Sleep wake cycle and insomnia

Question 1

Describe the role of arousal centres

Answer 1

-when awake, areas in the brainstem and hypothalamus called arousal centres stimulate the cerbral cortex

-arousal centres release neurotransmitters including ACh, histamine,5HT and orexin

Question 2

Describe the sleep promoting centre

Answer 2

-the ventrolateral preoptic nucleus in hypothalamus switches off arousal centres

-VPLO produces neurotransmitters GABA and galanin

-neurotransmitters cause arousal centres to shut down resulting in rapid changes into NREM sleep

Question 3

What is the sleep switch?

Answer 3

-mutual inhibition between wake-promoting neurons from the arousal centre and sleep-promoting neurons from the VPLO

-when cortex is activated by the sleep arousal centres there is a simultaneous inhibition of VLPO

Question 4

What happens when the arousal centre is stimulated?

Answer 4

histamine,5HT,NA stimulate the cortex promoting wakefullness and stops the messsage that makes us sleep

Question 5

What happens when we recieve the message to sleep?

Answer 5

-if histamine is released and inhibited then sleep will ensue

-happens because the VPLO blocks the production of histamine and other wake signs by GABA and galanin

-but histamine also blocks VPLO in which case switch will flip to wake state

Question 6

what is inhibited when you are awake and what is inhibited when you are asleep?

Answer 6

awake-GABA and galanin
sleep - histamines

Question 7

What are the two proccesses of the sleep wake cycle?

Answer 7

-24 hour circadian rythum of sleep and arousal-proccess c

-a sleep wake timer-homeostatic mechanism-proccess s

Question 8

Describe the circadian rhytm-proccess c

Answer 8

-the suprachiasmatic nucleus communicates the circadian rhythm to the body via the production of melatonin

-melatonin production by the pineal gland peaks in the middle of the night.

-melatonin does not induce sleep but simply signals the start of sleeping process

Question 9

What does the circadian rhythm control?

Answer 9

Tendency to sleep​
Sleep structure​
Level of alertness​
Temperature regulation​
Hormone production​
Melatonin​
Growth hormone​
Cortisol​
Cardiovascular function​
Respiratory function​
Glucose levels

Question 10

How is the SCN reset?

Answer 10

every daytime by light and every night time by melatonin

Question 11

Describe the homeostatic mechanism-proccess s

Answer 11

-Homeostatic mechanism ‘counts’ how long we have been awake or asleep and a ‘sleep pressure’ builds up with increasing wakefulness​

-The longer you remain awake, the higher the sleep pressure​

-As you sleep, the sleep pressure reduces and the likelihood of awakening increases

Question 12

What is sleep pressure?

Answer 12

the accumulation of adenosine in the cerebrospinal fluid whilst awake

Question 13

Describe the role of adenosine with regards to sleep pressure

Answer 13

-Adenosine is released from ATP as energy from glycogen is used during the day so levels increase the longer you are awake​

-Adenosine levels will drop during sleep as glycogen stores are replenished​

-Stimulants such as caffeine and theophylline (tea and chocolate) act as adenosine receptor antagonists and so reduce its ability to induce sleepiness

Question 14

Describe homeostatic system and circadian rhythm during the night

Answer 14

-during the first half of sleep the sleep pressure is still high whilst the circadian alerting signal has decreased

-sleep drive now has been reduced however the persistant low circadian alerting signal maintains sleep

-synchronization of these two systems allow consolidation periods of both alertness and sleep

Question 15

What external factors influence the quality of sleep we obtain?

Answer 15

-light
-pain
-medical condtions
-medication
-alcohol
-caffeine
-sleep environment

Question 16

Describe how light effects sleep

Answer 16

-light modulates circadian rhythm by influencing the timing of SCN

-light stimulates photosensitive cells of the retina which signal to the SCN via retinohypothalamic tract

-exposure to light during the night can reset the internal clock making sleep diffcult

Question 17

How does medication affect sleep?

Answer 17

-alpha and beta blocker reduce REM and NREM3 sleep and increases daytime sleepiness
-some antideppresants provoke insomnia, reduce REM sleep
-brain cells promoting alertness are inhibted by adenosine

Question 18

Why is caffeine a stimulant?

Answer 18

it is an adenosine receptor antagonist and so removes the inhibition by adenosine resulting in increased alertness

Question 19

what are the 6 main catergories of sleep disorders?

Answer 19

-insomnia
-sleep related breathing disorders (obstructive sleep apnoea
-central disorders of hypersomnolence-narcolepsy
-circadian rhythm sleep wake disorders
-parasomnias
-sleep related movement disorders

Question 20

What are the four main catergories of insomnia?

Answer 20

-chronic insomnia disorder
-short term insomnia disorder
-other insomnia disorder
-isolated symptoms and normal variant

Question 21

What are the main symptoms of chronic insomnia?

Answer 21

-difficulty initiating sleep
-difficulty maintaining sleep
-waking up earlier than desired

Question 22

When does chronic insomnia occur?

Answer 22

At least three times a week
-has been present for at least 3 months

Question 23

describe primary and secondary insomnia

Answer 23

p-main condtion
s-caused from another condition

Question 24

What are the identifiable groups of chronic insomnia?

Answer 24

-Psychophysiological insomnia
-idiopathic insomnia
-paradoxical insomnia

Question 25

What is psychophysilogical insomnia?

Answer 25

-a learned response where the patient does not go to bed when planned

-the patient has no difficulty sleeping when sleep is unplanned however bedtime or planned naps cause the patient difficulty

Question 26

Describe idiopathic insomnia

Answer 26

-debilitating and detrimental to health
-lifelong
-first identified in infancy
-no known cause

Question 27

Describe paradoxical insomnia

Answer 27

-subject complains of insomnia but there is no evidence
-patient complains of sleepless nights despite EEG evidnence to the contray
-a sleep diary can identify abnormal sleep habit, inconsistncies in bed times and daytime naps

Question 28

What causes short term insomnia disorder?

Answer 28

-Known cause- stress, excitement, new baby, money worries

-usually resolves when cause resolves

Question 29

What is other insomnia disorder?

Answer 29

patients have features of insomnia but do not fit the full criteria for chronic or short term insomnia

Question 30

Describe normal variant insomnia

Answer 30

-excessive time in bed
-short sleeper

Question 31

What are the causes of insomnia?

Answer 31

-due to a state of hyperarousal which impacts sleep onset
-can be caused by a range of different factors
(medical problems, mental health issues, poor sleep hygiene, eating or drinking substances which have a negative impact on sleep)

Question 32

What are some treatments of insomnia?

Answer 32

-if theres an underlying cause this should be addressed first
-non-pharmaceutical therapies
-drugs can be addictive so they should only ever be used for short periods of time

Question 33

Name some non-pharmaceutical therapies

Answer 33

-improvement in sleep hygiene
-stimulus control
-sleep restriction
-relaxation therapy
-CBT

Question 34

Name some drugs that can be used to treat insomnia

Answer 34

-antihistamines
-benzodiazepines
-antidepressants
-melatonin

Question 35

Why do antihistamines help insomnia?

Answer 35

-antihistamines stop histamine releases from arousal centres and prevents inhibition of VLPO sleep promoting centre

-antihistamines become less effective the longer they are taken

Question 36

How do benzodiazepines help insomnia?

Answer 36

-these are a group of drugs with sedative hypnotic and anxiolytic properties

-help sleep in most cases but have negative effects such as dependance, drowsiness, lack of concentration
-enhances the effect of GABA

Question 37

How do antideppressants help sleep?

Answer 37

-some evidence shows that these work by helping the sufferer relax before sleep
-some promote sleep some cause insomnia
-area is not fully researched

Question 38

How does melatonin help with sleep?

Answer 38

-less risk of dependance
-levels of melatonin decreases with age so supplementing levels can assist in sleep in the elderly
-comercially available
-can help with jet lag