Circadian Rhythm and EEG

Question 1

What does the hypothalamus excrete that is essential for being awake? What is a condition that has a deficiency of this?

Answer 1

An excitatory neurotransmitter called orexin/hypocretin.

Narcolepsy is a condition where the patient falls asleep suddenly due to a deficiency in orexin signalling.

Question 2

What is an EEG and what does it do?

Answer 2

Electroencephalogram

Monitors brain pattern by placing electrodes on the scalp to detect underlying neurones.

Question 3

What two things does an EEG display sleep as?

Answer 3

Frequency and Amplitude

Question 4

What type of waves are shown when relaxed and awake?

Answer 4

High frequency and amplitude alpha waves

Question 5

What type of waves are shown when alert and awake?

Answer 5

Higher frequency and low amplitude, asynchronous beta waves

Question 6

What type of waves are shown in deep sleep?

Answer 6

Low frequency and high amplitude delta waves

Question 7

What characterises theta waves and when do they occur?

Answer 7

Low frequency and varying amplitude waves.

Present in sleep, common in children. Adults can have them when emotionally stressed and frustrated.

Question 8

How many stages are there in the sleep cycle? How many are slow wave sleep and how many are fast wave sleep?

Answer 8

Five
Stage one to four are slow wave sleep
REM sleep is fast wave sleep

Question 9

What is stage one in the sleep cycle?

Answer 9

Light sleep and easily roused with slow eye movements. Low frequency and high amplitude theta waves.

Question 10

What is stage two in the sleep cycle?

Answer 10

Frequency slows further and eye movements decrease

Get sleep spindles (cluster of rhythmic waves)

Question 11

What is stage three in the sleep cycle?

Answer 11

Sleep spindle activity declines. Delta waves interspersed with short episodes of fast waves.

Question 12

What is stage four in the sleep cycle?

Answer 12

Deep sleep with only delta waves. Sleep walking/talking occurs here and the person can move position without making that decision.

Question 13

What is stage five in the sleep cycle?

Answer 13

REM/rapid eye movement sleep/paradoxical sleep

Skeletal muscles of whole body inhibited from pons to spinal cord apart from the eyes so cant act out dreams.

Question 14

What is a disease where the inhibition of skeletal muscles during REM doesn’t work?

Answer 14

REM sleep behavioural disorder

Question 15

What are some consequences of sleep deprivation

Answer 15

Decreased cognitive and physical function
Sluggishness
Irritability
Psychosis (uncommon)

Question 16

What are two types of insomnia?

Answer 16

Primary chronic insomnia where a cause is unclear

Secondary temporary insomnia where deep trauma causes a short lived insomnia, usually self limiting.

Question 17

Where in the brain is the circadian rhythm controlled and what are the stimulants?

Answer 17

Suprachiasmatic Nucleus (SCN) of the hypothalamus. Stimulated by light and dark. If SCN is destroyed then the circadian rhythm is lost.