Biological rhythms and their medical values

1.

BIOLOGICAL RHYTHMS
And Their MEDICAL
VALUES
NAME – AMIT KUMAR
GUIDED BY – ANNA ZHUKOVA

2.

1. Chronobiology-Study of biological timekeeping
2. Biological rhythm-Cyclical, repeated variation in a biological
function
3. Ultradian-High frequency – repeats many times in a day
4. Infradian-Repeats at intervals much longer than 24 hours
5. Circadian-Approximately a day (24 hours)
6. Circatidal- Approximately every 12.4 hours ( with the tide)
7. Circalunar-Approximately once a month
8. Circannual-Approximately once a year
9. Endogenous-Internally generated rhythm
10.Free-running-Not synchronized to external signals
11.Pacemaker-A structure that generates a rhythm
12.Target tissue-Tissue whose function is regulated by the
pacemaker
13.Overt rhythm-A visible, measurable rhythm
14.Nocturnal-Active at night
15. Diurnal-Active during the day
16.LL-Constant light
17.DD-Constant light
18.LD 12:12-12 hours of light; 12 hours of dark

3.

Circadian Rhythms
circa= about;
dian= day
Rhythms= sequence or cycle
Rhythms are amongst the most widely
studied rhythmic behaviors across a
wide range of organisms.

4.

What is a rhythm?
• Pattern
• Sequence
• Regularity
• Progression
• Time
• Measure
• Beat

5.

Rhythm = sequence of events that
repeat themselves in the same
order and with the same time
interval, over and over again.
Biological rhythm:
a biological
event or function with a pattern of
activity that is repeated over and
over again at a constant time
interval.

6.

Examples of Biological Rhythms?
• Heart rate
• Breathing
• Hormone secretion
• Menstrual cycle
• Body temperature
• Sleep/wake cycle

7.

Biological Rhythms are the product of an
internal biological timekeeping system which
is controlled by a biological clock
Chronobiology
Two Broad Categories of Biological Rhythms
•high frequency –
•Ultradian
•Those that have a constant relationship with
environmental rhythms –
•Have a geophysical counterpart

8.

ENVIRONMENTAL RHYTHMS
Semi-Daily Rhythms• Tidal
Daily Rhythms
• Solar
Monthly
• Lunar
Quarterly
• Seasons
Annual
• Longer than a year

9.

Spinning of earth on its axis
24h – solar day
Movement of earth around sun
365 days – year
Tilting of earth on its axis
seasons
Movement of moon around earth
24.53 days – lunar month
24.8h – lunar day

10.

Types of biological rhythms with a geophysical counterpart:
Period
Length
Name
Chronobiological Name
Example
12.4 h
tidal
CIRCA TIDAL
crab activity on shoreline
29 days
monthly
CIRCA LUNAR
menstrual cycle, marine reproduction.
365 days yearly
CIRCANNUAL
Hibernation, many reproductive cycles.
24 h
CIRCADIAN
(circa + diem)
sleep-wake cycle and many others
daily
infradian

11.

What is the purpose of having
biological timekeeping system?
a
• Promotes organism’s
ability to
survive by coordinating its activities
with changes in the environment
• Coordinates internal processes

12.

Du Monceau 1759
• Circadian rhythms do not depend on
temperature changes
Linneaeus 1751
• Circadian rhythms are genetically
determined

13.

Circadian rhythms are endogenous.
Endogenous rhythms are not exactly
24h.
The periods of Circadian rhythms are
genetically determined.
Endogenous rhythms are temperaturecompensated

14.

Stage
•1: Like deep relaxation
• Lowered heart rate, muscle tension
and
temperature.
• Easy to awaken.
•Stage
Theta waves (4 to 7 Hz)
•2: Has slower and larger desynchronised EEG
(electroencephalograph) waves, with some
quick bursts of high frequency waves
(spindles).
• Theta waves dominant but periodic
bursts of sleep spindles (12-16 Hz)
Stage
•3: Has even larger, slower waves.
• Heart rate and temperature falls.
• Delta waves (1-4 Hz) appear and
number of spindles fall.
Stage
•4: Has largest, slowest, deepest delta wave
Metabolic activity is low.
• Hard to wake as at this stage sleep is
deepest.
REM
(rapid eye movement) or Paradoxical
•sleep:
Most active part.
• Muscles lose tension but still twitch.
• Most vivid dreaming and rapid eye
movement.
• After progression from stage 4, (roughly
75 minutes) starts cycle again, but from
stage 2.
• May be increased heart rate and blood
pressure (resulting in erections and an
increase in vaginal flow) but difficult to
awaken.
• Full cycle is around 90 minutes.
Waking/Sleeping
•EEG’S:
Desynchronised: No regular pattern of electrical
activity.
Typically found during active, aroused state awake.
Synchronised: Regular pattern of electrical activity,
signifying millions of neurons firing together. Usually
recorded during sleep. Consist of wave patterns of
particular amplitude and frequency (Hz). Examples:
deep sleep = one large wave per second.
Differing
•waves:
Theta waves: smaller
waves.
•External
Delta waves: Larger
waves .lightens towards morning with production of
•Cues:
Sleep
serotonin in accordance with light levels, spending more
time in NREM stages 2 and REM (easier to awaken)
Focu
•s: There is more focus in studies on the nature and
functions of REM sleep rather than symbolism of
dreams as REM is a physiological state and dreams
have subjective meaning and can have different
interpretations.
Existence of dreams is only known through own
experiences
and reports of participants.
•Key There
is no objective method of measuring dreams
Studies:
unlike and
EEG’s
for sleep
waves.
Aserinsky
Kleitman
(1953)
and Derment and Kleitman
(1957) Jouvet (1967)
SAD (Seasonal affective disorder):
Type of depression. Reduced amount of
sunlight in autumn causes lack of brain
activity. Infradian Treatment is Light
Treatment. Main hormone: melatonin.
Key
•words:
Raphe nucleus: in RAS, initiates NREM (Jouvet (1967)).
• Locus Coeruleus: produces noradrenaline which leads to
REM sleep. Inactive during REM sleep and awake.
Involved in the special arousal that helps with memories,
explaining why we do not remember dreaming.
• Ascending Reticular Formation: Network of neurons.
Controls
brain arousal state.

15.

Shift Work:
• Started in 19th century with the
invention of light bulbs – allowing
unnatural distribution of external
zeitgebers.
Concerns:
• Performance affected.
• Depression.
• Fatigue.
• Illness.
Explanation:
• Between 2-4am, body tried to sleep.
• Also results in sleep deprivation
(prolonged exposure to little sleep) as
try to stay up to have social life.
Key Studies:
• Czeiser, Moore-Ede and Coleman
• Gordon et al
• Sack et al.
Rotation types:
• Forward shift rotation: Shift hours
go forward (Nights, mornings,
days)
• Backward shift rotation: traditional
shift work. Harder on participants.
Shift lengths:
• Multiple studies have found that
longer shift patterns (of around 21
days compared to traditional 7 days)
and better on the worker, socially
and biologically.
Jet Lag:
Rapid disruption of sleep rhythms.
Most frequently encountered.
Dislocation between body clock and local
zeitgebers, resulting in extreme tiredness,
depression, slow mental/physical reactions.
Phases:
Phase delay: east to west.
Wants to sleep in early evening and wake in early
hours.
Correctable by attempting to be alert/active when you
need to sleep.
Phase advance: west to east.
time is later than internal clock so have to
advance o catch up.
More difficult to correct.
Leads to tiredness, confusion and
desynchronisation of other rhythms (shown in
Siffre’s study).
Key Studies:
Recht, Lew and Schwartz.
Beaumont et al
•Sack et al
Reduce
effects:
• Sleep well before flight.
• Avoid caffeine.
• Try to adjust – sleep at correct times.
• Go out in daylight ASAP.
Factors effecting severity:
• Direction of travel (phase delay/phase advance)
• Number of time zones crossed.

16.

17.

Restoration Theory:
• Focuses on purpose of sleep
restoring body and mind from
days events.
Main Theories:
• Oswald (1966): NREM (stage 1-4)
are
all needed to repair the body.
• REM is essential to repair the brain.
• Horne: ‘Core Sleep’ is stage 4
and REM sleep. Its function is
to repair the brain.
• ‘Optional Sleep’ is stages 1-3 and
is
not needed.
• Restoration of the body
happens when we are awake
and relaxed.
Evidence for restoration theory:
• Total sleep deprivation studies:
Everson (rats), Michel Corke
(fatal familial insomnia), Peter
Trip (awake for 8 days)
• Partial sleep deprivation
studies: Jouvet (cats and
human study) and Dement
(human REM deprivation)
Evolutionary theory:
• Sleep is a period of vulnerability for
all animals affected by multiple
factors so must be very necessary
for us to sleep anyway.
• Size/environment/trophic position.
Main
•Theories:
Meddis: sleep keeps animals safe. By
being quite and still, they are less
likely to attract predators (especially in
low visibility at night.)
• However, they are more vulnerable if
they are sleeping while they are
discovered.
• Webb: sleep is similar to hibernation.
• Using energy would be inefficient at
night as retrieving food is harder.
• Sleep conserves energy when
resources are
hard.
Evidence for Webb’s evolutionary theory:
• Lesku et al: Animal species.
• Allison and Cicchetti: predator/prey.
• Savage and West: brain meta analysis.

18.

Newborns:
Sleep on average 16-18 hours a day.
In early months, an infant sleep is
divided equally between REM and
NREM (different for premature
babies).
EEG of sleeping infant in REM
sleep is highly similar to
waking EEG.
In REM, infants are restless, with
arms and legs moving almost
constantly (also happens before
birth).
Different sleep stages: entering REM
sleep immediately after falling to
sleep. Not until around 3 months
that NREM and REM are
established.
Regular sleeping pattern is
normally established around
20 weeks.
1-5:
Usually sleep about 13-14 hours.
Sleep stages occur ever 45-60
minutes.
5-10:
Sleep stages increase to
around 70 minutes.
(Borbely).
Between 5 and 12, nocturnal sleep
drops to around 9-10 hours.
10-12:
Experience ‘sleep-wake utopia’,
Teenagers:
Marks onset of adolescence and sexual and
pituitary growth hormones are released in
pulses during slow- wave sleep.
Melatonin is the hormone that determines the
biological clock in every cell in the body, but a
decrease in melatonin signals the body to begin
puberty.
Sleep quality and quantity do not change, but
various external pressure (school and shit)
may lead to some having a less regular sleep
cycle.
18-30:
Start sleeping/having deep sleep less
but isn’t significant enough to be
noticed.
Also experience daytime sleepiness (Dement)
30-45:
People start to notice swallowing and
shortening of sleep (sign of middleage).
Women suffer loss of hormones due to
menopause and men, less noticeably, through
andropause.
Causes earlier sleeping times, worsening
effects of sleep deprivation and poor
quality of sleep.
Duration falls to 7 hours and stage 4 all but
disappears.
Age related effects on the prostrate mean
sleep is disturbed.
Studies:
• Van Cauter.
• Floyd et al.
• Eaton-Evans and
Dugdale.
• Dement.
• Baird.
• Borbely et al.

19.

Dyssomnias:
• Problems with
amount/quality/time of sleep.
Key Studies:
• Often produces daytime
• Broughton et al.
tiredness.
• McMahon et al.
• Including insomnia and
• Scammell et al.
narcolepsy.
Parasomnias:
• Arii et al.
• Behavioural/psychological
events during sleep.
• Rarely associated with
daytime tiredness.
• Include sleep walking and
nightmares.
Insomnia
•: Secondary insomnia: single, underlying
medical, psychiatric or environmental cause,
meaning insomnia is a symptom for another,
main disorder (depression/heart disease).
• Common for those who do shift work or have
circadian rhythm disorders – result of
environmental factors such as caffeine.
• Diagnosis: sleep onset latency of 30 minutes.
Sleep efficiency of less than 85%. Increased
number of night time awakening. Symptoms
reoccur more than 3 times a week.
• Duration: transient insomnia (less than one
week and often associated with something in
particular. Short term – 1-4 week.)
Chronic/clinical insomnia (more than one
month. Has significant and distressing effect
on daytime functioning due to tiredness ad
irritability.)
Narcoleps
•y: Mitler – ‘sleepiness one feels when trying to complete a
boring
task at 3 a.m. after 72 hours of total sleep deprivation.’
• Extreme tiredness in the day, many also have cataplexy
(brief and sudden loss of muscle tone with no loss of
consciousness
– range of severity, from mild weakness to collapses),
disturbed sleep, sleep attacks, hypnogogic (sleep onset)
and hypnopompic (sleep offset) hallucinations (vivid
dream like experiences lasting seconds to 20 minutes
but easily aroused by touch or noise) and sleep
paralysis. These can occur immediately or after.
• Uncommon – affects between 0.03% and 0.18%
of the population (Nishino et al)
• Occurs in late teens, early twenties in most but 25%
only get symptoms at around 40 (Honda et al)
• Main symptom – sleep attack. Occur at times of
physical inactivity/boredom and preceded with
drowsiness. But can occur at any time with no
warning.
• They are easily awoken, feel refreshed, with another
attack unlikely for several hours.
• Most common trigger is sudden emotion – surprise,
laughter or anger.
Hypocretin is believed to be a main
factor.

20.

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