Week 3 sleep

Question 1

The amount of sleep an animal gets depends on…

Answer 1

amount of sleep decreases as their level of vulnerability and/or how much they need to eat increases.

Question 2

What is unihemispheric sleep?

Answer 2

One hemisphere (and the contralateral eye) sleeps while the other remains awake. Only slow wave sleep occurs not REM.

Question 3

What is inactivity theory?

Answer 3

An attempt to explain why sleep is necessary. Suggests inactivity at night helped animals to survive, as they did not injure themselves in the dark and were not killed by predators. This was therefore a trait that was passed on through natural selection. Major issue with this theory: it is always safer to remain conscious.

Question 4

What is energy conservation theory?

Answer 4

An attempt to explain why sleep is necessary. Food is not always easy to come by, especially at night, so we must conserve energy.

Question 5

What is restorative theories?

Answer 5

An attempt to explain why sleep is necessary. During sleep there is restoration of what has been lost from the body while awake (e.g. muscle mass, tissue cells).

Question 6

What is brain plasticity theory?

Answer 6

An attempt to explain why sleep is necessary. Sleep is a time in which the brain develops and changes, i.e. creating new neurons and pruning old connections.

Question 7

What is most powerful zeitgeber(time singal from the environment)?

Answer 7

light.

Question 8

What is social jet lag?

Answer 8

The impact of being a “evening person” forced into a “morning person” environment. Can lead to lower grades (despite high overall intelligence), increased alcohol use, overeating, and overall less happiness.

Question 9

What are circadian clocks?

Answer 9

collections of genes which regulate the expression of other genes critical for cell physiology and metabolism.

Question 10

What is the Suprachiasmatic Nucleus (SCN)?

Answer 10

the master circadian pacemaker, which synchronizes all circadian clocks in the body to the same 24-hour cycle. Also the main driver for rhythms of sleep.

Question 11

Where is the suprachiasmatic nucleus (SCN) located?

Answer 11

tucked in next to the hypothalamus.

Question 12

What is the retinohypothalamic path?

Answer 12

A small branch of the optic nerve through which light travels to reset the SCN.

Question 13

Explain the pineal gland.

Answer 13

Regulated by the SCN, the pineal gland is an endocrine gland that secretes melatonin and is located posterior to the thalamus.

Question 14

When does melatonin secretion begin?

Answer 14

2-3 hours before bedtime.

Question 15

Explain the brainstem.

Answer 15

The brainstem is responsible for mediating levels of arousal, including levels of REM and non-REM sleep.

Question 16

What is the reticular formation?

Answer 16

Within the brainstem, a collection of nuclei (bundles of cell bodies), fibres and tracts (bundles of axons) running through the Medulla, Pons and Midbrain.

Question 17

Several pathways from the hypothalamus increase wakefulness, what activating neurotransmitter does each pathway release?

Answer 17

acetylcholine, orexin (hypocretin)(not necessary for waking but necessary for staying awake), & histomine.

Question 18

In order to sleep, GABA-ergic neurons do what?

Answer 18

Increase their firing. This widespread release of GABA to the thalamus and the cortex inhibits the brain – producing sleep. For this reason, sleep pills always target GABA in some way.

Question 19

What does a polysomnograph do?

Answer 19

uses electrodes to record a combination eye-movement activity and EEG, can be used to help identify sleep stages.

Question 20

What is stage 1 sleeping?

Answer 20

The transition period between sleeping and waking. The EEG is dominated by irregular, jagged, low-amplitude waves of different frequencies.

Question 21

What is stage 2 sleep?

Answer 21

Characterized by sleep spindles and K-complexes.
Sleep spindles are 12-14Hz waves during a burst lasting at least 0.5 seconds. K-complexes are a sharp wave associated with temporary inhibition of neuronal firing

Question 22

What is stage 3 and 4 sleep?

Answer 22

Heart rate, breathing rate, and brain activity decrease. Slow-frequency (delta, 1-3Hz), large-amplitude waves become more common. Stage 4 sleep has a greater prevalence of slow-waves than stage 3, but there isn’t a very clear boundary. Often grouped together into a single sleep-stage (slow-wave sleep, or SWS).

Question 23

What is slow-wave sleep (SWS)?

Answer 23

Sleep stage 3 & 4 grouped together.

Question 24

What is stage 5 sleep?

Answer 24

The EEG shows irregular, low-amplitude, high-frequency oscillations indicating increased neuronal activity (somewhat similar to Stage 1) that suggests a ‘lighter’ sleep.

Question 25

Do dreams usually occur in REM or NREM sleep?

Answer 25

NREM sleep

Question 26

postural muscles of the body, including those in the neck, are more relaxed, and higher variability of heart and breathing rate, erections/vaginal moistening, and facial twitches are often found in what kind of sleep?

Answer 26

REM

Question 27

What is the sleep stage sequence?

Answer 27

stage 1 - 2 - 3 - 4 - 3 - 2 - REM. then begin again from 2. These cycles last about 90 minutes and there are typically 4-5 cycles a night.

Question 28

What is narcolepsy?

Answer 28

A condition characterised by frequent periods of sleepiness during the day, has a clear genetic component, with over 90% of sufferers carrying the HLA-DR2/DQ1 gene.

Question 29

What are the four main symptoms of narcolepsy?

Answer 29

Attacks of sleepiness during the day, Occasional cataplexy, Sleep paralysis, and Hypnogogic hallucinations

Question 30

What is the main hormone related to narcolepsy?

Answer 30

Orexin. People with narcolepsy lack the hypothalamic cells that produce and release orexin – potentially due to an auto-immune condition.

Question 31

What is REM behaviour disorder (RBD)?

Answer 31

For most people, the major postural muscles are inactive during REM sleep. People with REM behaviour disorder move around vigorously during REM, often violently, and frequently injure themselves or others, or damage property. Thought to be caused by inadequate inhibitory transmission (e.g. deficient GABA).

Question 32

Explain sleepwalking.

Answer 32

complex movement carried out during sleep, sometimes dangerous. occurs during NREM, causes not well understood, may run in family, may be linked to stress, alcohol consumption, etc.