Wakefulness and Sleep
 Rhythms of Waking and Sleeping

Endogenous Rhythms - is
an internal mechanism that
allows readiness for a
change.

Endogenous Circannual
Rhythm - a rhythm that
prepares the animals for
seasonal changes.

Endogenous Circadian
Rhythm - is responsible for
waking and sleeping.
 Setting and Resetting the Biological
Clock

biological clock - the body's
internal clock or workings
that produces natural timings.

zeitgeber (time-giver)
- the stimulus that resets the
circadian rhythm.
- light, tides (for marine
animals), arousal, exercise,
and etc.

jetlag – a disruption of
circadian rhythms due to
crossing time zones.

shift work - People who
sleep irregularly—such as
pilots, medical interns,and
shift workers in factories find
that their duration of sleep
depends on when they go to
sleep.

morning and evening
people - Among shift
workers, morning people are
most impaired when working
the night shift and evening
people are most impaired
when working the morning
shift.
 Mechanisms of the Biological Clock
 Curt Richter (1967)
- 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.
- 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. Even an hour or more
of induced hibernation often
fails to reset the biological
clock.
- Evidently, the biological
clock is a hardy, robust
mechanism.

 The Suprachiasmatic Nucleus
(SCN)





The main driver of rhythms for sleep
and body temperature.
A part of the hypothalamus.
A damage to the SCN, the body’s
rhythms become erratic.
The SCN generates circadian rhythms
itself in a genetically controlled
manner.
Even a single isolated SCN cell can
maintain a circadian rhythm, although
interactions among cells sharpen the
accuracy of the rhythm.
 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.

pineal gland - releases the
hormone melatonin.

Melatonin is a widespread
chemical, found in nearly all
animals—sponges are the
only known exception—as
well as in plants and bacteria.

It is released mostly at night.

In diurnal animals like
humans, it increases
sleepiness.

In nocturnal animals, it
increases wakefulness.
People who have pineal
gland tumors sometimes stay
awake for days at a time.
 Sleep and other interruptions of
consciousness

Sleep - is a state that the brain
actively produces, characterized by
decreased activity and decreased
response to stimuli.

Coma - is an extended period of
unconsciousness caused by head
trauma, stroke, or disease.
 Stages of Sleep

electroencephalograph
(EEG) - records an average
of the electrical potentials of
the cells and fibers in the
brain areas nearest to each
electrode on the scalp. The
EEG record rises or falls
when most cells do the same
thing at the same time.

Polysomnograph - A
combination of EEG and eyemovement records. A
polysomnograph is a
multichannel recording
made during sleep to evaluate
a variety of symptoms or
monitor gas exchange.

Paradoxical or REM Sleep
- is deep sleep in some ways
and light in others. (The term
paradoxical mean “apparently
self-contradictory.”)
- In short, REM sleep
combines aspects of deep
sleep, light sleep, and
features that are difficult to
classify as deep or light.
dorsolateral prefrontal cortex
but increased in parts of the
parietal and temporal cortex.

 Brain Mechanisms of Wakefulness,
Arousal, and Sleep

reticular formation - a cut
through the midbrain
decreases arousal by
damaging this organ.
 Sleep and the Inhibition of Brain
Activity
REM sleep is associated with
a distinctive pattern of highamplitude electrical
potentials known as PGO
waves, for pons-geniculateoccipital. Waves of neural
activity are detected first in
the pons, shortly afterward in
the lateral geniculate nucleus
of the thalamus, and then in
the occipital cortex.
 Sleep Disorders



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.
However, although
responsiveness decreases, a
moderate amount remains.

Phase Delayed – has a
trouble of falling asleep at the
usual time.

Phase Advance – falls asleep
easily but awakens early.

Insomnia - If you feel tired
during the day, you are not
sleeping enough at night.

Sleep Apnea – people with
sleep apnea have breathless
period of a minute or so from
which they awaken gasping
for breath.

Narcolepsy – a condition
characterized by frequent
periods of sleepiness during
the day.

Periodic Limb Movement
Disorder – characterized by
involuntary movement of the
 Brain Activity in REM Sleep

During REM sleep, activity
increased in the pons (which
triggers the onset of REM
sleep) and the limbic system
(which is important for
emotional responses).
Activity decreased in the
primary visual cortex, the
motor cortex, and the
legs and sometimes the arm
during the sleep.

REM Behavior Disorder –
move around vigorously
during their REM periods,
apparently acting out their
dreams.

Night Terrors and
Sleepwalking – an
experience of intense anxiety
from which a person awakens
screaming in terror.

Sleep Sex (sexsomnia) –
sleeping disorder in which
people engage in sexual
behavior, either with a
partner or masturbation and
do not remember it
afterwards.
 Why Sleep? Why Rem? Why
Dreams?

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Functions of Sleep – during
sleep we rest our muscles,
decrease metabolism,
perform cellular maintenance
in neurons, reorganize
synapses and strengthen
memories.
Sleep and Energy
Conservation – a likely
hypothesis is that sleep
originally functions and still
the important one is to save
energy.
Sleep and Memory – if you
do not get a good night’s
sleep, your memory and
cognition will suffer the next
day.

Functions of REM Sleep –
average persons about third
of his/her life asleep and
about a fifth of sleep in REM,
totaling about 600 hours of
REM per year.

Biological Perspective on
Dreaming – all we know
about dreams comes from
people self-reports, and
researchers have no way to
check the accuracy of those
reports.
Internal Regulation
 Temperature Regulation

Thermoregulation - is a
mechanism by which
mammals maintain body
temperature with tightly
controlled self-regulation
independent of external
temperatures.
 Homeostasis & Allostasis

Homeostasis - refers to
temperature regulation and
other biological processes
that keep body variables
within a fixed range.

Allostasis - the adaptive way
in which the body anticipates
needs depending on the
situation, avoiding errors
rather than just correcting
them.
more concentrated. You also
increase your secretion of
vasopressin while sleeping so
that you can preserve your
body water while you cannot
drink. Vasopressin helps you
get through the night without
going to the toilet.
 Controlling Body Temperature


basal metabolism - the
energy used to maintain a
constant body temperature
while at rest.
ectothermic - organisms that
depend on external sources
for body heat instead of
generating it themselves.

endothermic - they generate
enough body heat to remain
significantly above the
temperature of the
environment.

fever - an increased set point
for body temperature.

Osmotic Thirst - eating salty
foods.

Hypovolemic thirst - losing
fluid by bleeding or sweating.

sodium-specific hunger deficient in sodium shows an
immediate strong preference
for salty tastes, even for
extremely concentrated salt
solutions that it would
ordinarily reject.
 Hunger
 Thirst

Mechanisms of Water
Regulation

Your posterior pituitary
releases the hormone
vasopressin that raises
blood pressure by
constricting blood vessels.

The increased pressure helps
compensate for the decreased
blood volume. Vasopressin is
also known as antidiuretic
hormone (ADH) because it
enables the kidneys to
reabsorb water from urine
and therefore make the urine

digestive system - ·main
function is to break food into
smaller molecules that the
cells can use.


Tryptophan & Turkey
Tryptophan enters the brain
by an active-transport protein
that it shares with
phenylalanine and other large
amino acids. When you eat
carbohydrates, your body
reacts by increasing secretion
of insulin, which moves
sugars into storage, and also
moves phenylalanine into
storage (in liver cells and
elsewhere). By reducing the
competition
fromphenylalanine, this
process makes it easier for
tryptophan to reach the brain,
inducing sleepiness. In short,
the dessert at your big meal
induces sleepiness much
more than turkey does.


short and long term
regulation of
feeding - eating is far too
important to be entrusted to
just one mechanism. Your
brain gets messages from
your mouth, stomach,
intestines, fat cells, and
elsewhere to regulate your
eating.
leptin - leptin signals your
brain about your fat reserves.
When your fat reserves
decrease, leptin levels
decline, and you react by
eating more and becoming
less active, to save energy.
When leptin levels return to
normal, you eat less and
become more active.
leads to obesity
without other
physical or mental
abnormalities.
3. POLYGENIC OR
COMMON
OBESITY - relates to
many genes, each of
which slightly
increases the
probability of
obesity.
 Weight Loss Techniques

Many psychologist
recommend small changes in
diet or "eat a little less than
usual".

Promote good health by
getting good nutrition and
physical exercise, regardless
of what happens to weight.

Reduce or eliminate the
intake of soft drinks.

Another option is weight-loss
drugs.

Gastric bypass surgery.
 Genetics & Body Weight

3 TYPES OF
HERITABILITY FOR
OBESITY
1. SYNDROMAL
OBESITY - results
when a gene causes a
medical problem that
includes obesity.
2. MONOGENIC
OBESITY - occurs
when a single gene