Stages of sleep and brain mechanisms

Sleep

State that the brain actively produces, characterized by decreased activity and decreased response to stimuli

Coma

Extended period of unconsciousness caused by head trauma, stroke or disease characterized by low level of brain activity and no response to stimuli

People in comas

Have low level of brain activity and no response to stimuli , either die or begin to recover within a few

Unresponsive wakefulness syndrome ( vegetative state )

Alternates between sleep and moderate arousal but person shows no awareness of surroundings and no purposeful behavior

In vegetative state

Breathing is more regular and a painful stimulus increases heart rate, breathing and sweating. Eye movements occur , not following target May laugh/cry but not in response to external event

Minimally conscious state

Decreased brain activity with occasional, brief periods of purposeful actions & a limited amount of speech comprehension , can last for months /years

Brain death

Condition with no sign of brain activity & no response to any stimulus, no sign of brain activity for 24 hours

Polysomnograph

A combination of EEG & eye-movement records

Alpha waves

Steady series of brain waves at a frequency of 8 - 12 per second that are characteristic of relaxation

During stage 1 sleep

The EEG is dominated by irregular, jagged, low-voltage waves. Brain activity is less than in relaxed wakefulness but higher than in other sleep stages because most neurons are out of phase with one another, EEG full of short, rapid choppy waves

Stage 2 sleep

K-complexes and sleep spindles

K-complex

Sharp brain wave associated with temporary inhibition of neuronal firing

Sleep spindle

Burst of 12 - to 14- Hz waves that last atleast half a second , result from oscillating interactions between cells in the thalamus & the cortex

Sleep spindles increase

after new learning & the # of sleep spindles correlates positively with improvements in certain types of memory

Sleep spindles relate

To the consolidation of memory, consistent in amount of spindle ailing from one night to another

During Slow-wave sleep

Heart rate, breathing rate & brain activity decrease while slow, large - amplitude waves increase

Slow waves indicate

Neural activity is highly synchronized: activity driven part by spontaneous activity in the thalamus & partly by waves of blood flow

Stage 3 sleep

Fewer slow waves

Stage 4 sleep

More slow waves

Paradoxical sleep

“ Apparently self- contradictory “ sleep that is deep in some ways & light in others

Rapid eye movement sleep (REM)

Sleep stage with rapid eye movements, high brain activity, & relaxation of the large muscles

Non rapid eye movement ( nREM) sleep

Sleep stages other than REM

REM most common

Toward the end of the nights sleep

Histamine

Excitatory neurotransmitter released by one axon pathway from the hypothalamus which enhances arousal & alertness

Antihistamines

Produce drowsiness , ones that do not cross the blood-brain barrier avoid that side effect

Orexin

Peptide neurotransmitter released from the hypothalamus increases wakefulness and arousal

Somnambulism

Sleep walkers much of the brain is asleep but the motor cortex & few other areas

Sleep walkers

Have their eyes open, orient to he world well enough to find heir way around & sometimes remember but confused I vulnerable because most brain is not alert enough to process info & make reasonable decisions

Lucid dreaming