Introduction in chronobiology

13. Mandelbrot

27. NOBEL LAUREATES FOR MEDICINE 2017
Jeffrey C. Hall, Michael Rosbash şi Michael W. Youn
for their discoveries in controlling
molecular mechanisms of the circadian rhythm.
By using fruit flies as a model of an organism, laureates
The 2017 Nobel Prize in Medicine managed to isolate a gene
that can control the daily biological rhythm.
Specialists have proven that this gene holds a protein that can accumulate inside the cell
throughout the night and degrade throughout the day. Following the analyses, the three
researchers identified components of the protein through which the mechanism
underlying the rhythm inside the cell could be exposed. With great precision, the clock
inside the bodies can adapt according to the different phases of the day. This rhythm
regulates critical body functions such as behaviour, hormone levels, rest, body
temperature and metabolism. Currently, we can recognize the biological functions of the
circadian rhythm through the same principles in the cells of multicellular organisms,
including those of humans, say the laureates of the 2017 Nobel Prize for Medicine. When
this rhythm is disturbed, the well-being of the human being is affected. For example, we
can take into account when we travel from one time zone to another and feel extreme
fatigue or the phenomenon of "jet lag".

28. • Field of research:
• Cell biology
• Object of the research:
• Circadian rhythm
• Research level:
• Genetic mechanism
•
NOBEL LAUREATES FOR MEDICINE 2017

29. Bios (gr.) = life
Logos (gr.) = science
Biology is the science that deals with the study of life
and living organisms, including the structure, functions,
development and evolution of living organisms.
Biology – The Science of Life

30. CHRONOBIOLOGY

31. • Rhythm = sequence of events that are
repeated in the same order and with the
same period of time.
• Biological rhythm: an event or biological
function with a pattern of activity that is
repeated continuously over a constant time
interval.
•

33. • Heart rate
• Respiration
• Hormonal secretion
• Menstrual cycle
• Body temperature
• Sleep cycle / wakefulness
•
Time
BIOLOGICAL RHYTHMS

34. Definition
• Chronobiology (gr. chrono-time) is that
part of biology, which deals with the
observation and study of periodic
physiological phenomena and repeatable
behavioral patterns within living
organisms, which are continuously under
the influence of the action of external
factors: the succession of seasons, the
rotation of the Earth around its axis
(night / day).
• In the group of these cyclical phenomena
are also included biorhythms (lunar or
solar). Biochronology = the science of
biorhythms .
• Chronobiology is closely linked to other
branches of biology, such as
endocrinology, biochemistry, genetics,
ethology and human psychiatry.
•

35. Introduction to chronobiology
• The rotation of the Earth around its axis = 23h 56 min
• The movement of the Earth around the Sun = 365 days
• Tilting the Axis of the Earth
•

36. Introduction to chronobiology
The position of the Moon and Sun influences the waves on Earth:
alignment of the Sun with the Moon - the waves have longer
durations and small amplitude (flat)
The Sun and moon are perpandicular to Earth – the waves have
a shorter duration and a greater amplitude (higher)

37. Introduction to chronobiology
• As a consequence of the Earth's rotation around its
axis every 24 hours, most organisms on the planet are
exposed to fluctuations in temperature and light.
• At various levels, from cyanobacteria to humans,
species have developed specialized structures - the
so-called "endogenous biological clocks" for the
anticipation of these biophysical variations.
• The ability to anticipate environmental variations
allows optimizing the performance of organisms and
their survival.
•

38. Introduction to chronobiology

39. • Aristotle (322 BC) – makes the first reference to the fact
that the seasons have a cyclical appearance (repeat)
• Androsthene (325 BC) – notices that the leaves of the
plants descend during the night, but that with the
appearance of the Sun's rays, they rise, reaching the
maximum at 12 o'clock; when the Sun "goes to bed", they
descend again.
• Pythagoras (480 BC) – observes that all organisms,
including man, are influenced by the revolution of the
stars and as a result, their activity acquires rhythmicity
•
From observations to experiment...

40. • Descartes (1664) – states: "It is absolutely certain that the
birds return in the spring of each year, with the precision
of a clockwork"
• The first concept :
• The existence in the body of "something" that
determines the cyclicality of the return
• Ortus de Mairan (1729) – the raising / fall of leaves in
plants occurs in continuous darkness conditions
• Father of Chronobiology - The first experiment :
• The existence of the "endogenous rhythm generator"
in plants
•
From observations to experiment...

43. •1832 - by Candolle - Mimosa opens its leaves every
day two hours earlier
•
•1906 - Simpson and Gailbraith – temperature
patterns persist in monkeys and total darkness
•
•1922 - Richter – sustained rhythms of activity in
experimental animals (rats); the rhythm of
locomotor activity is generated endogenously
•
From observations to experiment...

44. • Aschoff si Wever (1962)
• - Rhythmicity is observed at all levels of the
organim
• In the same body the rhythms have different
durations
• In humans: electroencephalogram (EEG)
• electrocardiogram (EKG)
• 10 sec respiratory rhythm
• hours of hormonal secretion
• 24 hours sleep/wake cycle
• 28 day ovarian cycle
• The maximum amplitude of the cycles differs
depending on the time of day
• Each individual has its own system of
temporal perception
• It can be considered that the "biological
clock" arranges and synchronizes the rhythms
to the different variations in the body
Deepening research

45. • Richter (1967) – location of the biological
clock: anterior hypothalamus
• Stephan & Zuker /Moore & Eichler (1972)
suprachiasmatic nucleus (SCN) = “main
biological clock”
•
Deepening research

47. Recent studies

48. Now
• Genetic and molecular studies about the
periodicity of cellular, tissue events, at the
level of organ, system, organism
• Genetic programming in this regard
• In the future – necessary integrative studies
that allow interconnections and relationships
with various pathologies
•

49. ”Integrators”
• So called Zeitgeber („time synchronisator”)
which have the role of synchronizing the
internal clocks with the outside.
• The strongest of them is light.
• Other examples are temperature, social
interactions, the rhythm of meals
•

50. Environmental influences: the
light/dark cycle

53. PACEMAKER
Target tissues
Biological rhythms
(physiological rhythms)

54. ENDOGENOUS PACEMAKER
OWN RHYTHM
TARGET TISSUES
Biological rhythms
(physiological rhythms)
INTERMEDIATE ELEMENTS

55. • What is rhythmic in our body?
• All rhythms have the same frequency / period ?
• What are the rhythms you know?
• Is there a rhythm that matters to our lives?
• If YES, why?
• Is this importance valid in any environment?
• If YES, why?
• If NOT, in which environment is not valid?
• Could you notice a rhythm?
• Could you perceive a rhythm?
•
DISCUSSIONS

56. Thank you!