week 9 Wakefulness and Sleep

Question 1

What is the difference between an endogenous circannual rhythm and an endogenous circadian rhythm?

Answer 1

An endogenous circannual rhythm is an internal seasonal rhythm. eg migration, hibernation.
An endogenous circadian rhythm is an internal rhythm of close to 24 hours.

Question 2

What is the functional significance of the suprachiasmatic nucleus (SCN)?

Answer 2

The Suprachiasmatic Nucleus is the main driver for sleep and body temperature cycles.. Part of hypothalamus. Sits just above Optic Chiasm. Tonically active.

Question 3

From which brain structure is melatonin released and what is its function?

Answer 3

The Pineal Gland releases melatonin. Tends to be released more at night. In diurnal animals it increases sleepiness whereas in nocturnal animals it increases wakefulness. Melatonin also has a role in onset of puberty and in circannual cycles.
The SCN causes pinneal gland to produce melatonin. Melatonin has an inhibitory effect on the reticular formation.

Question 4

What happens when circadian rhythms are not reset?

Answer 4

Circadian rhythms usually follow 24 hours, and are usually adjusted internally based on light levels. Sometimes the cycle follows noises, periods of activity or temperature but these are far less powerful. In situations where not encountering triggers etc, tend to maintain an approx 24 hour cycle but gradually drifts a little each cycle.

Question 5

What are some common symptoms of jet lag? Which brain structure appears to be damaged when repeated adjustments of the circadian rhythm are made?

Answer 5

eg time zone changes, and one’s desired/required activities disallow one from sleeping at one’s previous cycle, will get tired, angry, lowered immune system, depression. Prolonged stress (jet lag) can damage the hippocampus.

Question 6

Understand what an electroencephalogram (EEG) is.

Answer 6

Many multiple electrodes over head receive electrical waves and displayed on a graph. These are a summation of electrical activity in different superficial regions of the brain.

Question 7

What are alpha waves and what state of consciousness do they correspond to?

Answer 7

Alpha waves are 8-12Hz and associated with relaxed but awake.
(nb Beta waves =alert awake 12-30Hz)

Question 8

You should be able to Understand the electrical (i.e., EEG) characteristics of stages 1 to 4 of sleep. In particular, you should be able to Understand and identify sleep spindles and K-complexes.

Answer 8

8.

Question 9

Distinguish between the electrical, physiological, and psychological characteristics of REM sleep in comparison to slow-wave sleep.

Answer 9

REM sleep;rapid eye movement sleep, irregular low voltage fast eeg waves similar to stage 1 sleep. Rapid eye movements. deeply relaxed neck muscles like deep sleep, erection/vaginal moistening, heart rate fluctuates, bp fluctuates, facial twitching.

Question 10

What is paradoxical about paradoxical sleep?

Answer 10

=REM sleep. Is paradoxical because some very active brain areas yet deeply relaxed muscles, yet also some movements.

Question 11

What is meant by the term polysomnograph?

Answer 11

Multiple measurements during sleep, including eeg and eye movements.

Question 12

During REM sleep, what is thought to be the significance of PGO waves, and which three brain structures seem to be involved in producing these waves (i.e., what do the letters P, G, and O stand for? …no, not the cruise ship)?

Answer 12

Pons, Geniculate (lateral), Occipital cortex. PGO waves start in pons then show in lateral geniculate and then Occipital cortex. Each wave corresponds to a rapid eye movement. Shows during rem sleep.

Question 13

List some of the neurotransmitters that appear to be critical for the development and maintenance of REM sleep.

Answer 13

Gaba released from ventral medulla promotes rem sleep.Acetylcholine inhibits inhibition of rem (therefore promoting it).
(Carbachol stimulates acetylcholine receptors and can cause a sleeper to progress to rem -in sleep studies).
serotonin and norepinephrin interrupt rem sleep.

Question 14

Understand the brain structures and neurotransmitters implicated in the regulation of arousal/excitation.

Answer 14

Reticular formation extends from medulla to forebrain. Ascending axons of reticular formation regulates arousal (this part is the pontomesencephalon). Does this with combination of gaba, acetylcholine, glutamate and dopamine.Potassium ion levels maintenance is how this is achieved. Arousal is created in the hypothalamus, thalamus and basal forebrain.
The Locus Coeruleus is a small structure in pons. Emits bursts of impulses in response to events (especially emotional) causing release norepinephrine in multiple cortical sites. This enhances attention and memory. Locus Coeuruleus is mostly inactive during sleep.The effect of the locus coerulus is to enhance whichever parts of the brain are most active at the time.
The hypothalamus has neurons involved in both wakefulness and sleep.Histamine is release from some pathways from hypothalamus and this promotes arousal/alertness. Orexin (=hypocretin) is released from the pathways from lateral and posterior nuclei of the hypothalamus and enhances wakefulness. Best for maintaining alertness not waking up.

Question 15

What is insomnia? What are common known causes of this sleep disturbance?

Answer 15

Inadequate sleep. Common causes are noise, uncomfortable temperature, adverse food reactions,stress, pain, medications etc.

Question 16

What is sleep apnoea? What are some possible causes?

Answer 16

.not breathing for 1 minute during sleep. Awaken gasping for breath. Might not remember awakening but are more tired as a result. Those with sleep apnoea at greater risk of stroke and heart issues, and cognitive and learning isses. The apnoea may result in some hypoxic neuronal damage.
Causes for sleep apnoea are genetics, hormones, older age, deterioration of brain resp patterns, being overweight is a big issue-need to compensate with faster resp but this harder to maintain when asleep. Tranquilisers and alcohol may play a part also.

Question 17

What is narcolepsy? What are some possible causes?

Answer 17

Frequent periods of sleepiness (and sleep) during the day. Approx 1 in 1000 affected, does not seem to run in families. H1N1 avian flu caused a high rate of narcolepsy. 4 main symptoms but not all affecteds will have all 4; Sleep attacks during the day,
occasional cataplexy (profound muscle weakness whilst awake),
sleep paralysis (inability to move whilst falling asleep or waking up), hypnagogic hallucinations (dreamlike states hard to tell if reality or dream) (often occurs at onset of sleep).
Cause is lack of orexin. seems to be a lack of the cells which produce it-possibly due to genetics(there are familial lines of dogs with it), post viral, lesion etc.
Tx is stimulants such as amphetamines. Orexin or synethetic of, so far not found that can cross bbb to reach target areas.

Question 18

What is REM behaviour disorder?

Answer 18

During REM, postural muscles are active and able to move around. Frequently injure self or others as literally acting out their dreams. Thought due to insufficient inhibition eg of gaba systems.

Question 19

Understand each of the following: Night terrors, sleepwalking.

Answer 19

Night Terrors-were dreaming and in non REM state and awaken screaming in terror and highly anxious. More common in children. Sleeping walking is more common during slow wave sleep, usually no dreaming. Walking etc whilst asleep. Awaken without memory of the episode. Most sleepwalkers often have another sleep disorder such as night terrors or bedwetting and it tends to run in families. Tends to occur more when sleep deprived or under much stress.

Question 20

Explain PER and TIM role

Answer 20

PER and TIM are proteins and per and tim are mRNA .
There are 2 genes called Period and Timeless and they produce the proteins PER and TIM. mRNA is responsible for production of the proteins PER and TIM. PER and TIM are both together both promote sleep states. the mRNA concentrations decline with negative feedback of high PER and TIM concentrations.The feedback cycle takes about 24 hours. Light also activates chemicals which breakdown TIM, and wakefulness occurs during the day when PER and TIM concentrations are lowest. This has been the case for fruitfly. It has been determined however that humans have similar systems. Mammals have 3 variations of PER and several variations of TIM. Mutations of Period or Timeless genes in people have been found to have shorter circadian rhythms and consistently sleepy in early evenings and awake very early in morning.

Question 21

general sleep stage trends through night.

Answer 21

Tend to fall asleep into stage 1 and move to stage 2 then slow wave. After an hour approx, cycle from slow, to stage 2 and then into REM. This sequence repeat, with each sequence approx 90min. Early in the sleep the sequence has mostly slow wave, but towards end of sleep, is mostly REM. Older adults have less slow wave and more awakenings during night.