Lecture 10 EEG, Sleep and Circadian Rhythm

Question 1

Why does sleep occur

Answer 1

due to active inhibitory processes that originate in the pons

Question 2

What is the consequence of the destruction of the brain stem at the level of the mid pons

Answer 2

creates a brain that never sleeps

Question 3

Many neutrons within the reticular are ___

Answer 3

serotonergic (nerve ending that releases and is stimulated by serotonin)

Question 4

Drugs that block serotonin formation would do what

Answer 4

Inhibit sleep

Question 5

Serotonin is a precursor for what

Answer 5

Melatonin

Question 6

What other structures are involved with the induction of sleep

Answer 6

Hypothalamus and Suprachiasmatic Nuclei

Question 7

Damage to the SCN would do what

Answer 7

Disrupt sleep

Question 8

Stimulation of the SCN would do what

Answer 8

Promote sleep

Question 9

What is the purpose of the SCN

Answer 9

demonstrates 24hr circadian rhythm and controls release of melatonin from pineal gland

Question 10

Light stimulates what type of neutrons in SCN

Answer 10

Inhibitory

Which inhibit the pineal gland releasing melatonin

Question 11

Dark has what affect on SCN

Answer 11

Increased activity of SCN to increase the release of melatonin from pineal gland and the feeling of sleepiness

Question 12

What is Melatonin linked to

Answer 12

The inhibition of Orexin

Question 13

What is Orexin

Answer 13

Excitatory neurotransmitter released from the hypothalamus and is required for wakefulness

Question 14

Defective orexin signalling would lead to what

Answer 14

Narcolepsy

Question 15

What is a common treatment for depression where sleep disruption is present

Answer 15

Serotonin selective reuptake inhibitors

Increase serotonin levels in synapse

Question 16

How would you assess the level of consciousness in an awake person

Answer 16

Look at behaviour, general alertness, speech patterns, speech content, reading, writing and calculating skills
Record brain activity using EEG

Question 17

What is the purpose of an EEG

Answer 17

Recordings show patterns that reflect the electrical activity of the brain

Question 18

Frequency increases with__

Answer 18

Neuronal excitation (being awake)

Question 19

Amplitude decreases with ___

Answer 19

Increasing neuronal excitation (being awake)

Question 20

What EEG would you expect to see from someone who is awake

Answer 20

High frequency

Low amplitude

Question 21

What EEG would you see with someone who is awake by relaxed

Answer 21

High frequency

High amplitude

Question 22

What EEG would you expect to see with someone who is awake and alert

Answer 22

Higher frequency

Low amplitude

Question 23

What are 4 types of wave patterns seen in EEGs

Answer 23

Alpha
Beta
Theta
Delta

Question 24

Why is the amplitude low in an awake person

Answer 24

Brain when awake has a low amplitude because the brain is doing a lot of things lots of desynchronised waves cancel each other out

Question 25

Describe Theta waves and where they are seen

Answer 25

Low frequency Amplitude varies Stage 2 sleep cycle

Question 26

Describe Delta waves

Answer 26

Low frequency High amplitude Occur in deep sleep (stage 3 & 4)

Question 27

Describe alpha waves

Answer 27

High frequency and high amplitude (relaxed awake stage) sometimes stage 1

Question 28

Describe Beta waves

Answer 28

Even higher frequency and low amplitude (alert awake )

Question 29

What is REM sleep

Answer 29

During deep sleep where there are rapid eye movements | and where dreams occur (25% of sleep)

Question 30

What are the physiological characteristics of deep, slow wave sleep

Answer 30

1. Deep sleep that occurs in the first hours of sleep 2. Most restful type of sleep. 3. Associated with decreased vascular tone (and therefore BP), respiratory and basal metabolic rate (hence drop in BT). 4. Dreams may occur but are rarely remembered.

Question 31

Physiological characteristics of REM sleep

Answer 31

1. Lasts 5-30mins every 90mins or so during a normal nights sleep, becoming more frequent as night progresses and rest and recovery are established. 2. Dreams mostly occur in REM sleep 3. Eye muscles show bursts of rapid activity. Profound inhibition of all other skeletal muscles due to inhibitory projections from pons to spinal cord 4. REM sleep is dependent on cholinergic pathways within the reticular formation and their projections to the thalamus, hypothalamus and cortex. Anticholinesterases increase time spent in REM sleep. 5. HR/RR become irregular and brain metabolism . EEG pattern mimics beta waves associated with highly alert, awake state. 6. Very difficult to arouse an individual from REM sleep, although we often spontaneously awaken in the morning from this stage of sleep, vividly recalling our dreams. 7. Whenever deprived of REM sleep, there is always a catch up when able to sleep again indicating that REM sleep must have an important physiological function.

Question 32

Why is sleep important

Answer 32

1. Impairment of cognitive function 2. Impairment of physical performance 3. Sluggishness 4. Irritability 5. Psychosis has also been observed in some subjects.

Question 33

What does sleep support

Answer 33

``` Neuronal plasticity learning and memory Cognition Clearance of wast products from CNS Conservation of whole body energy Immune function ```

Question 34

How does sleep change from childhood to adolescence to elderly

Answer 34

Percentage of REM sleep declines from 80% to 50% to 25% | May be absent in 80+

Question 35

Define insomnia

Answer 35

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

Question 36

What are the 2 types of insomnia

Answer 36

Chronic, primary - no identifiable cause | Temporary, secondary- in réponse to pain, bereavement or crisis

Question 37

Define nightmares

Answer 37

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

Question 38

Define night terrors

Answer 38

occur in deep, delta sleep and are common in children 3-8 years, typically occurring early in the night. Children thrash and scream and may sit or stand up with their eyes open but are not properly awake and often fail to recognise their parents. The child does not remember the episode on waking the following morning.

Question 39

Define Somnambulism (Sleep-walking)

Answer 39

occurs exclusively in non-REM sleep, mainly in Stage 4 sleep and is more common in children and young adults, probably due to the decline in Stage 4 sleep with age

Question 40

Define Narcolepsy

Answer 40

Enter directly into REM sleep with little warning. Symptoms could be interpreted as intrusion of REM sleep characteristics onto the waking state.