Chapter 14 Flashcards
(20 cards)
What is a circadian rhythm?
A roughly 24-hour endogenous biological cycle that regulates processes like the sleep-wake cycle.
Where is the brain’s biological clock located?
In the suprachiasmatic nucleus (SCN) of the hypothalamus, just above the optic chiasm.
How is the circadian rhythm synchronized to the environment?
By input from the eyes, which informs the SCN of light/dark conditions.
What does EEG activity show when you’re awake?
Low-amplitude, high-frequency electrical activity.
What are the stages of sleep?
Stage 1, Stage 2, Stage 3, Stage 4 (slow-wave sleep), and REM (rapid eye movement) sleep.
What happens to EEG activity during slow-wave sleep (SWS)?
It becomes higher in amplitude and lower in frequency.
What characterizes REM sleep?
Brain activity resembling the waking state and rapid movement of the eyes; most dreaming occurs here.
How many REM cycles do we typically have each night?
About 4 to 6 short episodes.
What did Randy Gardner’s sleep deprivation experiment show?
That sleep deprivation primarily affects the brain, not the body, and leads to speech, memory, and attention issues.
Why is sleep important for the brain?
It helps with recovery, resetting neural activity, and consolidating memory.
What neurotransmitter is involved in the brainstem activating system related to sleep transitions?
Adenosine, which accumulates to promote sleep.
What genetic mechanism regulates circadian rhythms in Drosophila and mammals?
The per and tim genes, which regulate their own protein synthesis in a feedback loop.
What is the function of the PER and TIM proteins?
They accumulate during the day, link together, and inhibit their own synthesis—reset by light exposure.
What does sleep research in genetically engineered VIPR2 knockout mice suggest?
That disrupting certain genes in the SCN can remove jet-lag, indicating light entrains circadian genes.
What parts of the body continue functioning normally during sleep?
Neurons controlling breathing and heart rate continue functioning.
How do the neurons of the SCN synchronize their activity?
Through many dendritic synapses that help coordinate their firing.
What is the evidence that sleep has an evolutionary advantage beyond just rest?
Its role in memory consolidation and neural maintenance suggests a deeper function.
Why do babies have more REM sleep than adults?
Likely due to its role in brain development and early learning.
What happens if humans are deprived of external cues to time (like in caves)?
Their circadian rhythms shift to about 25 hours—called free-running cycles.
What aspect of the brain is most affected by lack of sleep?
Cognitive functions, including attention, memory, and speech.
