Sleep

Question 1

What is the behavioural criteria for sleep?

Answer 1

o Stereotypic or species-specific POSTURE

o Minimal movement

o Reduced responsiveness to external stimuli

o Reversible via. stimulation
- unlike coma, anaesthesia or death

Question 2

How can you monitor sleep?

Answer 2

3 different methods

EEG, EOG or EMG

ONENOTE!!

Question 3

Outline Stages of Sleep?

Answer 3

Awake
Stage 1, 2, 3, 4 & 5

First 4 stages = Non-REM (NREM)
Last stage = REM

Question 4

‘Awake’ stage of Sleep?

Answer 4

FAST brain activity in EEG (beta-rhythm)
o 30Hz

Reasonable amount of MUSCLE TONE

Question 5

‘Stage 1 & 2’ of Sleep?

Answer 5

Light Sleep!

o EEG activity SLOWS as the person becomes drowsy
o Beta –> theta activity (4-8Hz)
o NO eye movements
o general muscle activity is REDUCED

Question 6

‘Stage 3 &4’ of Sleep?

Answer 6

Deep Sleep!

o Theta –> delta activiy
- slowest rhythm at around 1Hz
o Minimal eye movement
o Continued relaxation of muscles

Question 7

‘Stage 5’ of Sleep?

Answer 7

REM sleep

o Brain activity shifts back to a FAST RHYTHM
o REMs are seen
o Muscle activity is LOWEST - paralysed

Question 8

EEG, EOG & EMG of the different stages of Sleep?

Answer 8

ONENOTE!!

Question 9

Explain Sleep Cycles

Answer 9

Have multiple sleep cycles per night
o Each cycle lasts ~1-1.5hours

You tend to get
o MORE SLOW-WAVE sleep at the beginning of the night
o MORE REM sleep towards end of the might

Question 10

HR and RR during sleep?

Answer 10

Both are SLOW during slow-wave sleep

Both are FASTER during REM sleep

Question 11

What controls consciousness?

Answer 11

RAS
o starts in the brainstem and projects into
& influences the cerebral cortex

The effects of the RAS can be
o DIRECT
OR
o through intralaminar nuclei in the thalamus

Question 12

What controls the RAS and explain it?

Answer 12

Two nuclei located in the hypothalamus (hence control the wake/sleep cycle)

o Lateral hypothalamus - EXCITATORY input
- ACTIVE during the day

o Ventrolateral Preoptic Nucleus - NEGATIVE EFFECT
- this PROMOTES SLEEP

There is an ANTAGONIST relationship between the nuclei
o activity of one, inhibits the other

Question 13

What controls the Circadian Synchronisation of the Sleep/Wake Cycle?

Answer 13

Suprachiasmatic nucleus

- synchronises sleep with falling light level

Question 14

How is the Circadian Synchronisation of the Sleep/Wake Cycle controlled?

Answer 14

Suprachiasmatic nucleus - synchronises sleep with falling light level

o receives input from the retina via. a special type of ganglionic cell (NOT RGCs)
o light level fall = activates the SN = activate more nuclei within the hypothalamus
o this inhibits the LH nucleus = stimulates the VLP nucleus
o also has direct effect on the RAS, resulting in reduction of traffic

Question 15

Explain how else the SC nucleus controls the Circadian Synchronisation of the Sleep/Wake Cycle

Answer 15

Suprachiasmatic nucleus also has a projection to the PINEAL GLAND
o SC nucleus activates it
o secretes MELATONIN throughout the night
o this ADJUSTS the PHYSIOLOGICAL PROCESSES in the body to fit it with sleep

Question 16

Effects of sleep deprivation?

Answer 16

o Sleepiness & irritability
o Performance decrements/increased risk of error
o Concentration & learning difficulties
o Glucose intolerance
o Reduced leptin - increased appetite
o Hallucinations - after LONG sleep deprivation
o Death - fatal familial insomnia

Question 17

What happens after Sleep Loss to regulate it?

Answer 17

o Reduced latency to sleep onset
- if you lose a night’s sleep, you go to bed earlier the next day

o Increase of NREM (slow-wave sleep)
- so sleep for longer is sleep deprived

o Increase of REM sleep
- after specifically, selective REM sleep deprivation

Question 18

What is the function of sleep?

Answer 18

o Restoration & recovery
- but active individuals do NOT sleep more

o Energy conservation
- 10% drop is BMR but to lying still is just as effective

o Predator avoidance

o Specific brain function
- memory, consolidation

Question 19

Explain Dreams

Answer 19

Occur in REM and/or NREM sleep

• MORE frequently in REM sleep
• can be more easily recalled in REM sleep
• contents of dreams more emotional than ‘real-life’

Question 20

How does brain activity differ in dreams?

Answer 20

Brain activity is
o HIGHER in limbic system
o LOWER is the frontal lobe

Limbic system = emotions
Frontal lobe = logical thought and informed decision-making

Question 21

Function of dreams?

Answer 21

o Act as safety valve for antisocial emotions
o Sorting of memory
o Disposing of unwanted memories

o Memory consolidation

• NREM sleep = declarative memory (facts and events)
• REM sleep = procedural memory (learning skills)

Question 22

Sleep disorders?

Answer 22

Insomnia & Nacrolepsy

Also Shift-work

Question 23

Causes of Insomnia?

Answer 23

o Physiological
- e.g. sleep apnoea, chronic pain
o Brain dysfunction
- e.g. depression, fatal familial insomnia, night-work

High prevalence & most cases transient (comes and goes)

Question 24

Treatment for Insomnia?

Answer 24

o Remove cause

o Hypnotics
- enhance inhibitory circuits in the brain (GABAergic circuits)

Question 25

Narcolepsy?

Answer 25

Falling asleep repeatedly during the day

Disturbed sleep at night

Question 26

Cataplexy (part of narcolepsy)?

Answer 26

Sudden onset muscle weakness

• that may be precipitated by excitement or emotion
• sometimes in just one part of the body
• can occur in most muscles –> fall over
• REM sleep = LOW muscle tone (dysfunction of control of REM sleep)

Question 27

Causes of narcolepsy?

Answer 27

Orexin deficiency
o orexin is a neuropeptide which is the transmitter used by the lateral hypothalamus

• CAUSE could be genetic or autoimmune
• normally treatment is a strict regimen of sleeping routines

Question 28

Shift-work?

Answer 28

Night-working causes physiological processes to become desynchronised

This can lead to
o sleep disorders
o fatigue
o increased risk of some conditions e.g. obesity, diabetes, cancer