EEG, Sleep And Circadian Rhythms

Question 1

What is the definition of sleep

Answer 1

State of unconsciousness from which individual can be aroused by normal stimuli, light, touch, sound etc.

Sleep is predictable and cyclical

Question 2

What is a coma

Answer 2

State of unconsciousness from which individual cannot be aroused and does not respond to stimuli

COMA IS NOT DEEP SLEEP

Question 3

Where does the active inhibitory process that induces sleep occur

Answer 3

Pons

Destruction of brainstem at level of mid-pons creates a brain that never sleeps

Question 4

What molecules contribute to sleep (4)

Answer 4

Delta sleep inducing peptides (DSIP)
Adenosine
Melatonin
Serotonin

Question 5

What is the role of the suprachiasmatic nuclei (SCN) in induction of sleep

Answer 5

SCN has a 24hr circadian rhythm controlling the release of melatonin from the pineal gland

Question 6

What does light and darkness do to the SCN

Answer 6

Inhibitory neurons in SCN are stimulated by light and act to inhibit pineal gland, therefore no melatonin is released

Darkness removes the inhibition, stimulating the pineal gland —> increased melatonin release —> feeling sleepy

Question 7

What is the role of serotonin in sleep (how is this linked to treating depression)

Answer 7

Serotonin it’s a precursor of melatonin production

Serotonin selective reuptake inhibitors (SSRI’s) are a common treatment for depression where sleep disruption is often present - act to increase serotonin levels in synapse

Question 8

What is an electroencephalogram (EEG)

Answer 8

A recording of brain activity

Question 9

What happens to the frequency and amplitude of the waves on an EEG with increasing neuronal excitation

Answer 9

Frequency increases with increasing neuronal excitation
Amplitude decreases with increasing neuronal excitation

Question 10

What is stage 1 of the sleep cycle

Answer 10

Stage 1: slow wave, non-REM, S-Sleep

Slow eye movements, light sleep very early in the sleep cycle. Easily roused. High amplitude, low frequency

Question 11

What is stage 2 in the sleep cycle

Answer 11

Eye movements stop, frequency lows further but EEG shows bursts of rapid waves called “sleep spindles”

Question 12

what is stage 3 of the sleep cycle

Answer 12

High amplitude, very slow waves interspersed with short episodes of faster waves
Spindle activity declines

Question 13

What is stage 4 of the sleep cycle

Answer 13

Exclusively delta waves

Question 14

What are stage 3 and 4 of the sleep cycle known as (what characterises them)

Answer 14

Known as deep sleep
Very difficult to rouse from stage 3 & 4 - sleep walking/talking occurs in these stages

Question 15

What happens after stage 4 sleep

Answer 15

Move back up through stage 3 and 4 before entering REM sleep

Question 16

What is REM sleep

Answer 16

REM = rapid eye movements
Dreams occur during REM sleep
25% of sleep is REM
Low amplitude high frequency waves - eerily similar to awake state

Question 17

What happens to amplitude and frequency as you move through the stages of sleep

Answer 17

Increasing amplitude and decreasing frequency

Question 18

What does typical pattern of nights sleep in healthy young adult look like (no answer photo only)

Answer 18

Question 19

What are the physiological characteristics of deep sleep (stage 4) (4)

Answer 19

Deep sleep that occurs in first hours of sleep
Most restful type of sleep
Associated with decreased vascular tone (and therefore BP), respiratory and basal metabolic rate (hence drop in BP)
Hippocampus very active (making new memories)

Question 20

What are the physiological characteristics of REM sleep (4) (how long does it last and how often)

Answer 20

Lasts 5-30 minutes every 90 minutes
1. Dreams occur in REM sleep due to new neuronal connects being made
2. Eye muscles show bursts of rapid activity (profound inhibition of all other skeletal projections to prevent acting dreams out)
3. EEG pattern mimics beta waves associated with highly alert awake state
4. If deprived of REM sleep, there is a catch up when able to sleep again

Question 21

How does time spent sleeping change as you grow up

Answer 21

Time spent sleeping decreases rapidly through childhood and adolescence
Percentage of REM sleep also declines (may be absent 80+ years)

Question 22

What is insomnia

Answer 22

Chronic inability to obtain the necessary amount or quality of sleep to maintain adequate daytime behaviour

Question 23

What is the difference between chronic primary insomnia and temporary secondary insomnia

Answer 23

Chronic primary: no identifiable psychological or physical cause
Temporary secondary: in response to pain, bereavement or other crisis (usually short lived)

Question 24

What are nightmares

Answer 24

Strong visual component seen during REM sleep, typically occur quite far on through the night. waking will stop the nightmare and the individual will have a clear recollection of the “dream”

Question 25

What are night terrors

Answer 25

Occur in deep delta sleep common in children. Typically occur early in the night.
Children thrash and scream and may sit/stand up with their eyes open but aren’t properly awake
Doesn’t remember episode upon waking following morning

Question 26

What is somnambulism (sleep-walking)

Answer 26

Occurs exclusively in non-REM sleep (mainly stage 4)
Sleep walkers appear awake - eyes open, see and will avoid objects, carry out reasonably complex tasks such as preparing food and will often obey instruction but have no recollection when woken

Question 27

What is narcolepsy

Answer 27

Enter directly into REM sleep with little warning
Very dangerous because of accident risk (e.g. driving)
Occurs due to dysfunctional orexin release from hypothalamus