8.2: Stages of Sleep & Wakefulness

Reticular Formation

• integration & relay center for survival

  • motor control of areas in spinal cord

• decides what comes to our conscious attention

• excitatory & inhibitory

• medulla into forebrain

pontomesencephalon neurotransmitters

acetylcholine, glutamate

pontomesencephalon effects on behavior

increases cortical arousal

• in reticular formation

(P axons extend into forebrain)

locus coeruleus neurotransmitter

norepinephrine

• inc activity of more active neurons → enhanced memory

locus coeruleus effects on behavior

increases information storage during wakefulness → suppresses REM sleep

• small structure in pons

• emotional arousal

basal forebrain excitatory cells neurotransmitter

acetylcholine

basal forebrain excitatory cells function

• excites thalamus & cortex

• inc learning, attention

• shifts sleep NREM to REM

basal forebrain inhibitory cells neurotransmitter

GABA

basal forebrain inhibitory cells function

inhibits thalamus and cortex

hypothalamus histamine neurotransmitter function

increases arousal

hypothalamus (parts) neurotransmitters

histamine and orexin

hypothalamus orexin function

maintains wakefulness

• released form lateral and posterior nuclei of the hypothalamus

dorsal raphe and pons neurotransmitter

serotonin

dorsal raphe and pons function

interrupts REM sleep

insomnia behavior

inadequate sleep

insomnia causes

• disease → epilepsy, parkinsons

• mood disorders → depression, anxiety

• noise

• stress

• pain

• diet

• meds

sleep apnea behavior

inability to breathe — snoring

sleep apnea causes

• genetic

• hormones

• old age

• obesity

• deteriorating

narcolepsy behavior

• sudden attack of sleep

• a condition characterized by frequent periods of sleepiness during the day

narcolepsy causes

genetics, hormones

• lack of hypothalamic cells

• can be a cause of cataplexy which uses Ritalin (dopamine and norepinephrine)

periodic limb movement disorder behavior

involuntary leg kicking (sometimes arm)

periodic limb movement disorder causes

unknown

REM behavior disorder behavior

acting out dreams

REM behavior disorder causes

inadequate inhibitory NTS, like GABA

Night Terrors behavior

• wake screaming

• experiences of intense anxiety from which a person awakens screaming in terror; more severe than a nightmare

Night Terrors Causes

during NREM → unknown

Sleepwalking behavior

walking, not breathing

Sleepwalking causes

genetics, unknown though

• awake in motor cortex & others

alpha waves

a steady series of brain waves at a frequency of 8 to 12 per second that are characteristic of relaxation

basal forebrain

area anterior and dorsal to the hypothalamus

includes cell clusters that promote wakefulness and sleep

brain death

condition with no sign of brain activity and no response to any stimulus

coma

an extended period of unconsciousness with a low level of brain activity

K-complex

a sharp brain wave associated with temporary inhibition of neuronal firing → keep u asleep as long as there is a stimulus

locus coeruleus

a small structure in the pons that emits bursts of impulses in response to meaningful events, especially those that produce emotional arousal

minimally conscious state

condition of decreased brain activity with occasional, brief periods of purposeful actions and limited speech comprehension

orexin or hypocretin

neurotransmitter that increases wakefulness and arousal

paradoxical sleep

sleep that is deep in some ways and light in others

PGO waves

a distinctive pattern of high-amplitude electrical potentials that occur first in the pons, then in the lateral geniculate, and then in the occipital cortex

polysomnograph

a combination of EEG and eye-movement records

pontomesencephalon

part of the reticular formation that contributes to cortical arousal

rapid eye movement (REM) sleep

sleep stage with rapid eye movements, high brain activity, and relaxation of the large muscles

REM behavior disorder

a condition in which people move around vigorously during REM sleep REM sleep.

sleep spindle

12 to 14 Hz brain waves in bursts that last at least half a second

• activity rel to consolidation of memory

vegetative state

• dec brain activity

• btwn wakefulness & sleep

• limited responsiveness

• inc heart rate response to painful stimulus

histamine

enhances arousal and alertness throughout brain

how does sleep decrease sensory input in the cerebral cortex

• thalamus neurons hyperpolarized → dec response to stimuli → dec info transmitted

how r we unconscious despite sustained neuronal activity during sleep

• inhibition

  • GABA interferes spread of info btwn neurons → weaker connections

lucid dreams

• dreaming but aware of sleep

• 40z frontal and temporal cortex

pons function

triggers the onset of REM sleep

PET scan results

• radioactive chemical → plastic tube in arm while sleeping

• dec activity in primary vis, motor, and dorsolateral prefrontal cortex

• inc activity in parietal and temporal cortex

what axons promote REM sleep

axons from ventral medulla releasing GABA promotes REM

• initiate REM by inhibiting other neurons

drug carbachol

• stimulates acetylcholine synapses

• move quickly into REM

serotonin and norepinephrine __ REM sleep

interrupt