Chapter 15 openstax

What is chronobiology?

The study of biological clocks and biological rhythms within an organism.

What are circadian rhythms?

Biological rhythms that repeat approximately every 24 hours.

What are the types of biological rhythms?

Circadian, ultradian, infradian, and circannual rhythms.

What distinguishes external from internal (endogenous) control in biological rhythms?

External control is influenced by environmental cues, while internal control is regulated by biological clocks within the organism.

How do the hypothalamus and pineal gland control circadian rhythms?

The hypothalamus houses the suprachiasmatic nucleus (SCN), which regulates circadian rhythms, while the pineal gland secretes melatonin, a hormone that signals darkness.

What is the free-running period in circadian rhythms?

The time between wakings when an organism is kept in constant conditions, typically around 23.5 to 24.7 hours in humans.

What is the role of light in regulating circadian rhythms?

Light can shift the active period of biological rhythms, influencing sleep-wake cycles.

What is the function of the suprachiasmatic nucleus (SCN)?

The SCN acts as the master clock, receiving light input and regulating circadian rhythms.

What is the significance of melanopsin in the SCN?

Melanopsin is a photopigment in intrinsically photosensitive retinal ganglion cells that is sensitive to blue light, helping to regulate the SCN.

What happens to circadian rhythms when the SCN is lesioned?

Lesioning the SCN disrupts the 24-hour rhythm, leading to arrhythmic activity.

How do clock genes control circadian rhythms?

Clock genes regulate the expression of proteins that influence the timing of circadian rhythms through feedback mechanisms.

What is sleep?

Naturally-recurring changes in behavior and physiology characterized by decreased responsiveness to external stimuli and relative immobility.

Why do we sleep?

Sleep is essential for various physiological processes, including restoration of energy, memory consolidation, and overall health.

What brain areas regulate sleep?

Key areas include the hypothalamus, thalamus, and brainstem.

How much sleep do newborns (0-3 months) need?

12-18 hours per night.

How much sleep do teenagers (10-18 years) need?

8-10 hours per night.

How much sleep do adults (18 and older) need?

7-9 hours per night.

What is the amplitude in biological rhythms?

The difference between the peak and trough of the rhythm.

What is the phase in biological rhythms?

A marker or point in a daily rhythm that indicates timing.

What is the significance of the hypothalamus in sleep regulation?

The hypothalamus integrates signals to regulate sleep-wake cycles and hormonal activity.

What is the relationship between sleep and alertness?

Sleep patterns influence levels of fatigue and alertness throughout the day.

Which animals are known to sleep?

Cnidarians, nematodes, many insects, certain fish, amphibians, and all mammals.

What is unihemispheric sleep?

A sleep adaptation where some animals, like dolphins and whales, sleep one hemisphere of the brain at a time.

What are the main hypotheses for why we need sleep?

Restoration, energy conservation, and evolutionary adaptation.

What physiological changes occur during sleep?

Increased adenosine levels, activation of glymphatic systems, and lower metabolism.

What happens to animals that are deprived of sleep?

They can suffer severe physiological stress and may die within 2-3 weeks.

How is sleep measured?

Using polysomnography (PSG), which records brain activity (EEG), eye movements (EOG), and muscle movements (EMG).

What are the four major stages of sleep identified by PSG?

Awake, Non-REM (NREM) sleep (N1, N2, N3), and REM sleep.

What characterizes N1 sleep stage?

Transition from alpha to theta brain waves.

What characterizes N2 sleep stage?

Presence of sleep spindles and K-complexes with theta brain waves.

What characterizes N3 sleep stage?

Dominated by delta (slow) brain waves.

What are Process C and Process S in the Two Process Model of Sleep?

Process C refers to circadian rhythm, while Process S refers to sleep pressure.

What is the role of the ascending reticular activating system (ARAS)?

It supplies the cortex with arousal-promoting neurotransmitters, regulating wakefulness.

What is the function of the VLPO in sleep regulation?

The VLPO promotes sleep and is inhibited by the ARAS.

What are common sleep disorders?

Insomnia, hypersomnia, parasomnias, breathing disorders, and movement disorders.

What is insomnia?

Persistent difficulty with sleep, affecting approximately 30% of adults.

What are the symptoms of insomnia?

Difficulty falling asleep, staying asleep, early waking, and poor sleep quality.

What treatments are available for insomnia?

Non-pharmacological options like CBT-I and pharmacological options like hypnotics and melatonin.

What is sleep apnea?

A disorder characterized by the cessation of breathing during sleep, with obstructive and central types.

What is Restless Legs Syndrome (RLS)?

An overwhelming urge to move the legs, often accompanied by uncomfortable sensations.

What is narcolepsy?

A disorder characterized by excessive daytime sleepiness, cataplexy, and sleep paralysis.

What are the treatment options for narcolepsy?

Stimulants like modafinil and lifestyle adjustments such as scheduled naps and sleep hygiene.

What is social jet lag?

A mismatch between an individual's sleep/wake schedule during the week and on weekends, leading to poor sleep quality.

What are the public health concerns associated with insufficient sleep?

Cognitive impairments, memory loss, and increased risk of heart disease, obesity, and type 2 diabetes.

How do school start times relate to sleep?

Early start times can contribute to insufficient sleep among students.