brain & behavior ch. 10
Call Kai
Learn
Practice Test
Spaced Repetition
Match
Flashcards
Knowt Play1/118
There's no tags or description
Looks like no tags are added yet.
119 Terms
Biological rhythms
Regular fluctuations in biological processes or behavior.
Circadian rhythms
Biological rhythms with a period of approximately 24 hours.
Ultradian rhythms
Biological rhythms with periods shorter than 24 hours.
Infradian rhythms
Biological rhythms with periods longer than 24 hours.
Endogenous biological clock
Internal mechanism that generates biological rhythms without external time cues.
Free-running rhythm
Biological rhythm that continues without environmental time cues, following its natural period.
Entrainment
Synchronization of an internal biological rhythm to an external environmental cycle.
Zeitgeber
External time cue, such as light, that synchronizes biological rhythms.
Period
Time interval between corresponding points in successive biological cycles.
Phase shift
Change in the timing of a biological rhythm, often caused by environmental stimuli.
Diurnal animals
Animals primarily active during the day.
Nocturnal animals
Animals primarily active at night.
Major advantage of circadian rhythms
Allow organisms to anticipate predictable daily environmental changes.
Normal hamsters in constant dim light
Maintain a free-running activity rhythm that shifts slightly later each day.
Suprachiasmatic nucleus (SCN)
Hypothalamic nucleus that serves as the body's main circadian clock.
Effect of SCN lesions
Eliminate circadian rhythms of drinking, locomotion, and hormone secretion.
SCN-lesioned hamsters in constant dim light
Show randomly timed activity rather than a consistent circadian rhythm.
Evidence that SCN neurons contain a biological clock
Their metabolic and electrical activity continue cycling with circadian timing.
SCN transplant experiment
Transplanting an SCN from a short-period hamster restores the recipient's rhythm with the donor's period.
Conclusion of SCN transplant experiments
The SCN generates and determines the period of circadian rhythms.
Retinohypothalamic pathway
Neural pathway carrying light information from retinal ganglion cells to the SCN.
How does light entrain the SCN?
Retinal input releases glutamate onto SCN neurons and adjusts molecular clock activity.
Human sleep without external time cues
Sleep-wake timing free-runs, typically shifting later because the internal period exceeds 24 hours.
Clock/Cycle dimer
Protein complex that promotes transcription of Period and Cryptochrome genes.
Period and Cryptochrome proteins
Form a complex that inhibits Clock/Cycle activity through negative feedback.
Molecular circadian clock
A gene-protein feedback cycle that takes approximately 24 hours to complete; clock/cycle dimer binds to DNA, enhancing transcription of Per and Cry genes → Per/Cry complex inhibits activity of clock/cycle dimer, slowing transcription of Per and Cry genes → slower production of Per and Cry proteins, eventually break down and reset the cycle → retinal ganglion cells with axons in the retinohypothalamic tract release glutamate onto neurons in SCN, increase transcription of per gene → synchronize/entrain the molecular clock to the day/night cycle
Effect of Clock gene mutations in mice
Can produce severe loss of regular circadian activity under constant conditions.
Larks and night owls (humans)
People with different preferred sleep-wake timing, potentially influenced by clock gene variants.
Circadian changes at puberty
Adolescents tend to develop later sleep and wake times.
Two major classes of sleep
REM sleep and non-REM sleep.
REM sleep
Sleep characterized by rapid eye movements, wake-like EEG activity/fast EEG waves, no postural tension → muscle atonia
Non-REM sleep
Sleep divided into 3 stages with distinctive EEG patterns.
Paradoxical sleep
REM sleep; brain activity resembles wakefulness while skeletal muscles are largely paralyzed.
EEG
Electroencephalogram; recording of the brain's electrical activity.
EEG of an alert, awake individual
typically shows a fast, desynchronized pattern of brain waves, with high frequency and low amplitude.
Stage 1 sleep (N1)
Light sleep with irregular frequency/low-amplitude EEG activity and vertex spikes; heart rate slows, muscles relax, eyes roll about slowly; lasts several minutes
Vertex spikes
Sharp EEG waves characteristic of stage 1 sleep.
Stage 2 sleep (N2)
Sleep characterized by sleep spindles and K-complexes.
Sleep spindles
Brief bursts of approximately 12–14 Hz EEG activity during stage 2 sleep.
K-complexes
Large, sharp negative EEG potentials associated with stage 2 sleep.
Stage 3 sleep (N3)
Deep slow-wave sleep characterized by large-amplitude/very slow delta waves.
Delta waves
Very slow, high-amplitude EEG waves associated with stage 3 sleep.
Slow-wave sleep (SWS)
Deep non-REM sleep characterized by synchronized cortical activity.
EEG during REM sleep
Low-amplitude, high-frequency activity resembling wakefulness.
Muscle activity during REM sleep
Most skeletal muscles lose postural tone because motor neurons are inhibited.
Typical duration of sleep for young adults
Approximately 7–8 hours per night
Typical number of sleep cycles
Approximately 4–5 cycles per night.
Typical sleep cycle duration
Approximately 90–110 minutes.
Percentage of adult sleep spent in REM
Approximately 20%.
Most common sleep stage in young adults
Stage 2, accounting for about half of total sleep.
When is stage 3 sleep most common?
During the early part of the night.
When is REM sleep most common?
During the later part of the night.
REM dreams
Often vivid experiences with imagery, sounds, emotions, and a sense of being present.
Non-REM dreams
Usually more thought-like and less vivid than REM dreams.
Nightmares vs. night terrors
Nightmares are distressing dreams that occur during REM sleep, while night terrors are abrupt awakenings during Non-REM sleep, often causing fear without recall of the dream.
Activation-synthesis theory
Dreams arise as the cortex attempts to interpret internally generated neural activity.
Unilateral sleep
Sleep in which one cerebral hemisphere sleeps while the other remains relatively awake.
Animals demonstrating unilateral sleep
Dolphins and some birds.
Why do dolphins lack typical REM sleep?
REM-related muscle atonia could interfere with swimming and surfacing to breathe.
Infant sleep patterns
Infants have shorter sleep cycles, spend more time in REM, and can transition directly from wakefulness to REM.
Development of infant circadian rhythms
A stable 24-hour sleep-wake rhythm emerges around 16 weeks after birth.
REM sleep in newborns
Accounts for approximately half of total sleep.
Sleep changes with aging
Total sleep decreases, awakenings increase, and stage 3 sleep declines.
Elderly sleep compared with young adults
Older adults generally have more fragmented sleep and much less slow-wave sleep.
Consequences of sleep deprivation
Sleepiness, irritability, impaired concentration, and episodes of disorientation.
Sleep deprivation and academic performance
First-year college students who sleep more tend to have higher GPAs.
Prolonged sleep deprivation in rats
Sustained total sleep deprivation caused death within approximately 19 days in the experiments discussed.
Fatal familial insomnia
Rare inherited neurodegenerative disorder causing progressive severe insomnia and eventual death.
Recovery sleep
Increased sleep following deprivation, particularly involving stage 3 sleep and REM intensity.
Stage 3 rebound
Increased slow-wave sleep during recovery after sleep deprivation.
REM rebound
Increased intensity or amount of REM sleep following deprivation.
Does stage 3 recovery increase linearly with deprivation?
No, the increase in stage 3 sleep is not directly proportional to time spent awake.
Four proposed biological functions of sleep
Energy conservation, niche adaptation, body and brain restoration, and memory consolidation.
Energy conservation hypothesis
Sleep reduces energy expenditure during periods when activity is unnecessary.
Niche adaptation hypothesis
Sleep keeps animals inactive during times when activity would be dangerous or disadvantageous.
Restorative function of sleep
Sleep supports protein-related processes, immune function, and brain maintenance.
Brain cleanout during sleep
Glial-associated clearance processes help remove waste products from brain tissue.
Memory consolidation
Process by which newly learned information becomes more stable and is retained.
REM sleep and learning
REM sleep can improve consolidation of perceptual skills.
Slow-wave sleep and learning
SWS supports declarative memory and complex motor skill learning.
Odor-cued memory experiment
Reintroducing a learning-associated odor during SWS improved later recall of learned locations.
Neural replay during sleep
Neurons reactivate patterns associated with previous learning, often at an accelerated speed.
Natural short sleepers
Rare individuals who function normally on very little sleep, possibly because of genetic differences.
Sleep pattern of an extremely short sleeper
May involve reduced amounts of stage 1 and stage 2 sleep.
Can healthy humans function indefinitely without sleep?
No healthy individual has been identified who requires absolutely no sleep.
Hypothalamic region containing wake-promoting neurons inhibited by sleep-related GABA signaling; GABAA receptors, also stimulated by general anesthetics
Reticular formation activates the forebrain and promotes wakefulness; aka reticular activating system
Electrical stimulation of reticular formation awakens sleeping animals, while lesions can produce persistent sleep.
Loss of skeletal muscle tone caused by inhibition of spinal motor neurons