consciousness, unconsciousness and sleep Flashcards
what is consciousness?
a state if self-awareness, perception, ability to respond to stimuli, ability to act with judgement
what is sleep?
state of changed consciousness from which a person can be aroused by stimulation, alternating in an 24 hour cycle (circadian rhythm) with wakefulness
what is a coma?
a state of profound unconsciousness characterised by inability to sense and respond to external stimuli and loss of sleep wake cycle
what are the causes of a coma?
-intoxification
-acute neurologic injuries
-metabolic disorders
-CNS infection
-stroke
what is the duration of a coma?
generally a few days to a few weeks (2-5 weeks)
-some patients progress to a vegetative state or die
what is vegetative state?
-a state of unconsciousness in patients with severe brain injury
-frequently observed in patients in whom coma has progressed to certain state of wakefulness without awareness
what is brain death?
-irreversible coma, characterised by a lack of brain activity
-loss of pain responses and cranial nerve reflexes
what are examples of different biological rhythms?
-circadian rhythm - sleep/ wakefulness , hormone secretion etc
-infradian rhythm eg menstrual cycle
-ultradian rhythms - REM cycles
describe circadian rhythm
-24 hour biological clock
-a timing signal eg sunrise can reset the clock
what is metatonin?
-hormone secreted by the pineal gland in the brain
-secreted at night to help with sleep
what are the sleep stages?
- slow wave sleep (NREM) - stages I,II,III,IV
- Rapid eye movement (REM)
how long are the sleep stages and how many times are they repeated per night?
-90 min cycles
-repeated 5-6 times per night
what are brain waves measured on?
Electroencephalogram (EEG)
how can an EEG be applied clinically?
-sleep
-seizures
-altered consciousness
-focal and diffuse disturbances in cerebral functioning
Describe sleep stage 1
-light sleep, lasts for a few minutes
-easily awakened
-slow eye movements
-muscle activity slows down
-theta waves have a high amplitude on EEG
describe sleep stage 2
-eye movements stop
-brain waves become slower, with an occasional burst of rapid waves called spindels
Describe stage 3 of sleep (NREM)
-extremely slow brain waves called delta waves appear, interrupted by smaller, faster waves
describe stage 4 sleep
-nearly exclusive production of delta waves
-difficult to wake a person up
-latest and deepest stage of sleep before REM
what is the REM stage of sleep?
-the brain waves seen on an EEG during REM are similar to the waves seen when awake
-this stage of dreaming is associated with dreaming
what happens with sleep duration as we age?
total duration of sleep decreases
what are examples of benefits of sleep?
-improves cognitive ability
-solidifies memory
-processes & repackages newly learned lessons
-increases decision making skills
what physiological effects can sleep deprivation have on the body?
-increased BP
-increased HR
-disrupts glucose metabolism
-increases obesity
in what situations can the REM stage be reduced during sleep?
-during shortened sleep periods
-alcohol
-nicotine
medications eg anti-depressants
what part of the brain controls the REM/NREM cycles of sleep?
the reticular formation
what part of the brain controls the sleep/wake cycle?
suprachiasmatic nucleus
what system in the brain determines the level of alertness ?
the reticular activating system
what 2 types of neurons are important in the reticular activating system?
-neurons that synthesise ACH
-neurons which synthesise monoamines eg noradrenaline, serotonin and histamine
describe the changes in activity in arousal pathways (ie 2 types of neurons) - during sleep stages
-during NREM / slow wave sleep - cholinergic and monoaminergic pathways slow down
-during REM sleep, cholinergic neurons fire rapidly & monoaminergic neurons stop firing
what does the suprachiasmatic nucleus in the hypothalamus receive inputs from in order to control the sleep/wake cycle?
the retina
what are examples of sleep disorders?
-insomnia
-excessive daytime sleepiness
-obstructive sleep apnoea
-narcolepsy
-parasomnias eg sleep talking, sleep walking etc
-restless leg syndrome
what is fatigue?
-tiredness or weariness resulting in increased difficulty sustaining a high level of performance
what Is excessive daytime sleepiness?
-difficulty maintaining wakefulness and an increased likelihood of falling asleep in unsuitable situation
what is sleep apnea?
-disorder of interrupted breathing during sleep as the airflow is blocked
what are the causes of sleep apnea?
- can be central ie brain signal interuption
-or can be obstructive - windpipe collapse during inhalation
what are the symptoms & consequences of sleep apnea?
-snoring
-excessive daytime sleepiness
-high BP
what is narcolepsy?
a sleep disorder that causes people to have excessive daytime sleepiness
