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PSYC270 > Rhythms and Sleep > Flashcards

Rhythms and Sleep Flashcards

1
Q

What is a circadian rhythm?

A

Pattern that lasts approx. 24 hrs (ex. sleep)

  • Correlated with activity in posterior part of cortex
  • Persists without light
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2
Q

Define Zeitgeber

A
  • Stimulus that resets the circadian rhythm
  • ex. light, exercise, arousal, meals, environment, temperature
    • Social stimuli are ineffective
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3
Q

How does jet lag effect the circadian rhythm?

A
  • Disruption in circadian rhythm due to crossing time zones
    • Sleepiness during the day, sleeplessness at night
  • Results in phase delay or phase advance
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4
Q

What is the difference between phase delay and phase advance

A

Phase Delay:

- Going west
- Stay awake later and wake up later
- Easier to go west than east

Phase Advance:

- Going east
- Go to sleep and wake up earlier
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5
Q

What are the genes involved in sleeping patterns

A

Period (PER) gene produces PER protein
Timeless (TIM) gene produce TIM protein
TIM and PER protein promotes sleep and inactivity, oscillating in concentration
- PER and TIM start low at the beginning of the day and increase at night
Based on 24 hr feedback system
- light activates a chemical that breaks down the TIM protein, increasing wakefulness and synchronizing the internal clock to the external world

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6
Q

What did De Mairan study?

A
  • Heliotropic plants in 1729
  • Put plants inside cellar without light but leaves still open during the day time
    • Shows that they have a circadian clock
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7
Q

Describe the circadian rhythm studies on crickets

A
  • Crickets sleep during the day, active at night, males call at dusk
    Used LD and LL to measure calling patterns

Further Experiments:

  1. Separate the retina from the optic lobe
    • LD shows free running
  2. Separate optic lobe from the rest of the brain
    • Arhythmic calling
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8
Q

Conclusions of cricket studies

A
  • Have entrained cycle that is exactly 24 hrs in LD
  • Exhibit free running cycle of 26 hrs in LL
  • Further experiments shows that their internal clock is somewhere in the optic lobes
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9
Q

What is an entrained cycle?

A

Uses zeitgebers to make cycle more exact

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10
Q

Describe the circadian rhythm studies on hamsters

A
  • An electrolytic lesion to SCN eliminates the circadian rhythms and makes harder to entrain
  • Can also take SCN out of brain (in vitro)
    • Given the right nutrients, the SCN will continue to show rhythmic patterns
  • Transplant SCN to animal with a SCN lesion to restore rhythms
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11
Q

Conclusions of hamster studies

A
  • SCN acts as a clock and produces its own patterns even without any external stimuli
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12
Q

Pineal gland function

A
  • Secretes melatonin into the blood during darkness which increases sleepiness
  • Tumours in gland lead to disrupted sleep
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13
Q

Describe the circadian rhythm studies in drosophila

A
  • Benzer used random mutagenesis to measure circadian rhythms
    • Eclosion assay: come out of pupa (eclose) in light conditions early in day
      • Mapped 3 mutations on PER gene caused by single base pair mutations
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14
Q

PER protein in drosophilia

A
  • High levels of staining in photoreceptors in eyes and optic lobes
    • Concentration of PER protein decreased during the day and increased at night
    • Concentration of PER mRNA increased during the day and decreased at night
      • Show negative feedback system by PER protein
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15
Q

Compare comas, vegetative states, brain death, and sleep

A

Coma: extended period of unconsciousness caused by head trauma, stroke, or disease
Vegetative state: alternate between sleep and moderate arousal but has no awareness
Brain death: no sign of brain activity or response to stimulus
Sleep: actively produced by a network of brain regions

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16
Q

Compare the stages in NREM

A

Stage 1:

            - EEG has irregular, jagged, low voltage waves
            - Eye movement reduced

Stage 2:
- Sleep spindles + K complexes

Slow wave sleep:

            - Large amplitude waves
            - Associated with decreased HR, breathing and brain activity
            - Prodominates early in the night - Contains stage 3 (fewer slow waves) and stage 4 (more slow waves)
            - Indicates that neuronal activity is highly synchronized
            - Older adults have less slow wave sleep and more awakenings
17
Q

What are sleep spindles

A

In stage 2 sleep

                - Low amplitude
                - Burst of 12-14 Hz waves for at least 1/2 sec
                - Results from oscillating interactions between cells in the thalamus and cortex
                - Increases after new learning and correlates with improvements in memory
18
Q

What are K-complexes

A

In stage 2 sleep

- Sharp wave associated with temporary inhibition of neuronal firing

19
Q

Describe REM sleep

A

EEG shows irregular low voltage, fast waves; Like light sleep
Muscles are very relaxed; Like deep sleep
- Pons + medulla send messages to inhibit motor neurons controlling large muscles
Prodominates later at night
Amount of REM depends on the time of day, not the length of sleep
-Activity increases in the pons triggering REM onset and limbic system
- Decreased activity in visual + motor cortex and dorsolateral prefrontal cortex

20
Q

What is the sleep stage cycle?

A

1 → 2 → 3 → 4 → 4 → 3 → 2 → REM → Repeat back to 2

Cycle lasts 90 min

21
Q

Describe PGO waves

A
  • High amplitude

- Waves first detected in the pons → LGN → Occipital cortex

22
Q

Functions of REM

A
  • REM varies more than NREM between individuals and species
    - Strengthening memory
    - Shaking of eyes is to get sufficient oxygen to the corneas
23
Q

Describe Somnambulism

A
  • Individual is awake in their motor cortex while other parts of the brain are inactive
    - Not alert enough to process information
    - Most common in slow wave sleep
24
Q

How is GABA used in sleep mechanisms?

A
  • More GABA released during sleep
    - Interferes with the spread of info by neurons
    - Sleep can therefore be localized in one area with more inhibition in one than another
25
Q

Describe lucid dreaming

A
  • Individual becomes aware they are dreaming

- Activity occurring in the temporal and frontal cortex enables the conscious monitoring of dreams

26
Q

Describe the SCN role in circadian rhythms

A
  • Damage results in erratic body rhythms
  • Continues to produce the circadian rhythm action potentials even when its neurons are disconnected/removed from the brain
    • SCN controls pineal gland which secretes melatonin at night to increase sleepiness
      Efferent projections: Reticular formation, locus coeruleus, basal forebrain
27
Q

Effects of light on SCN

A 
Retinohypothalamic path (small branch of optic nerve) goes from retina → SCN and alters SCN settings
    - Originates from retinal ganglion cells that have photopigment called melanospin
28
Q

Describe melanopsin

A
  • Retinal ganglion cells with their own photopigment without input from rods and cones
    - Respond directly to the overall amount of light (not instantaneous changes)
    - Respond to blue (short) wavelengths
29
Q

Reticular formation and sleep

A
  • In midbrain, promotes wakefulness
    • Damage leads to prolonged sleep
  • Contains Pontomesencephalon
    • Projects to Hypothalamus, thalamus, cortex, basal forebrain
30
Q

What is the Pontomesencephalon?

A

In retiuclar formation

  • Receives input from sensory systems and generates own activity
    - Axons extend into forebrain
    - Some axons release GABA — inhibits behavior, promotes slow-wave sleep
    - Other axons release acetylcholine, glutamate, dopamine, producing arousal in hypothalamus + thalamus + basal forebrain. Regulates potassium levels to produce arousal
31
Q

Locus coerulus and sleep

A
  • Located in the pons
    • Usually inactive but emits bursts of impulses in response to meaningful events, especially those associated with emotional arousal
    • Releases norepinephrine to hypothalamus (SCN) and cortical areas in response to meaningful events
    • Output increases “gain” — increases activity of most active neurons, decreases activity of less active
      • Leads to enhanced attention to important information and memory
32
Q

Hypothalamus and sleep

A
  • Contains SCN, lateral hypothalamus and histaminergic neurons
33
Q

What are histaminergic neurons

A
  • Releases histamine (excitatory neurotransmitter)
    • Enhances arousal and alertness
    • Antihistamines counteract and produce drowsiness
34
Q

Lateral hypothalamus and sleep

A

Contains orexin neurons

    - Released from lateral and posterior nucleus
    - Orexin stimulates ACh-releasing cells in basal forebrain to promote arousal/wakefulness
    - Necessary for staying awake - There are few orexin neurons but they project widely
35
Q

Basal forebrain and sleep

A
  • Axons extend to thalamus and cortex
  • Acetylcholine stimulates BFb cells that promote wakefulness
  • Releases ACh and GABA
  • Alzheimer’s produces damage in BFb
36
Q

Describe Insomnia

A
  • Inadequate sleep either from trouble falling asleep (phase delay) or waking up too early (phase advance)
37
Q

Describe Sleep apnea

A
  • Impaired breathing during sleep

- Caused by genetics, hormones, old age and obesity

38
Q

Describe narcolepsy

A

Main Symptoms:

1. Frequent periods of sleepiness during the day
2. Occasional catalepsy — muscle weakness while awake
3. Sleep paralysis
4. Hypnagogic hallucinations
- Caused by a lack of hypothalamic cells producing orexin
    - Individual alternates between short waking and sleepy periods
39
Q

Hypothesis for why we dream

A

Activation-Synthesis Hypothesis:

- Dream represents an effort to make sense of sparse and distorted information
- Predictions for this hypothesis are vague

Neurocognitive Hypothesis:

- Dreams is just thinking taking place under unusual conditions
- Dreams begin with spontaneous brain activity related to recent memories

PSYC270 (6 decks)

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