Sleep ( + Textbook Chapter 8 )

Question 1

Fill-in-the-Blank:

Biological rhythms are largely ____ ____.

Answer 1

endogenous systems

Question 2

True or False:

If the suprachiasmatic nucleus (SCN) was removed, the cells comprising it would continue to fire with an approximate 24 hour rhythm.

Answer 2

True

This brain region is known for being an internal clock or biological pacemaker used to help drive endogenous rhythms.

Question 3

Define:

Zeitgeber

Answer 3

Environmental cues that help organisms entrain their internal rhythms to their external environment.

Question 4

True or False:

Even under artificial conditions, some active period patterns may still occur.

Answer 4

True

These endogenously driven activity patterns may still occur, but likely with some kind of drift in the onset of activity due to biological rhythms seldom being perfectly 24 hours or one year etc.

Question 5

List:

FIVE examples of potential circannual rhythms exhibited by humans.

Answer 5

• Cortisol levels
• Suicide
• Birth weight
• Sleep
• OCD symptoms

Swaab, D. F., Van Someren, E. J., Zhou, J. N., & Hofman, M. A. (1996). Biological rhythms in the human life cycle and their relationship to functional changes in the suprachiasmatic nucleus. Progress in brain research, 111, 349–368. https://doi.org/10.1016/s0079-6123(08)60418-5

Question 6

What happens to our body temperature during a 24 hour sleep-wake cycle?

Answer 6

It rises during our active period, and then drops to its lowest during the sleep period.

Question 7

What is the role of cortisol in the circadian sleep-wake cycle?

Answer 7

Mobilising energy when we wake up.

Question 8

True or False:

The midpoint of sleep time gets later in early adulthood, even when taking cultural factors into account.

Answer 8

True

It has also been observed in other species too.

Question 9

True or False:

Whether you are a ‘morning’ or ‘night’ person may be largely genetically influenced.

Answer 9

True

Question 10

Define:

Sleep

Answer 10

A state of unconsciousness, decreased activity, and primarily only responsive to internal stimuli.

Question 11

What are the TWO main methods for measuring brain activity during sleep?

Answer 11

• EEG (electroencephalography).
• EOG (electrooculography).

Question 12

What kind of waves predominate during wake periods?

Answer 12

Large amplitude α waves, with a regular pattern of typically 8 - 12 Hz.

Question 13

List:

THREE key descriptors for stage one sleep.

Answer 13

• Jagged activity pattern (brainwaves).
• Low amplitude.
• Short-lived

Question 14

Define:

Sleep spindles

Answer 14

Bursts of neural oscillitory activity during non-rapid eye movement sleep (NREM) that usually last for at least 0.5 seconds.

These have a higher frequency than α waves, but occur regularly.

These are hypothesised to indicate the process of learning and memory consolidation during sleep.

Question 15

Define:

K-complex

(During sleep)

Answer 15

Larger-amplitude patterns of brain activity, and may be due to short-lived external stimuli.

Like sleep spindles this is yet another Stage 2 waveform exhibited in an EEG.

Question 16

List:

THREE key descriptors of stage two sleep.

Answer 16

• Larger amplitude than stage one (brain waves).
• Sleep spindles.
• K-complexes

Question 17

List:

TWO key changes of slow wave sleep.

Answer 17

• Brainwave frequency decreases.
• Physiological functions slow down.

Question 18

List:

THREE key features of REM sleep.

Answer 18

• Rapid eye movements.
• Body movements.
• Final stage of sleep.

Typically, sleeping for longer leads to more REM sleep.

Question 19

Does the pattern of sleep stages change with age?

Answer 19

Yes

The transition through each sleep stage is not a perfect cycle, and older people may have far greater wake periods and less REM overall.

Sleep cycles become more fragmented in elderly individuals.

Question 20

Which sleep stage predominates early in the night?

Answer 20

Slow wave.

Question 21

Later in a sleep period, which sleep stage(s) predominate?

Answer 21

Stage two sleep & REM.

Question 22

During which sleep stage does fine-tuning and consolidation of motor-skill learning occur?

Answer 22

Stage two sleep.

The motor cortex, pons, cerebellum, and thalamus become active during this time.

Question 23

What TWO proteins were discovered to be crucial for neurobiological sleep rhythms?

Answer 23

Period (Per) and timeless (Tim) proteins.

This is true for many organisms, and was discovered in experiments with fruit flies.

Question 24

What zeitgeber is particularly vital for sleep-wake cycles?

Answer 24

Light

Question 25

What are **melanopsin retinal ganglion cells**?

Answer 25

A small number of ganglion cells of the **retina** which project to the **SCN** and are affected by light even if rods and cones are disrupted or dysfunctional. ## Footnote These help **entrain** the circadian rhythm of the **SCN** to light as a zeitgeber. They are mainly close to the nose area and are sensitive to **blue light**.

Question 26

Do **melanopsin retinal ganglion cells** have a **slow** or a **fast** (de)activation?

Answer 26

They are **slow** to activate and deactivate.

Question 27

Which **protein(s)** induce **sleepiness**?

Answer 27

Both **period** (Per) and **timeless** (Tim) proteins.

Question 28

When is **Per** and **Tim** **mRNA** concentration at its highest?

Answer 28

During the **wakefulness period**.

Question 29

When are **Per** and **Tim** protein concentrations at their highest?

Answer 29

Towards the **end** of the **sleep period**. ## Footnote This is because it takes a while for concentrations to build up from the beginning of the sleep period.

Question 30

What effect do **Per** and **Tim** proteins have on the **clock gene**?

Answer 30

**Inhibition** ## Footnote The **clock gene** activity stimulates **mRNA synthesis**, so Per and Tim act in a **negative feedback loop**.

Question 31

# True or False: **Per** and **Tim** concentrations are relatively **independent** of whether you have actually slept or not.

Answer 31

**True** ## Footnote This may partially explain the feeling of a 'second wind' when you pull an all-nighter!

Question 32

# True or False: **Melatonin** is only produced by **diurnal** animals during the night.

Answer 32

**False** ## Footnote Melatoin levels are at their highest mostly during the night for nocturnal animals too, however it has the opposite effect and instead induces wakefulness.

Question 33

What is the important role of the **pituitary gland** in **sleep-wake cycles**?

Answer 33

**Melatonin production**.

Question 34

For **diurnal animals**, what role does **melatonin** play in **sleep-wake cycles**?

Answer 34

**Staying asleep**. ## Footnote Rather than *falling* asleep. Sleep disturbances and imbalances in melatonin production are seen in many disorders, such as depression.

Question 35

What is a **strong inhibitor** of **melatonin**?

Answer 35

**Caffiene** ## Footnote Unless highly addicted, this substance can often lead to sleep difficulties.

Question 36

# Describe: The **reticular formation**.

Answer 36

A network of **brainstem nuclei** that have extensive **ascending** and **descending pathways** to the spinal cord, and acts as a **major relay** and **integration** location. ## Footnote There are a wide variety of cell and neurotransmitter types here.

Question 37

What brain region is primarily responsible for **regulating arousal** and **consciousness**?

Answer 37

The **reticular formation**.

Question 38

What is the role of the **pontomesencephalon** in **wakefulness** and **sleep**?

Answer 38

It receives information and **stimulates activity** of certain **neurotransmitter receptors** with the **circadian rhythm**. ## Footnote For this, it receives information from the SCN too.

Question 39

Name the TWO **neurotransmitters** that **promote wakefulness** in the **reticular formation**.

Answer 39

**Acetylcholine** & **Glutamate**

Question 40

Name the **neurotransmitter** that **promotes sleep** in the **reticular formation**.

Answer 40

**GABA** ## Footnote This is one of the strongest **inhibitory** neurotransmitters.

Question 41

**Agonists** of what **neurotransmitter** are often used for **sedation** or **sleep disorders**?

Answer 41

**GABA**

Question 42

**Ketamine** is an **agonist** or **antagonist** of what neurotransmitter?

Answer 42

A **glutamate antagonist**. ## Footnote This induces **general anaesthesia**.

Question 43

**Propofol** is an **agonist** or **antagonist** of what neurotransmitter?

Answer 43

A **GABA agonist**. ## Footnote This induces **general anaesthesia**.

Question 44

# True or False: **Ketamine** has **antidepressant** properties separate from its role in inducing general anaesthesia.

Answer 44

**True** ## Footnote However, its other side effects make it not viable as a long-term treatment option.

Question 45

# List: THREE key descriptors of the **locus coeruleus**. ## Footnote (In relation to **sleep-wake** functions)

Answer 45

- **Homogenous structure**. - **Noradrenaline**/**norepinephrine**. - **Increases arousal**/**alertness**/**attentive processes**.

Question 46

What relationship between **histamine** and the **hypothalamus** in regards to **sleep-wake** processes?

Answer 46

**Histaminergic neurons** are localised to the **tuberomammillary nucleus** of the hypothalamus, and play a role in **increasing alertness**. ## Footnote Hence, antihistamine drugs (a direct antagonist) may often induce drowsiness.

Question 47

What effect does **orexin** play in the hypothalamus?

Answer 47

**Inreases wakefulness** and **alertness**. ## Footnote It was originally identified for its role in eating.

Question 48

What changes occur with **GABA** in the early stages of **sleep**?

Answer 48

[**GABA**] increases, which **decreases activity** in the **thalamus**. ## Footnote This stage is where you begin to 'shut out the noise'. This also interferes with the spreading of signals and information throughout the brain.

Question 49

What kind of **neurons** are associated with **GABA**?

Answer 49

**Small** / **interneurons**.

Question 50

Why can some people sleep with their **eyes open**?

Answer 50

**Thalamic activity** that processes and transfers external information has **decreased**, and so you don't process seeing things!

Question 51

What gives rise to sleep disturbances such as **sleep walking** or **talking**?

Answer 51

This occurs when **most** of the brain has **inhibited activity** but not all, such as motor regions. ## Footnote This occurs more commonly in children.

Question 52

# Define: **Lucid dreaming**

Answer 52

Being **aware** that one is dreaming, with some being able to **manipulate** the dreams to varying extents. ## Footnote This is actually relatively common (~23% of people regularly according to some accounts).

Question 53

Much like other **sleep disturbances** such as walking or talking, **lucid dreaming** is associated with certain brain regions still being **active** during sleep. *Which brain regions are associated with this?*

Answer 53

The **frontal** and **temporal** cortices.

Question 54

# List: FOUR examples of **negative outcomes** associated with **sleep disorders** such as **insomnia** or **hypersomnia**.

Answer 54

- **Aggression** - **Irritability** - **Accidents** - **Psychiatric disorders** (exacerbation). ## Footnote MDD is associated with both of these sleep disorders depending on the individual.

Question 55

# Define: **Desynchronised circadian rhythms**.

Answer 55

**Internally** or **externally** driven misalignments in **endogenous sleep-wake rhythms** which lead to disrupted sleep patterns. ## Footnote Internal factors may be misregulation of body temperature fluctuations, whilst external factors may include travelling to different time zones.

Question 56

# Define: **Sleep apnea**

Answer 56

Repetitive **breathing disruption** during sleep. ## Footnote Multiple factors may cause this condition, such as **genetics**, **hormones**, or **obesity** (particularly in men).

Question 57

What are FIVE examples of **side effects** associated with **sleep apnea**?

Answer 57

- **Increased sleepiness** - **Learning defecits** - **Decreased rationality** - **Impulse control issues** - **Attentional issues** ## Footnote This is a potentially very serious condition as it increases risk of **stroke**, **heart issues**, and **neuronal loss**.

Question 58

# Define: **Narcolepsy**

Answer 58

Sudden bouts of **sleepiness** or **sleep paralysis**. ## Footnote **Cataplexy** (sudden loss of control over muscles or sleep paralysis) occurs only in narcoleptic patients, but is not a symptom of all sufferers. **Strong emotions** or **stimulation** tends to trigger **cataplexy**.

Question 59

What **neurophysiological** changes are associated with **narcolepsy** / **cataplexy**?

Answer 59

Reduction in **orexin** transmission, particularly in the **lateral hypothalamus** (involved in wakefulness). ## Footnote **Genes** or **environment** may contribute to this condition, and is often triggered by **stress**.

Question 60

# List: THREE **hypotheses** for the **purpose of sleep**.

Answer 60

- **Energy conservation** - **Cellular maintenance** - **Synaptic strengthening** ## Footnote The final point is associated with **memory consolidation** and **learning**.

Question 61

What is the importance of the '**energy conservation**' hypothesis of sleep in terms of an **evolutionary perspective**?

Answer 61

It may account for why **different species** have **different sleep requirements**. ## Footnote (i.e. duration and regularity). For example, grazers spend less time sleeping as they need to maximise time eating food for energy.

Question 62

According to the '**energy conservation**' hypothesis of sleep, why do humans tend to sleep at night?

Answer 62

Because we a **sight-based** organisms who hunt and gather best during the day; sleeping at night allows us to conserve energy.

Question 63

# True or False: Humans **dream** *only* during **REM** sleep.

Answer 63

**False** ## Footnote Although we do dream more during this phase.

Question 64

What is the **activation pattern** of certain brain regions during **REM** sleep?

Answer 64

1. **Pons** 2. **Thalamic geniculate nucleus** 3. **Occipital cortex** ## Footnote **PGO** (ponto-geniculo-occipital) waves are the propagating activity between these regions during REM.

Question 65

# State: TWO functions of **REM** sleep. ## Footnote (Other than dreaming)

Answer 65

- **Memory formation** - **Cornea oxygenation** ## Footnote This especially is linked to **habit** formation too.

Question 66

# Define: The **activation-synthesis** hypothesis.

Answer 66

A hypothesis put forth to explain the occurrence of **dreams** as a result of **cortical interpretations** of **random neural stimulation**. ## Footnote It was first proposed in 1977 by John Allan Hobson and Robert McCarley.

Question 67

# Define: The **neurocognitive** theory of **dreaming**.

Answer 67

Dreaming is the result of our brains trying to **recall** or **imagine events**, but due to inhibition of the PFC, the logic is erratic or doesn't make sense.