Chapter 8
Endogenous circannual rhythm = naturally occurring cycles within our bodies; rhythm that
prepare us for seasonal changes.
Endogenous circadian rhythms = rhythms that last about a day.
Circadian rhythms affect much more than just waking and sleeping. We have circadian
rhythms in our eating and drinking, urination, hormone secretion, metabolism, sensitivity to
drugs, and other variables.
Zeitgeber = time-giver; the stimulus that resets the circadian rhythm.
→ light is by far the dominant zeitgeber for land animals.
Jet lag = a disruption of circadian rhythms due to crossing time zones.
→ is stressful, stress elevates blood levels of the adrenal hormone cortisol → prolonged
elevations of cortisol damage neurons in the hippocampus.
Suprachiasmatic nucleus (SCN) = main driver of rhythms for
sleep and body temperature; part of the hypothalamus.
Retinohypothalamic path = a small branch of the optic nerve,
from the retina to the SCN; alters the SCN’s settings.
People who are blind because of cortical damage can still
synchronize their circadian rhythm to the local pattern of day and
night, because If the retina is intact, melanopsin-containing ganglion cells can still send
messages to the SCN, resetting its rhythm.
SCN neurons: Protein (PER and TIM) synthesis through mRNA transcription. The genes
that lead to the synthesis of the PER and TIM proteins are silenced by high concentrations of
PER and TIM, producing a self-regulatory (endogenous) rhythm with a period of 24 hours.
Pineal gland releases the hormone melatonin
Melatonin = a widespread chemical, released mostly at night, increases sleepiness in
diurnal animals (humans) and increases wakefulness in nocturnal animals.
Sleep = a 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.
Vegetative state = alternates between periods of sleep and moderate arousal, although
even during aroused state, the person shows no awareness of surroundings and no
purposeful behavior.
Minimally conscious state = brief periods of purposeful actions and a limited amount of
speech comprehension.
Brain death = condition with no sign of brain activity and no response to any stimulus.
42
,Polysomnograph = a combination of EEG and eye-movement records.
Alpha waves = waves during sleep; characteristic of relaxation, not of all wakefulness.
K-complex = a sharp wave associated with temporary inhibition of neuronal firing.
Sleep spindle = a burst of 12- to 14-Hz waves for at least half a second; result from
oscillating interactions between cells in the thalamus and the cortex.
→ consolidation of memory
Slow-wave sleep = heart rate, breathing rate and brain activity decrease, whereas slow,
large-amplitude waves become more common.
→ slow waves indicate that neuronal activity is highly synchronized.
Paradoxical sleep = deep sleep in some ways and light in others; involves seemingly
contradictory states of an active mind and a sleeping body.
Rapid eye movement (REM) sleep = synonymous with paradoxical sleep; a person's brain
activity, breathing, heart rate, and blood pressure fluctuate, and the eyes move rapidly while
closed; combination of deep sleep, light sleep and is associated with erections and vaginal
moistening.
→ during both paradoxical and REM sleep, EEG shows irregular, low-voltage fast waves,
indicating increased neuronal activity.
non-REM sleep = stages other than REM sleep.
Sleep cycle: stage 1 → stage 2 → slow-wave sleep → stage 2 → REM (& repeat)
about 90 min.
Reticular formation = a structure that extends from the medulla into the forebrain; arousal
Pontomesencephalon = part of the reticular formation; contributes to cortical arousal.
43
,Locus coeruleus = a small structure in the pons, is usually inactive (especially during sleep)
but it emits bursts of impulses in response to meaningful events (especially those that
produce emotional arousal).
→ release norepinephrine
Hypothalamus pathway releases:
Histamine → enhances arousal and alertness throughout the brain.
Orexin (hypocretin) → enhancing wakefulness and activity; for staying awake
Basal forebrain = their cells provide axons that extend throughout thalamus and cerebral
cortex, some of them increasing wakefulness and others inhibiting it. Stimulated by
acetylcholine.
During sleep, neurons in the thalamus become hyperpolarized, decreasing their readiness
to respond to stimuli and decreasing the information they transmit to the cortex.
How do we remain unconscious in spite of sustained neuronal activity: inhibition by release
of GABA.
Sleepwalkers → asleep in most of the brain, but awake in the motor cortex and a few other
areas.
During REM sleep → activity increased in the pons and the limbic system; activity
decreased in the primary visual cortex but increased in parts of the parietal and temporal
cortex.
→ REM is initiated by inhibiting other inhibitory neurons (+).
PGO waves = propagating activity between three key brain regions, being the pons, lateral
geniculate nucleus and occipital cortex.
Insomnia = inadequate sleep
→ causes could be noise, uncomfortable temperatures, stress, pain, diet and medications or
epilepsy, parkinson’s disease, brain tumors, depression, anxiety or other neurological or
psychiatric conditions.
Sleep apnea = one type of insomnia; impaired ability to breathe while sleeping.
→ caused by genetics, hormones, and old-age deterioration of the brain mechanisms that
regulate breathing.
Narcolepsy = a condition characterized by frequent periods of sleepiness during the day.
→ has 4 main symptoms:
1. Attacks of sleepiness during the day.
2. Occasional cataplexy, an attack of muscle weakness while the person remains
awake (triggered by strong emotions).
3. Sleep paralysis, an inability to move while falling asleep or waking up.
4. Hypnagogic hallucinations, dreamlike experiences that the person has trouble
distinguishing from reality, often occurring at the onset of sleep.
→ people with narcolepsy lack the hypothalamic cells that produce and release orexin.
44
, REM behavior disorder = disorder where people move around vigorously during their REM
periods, apparently acting out their dreams.
Night terrors = experiences of intense anxiety from which a person awakens screaming in
terror; more severe than a nightmare.
Sleep serves many functions:
● rest our muscles
● decrease metabolism
● perform cellular maintenance in neurons
● reorganize synapses
● strengthen memories
→ even one night of sleeplessness activates the immune system, you at as if you’re ill
Sleep’s ‘first’ function: to serve energy during inefficient times (also for hibernation)
Hibernating animals
→ decrease their body temperature to only slightly above that of the environment, but not
low enough for their blood to freeze.
→ heart rate drops to almost nothing, brain activity drops to almost nothing, neuron cell
bodies shrink and many synapses disappear, regenerating later when body temperature
increases.
→ live longer, cause hibernation retards or suspends the aging process
Birds that have to fly for a long time (can take up to 2 years) alternate between the two
hemispheres in sleep.
Patterns that occurred in the hippocampus during learning, also occurred during sleep but
they were more rapid during sleep.
Hypothesis: REM sleep is to get oxygen to the cornea to prevent them from damaging as
they normally get oxygen from the air, but the eyes are closed during sleep (no clear
evidence).
Activation-synthesis hypothesis = a dream represents the brain’s effort to make sense of
sparse and distorted information. Dreams begin with periodic bursts of spontaneous activity
in the pons (PGO waves) that activate some parts of the cortex but not others.
Neurocognitive hypothesis = regards dreams as thinking that takes place under unusual
conditions. It emphasizes that dreams begin with spontaneous brain activity related to recent
memories.
The idea of dreams is that either internal or external stimulation activates parts of the
parietal, occipital, and temporal cortex. The arousal develops into a hallucinatory perception,
with no sensory input from area V1 to override it.
45
Endogenous circannual rhythm = naturally occurring cycles within our bodies; rhythm that
prepare us for seasonal changes.
Endogenous circadian rhythms = rhythms that last about a day.
Circadian rhythms affect much more than just waking and sleeping. We have circadian
rhythms in our eating and drinking, urination, hormone secretion, metabolism, sensitivity to
drugs, and other variables.
Zeitgeber = time-giver; the stimulus that resets the circadian rhythm.
→ light is by far the dominant zeitgeber for land animals.
Jet lag = a disruption of circadian rhythms due to crossing time zones.
→ is stressful, stress elevates blood levels of the adrenal hormone cortisol → prolonged
elevations of cortisol damage neurons in the hippocampus.
Suprachiasmatic nucleus (SCN) = main driver of rhythms for
sleep and body temperature; part of the hypothalamus.
Retinohypothalamic path = a small branch of the optic nerve,
from the retina to the SCN; alters the SCN’s settings.
People who are blind because of cortical damage can still
synchronize their circadian rhythm to the local pattern of day and
night, because If the retina is intact, melanopsin-containing ganglion cells can still send
messages to the SCN, resetting its rhythm.
SCN neurons: Protein (PER and TIM) synthesis through mRNA transcription. The genes
that lead to the synthesis of the PER and TIM proteins are silenced by high concentrations of
PER and TIM, producing a self-regulatory (endogenous) rhythm with a period of 24 hours.
Pineal gland releases the hormone melatonin
Melatonin = a widespread chemical, released mostly at night, increases sleepiness in
diurnal animals (humans) and increases wakefulness in nocturnal animals.
Sleep = a 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.
Vegetative state = alternates between periods of sleep and moderate arousal, although
even during aroused state, the person shows no awareness of surroundings and no
purposeful behavior.
Minimally conscious state = brief periods of purposeful actions and a limited amount of
speech comprehension.
Brain death = condition with no sign of brain activity and no response to any stimulus.
42
,Polysomnograph = a combination of EEG and eye-movement records.
Alpha waves = waves during sleep; characteristic of relaxation, not of all wakefulness.
K-complex = a sharp wave associated with temporary inhibition of neuronal firing.
Sleep spindle = a burst of 12- to 14-Hz waves for at least half a second; result from
oscillating interactions between cells in the thalamus and the cortex.
→ consolidation of memory
Slow-wave sleep = heart rate, breathing rate and brain activity decrease, whereas slow,
large-amplitude waves become more common.
→ slow waves indicate that neuronal activity is highly synchronized.
Paradoxical sleep = deep sleep in some ways and light in others; involves seemingly
contradictory states of an active mind and a sleeping body.
Rapid eye movement (REM) sleep = synonymous with paradoxical sleep; a person's brain
activity, breathing, heart rate, and blood pressure fluctuate, and the eyes move rapidly while
closed; combination of deep sleep, light sleep and is associated with erections and vaginal
moistening.
→ during both paradoxical and REM sleep, EEG shows irregular, low-voltage fast waves,
indicating increased neuronal activity.
non-REM sleep = stages other than REM sleep.
Sleep cycle: stage 1 → stage 2 → slow-wave sleep → stage 2 → REM (& repeat)
about 90 min.
Reticular formation = a structure that extends from the medulla into the forebrain; arousal
Pontomesencephalon = part of the reticular formation; contributes to cortical arousal.
43
,Locus coeruleus = a small structure in the pons, is usually inactive (especially during sleep)
but it emits bursts of impulses in response to meaningful events (especially those that
produce emotional arousal).
→ release norepinephrine
Hypothalamus pathway releases:
Histamine → enhances arousal and alertness throughout the brain.
Orexin (hypocretin) → enhancing wakefulness and activity; for staying awake
Basal forebrain = their cells provide axons that extend throughout thalamus and cerebral
cortex, some of them increasing wakefulness and others inhibiting it. Stimulated by
acetylcholine.
During sleep, neurons in the thalamus become hyperpolarized, decreasing their readiness
to respond to stimuli and decreasing the information they transmit to the cortex.
How do we remain unconscious in spite of sustained neuronal activity: inhibition by release
of GABA.
Sleepwalkers → asleep in most of the brain, but awake in the motor cortex and a few other
areas.
During REM sleep → activity increased in the pons and the limbic system; activity
decreased in the primary visual cortex but increased in parts of the parietal and temporal
cortex.
→ REM is initiated by inhibiting other inhibitory neurons (+).
PGO waves = propagating activity between three key brain regions, being the pons, lateral
geniculate nucleus and occipital cortex.
Insomnia = inadequate sleep
→ causes could be noise, uncomfortable temperatures, stress, pain, diet and medications or
epilepsy, parkinson’s disease, brain tumors, depression, anxiety or other neurological or
psychiatric conditions.
Sleep apnea = one type of insomnia; impaired ability to breathe while sleeping.
→ caused by genetics, hormones, and old-age deterioration of the brain mechanisms that
regulate breathing.
Narcolepsy = a condition characterized by frequent periods of sleepiness during the day.
→ has 4 main symptoms:
1. Attacks of sleepiness during the day.
2. Occasional cataplexy, an attack of muscle weakness while the person remains
awake (triggered by strong emotions).
3. Sleep paralysis, an inability to move while falling asleep or waking up.
4. Hypnagogic hallucinations, dreamlike experiences that the person has trouble
distinguishing from reality, often occurring at the onset of sleep.
→ people with narcolepsy lack the hypothalamic cells that produce and release orexin.
44
, REM behavior disorder = disorder where people move around vigorously during their REM
periods, apparently acting out their dreams.
Night terrors = experiences of intense anxiety from which a person awakens screaming in
terror; more severe than a nightmare.
Sleep serves many functions:
● rest our muscles
● decrease metabolism
● perform cellular maintenance in neurons
● reorganize synapses
● strengthen memories
→ even one night of sleeplessness activates the immune system, you at as if you’re ill
Sleep’s ‘first’ function: to serve energy during inefficient times (also for hibernation)
Hibernating animals
→ decrease their body temperature to only slightly above that of the environment, but not
low enough for their blood to freeze.
→ heart rate drops to almost nothing, brain activity drops to almost nothing, neuron cell
bodies shrink and many synapses disappear, regenerating later when body temperature
increases.
→ live longer, cause hibernation retards or suspends the aging process
Birds that have to fly for a long time (can take up to 2 years) alternate between the two
hemispheres in sleep.
Patterns that occurred in the hippocampus during learning, also occurred during sleep but
they were more rapid during sleep.
Hypothesis: REM sleep is to get oxygen to the cornea to prevent them from damaging as
they normally get oxygen from the air, but the eyes are closed during sleep (no clear
evidence).
Activation-synthesis hypothesis = a dream represents the brain’s effort to make sense of
sparse and distorted information. Dreams begin with periodic bursts of spontaneous activity
in the pons (PGO waves) that activate some parts of the cortex but not others.
Neurocognitive hypothesis = regards dreams as thinking that takes place under unusual
conditions. It emphasizes that dreams begin with spontaneous brain activity related to recent
memories.
The idea of dreams is that either internal or external stimulation activates parts of the
parietal, occipital, and temporal cortex. The arousal develops into a hallucinatory perception,
with no sensory input from area V1 to override it.
45
