Chapter 11 - Sleep Flashcards
What’s a biorhythm?
- Cyclical changes in behaviour or bodily functions.
What are the different types of biorhythms?
- Circannual - yearly cycle
- Circadian - daily cycle
- Ultradian - less than a day
- Intradian - More than a day
T/F: Circadian rhythms are less extreme in the southern and northern hemispheres.
- FALSE
- They’re more extreme in the two hemispheres
T/F: Circadian rhythms are present at the cellular level.
- TRUE
What type of mechanism is an biological clock?
- Biological clocks are produced by an endogenous mechanism that times behaviour by producing biorhythms
- Endogenous = innate to the organism
What are free-running rhythms?
- Rhythms of the body’s own devising in the absence of all external cues (ex. light), so they’re driven solely by the body
- Somewhat accurate although these rhythms tend to drift in the absence of light
What are zeitgebers?
- Environmental events that entrain biological rhythms
- i.e., they’re time setters
- Important because an entrained biological clock allows an animal to synchronize its daily activity across seasonal changes
What’s the effect of light pollution on circadian rhythms?
- Very disruptive to circadian rhythms
- Causes behavioural consequences such as accidents daytime fatigue, altered emotions and can lead to metabolic syndromes
What is a metabolic syndrome?
- Combinations of medical disorders including obesity, and insulin abnormalities that collectively increase the risk of developing cardiovascular disease and diabetes
What’s seasonal affective disorder (SAD)?
- A depression disorder that occurs during winter
- 5X more common in women
- Affects up to 10% of people in the northern latitudes
- Phototherapy treatment = exposure to bright white light containing the blue frequency
What part of the brain is mainly responsible for maintaining circadian rhythms?
- The suprachiasmatic nucleus (SCN) found in the hypothalamus
- If SCN is damaged, activities occur haphazardly
- SCN cells are more electrically and metabolically active in light periods
- SCN neurons maintain rhythmic activity in absence of input and output (entrainment depends on external inputs)
What cells are responsible for transmitting light signals to the SCN?
- melanopsin-containing RGCs (mRGCs or ipRGCs) found on the retina
- Referred to as the retinohypothalamic tract
- mRGCs are sensitive to 460-480nm (blue light)
- These cells allow light to entrain the SCN
Can a lesioned SCN be restored using a transplant when performed in rats?
- Yes, which in turn restores the circadian rhythm.
How do we measure sleep?
- Use a polysomnography (PSG)
- Involves hooking up an EEG (brain), an EMG (muscles), and an EOG (eyes)
What are the stages of waking and sleep?
1) Waking (W) - Includes beta rhythms
2) N1-Sleep - Feel drowsy/sleep onset starts, characterized by theta waves
3) N2-Sleep - Have now fallen asleep. Includes sleep spindles and K-complexes
4) N3-Sleep - Now in deep sleep, characterized by delta waves
5) R-Sleep - In REM sleep, characterized by beta rhythms which can include sawtooth waves
What are the physical properties of the different sleep waves?
- Beta rhythms (W, R-sleep) - low amplitude, high frequency
- Theta rhythm (N1-sleep) - Slightly larger amplitude than beta, slightly lower frequency than beta.
-Delta rhythm (N2 and N3-sleep) - High amplitude, low frequency