Samenvatting
Samenvatting biopsychologie deeltentamen 2
Samenvatting van biopsychologie voor deeltentamen 2; hoofdstuk 8 tot en met 14; James W. Kalat
[Meer zien]Voorbeeld 4 van de 39 pagina's
Voorbeeld 4 van de 39 pagina's
In winkelwagengesponsord bericht van onze partner
Gekoppeld boek
Titel boek:
Auteur(s):
- Uitgave:
- ISBN:
- Druk:
1 beoordeling
Door: pontusvdb • 5 jaar geleden
Voorbeeld van de inhoud
Biological PsychologyChapter 8: Wakefulness and Sleep
Learning Objectives:
1. Define and describe endogenous rhythms.
2. Explain the mechanisms that set and reset the biological clock.
3. List and characterize the stages of sleep.
4. Describe the brain mechanisms of waking and sleeping.
5. Discuss several consequences of thinking of sleep as a localized phenomenon.
6. List several sleep disorders with their causes.
7. Evaluate possible explanations of the functions of sleep.
8. Describe possible explanations of dreaming.
Module 8.1: Rhythms of Waking and Sleeping
Endogenous Rhythms
Animals’ readiness for a change in seasons comes partly from internal mechanisms. An
endogenous circannual rhythm prepares animals for seasonal changes. Endogenous
circadian rhythms last about a day. Humans generate 24-hour wake-sleep rhythms, and we
can modify them only a little.
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.
Setting and Resetting the Biological Clock
Our circadian rhythms generate a period close to 24 hours, but they are not perfect. We
readjust our internal workings daily to stay in phase with the world.
Although circadian rhythms persist without light, light is critical for resetting them.
The stimulus that resets the circadian rhythm is referred to by the German term zeitgeber.
Light is the dominant zeitgeber for land animals, whereas the tides are important for some
marine animals. Although additional zeitgebers modify the effects of light, they have only
weak effects on their own.
Even when we try to set our wake-sleep cycles by the clock, sunlight has its influence.
What about blind people, who need to set their circadian rhythms by zeitgebers other
than light? These results vary.
Jet Lag
A disruption of circadian rhythms due to crossing time zones is known as jet lag. It results
from the mismatch between internal circadian clock and external time. Most people find it
easier to adjust to crossing time zone going west then east. Going west, we phase delay our
circadian rhythms; going east, we phase-advance to sleep earlier and awaken earlier.
Adjusting to a jet lag is often stressful. Stress elevates blood levels of the adrenal
hormone cortisol, and many studies have shown that prolonged elevations of cortisol
damage neurons in the hippocampus, a brain area important for memory.
Shift Work
People who sleep irregularly find that their duration of sleep depends on when they go to
sleep. When they have to sleep in the morning or early afternoon, they sleep only briefly,
even if they have been awake for many hours.
, People adjust best to night work if they sleep in a very dark room during the day and
wok under very bright lights at night.
Morning People and Evening People
Circadian rhythms differ among individuals. Some people awaken early, reach their peak of
productivity early, and become less alert later in the day (“morning people”). Others warm
up more slowly, both literally and figuratively, reaching their peak in the late afternoon or
evening (“evening people”). Being a morning person or an evening person depends partly on
age. It also depends on genetics and other factors.
Mechanisms of the Biological Clock
How does the body generate a circadian rhythm? Curt Richter introduced the concept that
the brain generates its own rhythms – a biological clock – and he reported that the biological
clock is insensitive to most forms of interference. Evidently, the biological clock is a hardy,
robust mechanism.
The Suprachiasmatic Nucleus (SCN)
Although cells throughout the body generate circadian rhythms, the main driver of rhythms
for sleep and body temperature is the suprachiasmatic nucleus (SCN), a part of the
hypothalamus. It generates circadian rhythms itself in a genetically controlled manner.
How Light Resets the SCN
A small branch of the optic nerve, known as the retinohypothalamic path, from the retina to
the SCN, alters the SCN’s settings. Most of the input to that path, however, does not come
from normal retinal receptors. The explanation for how light resets the SCN is that the
retinohypothalamic path to the SCN comes from a special population of retinal ganglion cells
that have their own photopigment, called melanopsin, unlike the ones found in rods and
cones. These cells receive some input from rods and cones, but even if they do not receive
that input, they respond directly to light. These ganglion cells respond mainly to short-
wavelength (blue) light.
The Biochemistry of the Circadian Rhythm
The suprachiasmatic nucleus produces the circadian rhythm, but how? There are several
genes found to be responsible for a circadian rhythm. Two of these genes, known as period
(PER) and timeless (TIM), produce the proteins PER and TIM. The concentration of these two
proteins, which promote sleep and inactivity, oscillates over a day, based on feedback
interactions among neurons.
Mammals have three versions of the PER protein and several proteins closely related
to TIM.
Melatonin
The SCN regulates waking and sleeping by controlling activity levels in other brain areas,
including the pineal gland, an endocrine gland located just posterior to the thalamus. The
pineal gland releases the hormone melatonin, which influences both circadian and
circannual rhythms.
Melatonin pills are sometimes helpful for people who travel across time zones and
need to sleep at an unaccustomed time.
,Module 8.2: Stages of Sleep and Brain Mechanisms
Sleep and Other Interruptions of Consciousness
Sleep is a state that the brain actively produces, characterized by decreased response to
stimuli. In contrast, coma is an extended period of unconsciousness caused by head trauma,
stroke, or disease.
Someone in a vegetative state alternates between periods of sleep and moderate
arousal, although even during the more aroused state, the person shows no awareness of
surroundings and no purposeful behavior. A minimally conscious state is one stage higher,
with occasional, brief periods of purposeful actions and a limited amount of speech
comprehension.
Brain death is a condition with no sign of brain activity and no response to any
stimulus.
The Stages of Sleep
A polysomnograph is a combination of EEG and eye-movement records. Alpha waves are
characteristic of relaxation. Sleep spindles result from oscillating interactions between cells
in the thalamus and the cortex. A K-complex is a sharp wave associated with temporary
inhibition of neuronal firing. Slow-wave sleep (SWS) consists of stage 3 and 4. Slow waves
indicate that neuronal activity is highly synchronized.
Paradoxical or REM Sleep
Paradoxical sleep is deep sleep in some ways and light in others. Another term is rapid eye
movement (REM) sleep. During REM sleep, the EEG shows irregular, low-voltage fast waves
that indicate increased neuronal activity. In addition to its steady characteristics, REM sleep
has intermittent characteristics such as facial twitches and eye movements. The stages other
than REM are known as non-REM (NREM) sleep. Each sleep cycle lasts about 90 minutes.
Brain Mechanisms of Wakefulness, Arousal, and Sleep
Philosophers distinguish between the “easy” and “hard” problems of consciousness. The
hard problem is why consciousness exists at all. The easy problems are philosophically easy,
but scientifically complex.
Brain Structures of Arousal and Attention
The midbrain does more than just relay sensory information; it has its own mechanisms to
promote wakefulness.
A cut through the midbrain decreases arousal by damaging the reticular formation, a
structure that extends from the medulla into the forebrain. Some neurons of the reticular
formation have axons ascending into the brain, and some have axons descending into the
spinal cord. One part of the reticular formation that contributes to cortical arousal is known
as the pontomesencephalon. These neurons receive input from many sensory systems and
generate spontaneous activity of their own. It maintains arousal during wakefulness and
increases it in response to new or challenging tasks. However, subsystems within the
pontomesencephalon control different sensory modalities, so a stimulus sometimes arouses
one part of the brain more than others.
The locus coeruleus, a small structure in the pons, is usually inactive, but it emits
bursts of impulses in response to meaningful events, especially those that produce
emotional arousal. Output from the locus coeruleus increases the activity of the most active
neurons and decreases the activity of the most active neurons and decreases the activity if
less active neurons.
, The hypothalamus has several axon pathways that influence arousal. One pathway
releases the excitatory neurotransmitter histamine, which enhances arousal and alertness
throughout the brain.
Another pathway, mainly from the lateral and posterior nuclei of the hypothalamus,
releases a peptide neurotransmitter called orexin or hypocretin. It is necessary for staying
awake.
Other pathways from the lateral hypothalamus regulate cells in the basal forebrain.
These cells provide axons that extend throughout the thalamus and cerebral cortex.
Sleep and the Inhibition of Brain Activity
Sleep depends partly on decreased sensory input to the cerebral cortex. During sleep,
neurons in the thalamus become hyperpolarized, decreasing their readiness to respond to
stimuli and decreasing the information they transmit to the cortex. When they do fire, they
often fire in synchronous bursts.
How do we remain unconscious despite neuronal activity? The answer is inhibition.
During sleep, axons that release the inhibitory neurotransmitter GABA increase their activity,
interfering with the spread of information from one neuron to another.
Thinking of sleep as a local phenomenon helps make sense of some otherwise
puzzling phenomena, such as sleepwalking of lucid dreaming.
Brain Function in REM Sleep
During REM sleep, activity increased in the pons and the limbic system. Activity decreased in
the primary visual cortex, the motor cortex and the dorsolateral prefrontal cortex, but
increased in parts of the parietal and temporal cortex. REM sleep is associated with a
distinctive pattern of high-amplitude electrical potentials known as PGO waves, for pons-
geniculate-occipital.
REM sleep apparently depends on a relationship between the neurotransmitters
serotonin and acetylcholine.
Sleep Disorders
Insomnia is inadequate sleep.
Sleep Apnea
One type of insomnia is sleep apnea, impaired ability to breathe while sleeping.
Narcolepsy
Narcolepsy is a condition characterized by frequent periods of sleepiness during the day. It
has four main symptoms, although not every patient has all four:
1. Attacks of sleepiness during the day.
2. Occasional cataplexy – an attack of muscle weakness while the person remains
awake.
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.
Periodic Limb Movement Disorder
Another sleep disorder is periodic limb movement disorder, characterized by repeated
involuntary movement of the legs and sometimes the arms during sleep.
REM Behavior Disorder
People with REM behavior disorder move around vigorously during their REM periods,
apparently acting out their dreams.
Voordelen van het kopen van samenvattingen bij Stuvia op een rij:
Verzekerd van kwaliteit door reviews
Stuvia-klanten hebben meer dan 700.000 samenvattingen beoordeeld. Zo weet je zeker dat je de beste documenten koopt!
Snel en makkelijk kopen
Je betaalt supersnel en eenmalig met iDeal, creditcard of Stuvia-tegoed voor de samenvatting. Zonder lidmaatschap.
Focus op de essentie
Samenvattingen worden geschreven voor en door anderen. Daarom zijn de samenvattingen altijd betrouwbaar en actueel. Zo kom je snel tot de kern!
Veelgestelde vragen
Wat krijg ik als ik dit document koop?
Je krijgt een PDF, die direct beschikbaar is na je aankoop. Het gekochte document is altijd, overal en oneindig toegankelijk via je profiel.
Tevredenheidsgarantie: hoe werkt dat?
Onze tevredenheidsgarantie zorgt ervoor dat je altijd een studiedocument vindt dat goed bij je past. Je vult een formulier in en onze klantenservice regelt de rest.
Van wie koop ik deze samenvatting?
Stuvia is een marktplaats, je koop dit document dus niet van ons, maar van verkoper frderikedrijfhout. Stuvia faciliteert de betaling aan de verkoper.
Zit ik meteen vast aan een abonnement?
Nee, je koopt alleen deze samenvatting voor €4,49. Je zit daarna nergens aan vast.
Is Stuvia te vertrouwen?
4,6 sterren op Google & Trustpilot (+1000 reviews)
Afgelopen 30 dagen zijn er 54879 samenvattingen verkocht
Opgericht in 2010, al 14 jaar dé plek om samenvattingen te kopen