Chapter 8 - Wakefulness and Sleep

What did early psychologists believe controlled sleep and wake cycles?

They believed external factors controlled sleep and wake cycles.

What was Curt Richter’s contribution to understanding sleep and wake cycles in 1922?

He suggested that the body generates its own internal activity and rest cycles.

What are circannual rhythms and give examples.

Internal yearly rhythms in animals, such as bird migration and storing food for winter.

What are circadian rhythms?

Internal daily rhythms that last about 24 hours, present in all animals.

What functions are controlled by circadian rhythms?

Sleep, eating and drinking, body temperature, hormone release, DNA repair, and mood.

How was a flying squirrel’s activity recorded in a constant darkness experiment?

Using a running wheel that tracked its movement, shown as thick marks for active periods.

What was discovered about the flying squirrel’s activity cycle in constant darkness?

It followed a free-running cycle slightly shorter than 24 hours.

When is body temperature typically lowest during the daily cycle?

About 2 hours after falling asleep.

When is body temperature typically highest during the daily cycle?

About 6 hours before falling asleep.

What is the biological clock and why must it be reset?

The biological clock aligns internal rhythms with the external world and runs slightly over 24 hours without cues, so it must be reset periodically.

What is a zeitgeber and what are common examples?

A zeitgeber (“time giver”) is a stimulus that resets the biological rhythm, such as sunlight, exercise, meals, and temperature.

What issues can arise from using weak zeitgebers like artificial light?

Using weak zeitgebers can lead to mood problems and reduced performance.

Why might blind individuals have difficulty regulating their biological rhythms?

Because they may lack access to strong external cues like sunlight, making rhythm regulation challenging.

What causes jet lag?

caused by disruption of circadian rhythms due to crossing time zones, creating a mismatch between the internal clock and external time.

What are common symptoms of jet lag?

Sleepiness during the day, sleeplessness at night, and impaired concentration.

How does traveling west affect circadian rhythms?

Traveling west causes a “phase-delay,” shifting the circadian rhythm later.

How does traveling east affect circadian rhythms?

Traveling east causes a “phase-advance,” shifting the circadian rhythm earlier.

How does sleep duration relate to night work?

Sleep duration depends on when a person goes to sleep, not just night work itself.

Does night work reliably change the circadian rhythm?

No, working at night does not reliably shift the circadian rhythm.

What symptoms do night workers commonly experience even after long-term adjustment?

Grogginess, poor daytime sleep, and body temperature peaking during sleep instead of work hours.

What environmental conditions help people adjust better to night work?

Sleeping in a very dark room during the day and working under very bright lights at night.

How do different light wavelengths affect night work adjustment?

Exposure to short-wavelength (blue) light is more effective in influencing circadian rhythms than long-wavelength light.

What part of the brain acts as the main biological clock?

The suprachiasmatic nucleus (SCN).

How do genes influence circadian rhythms?

Genes produce certain proteins that regulate the timing of circadian rhythms.

What hormone is involved in signaling biological clock timing?

Melatonin.

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

It is the main control center of circadian rhythms for sleep and temperature.

Where is the SCN located?

Above the optic chiasm, part of the hypothalamus.

What happens if the SCN is damaged?

Body rhythms become less consistent and lose synchronization with light-dark cycles.

Does the SCN generate circadian rhythms on its own?

Yes, it generates circadian rhythms automatically.

What effect does transplanting SCN tissue have?

Transplanted SCN tissue from hamster fetuses can restore circadian rhythms in adult hamsters.

How does light reset the SCN?

via the retinohypothalamic path, a small branch of the optic nerve.

Where does the retinohypothalamic path travel?

Directly from the retina to the SCN.

What special cells form the retinohypothalamic path?

A special group of ganglion cells containing the photopigment melanopsin.

Do these ganglion cells require rods or cones to respond to light?

No, they respond directly to light without input from rods or cones.

Which two types of genes generate the circadian rhythm?

Period (PER) and Timeless (TIM) genes.

What proteins do the Period and Timeless genes produce?

PER and TIM proteins.

How do PER and TIM proteins affect the SCN?

They increase activity of neurons in the SCN that regulate sleep and waking.

What happens if there is a mutation in the PER gene?

It can cause irregular circadian rhythms or decreased alertness after poor sleep.

How does the SCN control sleep and wakefulness?

By influencing other brain areas, including regulating the pineal gland.

What hormone does the pineal gland release to promote sleep?

Melatonin.

When do melatonin levels start to rise?

2-3 hours before bedtime.

How does melatonin help with the circadian clock?

It helps reset the clock via SCN receptors.

What effect does taking melatonin in the afternoon have?

It can advance the circadian clock and is useful as a sleep aid.

How is sleep characterized in terms of brain activity?

is an active brain state with moderate decrease in brain activity and reduced response to stimuli.

How does sleep differ from coma and brain death?

Sleep is reversible and involves active brain processes, whereas coma, unresponsive wakefulness syndrome, minimally conscious state, and brain death are states of severely impaired or absent consciousness.

What characterizes a coma?

Extended unconsciousness with low, steady brain activity and little response to stimuli.

What is unresponsive wakefulness syndrome?

A state where a person alternates between sleep and moderate arousal but lacks awareness of their surroundings.

How does unresponsive wakefulness syndrome respond to stimuli?

Shows some autonomic arousal to pain but no purposeful activity or response to speech.

What defines a minimally conscious state?

Occasional brief periods of purposeful action and limited speech comprehension, slightly higher than a vegetative state.

What is brain death?

Complete absence of brain activity and no response to any stimulus.

What brain waves are present during relaxation before sleep?

Alpha waves.

What characterizes Stage 1 sleep?

The beginning of sleep with irregular, jagged, low-voltage EEG waves and declining brain activity.

What are the key features of Stage 2 sleep?

Presence of sleep spindles (linked to memory consolidation) and K-complexes.

What characterizes slow-wave sleep (SWS) on an EEG?

Slow, large-amplitude waves.

What physiological changes occur during slow-wave sleep?

Slowing of heart rate, breathing rate, and brain activity.

How is neuronal activity during slow-wave sleep described?

Highly synchronized.

What were the previous names for slow-wave sleep stages?

Stage 3 and stage 4 sleep.

What does NREM stand for?

Non-REM sleep, referring to all sleep stages except REM.

What is the typical sequence of sleep stages when falling asleep?

Stages 1 → 2 → slow-wave sleep (SWS) in order.

How does the sleep cycle progress after the first hour?

Cycles back from slow-wave sleep to stage 2 and then REM sleep.

How long does a full sleep cycle last?

Approximately 90 minutes.

When does slow-wave sleep (SWS) predominate during the night?

Early in the night.

How does the length of slow-wave sleep change over the night?

It decreases as the night progresses.

When does REM sleep predominate during the night?

Later in the night.

How does the length of REM sleep change as the night progresses?

It increases over the course of the night.

What is REM sleep strongly associated with?

Dreaming, though dreams can occur in other sleep stages too.

What brain structure is primarily responsible for wakefulness and arousal?

The reticular formation.

Where is the reticular formation located?

It extends from the medulla to the forebrain in the midbrain area.

What is the main function of the reticular formation?

Responsible for arousal and maintaining wakefulness.

What is the pontomesencephalon?

A part of the reticular formation in the midbrain involved in cortical arousal.

Where do axons from the pontomesencephalon project?

To the hypothalamus, thalamus, and basal forebrain.

What neurotransmitters are released by the pontomesencephalon’s target areas?

Acetylcholine, glutamate, GABA, and dopamine.

What effects does the pontomesencephalon have on the cortex?

Produces excitatory and inhibitory effects across widespread cortical areas.

What happens when the pontomesencephalon is stimulated?

It awakens sleeping individuals and increases alertness in awake individuals.

What is the locus coeruleus?

A small structure in the pons involved in arousal and wakefulness.

What neurotransmitter does the locus coeruleus release?

Norepinephrine.

What is the function of norepinephrine released by the locus coeruleus?

To arouse various areas of the cortex and increase wakefulness.

When is the locus coeruleus usually inactive?

While asleep.

What role does the hypothalamus play in wakefulness?

It contains neurons that release histamine, producing widespread excitatory effects in the brain.

What effect do antihistamines have on wakefulness?

They cause sleepiness by blocking histamine’s excitatory action.

Where is orexin released from in the brain?

The lateral and posterior nuclei of the hypothalamus.

What type of neurotransmitter is orexin?

A peptide neurotransmitter, also known as hypocretin.

What is orexin’s primary function?

To help maintain wakefulness (needed to stay awake rather than just to wake up).

Where does orexin act to promote wakefulness?

It is released into the basal forebrain to stimulate neurons responsible for arousal.

Where is the basal forebrain located?

Just anterior and dorsal to the hypothalamus.

What distinctive neural activity is associated with REM sleep?

High-amplitude electrical potentials called PGO waves.

In what sequence do PGO waves travel during REM sleep?

From the pons → lateral geniculate of the hypothalamus → occipital cortex.

What neurotransmitter initiates REM sleep?

Dopamine release in the amygdala.

What role does GABA play during sleep?

It inhibits brain activity by decreasing neuronal stimulation.

How does GABA affect body temperature and metabolism during sleep?

It helps decrease temperature and metabolic rate.

What is insomnia?

A sleep disorder characterized by inadequate or poor-quality sleep.

What are common external causes of insomnia?

Noise, stress, pain, diet, and medications.

What medical or psychological conditions can lead to insomnia?

Epilepsy, Parkinson’s disease, depression, anxiety, and other health conditions.

How can substance use affect insomnia?

Dependence on sleeping pills or alcohol can worsen insomnia.

How does circadian rhythm disruption relate to insomnia?

Shifts in circadian rhythms can interfere with the ability to fall or stay asleep.

What is sleep apnea?

A sleep disorder in which a person is unable to breathe properly during sleep for prolonged periods.

What are the consequences of sleep apnea?

Daytime sleepiness, impaired attention, depression, heart problems, and cognitive impairment.

What are common causes of sleep apnea?

Genetics, hormones, aging, obesity, and deterioration of brain mechanisms that control breathing.

How does sleep apnea affect cognitive function?

It can lead to cognitive impairment due to poor sleep quality and oxygen deprivation.

What is narcolepsy?

sudden daytime sleep attacks.