Complex brain function: Neural rhythms and behaviour and Neuro-hormones Flashcards
LO
- Define Sleep and explain its contribution to health and well-being
- Discuss the regulation of sleep
- Illustrate the homeostatic and circadian control of sleep using the model organism Drosophila melanogaster as an example.
What is sleep?
- Altered consciousness
- Reduced movement and responsiveness
- Typical posture
- Homeostatic regulation
- Daily rhythmicity
What is more specific to sleep in higher animals?
- Brainwave patterns
- Loss of muscle tone during sleep
- Sporadic eye movement (REM sleep)
Where are cholinergic neurons found?
Tell me about their role in sleep
They are found near the junction of the pons and midbrain
- Stimulate cholinergic neurons in reticular activating system then experiments on cats showed the brain activity would shift from being sleep to more awake
- Stimulate thalamus then the slow waves will mimic those in non-REM sleep from awake state
- Brain activity in brain by stimulation or inhibition of different areas of the brain
What is an EEG used for?
- Can measure brain waves from different locations in the head
- slow wave patterns during non REM sleep are a result of synchronised firing in regions of the brain
An EEG recording was taken during the 1st hour of sleep, tell me the different waves seen over the one hour period, and at what times they were seen. Tell me about the frequency range for each wave type
Whats are sleep spindles?
Sleep spindles are bursts of neural oscillatory activity that are generated by interplay of the thalamic reticular nucleus (TRN) and other thalamic nuclei during stage 2 NREM sleep in a frequency range of ~11 to 16 Hz (usually 12–14 Hz) with a duration of 0.5 seconds or greater (usually 0.5–1.5 seconds).
tell me some features of NREM sleep?
- Reduced physiological activity
- Shift to Parasympathetic activity
- Thermoregulation maintained
Tell me about the average sleep cycle
- REM periods every 90-120min
- First REM period is shortest
- Most REM sleep occurs late
- Most deep sleep (stage3,4) early
How does the sleep cycle vary with age?
- Similar amount of REM sleep
- Diminishing stage 3,4 sleep
- Increasing sleep fragmentation
- All varies across ages
Whats a polysomnogram?
Polysomnography, also called a sleep study, is a comprehensive test used to diagnose sleep disorders. Polysomnography records your brain waves, the oxygen level in your blood, heart rate and breathing, as well as eye and leg movements during the study.
What stage of sleep is dreaming associated with?
REM
In what ways does REM resemble the wake state?
- brain activity
- heart rate
- respiration
In whats ways does REM sleep diverge from the wake state?
- eye movement
- muscle tone less
- suspended thermoregulation (core temp drops and peripheral increases)
- penile erection/vaginal lubrication
Tell me about the suppression of somatosensory response and muscle relaxation during REM sleep
- GABA NT released which is an inhibitory signal
- Inhibition of different centres that are signalling using a variety of NT
- One in diagram uses serotonin (5-HT) and noradrenaline
- Cholinergic centre and glutamatergic centres also present
- Glycinergic centre goes down to spinal cord
- Due to GABAergic signal initially all of this connected will suffer from inhibition
- Get inhibition of lower motor neuron pathways which results in paralysis during sleep
- Other way around, if go to cortex there is 2 negatives which makes a positive so cortical activity is no repressed which is why we see, with electrodes, a similar brain activity pattern as to when we are asleep
- Explains why relax body but keep brain active when we are asleep
What are the areas that are inactivated/ activated during REM sleep?
Tell me 4 areas of the brain associated with arousal and what are the NT expressed/secreted from here?
- Cholinergic nuclei: ACh
- Raphe nuclei: 5-HT/ serotonin
- Tuberomammillary nucleus of hypothalamus: Histamine
- Locus Coeruleus: Noradrenaline
Label the following areas/ nuclei and what part of sleep they are involved with
(bottom left)
Toggle switch
Sleep/wake toggle switch
An experiment was done on rats to look at the effects caused by depriving one of sleep. The experiment had 2 rats on a disc. One rat was not allowed to sleep where as the other was. When the no sleep rat would fall asleep, the disc it was on would spin and the rat would fall in the way and wake up. What are some of the side effects the rat experienced from sleep deprivation?
- debilitated appearance
- skin lesions
- swelling of the paws
- loss of motor control
- loss of EEG amplitude
- respiratory symptoms
- stomach ulcers
Tell me some cognitive impairments of sleep disruption
- Inattention
- Changes in cortical EEG responses
- Slower computational speed
- Impaired verbal fluency
- Reduced creativity
- Reduced abstract problem solving
- Learning issues
- Lower IQ scores
Name some examples of sleep disorders (dyssomnia)
- Primary Insomnia
- Primary Hypersomnia
- Narcolepsy
- Breathing Related Sleep Disorder
- Circadian Rhythm Sleep Disorder
Tell me about primary insomnia…
Primary insomnia (1-10% population)- most common one
- Initial (Anxiety disorders)
- Middle (Maintenance)
- More common in women & elderly
- Sudden onset
- Continuation (vicious cycle) so hard to deal with
- Drug abuse can make this worse as makes everything heightened
Tell me about narcolepsy…
- Daytime sleepiness
- ‘Sleep attacks’
- Cataplexy (emotional trigger)
- Sleep paralysis
- Excessing dreaming & waking at night
- Orexin signalling defect (orexin associated with the lateral hypothalamic area)- this was found by the research in narcoleptic dogs as slip out of wake state and into REM sleep. Turn over or neurodegeneration problems
What are examples of breathing-related sleep disorders?
- Primary snoring
- Obstructive sleep apnoea
What primary snoring?
Tissues in the back of the throat vibrate
Tell me about obstructuve sleep apnoea and some risk factors associated with this disorder
What advice is given to people with this disorder?
Obstructive Sleep Apnoea
- what it is: Blocked airway (blood oxygenation↓, wake)
- risks: risk↑ cardiovascular disease, (pre-)diabetes, depression
- advice: losing weight and not sleeping on the back are advice for people with sleep apnoea to prevent the airway becoming blocked
Name some circadian rhythm sleep disorders
- Normal sleep wake cycle
- Non-24h sleep wake syndrome: Non-24-hour sleep-wake disorder (N24) is a circadian rhythm sleep disorder in which an individual’s biological clock fails to synchronize to a 24-hour day. Instead of sleeping at roughly the same time every day, someone with N24 will typically find their sleep time gradually delaying by minutes to hours every day.
- Irregular sleep wake syndrome: disrupted sleep that’s often unstructured. Likely sleep for under four hours at a time
- Delayed sleep phase syndrome: Delayed sleep-wake phase disorder (DSWPD) is a disorder in which a person’s sleep is delayed by two or more hours beyond the socially acceptable or conventional bedtime. This delay in falling asleep causes difficulty in waking up at the desired time.
- Advanced sleep phase syndrome: Advanced sleep-wake phase disorder (ASP) is one of several circadian rhythm sleep disorders. These disorders occur in people who sleep at times that seem to be out of order with “normal” sleep times. People with ASP have an “early bird” circadian clock. They fall asleep several hours before a normal bedtime.
What two ways control sleep?
- Rhythmically (C)
- Homeostatically (S)
What is meant by eclosion
The emergence of an adult insect from a pupa or a larva (or nymph) from an egg is called eclosion
What is the evidence for a daily timekeeper (circadian clock)?
- Control of overt rhythms
- Entrainment
- Free-running rhythms
- Temperature compensation
The molecular clockwork: delayed negative feedback of gene expression
SCF-mediated protein degradation
SCF-mediated protein degradation of per
SCF-mediated light induced protein degradation of TIM
Light in early night ‘late dusk’: phase delay
Light in late night ‘early dawn’: phase advance
Remarkable conservation of animal clocks
Clock-controlled gene link to output
Circadian regulation of sleep (drosophila)
Homeostatic regulation of sleep (drosophila)