is the site of circadian control of homeostatic function?
SCN - suprachiasmatic nucleus
where is the SCN located?
anterior hypothalamus
what happens when the SCN is activated?
- impulse travels to synapse in paraventricular nucleus of hypothalamus
- descend into IML zone (intermediolateral) in lateral horns of spinal cord
- modulates neurons of superior cervical ganglia
- axons project into pineal gland = melatonin secretion
what happens to melatonin as light in the environment decreases?
increases
what system mediates wakefulness and increases arousal?
ascending arousal system
what are the two components of the ascending arousal system?
- thalamus to cerebral cortex
- lateral hypothalamus –> basal forebrain –> cerebral cortex
what is orexin?
a neurotransmitter that regulates arousal, wakefulness and
appetite
during REM sleep, what happens to the activity of orecin neurons?
reduces
what does sleep consist of?
non-REM stages and REM stage
how is sleep different to a coma or general anaesthetic?
sleep is readily reversible
how many sleep cycles are there usually in a 8h sleep period?
4-6
how much of the sleep cycle is spent in non-REM sleep? how much of the sleep cycle is spent in REM sleep?
non-REM = 80%
REM = 20%
non-REM sleep is induced by what?
- GABA neurons in hypothalamus
- serotonin from raphe nuclei
non-REM sleep is characterised by what on an EEG?
progressively sychronised EEG
how many stages of non-REM sleep are there?
4
Fill in this table of NREM sleep
REM sleep is characterised by what change on EEG?
synchronised > desynchronised EEG
during NREM sleep what happens to skeletal muscle?
skeletal muscles relax and maintain their tone
what happens to muscle tone in REM sleep?
atonia - loss of muscle tone
non-REM sleep lasts roughly how long?
90 mins
when do most dreams occur?
REM sleep
what are the two theories about why we sleep?
- theory of restoration
- theory of adaptions
what is consciousness?
alert cognitive state in which ou are continualy aware of external and internal environements
for a person to be fully conscious they must be both what?
awake (ascending reticular activating system) and aware (functioning cerebral cortex)
what is a concussion?
reversible state of unconsciousness that lasts only a brief amount of time, without strucutral or pathological alteration
what is a coma?
profound state of unconsciousness that is associated with depressed cerebral activity
what scale is used to assess consciousness>
GCS
what are the 3 sections of the GCS?
- eye opening
- verbal response
- best motor response
