Saskia Ensel (2023)
Samenvatting Literatuur
deeltentamen 2: Hersenen en
gedrag.
Schooljaar 2023-2024. Universiteit Utrecht.
Inhoud
Brain and Behavior, 4th customized edition 2023 (Kalat, Cacioppo, Freberg, & Cacioppo) ............ 1
Kalat H8: Wakefulness and sleep ....................................................................................... 1
Kalat H10: Reproductive behaviors .................................................................................... 9
Kalat H11: Emotional Behaviors (11.1 & 11.2) .................................................................. 15
Kalat H13.3: Making decisions and social neuroscience....................................................... 19
Kalat H14: Psychopathology (14.2 & 14.3) ....................................................................... 20
Cacioppo H16: The healthy mind (p378-412) .................................................................... 26
Brain and Behavior, 4th customized edition 2023 (Kalat, Cacioppo,
Freberg, & Cacioppo)
Kalat H8: Wakefulness and sleep
H8.1 Rhythms of waking and sleeping
Pagina 212-220
Endogenous rhythms
The brain is keeping track of the date to generate an endogenous
circannual rhythm (= rhythm that prepares for seasonal changes).
Animals also produce endogenous circadian rhythms that last
about a day. Humans also generate 24-hour wake-sleep rhythms
which we can modify only a little. We have circadian rhythms in our
hunger, thirst, liver activity, insulin secretion, intestinal activity, body
temperature, DNA repair and much else. We also have circadian
rhythms in mood.
Two-process model: waak vs. slaapdruk
C → circadiane process (de druk om wakker te blijven).
S → homeostatische druk om te slapen.
Fysiologische componenten van C & S:
• C → SCN-activiteit, melatonine, cortisol & temperatuur als markers.
• S → mogelijke adenosine (neemt toe gedurende de dag).
Setting and resetting the biological clock
Your circadian rhythm is close to 24 hours. Unless something resets your circadian rhythm, it
would gradually drift away from the correct time.
,Saskia Ensel (2023)
• Zeitgeber = the stimulus that resets your circadian rhythm is referred to by the term
zeitgeber. Light is the dominant zeitgeber for land animals, tides are important for marine
animals. Other zeitgebers include: exercise, arousal, meals and the temperature of the
environment. These additional zeitgebers only have weak effects.
When we try to set our wake-sleep cycles by the clock, sunlight still has its influence. Sociale
stimuli niet effectief. Problems might happen when changing to summer or wintertime. Or on the
weekend, when you might stay up later and wake up later.
Some blind people set their circadian rhythms by noise, temperature, meals and activity.
However, those who are not as sensitive to these secondary zeitgebers produce circadian rhythms
that are a little longer than 24 hours. Most blind people report frequent sleep problems.
Zonder externe cues (van bv. de tijd) beginnen mensen met het volgen van hun interne klok (=
free running time). Dan staan we elke dag iets later op en gaan iets later naar bed:
Jet lag
A disruption of circadian rhythms after crossing time zones is known as jet lag. Most people find it
easier to adjust to crossing time zones going west than east. Going west, we stay awake later at
night and then awaken late the next morning, already partly adjusted to the new schedule. We
phase-delay our circadian rhythms. Going east, we phase-advance to sleep earlier and awaken
earlier. Adjusting to jet lag stressful. Stress elevates blood levels of cortisol, and prolonged
elevation of cortisol damages neurons in the hippocampus. On average, flight attendants have
smaller than average volumes of the hippocampus and surrounding structures, they also show
memory impairments.
Night work
People who work on a night shift try to sleep during the day. Even after months or years on such a
schedule, many workers continue to feel groggy on the job, they sleep poorly during the day and
their body temperature continues the peak when they are sleeping during the day. On average,
night-shift workers have more accidents than day-shift workers.
It is difficult to adjust the circadian rhythm to work at night, because most buildings use
artificial lighting in the range of 150-180 lux, which is only moderately effective in resetting the
rhythm. People adjust better when they sleep in a very dark room during the day and work under
very bright lights at night. Short-wavelength (blueish) light resets the circadian rhythm the best.
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. Others warm up slowly, reaching their peak in the
late afternoon or evening. Many people are intermediate between the two extremes. Being a
morning person or an evening person depends partly on age. It also depends on genetics and
several environmental factors. In low-tech societies without electric lights, people go to sleep
about three hours after sunset. After a society gains lectic lights, people stay awake later and get
less sleep.
, Saskia Ensel (2023)
Mechanisms of the biological clock
Richter (1967) first demonstrated that the brain generates its own rhythms – a biological clock –
and he found that the biological clock is insensitive to most forms of interference. The circadian
rhythm remains surprisingly steady despite food or water deprivation, X-rays, tranquilizers,
alcohol, anesthesia, lack of oxygen, most kinds of brain damage, or the removal of endocrine
organs.
• Suprachiasmatic nucleus (SCN) → (part of
the hypothalamus) main driver of the rhythms
for sleep and body temperature. The SCN
generates circadian rhythms automatically. A
single SCN cell can maintain a circadian rhythm
(not very accurately). Interactions among
neurons and astrocytes sharpen the accuracy.
SCN cells isolated from the body continue to
produce a circadian rhythm.
• Resetting the SCN → a small branch of the
optic nerve, the retinohypothalamatic path
from the retina to the SCN, alters the SCN’s
settings. Most of the input to that path does
not come from normal retinal receptors. The
retinohypothalamic path to the SCN comes
from certain retinal ganglion cells that have
their own photopigment, melanopsin. These
special ganglion cells receive some input from
rods and cones, but even without that input,
the respond directly to light. They convey
information about light to the SCN. They are
located mainly near the nose, and therefore
they see toward the periphery. Because they
respond slowly when light comes on and
decline slowly when the light ceases, the respond to the overall average amount of light, not to
instantaneous changes in light. The average intensity is exactly the information the SCN needs
to gauge the time of day.
Licht zorgt voor een reset zodat we altijd gelijk lopen met de externe wereld. In het oog zitten
kegeltjes en staafjes, deze liggen achter het netvlies. Licht moet eerst door de intrinsically
photosensitive retinal ganglion cells heen.
Biochemistry of the circadian rhythm
Study of the fruit fly: they found genes that produce a circadian rhythm. Those of these genes
known as Period (PER) and Timeless (TIM), produce the proteins PER and TIM. The concentration
of these proteins are based on feedback interactions:
• Early in the morning, the messenger RNA levels responsible for producing PER and TIM, start
at low concentrations. As they increase during the day they slowly increase synthesis of the
proteins.
• As the PER and TIM protein concentrations increase they feedback to inhibit the genes that
produce the RNA molecules. During the night the PER and TIM concentrations remain high,
promoting sleep, but the messenger RNA concentrations are declining.
• By the next morning, PER and TIM protein levels have declined, the fly awakens and the cycle
is ready to start again. In addition to the automatic feedback, light activates a chemical that
