sleep and circadian rhythms

Question 1

how can physiological activity be measured during sleep?

Answer 1

• electromyography measures muscle movements
• electro-oculography measures eye movements
• electroencephalography measures brain activity

Question 2

how does an electroencephalogram work?

Answer 2

• electrodes placed on surface of scalp to detect electrical fields
• linked to an electrical amplifier and a monitor

Question 3

what does an electroencephalogram measure?

Answer 3

electrical activity from large populations of neurons in the brain
caused by cellular, ionic movement, which creates an electric field

Question 4

properties of electroencephalogram

Answer 4

• high temporal resolution - millisecond precision as electrodes in direct contact with scalp
• low spatial resolution - electrodes on scalp far away from neurons, signals decay and blur

Question 5

five main stages of sleep

Answer 5

stage 1 - drowsiness (non-REM)
stage 2 - light sleep (non-REM)
stage 3 - deep sleep (non-REM)
stage 4 - very deep sleep (non-REM)
stage 4 - REM sleep

Question 6

properties of non-REM sleep

Answer 6

• low neuronal activity
• low metabolic rate and brain temp
• heart rate and blood pressure decline (decreased sympathetic nervous system)
• increase in parasympathetic nervous system
• muscle tone and reflexes are intact

Question 7

properties of stage 1 sleep

Answer 7

drowsiness
- awakened easily
- slow eye movement and muscle activity

Question 8

properties of stage 2 sleep

Answer 8

light sleep
- eye movement stops
- brain waves slow with occasional burst of rapid brain
- body temp drops, heart rate slows
- begins to prepare for deep sleep

Question 9

electrical characteristics of stage 1 sleep

Answer 9

EEG shows low-voltage activity of mixed frequencies (mostly theta waves)

Question 10

electrical characteristics of stage 2 sleep

Answer 10

bursts of sinusoidal waves called ‘sleep spindles’ and biphasic waves called K complexes

Question 11

properties of stage 3 sleep

Answer 11

deep sleep
- sleepwalking, night terrors, talking during sleep

Question 12

electrical characteristics of stage 3 sleep

Answer 12

• slow delta waves interspersed with smaller, faster waves

Question 13

properties of stage 4 sleep

Answer 13

very deep sleep
- disorientation for several minutes following arousal

Question 14

electrical characteristics of stage 4 sleep

Answer 14

• delta waves almost exclusively
• slow wave activity dominates EEG

Question 15

properties of stage 5 sleep

Answer 15

REM sleep
- eyes move rapidly from side-to-side
- EEG mimics wakefulness

Question 16

why is REM sleep paradoxical?

Answer 16

REM-neuronal firing very like in wakefulness despite most muscles being relaxed

Question 17

behavioural characteristics of REM sleep

Answer 17

• brain temp and metabolic rate rise
• skeletal muscles are atonic (paralysed)
• muscles controlling eye movement, middle ear ossicles and diaphragm remain active (to breathe and hear impending danger)

Question 18

what regulates the circadian rhythm?

Answer 18

retinohypothalamic tract from eye to suprachiasmatic nucleus (internal clock) in anterior hypothalamus

Question 19

what is the role of the visual system in circadian rhythm?

Answer 19

intrinsically photosensitive ganglion cells provide input to the suprachiasmatic nucleus

Question 20

how is the brain stem associated with sleep?

Answer 20

brain stem regulates wakefulness
- lesion of brain stem can cause sleep and coma
- activation of neurons in brain stem precedes awakening

Question 21

what are the roles of the raphe nuclei and locus coeruleus in sleep?

Answer 21

they are brain stem nuclei
- raphe nuclei source of 5-HT
- locus coeruleus source of norepinephrine
both important neurotransmitters in regulating sleep