PSYC317: Biopsychology Lecture 16: Sleep 2 Flashcards

Flashcards generated from Lecture 16 notes on Sleep 2, focusing on circadian rhythms, SCN, Zeitgebers, and melatonin.

What is the anterior hypothesis associated with?

Sleep onset.

What stabilizes wakefulness signals in the brain?

Orexin.

What is the typical duration of human sleep cycles?

24-25 hours.

What is the term for a biological process that occurs in approximately 24-hour cycles?

Circadian rhythm.

Name three circadian rhythms in the human body.

Sleep-wake cycle, body temperature, and hormone levels.

How does circadian rhythm change throughout the lifespan?

It dictates the quality of sleep, making it harder to stick to the day and night cycle as one ages.

What term describes species being awake during the light phase?

Diurnal.

What term describes species being awake during the night phase?

Nocturnal.

Which type of animals are typically diurnal?

Humans.

Which type of animals are typically nocturnal?

Mice and rats.

What is a Zeitgeber?

An environmental cue that tells your body what time it is along a particular cycle.

What is the major Zeitgeber for humans?

Light.

What is the biological term for getting one cycle to follow after another, such as the day-night cycle entraining our bodily rhythms?

Entrainment.

Name two Zeitgebers other than light.

Clocks, food, social interactions, or activity (exercise).

What happens if a Zeitgeber is manipulated, for example, by traveling to a different country?

The circadian rhythm becomes out of sync, leading to jet lag.

What happens to the body's sleep cycle if all external Zeitgebers are removed?

The body still follows a 24-25 hour cycle.

Which part of the brain was identified in the 1960s as being crucial for sleep-wake cycles?

The hypothalamus, specifically the SCN.

What happens if the Suprachiasmatic Nucleus (SCN) is lesioned?

It results in disrupted sleep-wake cycles.

What is the primary role of the SCN in relation to circadian rhythms?

It is very important for generating circadian rhythms.

How was the SCN identified as a major internal circadian clock through a hamster experiment?

SCN from hamsters with a 20-hour cycle was transplanted into regular hamsters, causing the recipients to adopt a 20-hour cycle.

What is the retina?

A thin strip of tissue at the back of the eyeball, which is an extension of the brain.

What are rods and cones responsible for in the visual system?

They are photosensitive cells located in the retina that give us vision.

What does ipRGC stand for?

Intrinsically photosensitive Retinal Ganglion Cells.

What specialized protein do ipRGCs contain that makes them light-sensitive?

Melanopsin.

What type of light are ipRGCs particularly sensitive to?

Blue-wavelength light.

Where are ipRGCs primarily located in the retina, and what light do they typically receive?

They are enriched along the bottom of the retina and receive blue light from above, like the sky.

How do ipRGCs contribute to circadian rhythm even if rods and cones are damaged?

They can still detect light and maintain the body's 24-25 hour rhythm, even if vision is lost.

What is the direct pathway for light information from ipRGCs to the circadian clock?

ipRGCs send electrical impulses down the optic nerve to the SCN nucleus.

Describe the human pathway from light detection to wakefulness activation.

Light detected by ipRGCs projects to SCN, which projects to the sub-PV zone, then to the dorsomedial nucleus, sending excitatory signals to LH (orexin neurons) and inhibitory projections to POA (shutting off sleep neurons).

How does light affect nocturnal animals' sleep?

Light activates sleep neurons, inhibiting wakefulness and allowing sleep to happen during the daytime.

Besides light, what other factor can cause a feeling of sleepiness due to a non-light driven circadian rhythm?

Feeding (e.g., feeling full after a big meal removes orexin signals, leading to sleepiness).

According to the notes, what primarily entrains adolescent sleep-wake cycles?

Social time rather than sun-time.

What is the 'night owl effect' observed in adolescents?

Adolescents tend to start sleeping later and later at night.

How do scientists know the SCN has its own internal circadian rhythm?

When placed in a petri dish without Zeitgebers, its gene expression patterns still follow a 24-25 hour cycle.

What is the effect of a Per 2 genetic mutation on the sleep-wake cycle?

It causes a 4-hour advance, meaning a person might sleep at 6 PM instead of 10 PM.

What is the effect of a Per 3 genetic mutation on the sleep-wake cycle?

It causes a 4-hour delay, meaning a person might sleep at 2 AM.

What hormone is produced by the pineal gland and is involved in regulating circadian rhythms?

Melatonin.

How do light levels affect melatonin production?

Light inhibits melatonin production, causing levels to decrease rapidly.

Are melatonin supplements highly effective as a standalone sleep aid according to meta-analysis?

No, meta-analysis data suggests they don't do much as a primary sleep aid.

What is considered the best Zeitgeber to promote a better night's sleep and sync with solar time?

Natural sunlight.