Circadian Rhythms and Sleep - Key Terms (Video Notes)

Vocabulary flashcards covering key terms from the lecture notes on sleep, circadian rhythms, and Drosophila clock biology.

Drosophila melanogaster

Fruit fly used as a model organism to study circadian clocks and genetics of sleep.

CLK (Clock)

A transcription factor that forms a heterodimer with CYC to drive clock gene expression via the E-box.

CYC (Cycle)

A transcription factor that partners with CLK to activate clock gene transcription at the E-box.

E-box

DNA motif bound by CLK-CYC to promote transcription of clock genes like per and tim.

PER (Period)

Clock protein that accumulates and inhibits CLK-CYC, creating negative feedback in the clock.

TIM (Timeless)

Clock protein that partners with PER; its stability is regulated by light via CRY.

DBT (Doubletime)

Kinase that phosphorylates PER, targeting it for degradation.

CRY (Cryptochrome)

Blue-light photoreceptor that mediates TIM degradation and clock resetting in Drosophila.

SCF complex

E3 ubiquitin ligase complex (Skp1, Cul-1, F-box protein) that tags clock proteins for degradation.

26S proteasome

Proteasome that degrades ubiquitylated clock proteins as part of turnover.

DN1

Dorsal neuron group 1; a cluster of clock neurons coordinating circadian rhythms.

DN2

Dorsal neuron group 2; clock neurons involved in circadian regulation.

DN3

Dorsal neuron group 3; clock neurons contributing to rhythms.

LNd

Dorsal Lateral Neurons; clock neurons contributing to circadian output.

LNv

Ventral Lateral Neurons; clock neurons including small (s-LNv) and large (l-LNv) groups.

s-LNv

Small ventral lateral neurons; key PDF-expressing clock neurons driving morning activity.

I-LNv

Interneuron subset of Iv-neurons within the LNv cluster; part of the clock network.

PDF (Pigment Dispersing Factor)

Neuropeptide expressed by certain clock neurons that coordinates circadian rhythms.

sNPF (short Neuropeptide F)

Neuropeptide involved in sleep/wake regulation; analog of NPY in mammals.

DH44

Diuretic Hormone 44; CRH-like neuropeptide in Drosophila that acts on sleep circuits.

HUG (Hugin)

Neuropeptide-producing neurons; neuromedin U-like; interacts with PDF and sleep circuits.

PI (Pars Intercerebralis)

Neurosecretory structure in the Drosophila brain involved in hormonal outputs.

SEZ (Subesophageal Zone)

Brain region where HUG neurons project and interact with sleep circuits.

DA (Dopamine)

Neuromodulator involved in wakefulness; connects to sleep networks.

PPM3

Dopaminergic neurons that link to the Ellipsoid Body to influence sleep/wake rhythms.

Ellipsoid Body

Part of the Drosophila central complex; involved in sleep/wake regulation.

VLPO

Ventrolateral preoptic nucleus; mammalian sleep-promoting GABAergic region.

MPOA

Medial preoptic area; brain region involved in sleep-wake regulation and homeostasis.

LH (Lateral Hypothalamus)

Brain region containing arousal-promoting neurons, including orexin neurons.

Orexin

Hypocretin; wake-promoting neuropeptide produced by LH neurons.

TMN (Tuberomammillary nucleus)

Histaminergic region promoting wakefulness in mammals.

LC (Locus Coeruleus)

Norepinephrine-producing region involved in arousal and attention.

Raphe

Serotonin-producing nuclei in the brainstem; modulates sleep/wake states.

ACh (Acetylcholine)

Neurotransmitter involved in wakefulness and REM sleep regulation.

NE (Norepinephrine)

Neurotransmitter from LC promoting alertness and arousal.

5-HT (Serotonin)

Neurotransmitter involved in modulation of sleep and mood.

Glu (Glutamate)

Excitatory neurotransmitter implicated in wake-related signaling.

GABA

Gamma-aminobutyric acid; principal inhibitory neurotransmitter promoting sleep.

Glycine

Inhibitory neurotransmitter that contributes to REM atonia by suppressing motor neurons.

REM sleep

Rapid Eye Movement sleep; dreaming, brain activity resembles wake, but with muscle atonia.

NREM sleep

Non-REM sleep; stages I–IV with progressively deeper sleep and reduced physiological activity.

Sleep spindle

A 12–14 Hz EEG burst typical of Stage II sleep.

EEG

Electroencephalography; recording of brain electrical activity.

Entrainment

Synchronization of the circadian clock to external cues (e.g., light-dark cycles).

Free-running rhythms

Endogenous circadian rhythms persisting without external time cues.

Temperature compensation

Maintenance of near-24h circadian period across a range of temperatures.

Jet lag

Disruption of sleep-wake rhythms caused by rapid travel across time zones.

Circadian rhythm

Endogenous ~24h physiological cycle regulated by clock genes.

Eclosion

Emergence of an adult fly from the pupal case; a clock-regulated behavior.

Clock-controlled genes

Genes whose expression is regulated by the circadian clock to drive outputs.

Phase delay

Phase shift where light exposure in early night delays the clock.

Phase advance

Phase shift where light exposure in late night advances the clock.

2017 Nobel Prize

Prize awarded to Hall, Rosbash, and Young for discoveries of circadian molecular mechanisms.

Delayed Negative Feedback

Core clock mechanism where PER/TIM buildup inhibits CLK-CYC, creating cycles.

Light-dependent TIM degradation

Light promotes TIM breakdown via CRY, resetting the clock.