Chapter 8 Flashcards
Endogenous Circannual Rhythms
ANd
endogenous circadian rhythms
Some animals generate endogenous circannual
rhythms, internal mechanisms that operate on an
annual or yearly cycle
– Example: birds migratory patterns; animals storing food
for the winter
All animals produce endogenous circadian rhythms, internal mechanisms that operate on an approximately 24-hour cycle – Sleep cycle – Frequency of eating and drinking – Body temperature – Secretion of hormones – Urination – Sensitivity to drugs
notes from lecture:
effected by external cues
environmental change can have major impact on animals migratory patterns
book: your urge to sleep depends partly on the time of day , not just how many hours you’ve been awake.
The Daily Activity of a Squirrel Kept in Total Darkness
Book:
Represents the activity of a flying squirrel kept in total darkness for 25 days
Each horizontal line represent one 24-hour day
A thickening of the line represent a period of activity by the animal
Even in this unchanging environment , the animal produce a regular rhthym of activity and sleep.
Waking period starts earlier each day than the last
Sleep period starts earlier each day than the last
check diagram 5
Daily Pattern of Body Temperature
slide 6
human body temp at 37 degrees normally
it will fluctuate over the course of the day from a low of 36.7 at night to almost 37.2 in the afternoon
Daily Pattern of Positive Moods
slide 7
Setting and Resetting the Biological Clock
Purpose of it ?
How long is the clock ?
The purpose of the circadian rhythm is to keep our
internal workings in phase with the outside world
• The human circadian clock generates a rhythm slightly
longer than 24 hours when it has no external cue to set
it
• Resetting our circadian rhythms is sometimes
necessary
Zeitgeber:
means what in german ?
German meaning “time giver”; refers to the
stimulus that resets the circadian rhythm
– Examples: sunlight, tides, exercise, meals, arousal of
any kind, meals, temperature of environment, and so on. – Depression, irritability, and impaired job performance are
effects of using something other than sunlight as a
zeitgeber
Difference in Sun Time Between East and West Germany
half an hour difference between the east and west
so, the sun in the east rise 30 min before the west
everyone in germany are on the same clock time
People at the eastern edge has a sleep midpoint about 30 min earlier than those at the west .
This correspond to the rising of the sun
Jet Lag
Refers to the disruption of the circadian rhythms due to
crossing time zones
– Stems from a mismatch of the internal circadian clock
and external time – Sleepiness during the day, sleeplessness at night, and
impaired concentration
• Traveling west “phase-delays” our circadian rhythms
• Traveling east “phase-advances” our circadian rhythms
Is it more difficult to fly east or west ?
why ?
More Difficult Flying East
Book:
Going west, we stayed awake later at night and then awaken late the next morning , already partly adjusted to the new schedule. Called phase delay our circadian rythms .
East : phase advance , to sleep earlier and to wake up earlier.
Shift Work
Sleep duration depends on when one goes to sleep
• Working at night does not reliably change the circadian
rhythm
– Even after long periods of working at night, people can
still feel groggy, sleep poorly during the day, and body temperature peaks while sleeping instead of while working
• People adjust best to night work if they sleep in a very
dark room during the day and work under very bright
lights at night
Morning People and Evening People
Cycles can differ between people and lead to different
patterns of wakefulness and alertness • Change as a function of age
– Young children are morning people
– Adolescents are often night people • As an adult, it partially depends upon genetics
book:
circadian rhythm differs among ppl
morning ppl: awaken early, quickly become productive and become less alert as the day progresses
night owl: warm up slowly, reaching their peak in the afternoon , or evening. They tolerate staying up all night better than morning ppl .5
Age and Gender Differences in Circadian Rhythms
slide 15
Notes from ppw:
Midpoint is lower for women than it is for men
This is the case until the 60s
13 hours for men , which they would normally sleep for
Mechanisms of the Biological Clock
Mechanisms of the circadian rhythms
– The suprachiasmatic nucleus (SCN)
– Genes that produce certain proteins
– Melatonin levels
the Suprachiasmatic Nucleus (SCN)
The main control center of the circadian rhythms of
sleep and temperature
– Located above the optic chiasm and part of the
hypothalamus
• Damage to the SCN results in less consistent body
rhythms that are no longer synchronized to
environmental patterns of light and dark
Supra = above the optic chiasm
The Suprachiasmatic Nucleus (SCN) and the Circadian Rhythm
Generates circadian rhythms in a genetically controlled,
unlearned manner • Single cell extracted from the SCN and raised in tissue
culture continues to produce action potential in a
rhythmic pattern • Various cells communicate with each other to sharpen
the circadian rhythm
The Suprachiasmatic Nucleus (SCN) and the Retinohypothalamic Path
Light resets the SCN via a small branch of the optic
nerve called the retinohypothalamic path
– Travels directly from the retina to the SCN
• The retinohypothalamic path comes from a special
population of ganglion cells that have their own
photopigment called melanopsin
– The cells respond directly to light and do not require any
input from the rods or cones
Notes from class:
If you keep your eyes away from light, you can trick your brain
blind ppl have medications that we give to them in order to reset your SCN
The Biochemistry of the Circadian Rhythm
what are the 2 genes for generating the circadian rythm
Two types of genes are responsible for generating the
circadian rhythm
– Period: produce proteins called PER
– Timeless: produce proteins called TIM
• PER and TIM proteins increase the activity of certain
kinds of neurons in the SCN that regulate sleep and
waking
– Mutations in the PER gene result in odd circadian
rhythms or decreased alertness if deprived of a good night’s sleep
Interaction of MRNA with PER and TIM Proteins
check diagram on slide 23
Melatonin
The SCN regulates waking and sleeping by controlling
activity levels in other areas of the brain
• The SCN regulates the pineal gland, an endocrine
gland located posterior to the thalamus
• The pineal gland secretes melatonin, a hormone that
increases sleepiness
Melatonin secretion usually begins two to three hours
before bedtime
• Melatonin feeds back to reset the biological clock
through its effects on receptors in the SCN
• Melatonin taken in the afternoon can phase-advance
the internal clock and can be used as a sleep aid
Sleep
Sleep is a state that the brain actively produces
– Characterized by a moderate decrease in brain activity
and decreased response to stimuli
• Sleep differs from the following states:
– Coma, vegetative state, minimally conscious state, and
brain death
Relaxation and Stage 1 Sleep
Alpha waves are present when one begins a state of
relaxation
• Stage 1 sleep is when sleep has just begun
– The EEG is dominated by irregular, jagged, and low
voltage waves – Brain activity begins to decline
Stage 2 Sl eep
Stage 2 sleep is characterized by the presence of:
– Sleep spindles: 12- to 14-Hz waves during a burst that
lasts at least half a second – K-complex: a sharp wave associated with temporary
inhibition of neuronal firing
