Endogenous Rhythms and Sleep Mechanisms

Endogenous Rhythms

Biological rhythms generated internally by organisms.

Circannual Rhythm

Yearly rhythm preparing for seasonal changes.

Circadian Rhythm

Daily rhythm lasting approximately 24 hours.

Posterior Cerebral Cortex

Brain region correlating with circadian activity.

Wake-Sleep Rhythm

Human cycle of wakefulness and sleep lasting 24 hours.

Circadian Eating Rhythm

Daily pattern of eating and drinking behaviors.

Circadian Hormone Secretion

Daily cycle of hormone release in humans.

Body Temperature Fluctuation

Human temperature varies from 36.7°C to 37.2°C.

Circadian Mood Rhythm

Daily variation in human mood levels.

Zeitgeber

External stimulus resetting the circadian rhythm.

Light as Zeitgeber

Primary external cue for resetting circadian rhythms.

Marine Zeitgeber

Tides serve as primary cues for marine animals.

Secondary Zeitgebers

Other cues like noise and meals influence rhythms.

Jet Lag

Circadian rhythm disruption from crossing time zones.

Phase Delay

Easier adjustment when traveling westward.

Phase Advance

Harder adjustment when traveling eastward.

Cortisol and Jet Lag

Stress hormone linked to jet lag effects.

Shift Work Effects

Disrupted sleep patterns from irregular work hours.

Artificial Lighting

Moderately effective in resetting circadian rhythms.

Short Wavelength Light

More effective in resetting circadian rhythms.

Larks and Owls

Morning people are larks; evening people are owls.

Cultural Sleep Patterns

Sleep tendencies vary across cultures and ages.

Adolescent Sleep Trends

Adolescents generally sleep and wake later.

Morning people

Individuals more honest in the morning.

Evening people

Individuals more honest in the evening.

Biological clock

Brain's internal mechanism generating rhythms.

Suprachiasmatic Nucleus (SCN)

Hypothalamus region regulating sleep and temperature.

Optic chiasm

Location just above the SCN in the brain.

Erratic body rhythms

Disordered rhythms due to SCN damage.

Circadian rhythm

24-hour cycle of physiological processes.

Retinohypothalamic path

Optic nerve branch altering SCN settings.

Melanopsin

Ganglion cells responding directly to light.

Photopigments

Light-sensitive proteins in melanopsin cells.

Short wavelength light

Primarily blue light affecting circadian rhythms.

PER protein

Gene product promoting sleep and inactivity.

TIM protein

Gene product inhibiting RNA messenger production.

Messenger RNA

Molecule responsible for protein synthesis.

Melatonin

Hormone released by pineal gland at night.

Pineal gland

Gland controlling melatonin release, located posteriorly.

Sleep impairments

Disruptions in normal sleep patterns.

Depression

Mood disorder linked to sleep issues.

Circadian cycle duration

Approximately 24 hours for biological rhythms.

Melatonin secretion timing

Begins 2-3 hours before bedtime.

Pineal gland tumors

Cause prolonged wakefulness in affected individuals.

Coma

Extended unconsciousness with low brain activity.

Vegetative State

No awareness or purposeful behavior present.

Minimally Conscious State

Brief purposeful behaviors and limited speech comprehension.

Brain Death

No brain activity or response to stimuli.

Electroencephalogram (EEG)

Records electrical activity in the brain.

Polysomnograph

Combines EEG and eye movement records.

Alpha Waves

Brain waves at 8-12 Hz, indicating relaxation.

Stage 1 Sleep

Light sleep with irregular, low voltage EEG waves.

Stage 2 Sleep

Characterized by sleep spindles and K complexes.

Sleep Spindle

Burst of 12-14 Hz waves lasting half a second.

K Complex

Sharp wave indicating temporary neural inhibition.

Slow Wave Sleep

Decreased heart rate and synchronized neuronal activity.

Paradoxical Sleep

Deep sleep with light characteristics; also REM.

Rapid Eye Movement (REM) Sleep

Period of rapid eye movements during sleep.

Non-REM (NREM) Sleep

Stages of sleep excluding REM sleep.

Neuronal Activity in REM

Irregular, low voltage fast waves indicate increased activity.

Postural Muscle Relaxation

Muscles are more relaxed during REM sleep.

Sleep Cycle Duration

Each cycle lasts about 90 minutes.

Slow Wave Sleep Predominance

Occurs earlier in the night.

REM Sleep Predominance

Increases as night progresses.

Aging and Sleep

Older adults experience less slow wave sleep.

Reticular Formation

Promotes wakefulness and relays sensory information.

Midbrain Function

Relays sensory information and promotes arousal.

Reticular Formation

Neurons regulating arousal and motor control.

Medial Tract

Pathway for descending motor control axons.

Cortical Arousal

State of heightened alertness and awareness.

Pontomesencephalon

Region contributing to cortical arousal.

Circadian Rhythm

Biological clock influencing sleep-wake cycles.

GABA

Inhibitory neurotransmitter promoting slow wave sleep.

Acetylcholine

Neurotransmitter enhancing arousal in the brain.

Glutamate

Excitatory neurotransmitter involved in wakefulness.

Dopamine

Neurotransmitter linked to arousal and motivation.

Locus Coeruleus

Pons structure promoting emotional arousal responses.

Norepinephrine

Neurotransmitter released by locus coeruleus.

Histamine

Excitatory neurotransmitter enhancing brain alertness.

Antihistamine Drugs

Medications inducing drowsiness by blocking histamine.

Orexin

Peptide promoting wakefulness from the hypothalamus.

Hypocretin

Alternative name for orexin, regulating wakefulness.

Suvorexant

Drug blocking orexin receptors to induce sleep.

Basal Forebrain

Region regulating wakefulness and sleepiness.

Acetylcholine in Basal Forebrain

Stimulates wakefulness-promoting neurons.

Hyperpolarization

Decreased neuron response during sleep.

Sleepwalking

Somnambulism; brain partially awake during sleep.

Lucid Dreaming

Awareness during dreaming with active brain regions.

REM Sleep

Stage where large muscle control is inhibited.

REM Sleep

Stage of sleep with rapid eye movement.

Pons

Brain region that regulates REM sleep.

PGO Waves

High amplitude electrical potentials in REM sleep.

Acetylcholine

Neurotransmitter essential for REM sleep.

GABA

Inhibitory neurotransmitter promoting REM sleep.

Sleep Deprivation

Lack of sleep affecting memory and cognition.

Insomnia

Inadequate sleep leading to daytime fatigue.

Circadian Rhythms

Biological clock regulating sleep-wake cycles.

Sleep Apnea

Impaired breathing during sleep causing daytime sleepiness.

Narcolepsy

Condition causing excessive daytime sleepiness.

Cataplexy

Sudden muscle weakness triggered by emotions.