consciousness, unconsciousness and sleep

Question 1

what is consciousness?

Answer 1

a state if self-awareness, perception, ability to respond to stimuli, ability to act with judgement

Question 2

what is sleep?

Answer 2

state of changed consciousness from which a person can be aroused by stimulation, alternating in an 24 hour cycle (circadian rhythm) with wakefulness

Question 3

what is a coma?

Answer 3

a state of profound unconsciousness characterised by inability to sense and respond to external stimuli and loss of sleep wake cycle

Question 4

what are the causes of a coma?

Answer 4

-intoxification
-acute neurologic injuries
-metabolic disorders
-CNS infection
-stroke

Question 5

what is the duration of a coma?

Answer 5

generally a few days to a few weeks (2-5 weeks)
-some patients progress to a vegetative state or die

Question 6

what is vegetative state?

Answer 6

-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

Question 7

what is brain death?

Answer 7

-irreversible coma, characterised by a lack of brain activity
-loss of pain responses and cranial nerve reflexes

Question 8

what are examples of different biological rhythms?

Answer 8

-circadian rhythm - sleep/ wakefulness , hormone secretion etc
-infradian rhythm eg menstrual cycle
-ultradian rhythms - REM cycles

Question 9

describe circadian rhythm

Answer 9

-24 hour biological clock
-a timing signal eg sunrise can reset the clock

Question 10

what is metatonin?

Answer 10

-hormone secreted by the pineal gland in the brain
-secreted at night to help with sleep

Question 11

what are the sleep stages?

Answer 11

1. slow wave sleep (NREM) - stages I,II,III,IV
2. Rapid eye movement (REM)

Question 12

how long are the sleep stages and how many times are they repeated per night?

Answer 12

-90 min cycles
-repeated 5-6 times per night

Question 13

what are brain waves measured on?

Answer 13

Electroencephalogram (EEG)

Question 14

how can an EEG be applied clinically?

Answer 14

-sleep
-seizures
-altered consciousness
-focal and diffuse disturbances in cerebral functioning

Question 15

Describe sleep stage 1

Answer 15

-light sleep, lasts for a few minutes
-easily awakened
-slow eye movements
-muscle activity slows down
-theta waves have a high amplitude on EEG

Question 16

describe sleep stage 2

Answer 16

-eye movements stop
-brain waves become slower, with an occasional burst of rapid waves called spindels

Question 17

Describe stage 3 of sleep (NREM)

Answer 17

-extremely slow brain waves called delta waves appear, interrupted by smaller, faster waves

Question 18

describe stage 4 sleep

Answer 18

-nearly exclusive production of delta waves
-difficult to wake a person up
-latest and deepest stage of sleep before REM

Question 19

what is the REM stage of sleep?

Answer 19

-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

Question 20

what happens with sleep duration as we age?

Answer 20

total duration of sleep decreases

Question 21

what are examples of benefits of sleep?

Answer 21

-improves cognitive ability
-solidifies memory
-processes & repackages newly learned lessons
-increases decision making skills

Question 22

what physiological effects can sleep deprivation have on the body?

Answer 22

-increased BP
-increased HR
-disrupts glucose metabolism
-increases obesity

Question 23

in what situations can the REM stage be reduced during sleep?

Answer 23

-during shortened sleep periods
-alcohol
-nicotine
medications eg anti-depressants

Question 24

what part of the brain controls the REM/NREM cycles of sleep?

Answer 24

the reticular formation

Question 25

what part of the brain controls the sleep/wake cycle?

Answer 25

suprachiasmatic nucleus

Question 26

what system in the brain determines the level of alertness ?

Answer 26

the reticular activating system

Question 27

what 2 types of neurons are important in the reticular activating system?

Answer 27

-neurons that synthesise ACH
-neurons which synthesise monoamines eg noradrenaline, serotonin and histamine

Question 28

describe the changes in activity in arousal pathways (ie 2 types of neurons) - during sleep stages

Answer 28

-during NREM / slow wave sleep - cholinergic and monoaminergic pathways slow down
-during REM sleep, cholinergic neurons fire rapidly & monoaminergic neurons stop firing

Question 29

what does the suprachiasmatic nucleus in the hypothalamus receive inputs from in order to control the sleep/wake cycle?

Answer 29

the retina

Question 30

what are examples of sleep disorders?

Answer 30

-insomnia
-excessive daytime sleepiness
-obstructive sleep apnoea
-narcolepsy
-parasomnias eg sleep talking, sleep walking etc
-restless leg syndrome

Question 31

what is fatigue?

Answer 31

-tiredness or weariness resulting in increased difficulty sustaining a high level of performance

Question 32

what Is excessive daytime sleepiness?

Answer 32

-difficulty maintaining wakefulness and an increased likelihood of falling asleep in unsuitable situation

Question 33

what is sleep apnea?

Answer 33

-disorder of interrupted breathing during sleep as the airflow is blocked

Question 34

what are the causes of sleep apnea?

Answer 34

• can be central ie brain signal interuption
  -or can be obstructive - windpipe collapse during inhalation

Question 35

what are the symptoms & consequences of sleep apnea?

Answer 35

-snoring
-excessive daytime sleepiness
-high BP

Question 36

what is narcolepsy?

Answer 36

a sleep disorder that causes people to have excessive daytime sleepiness