Neural and Behavioral Mechanisms of Sleep and Circadian Rhythms in Biology

What are endogenous rhythms?

Rhythms that occur naturally in the body, even in a constant environment.

What is the circadian rhythm?

A roughly 24-hour cycle that includes sleep/wake patterns.

What is the role of the suprachiasmatic nucleus (SCN) in circadian rhythms?

The SCN in the hypothalamus generates circadian rhythms and regulates activity levels.

How does the SCN affect diurnal animals?

It shows high activity during the day and low activity at night.

What happens to normal hamsters with SCN cells from mutant hamsters?

They exhibit 20-hour rhythms, demonstrating the SCN's role in rhythm generation.

What are the three major proteins involved in the clock mechanism within SCN neurons?

Period, Timeless, and Clock.

How does light affect the clock proteins in the SCN?

A pulse of light during sleep can inhibit Timeless and decrease Clock levels.

What is the significance of sleep in animals?

Sleep is a highly regulated behavior essential for recuperation and memory consolidation.

What is the EEG and what does it measure?

An electroencephalogram (EEG) measures the average activity of thousands of neurons.

What characterizes REM sleep?

EEG desynchrony, rapid eye movements, lack of muscle tonus, and vivid dreams.

What is the difference between slow-wave sleep and REM sleep?

Slow-wave sleep shows EEG synchrony with slow waves, while REM sleep shows desynchrony with rapid waves.

What is insomnia?

A sleep disorder characterized by difficulty falling or staying asleep.

What causes sleep apnea?

Cessation of breathing during sleep, leading to repeated awakenings.

What is narcolepsy?

A sleep disorder that includes irresistible sleep attacks and may involve cataplexy.

What is the role of orexin in narcolepsy?

Orexin is a neuropeptide that regulates wakefulness; its deficiency is linked to narcolepsy.

What are the two types of memory affected by sleep?

Declarative (episodic) and non-declarative (procedural) memories.

What neurotransmitter is primarily involved in arousal?

Acetylcholine (ACh) is released during wakefulness and REM sleep.

What is the function of the ventrolateral preoptic area (v1POA)?

It releases GABA to inhibit arousal neurons, promoting sleep.

What is the flip-flop concept in sleep regulation?

It describes the balance of excitation and inhibition between arousal and sleep-producing neurons.

How does adenosine affect sleep regulation?

Adenosine accumulates during wakefulness and promotes sleep by inhibiting arousal neurons.

What is the difference between CT and MRI scans?

CT uses X-rays for structural imaging, while MRI uses magnetic fields and has higher spatial resolution.

What does fMRI measure?

Functional Magnetic Resonance Imaging measures blood oxygen level dependent (BOLD) signals to assess brain activity.

What is the significance of diffusion tensor imaging (DTI)?

DTI reveals the orientation of myelinated axons in the brain by tracking water molecule movement.

What happens to SCN activity in response to light?

Light exposure can reset the SCN's clock, influencing circadian rhythms.

What are sleep spindles and K complexes?

Sleep spindles are bursts of 12-14 Hz activity, while K complexes are sudden sharp waveforms during sleep.