Sleep and Circadian Rhythms

Flashcards about the content of the Sleep and Circadian Rhythms lecture

What is measured by electroencephalograms (EEGs)?

The electrical activity of large populations of neurons in the brain.

What are the limitations of electroencephalograms regarding resolution?

High temporal resolution but low spatial resolution.

How is sleep behaviorally defined?

Reduced motor activity, reduced response to stimulation, stereotypic postures, and relatively easy reversibility.

What physiological activities can be measured using electrical recordings?

Muscle movements (electromyography), eye movements (electro-oculography), and brain activity (electroencephalography).

What causes the electrical activity measured by an EEG?

Cellular, ionic movement which creates an electric field.

Why does EEG have low spatial resolution?

Electric fields follow an inverse square law, so only cortical activity is detectable.

Describe neuronal activity during non-REM sleep.

Neuronal activity is low with not much action potential firing.

What happens to heart rate and blood pressure during non-REM sleep?

They decline due to decreased sympathetic nervous system outflow and increased parasympathetic nervous system.

What is the main characteristic of Stage 2 sleep?

Bursts of sinusoidal waves called ‘sleep spindles’ and biphasic waves called K complexes.

What characterizes Stage 3 and 4 sleep?

High amplitude, slow delta waves dominating the EEG record; also known as slow wave sleep.

Why is REM sleep considered paradoxical?

EEG during human REM is similar to Stage 1/Awake and neuronal firing is very like in wakefulness.

What happens to skeletal muscles during REM sleep?

All skeletal muscles are atonic, flaccid, and paralyzed except for those controlling eye movements, middle ear ossicles, and the diaphragm.

What is the typical duration of the first REM phase during sleep?

8-10 minutes.

What percentage of sleep time is spent in Stage 2 sleep?

50-60%.

What happens during the Non-REM stage?

Delta rhythms: activity in the thalamus, Decrease of firing in the brain stem, Spindles – correlated activity in the thalamus.

What are the theories of dreaming?

‘Circuit Testing’, ‘Memory consolidation’, Strange imagery-brain not fully functioning, Exercises synapses when no external activity.

What modulates circadian rhythms?

External timing cues known as 'zeitgebers'.

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

Regulates the timing of sleep; major internal clock

How does the visual system contribute to circadian rhythms?

Intrinsically photosensitive ganglion cells provide input to the suprachiasmatic nucleus.