9.2 Stages Of Sleep And Brain Mechanisms Flashcards
Sleep is a state that the brain actively produces, characterised by decreased response to stimuli. In contrast, ____ is an extended period of unconsciousness caused by head trauma, stroke, or disease.
coma
A person on a coma has a ___ ____ of brain activity throughout the day, and little or no response to stimuli, including those that are ordinarily painful.
low level
Any movements of a person in a coma are purposeless and not directed toward anything. Typically, someone in a coma ever dies or begins to recover ________.
within a few weeks
Someone in a ____ ____ alternates between periods of sleep and moderate arousal, although even during the more aroused state, the person shows no awareness of surroundings.
vegetative state
In a person in a vegetative state breathing is more regular, and a painful stimulus produces at least the ____ ____ of increased heart rate, breathing, and sweating. The person does not speak, respond to speech, or show any purposeful activity.
automatic responses
A ____ ____ ____ is one state higher, with occasional, brief periods of purposeful actions and a limited amount of speech comprehension. A vegetative or minimally conscious state can last for months or years.
minimally conscious state
____ ____ is a condition with no sign of brain activity and no response to any stimulus. Physicians usually wait until someone has shown no sign of brain activity for 24 hours before pronouncing brain death, at which point most people believe that it is ethical to remove life-support.
Brain death
The ____ (EEG), records an average of the electrical potentials of the cells and fibres in the brain areas nearest each electrode on the scalp.
electroencephalograph
On an electroencephalograph, if half the cells in some area increase their electrical potential while the other half decrease, they ____ ___.
cancel out
The EEG record ____ or ____ when most cells do the same thing at the same time.
rises or falls
A ____ is a combination of EEG and eye-movement records.
polysomnograph
____ ____ are characteristic of relaxation, not of all wakefulness.
Alpha waves
During sleep ____ ___, the EEG is dominated by irregular, jagged, low-voltage waves. Overall brain activity is less than in relaxed wakefulness but higher than other sleep stages.
stage one
The most prominent characteristics of sleep ____ ___ are sleep spindles and K-complexes.
stage two
A ____ ____ consists of 12- to 14-Hz waves during a burst that lasts at least half a second. Sleep spindles result from oscillating interactions between cells in the thalamus and the cortex.
sleep spindle
A ____ is a sharp wave associated with temporary inhibition of neuronal firing.
K-complex
In the succeeding stages of sleep, heart rate, breathing rate, and brain activity ____, while slow, large-amplitude waves become more common.
decrease
By sleep ____ ____, more than half the record includes large waves of at least a half-second duration.
stage four
Stages 3 and 4 together constitute ____ ____ (SWS). Slow waves indicate that neuronal activity is highly synchronised.
slow-wave sleep
____ ____ is so named because it is deep sleep in some ways and light in others.
Paradoxical sleep
Periods of rapid eye movement occurs during sleep. They called these periods ____ ___ ____ (REM) sleep and soon realised that REM sleep was synonymous with what Jouvet called paradoxical sleep.
rapid eye movement
Researchers use the term REM sleep when referring to humans but often prefer the term paradoxical sleep for nonhumans because many species lack ___ ____.
eye movements
During paradoxical or REM sleep, the EEG shows irregular, low-voltage fast waves that indicate increased ____ ____. In this regard REM sleep is light.
neuronal activity
However, the postural muscles of the body, including those that support the head, are more relaxed during REM than in other stages. In this regard, REM is ____ ____.
deep sleep
REM is also associated with ____ in males and vaginal moistening in females.
erections
Heart rate, blood pressure, and breathing rate are more ____ in REM than in stages 2 through 4. In short, REM sleep combines deep sleep, light sleep, and features that are difficult to classify as deep or light.
variable
In addition to its steady characteristics, REM sleep has intermittent characteristics such as ____ ____ and ___ ____.
facial twitches and eye movements
The sleep stages other than REM are known as _____ (NREM) sleep.
non-REM sleep
When you fall asleep, you start in stage one and slowly progressed through stages two, three, and four in order. After about an hour of sleep you begin to cycle back from stage four through stages three, two, and then REM. The sequence repeats, with each cycle lasting about _______.
90 minutes
Early in the night, stages three and four predominate. Towards the morning, REM occupies an ____ percentage of the time.
increasing
