Biological Rhythms and Sleep

Question 1

What is a biological Rhythm? What are 3 different types?

Answer 1

Biological Rhythms: regular flucuations in a living process

Circadian Rhythm: biological flucuations that follow a 24hour period

Ultradian Rhythm: shorter than 24 hours, occurs more than once a day (feeding, hormone release)

Infradian Rhythm: longer than 24 hours, occurs less than once a day. (e.g. mensturation.)

Question 2

What is an endorgenous clock and how does it relate to a free-running animal?

Answer 2

An internal clock, it governs our biological rhythms. While our bodies take cues from the external environment; we also operate on an internal clock that is consistent even without environmental stimulus.

A free running animal is an animal maintaining it’s biological rhythm without any external stimulus. Although not exactly 24 hours, this endrogenous extremely accurate and consistent.

Question 3

What do the following terms mean in the context of circadian rhythm?

• Phase shift
• Entrainment
• Zeitgber

Answer 3

Phase Shift: the shift in activity in response to a synchronizing stimulus (like light.) an example would be waking up from sleep with an increase in light.

Entrainment: the process of shifting rhythms

Zeitgber: literally “time-giver”; the cue that we use to synchronize with the environment.

Question 4

What is the significance of an internally regulated circadian rhythm?

Answer 4

An internally regulated circadian rhythm allows us to anticiapte an event and begin to physiologically and behaviourally prepare for it.

Question 5

What region of the brain is responsible for our internal clock? What research has confirmed this?

Answer 5

The suprahiasmatic nucleus in the hypothalamus.

• Animals who have lesions in the SCN region display distrupted circadian rhythms.
• Isolated SCN cells maintain electrical activity synchronized with their previously learned light cycle.
• Transplants of SCN cells have resulted in animals conforming to the transplant cell’s circadian rhythm (e.g. animals who previously exhibited a 24h biological rhythm with SCN transplant cells with a 20h rhythm will start displaying a 20h rhythm instead.

Question 6

What are different ways that the circaidan Rhythm entrains to light-dark cycles?

Answer 6

Melotonin: Melotonin will inform the brain about the presence or abscence of light.

Some ganglion cells in the eye are specialized and part of the retinohypothalamic pathway. These ganglion cells do not communicate with rods and cones. Instead they have their own photoreceptors called melanopsin and their axons project straight to the Suprahiasmatic nucleus.

Question 7

What is the molecular process in SCN cells that controls our circadian rhythm?

Answer 7

1. SCN cells produce two protiens: clock and cycle.
2. Clock and cycle bind together to form a dimer
3. Clock/cycle dimers promote the transcription of two genes: period and crytochrome (per and cry).
4. per and cry bind together to form a complex (protien)
5. The per/cry protien enters the nucleus and inhibits the activity of the clock/cycle dimer which results in the inhibition of per/cry transcription.
6. This inhibitory effect stays in place until the per/cry protien degrades (which takes about 24h).

Question 8

How do gene mutations affect the molecular process behind our circadian rhythm?

Answer 8

Double clock mutants: result in severly arhythmic circaidan rhythms

Morning people and night owls appear to have different versions of the clock gene

Question 9

How is the molecular process in SCN that controls our circadian rhythm entrained to day/night cycles?

Answer 9

The retinal ganglion cells that detect light with melanopsin release glutimate onto neurons in the SCN. The glutimate stimulation increases the transcription of the Per gene, entraining the molecular clock to the day/night cycle

Question 10

What are the two distinct classes of sleep?

Answer 10

Slow Wave sleep (aka SWS or Non-REM sleep). This class can be divided into three stages and is characterized by slow wave EEG activity.

REM sleep: rapid eye-movement. Is characterized by small amplitude fast EEG activity, no posteral tension, and rapid eye movement.

Question 11

What is beta and alpha EEG activity?

Answer 11

Beta Activity: desynchronized EEG activity, dominated by fast frequency, low amplitude waves. Occurs when you are awake.

Alpha Activity: regular oscilation of waves at 8-12Htz. Occurs during periods of rest, often occurs before the first stage of sleep.

Question 12

What are the characteristics of stage 1 and 2 sleep?

Answer 12

Stage 1: EEG activity is vertex spikes intermit small amplitude waves of irregular frequency. The heart rate lowers and muscle tension reduces, eyes move a little. Stage 1 lasts only a few minutes

Stage 2: EEG waves occur in 12-14Hz called sleep spindles as well as k-complexes (sharp negative potentials.)

Question 13

What are the characteristics of Stage 3 sleep?

Answer 13

Also called slow wave sleep. Is defined by the presence of large amplitude, slow delta waves. Delta waves occur about 1/second

There is widespread cortical synchronization. Stage 3 lasts ~1 hour before dipping back into stage 2 briefly

Question 14

What are the characteristics of REM sleep?

Answer 14

Has small amplitude, high frequency waves; rapid eye movement, muscle atonia (complete absence of muscle tone), inhibition of motor neurons, vivid dreams, irregular breathing and irregular pulse.

Question 15

Describe a typical night of sleep for a young adult.

Answer 15

Time ranges between 7-8 hours with 45-50% of the time spent in stage 2 sleep and 20% in REM.

Cycles of sleep tend to last about 90 minutes with early cycles having more stage 3 and later cycles having more REM. We often go through 4-5 cycles per a night.

Question 16

How does our sleep change through development?

Answer 16

Infants have a higher ratio of REM sleep than any other age, REM sleep declines with age.

At puberty, our circadian rhythms tend to shift so that you get up later in the day (and yet high school tends to start earlier than elementary school).

Question 17

When do dreams occur? What are different kinds?

Answer 17

Dreams mostly occur during REM sleep. In REM, dreams are vivid, have strong visual imagery, and give the sense of really being there. We can dream during other stages but they are usually more like thinking than like participating in a story.

Nightmares are just scary dreams, they occur during REM like a regular dream. Night Terrors are different. They occur during stage 3 and are characterized by a sudden arousal from stage 3 SWS accompanied by intense fear and high autonomic activity.

Question 18

How does REM sleep present in other animals besides humans?

Answer 18

REM is present in almost all mammals, vertibrates, and and reptiles which suggests that it evolved early in our shared ancestry.

Not all animals show REM however. Some animals, like dolphins and some birds have different sleep cycles because REM would be counterproductive to their survival. E.g. Dolphins do not enter REM but instead show unilateral sleep so that they are still able to go to the surface for air. Some birds do the same so that they are able to fly long distances without stopping. Unilateral sleep is when one hemisphere sleeps at a time.

Question 19

What is sleep deprivation?

Answer 19

The partial or total prevention of sleep. It leads to irritability, difficulty in concentrating and attention, episodes of disorientation, and slow reaction times

We can be sleep deprived even if we don’t know it. You don’t necessarily feel sleepy when you are sleep deprived.

Prolonged sleep deprivation leads to compromised immune functioning and eventual death.

Question 20

What occurs during sleep recovery?

Answer 20

Recovering from sleep deprivation does not necessarily require you to sleep more. You might sleep a bit longer at first but instead your sleep is more intense

Stage three sleep has a much higher ratio than normal, and stage 2 is lower as a result. REM sleep also increases and is more intense with more rapid movement of eyes than usual.

Question 21

What is fatal familial insomnia?

Answer 21

It is a genetically inherited disease where people stop being able to sleep in midlife due to a mutated gene affecting the thalamus. They usually die 7-24months after onset. It is incurable

Question 22

What are the 4 biological functions of sleep?

Answer 22

1. Energy Conservation
2. Niche Adaption
3. Physical Restoration
4. Memory Consolidation:

Question 23

How does sleep aid in the conservation of energy?

Answer 23

Sleep takes less energy than being awake because muscular tension, heart rate, blood pressure, temperature and rate of respiration are all reduced. Evidence for this theory: small animals with higher metabolic rates sleep more than large animals with lower rates. However there is not enough energy conservation for this to be the sole reason for sleep.

Question 24

How does sleep contribute to Niche adaption?

Answer 24

The specialization of daytime night time activity is part of each species ecological niche. Sleep helps animals to avoid predators.

Question 25

How does sleep work at body and brain restoration?

Answer 25

Sleep helps us rebuild and restore materials used while awake (such as proteins.) Growth hormones are released during SWS. Sleep may also help clean out the brain. the glial cells work more efficiently while we sleep. Sleep is also vital for our immune functioning.

Question 26

How does sleep aid memory consolidation?

Answer 26

Sleeping during the interval between learning and recall improves retention, perceptual skills are particularly improved by REM sleep.

Consolidation of declarative memory tasks and complicated motor skills seems to benefit from SWS

REM sleep might not be necessary for learning but neural pruning takes place during this stage.

Question 27

What is the major challenge for sleep theories?

Answer 27

That not everyone requires the same amount of sleep and, especially, that there are select people who can survive on very little sleep (as little as an hour a night). While they are anomalies, sleep theories need to be able to explain how these exceptions to the general rule are possible.

Question 28

What are the 4 neural systems that underlie sleep?

Answer 28

The Fore Brain: generates SWS

The Brain stem system: activates the forebrain into wakefulness

The Pontine system: triggers REM sleep

The Hypothalamic system: coordinates the other three systems.

Question 29

What are isolated brain studies and how have they contributed to our understanding of sleep?

Answer 29

Isolated brain studies: an incision is made between the medulla and the spinal cord. these transection experiments have shown that sleep is a process that takes place in the brain and has helped us to isolate the areas responsible for sleep

We founded that an isolated brain still showed signs of typical sleep patterns

An isolated forebrain however (transection made at the midbrain) showed constant SWS but no indication of wakefulness or REM. This means that the forebrain can generate SWS on its own but other areas are necessary for the other stages of sleep.

Question 30

How does the Forebrain system function for sleep?

Answer 30

The basal forebrain is responsible for generating SWS.

Neurons in the basal forebrain release GABA at sleep onset. This GABA activates receptors in the tuberomamillary nucleus in the hypothalamus. (these are the same GABAa Receptors that are activated by general anesthetics.

Question 31

How does the brainstem system function for sleep?

Answer 31

The reticular formation (reticular activation system, RAS) in the brainstem wakes up the forebrain. In studies, stimulation of the RAS wakes up sleeping animals while Lesions in the RAS produce persistent sleep.

Question 32

How does the pontine system function for sleep?

Answer 32

A cluster of neurons ventral to the locus coeruleus regulate REM. Some of these neurons are only active during REM suggesting that is their only function. These neurons release GABA and Glycine to inhibit motorneurons to keep them from firing during REM. This is what creates sleep paralysis.

Question 33

How does the hypothalamic system function for sleep?

Answer 33

Orexin neurons in the hypothalamus project to other sleep regions (including the basal forebrain, the tuberomamillary nucleus, the reticular formation, and the locus coeruleus of the pontine system.

The hypothalamus seems to contain orexin switches that determine wakefulness, non-REM sleep, or REM sleep.

Question 34

What is Narcolepsy?

Answer 34

Entering REM sleep suddenly and unintentionally during waking hours. Epidsodes can occur any time, usually multiple times a day. They last 5-30 minutes usually. Can also have cataplexy: a sudden loss of muscle tone leading to a collapse (but not a loss of consciousness.)

Narcoleptic dogs have a mutant gene for orexin receptors. Orexin usually prevents the transition from wakefulness directly to REM. This suggests that there is something wrong with the hypothalamic system.

Question 35

What is sleep paralysis?

Answer 35

Sleep paralysis is the brief inability to move just before falling asleep or just after waking up. Caused by the pontine center continuing to impose muscle paralysis even after you wake up. Occasional episodes of sleep paralysis are not uncommon, concern is only necessary if the paralysis occurs often or for long periods of time.

Question 36

What is REM behaviour Disorder?

Answer 36

Is characterized by organized behaviour in a person who appears to be asleep. Is more common in middle aged men and is usually followed by early symptoms of Parkinson’s or dementia. This suggests that the widespread neural damage of these diseases actually starts in the brainstem region that imposes muscle atonia.

Question 37

What are sleep disorders common to children?

Answer 37

Common sleep disorders in children include: sleep enuresis and night terrors, both associated with SWS

Somnambulism (sleepwalking) is also more common in children but may persist into adulthood. It also occurs during SWS.

Question 38

What are different types of insomnia?

Answer 38

Sleep onset insomnia: difficulty falling asleep

Sleep maintenance insomnia: difficulty staying asleep

insomnia is often caused by situational factors (like shift work, or jet lag) or by drugs, or neurological factors or psychiatric factors (e.g. stress)

Question 39

What is Sleep Apnea?

Answer 39

Sleep apnea is when breathing may stop or slow during sleep. It is caused by the muscle in the chest and diaphragm being too relaxed during sleep. Or it is caused by changes in the pacemaker respiratory neurons in the brainstem.

Sleep apnea is usually accompanied by snoring

Question 40

What is Sleep state misperception?

Answer 40

This is when you think you are not asleep but you actually have been (EEG activity is in line with sleeping behaviour)

Question 41

What is Sudden Infant Death Syndrome?

Answer 41

SIDS, a sudden unexpected death of an apparently healthy infant who stops breathing, usually during sleep. May arise from sleep apena due to immature respiratory pacemaker systems or arousal mechanisms.

Putting babies on their back to sleep has cut SIDS cases down by almost half.

Question 42

What do sleeping pills do and what are some problems with them?

Answer 42

Most sleeping pills bind to GABA receptors.

Problems with sleeping pills include the fact that they can produce marked changes in sleep patterns that persist for days after use, they can become ineffective over time, and can lead to daytime drowsiness and memory gaps.

They do not truly support healthy sleep, they can be effective for short term solutions but only healthy sleep behaviour can produce healthy sleep.