Lecture 2

Question 1

What is the encephalitis Lethargica and what can it tell us about the role of the hypothamulus in sleep?

name = CvE

Lesions
AH (VLPO)
PH (ARAS)

Answer 1

A type of flu
- first described by Constantin von Economo 1917
- diease that attacks the brain leaving patients conscious byt not fully awake - motionaless and speechless, lacking energy
Registered what went on around them with profound indifference
- slept up to 20 hours a day OR suffered insomnia and only slept for a couple
Cog fucntions intact

• post mortem revealed lesions specifically to the hypothalamus
  brain conatined different areas that regulate sleep-wake

hypothesised
the exisitence of a sleep centre in the anterior hypothealamus (lessions would cause insomnia) and the wake centre in posterior hypothalamus (lesions would cause excessive sleepiness)

indicated the importance of the hypothalamus in sleep regulation

Question 2

ARAS and how is it involved in sleep regulation?

activated by realse of NT orexin,

Answer 2

ARAS series of pathways from the brain stem via midbran which activates the FB

input at BS keeps FB awake

Specific cell groups release NTs (histamines, dopamin, serotonin, norarenaline and Ach, orexin

ARAS is activated by direct porjections from orexin-producing neurons in the lateral hypothalamus!!

Destructions of orexin-producing neurons results in Narcolepsy

Wakefulness (activation of orexin producing neurons) inhibits the VLPO by multiple iputs of monoamniergic systems and other brain areas inc the hpyothalamus

Question 3

VLPO

inhibits through inhibitory neruons GABA and galanin

Answer 3

The VLPO has an inhibitory function it inhibits the APRAS through inhibitory neurot

Question 4

Describe the flip-flop circuit model

Answer 4

The wake and sleep circuits compete they are mutally inhibirtory
When one side gains an advantage it shits down inhibition form the other

A state transition occurs quickly
<1-2% of the time is spent falling asleep or waking up

Following the flu epidemic an increase in cases of N was seen:
damage to orexin nuerons in the hypothalmus
orexin neruons reicforced the arousal systems
loss of orexin neruons alters the balance of the wake-sleep flipflop and leads to suffen state transitions

Small changes in the neuromodualtory enviornment can have profound behavioural consequences

orexin stimulates the ARAS and the VLPO inhibits orexin thorugh the NTs GABA and galanin

wake and sleep circuits are mutually inhibitory
compete with each other and if one side gains an advantage it shuts down inhibition from the other
Quick state transition and see-saw effect

Question 5

what are the two protocols for distinguishing sleep

Answer 5

Forced Desynchrony

Constant Routine

Question 6

WHat are all models of sleep regulation a simplification (what lims are there 6)

Answer 6

• physiology of S and C
• stress/emotion/cog affect PS and PC?
  -NREM REM transitions
  EEG phenomena ptjer tjam SWA (spindles, K complex, certex sharp waves)
• how do local and global processe fit