Biological rhythms are internal cycles that regulate biological processes over time scales ranging from hours to years. The pineal gland produces melatonin, which regulates circadian rhythms that follow a 24-hour cycle, such as the sleep-wake cycle. Other cycles include ultradian rhythms that occur over minutes to hours, like attention span fluctuations, and infradian rhythms that occur over weeks, months, or years, like the menstrual cycle or seasonal affective disorder. Disruptions to circadian rhythms can cause sleep disorders like delayed sleep phase or jet lag. Shift work disorder involves difficulty adjusting sleep schedules to night shifts.

1. Biological Rhythms
Mital Chandegara
MSc BT(IV)
Roll No. 10

2. Outline
• Introduction
• Pineal gland
• Melatonin
• Classification:
a) Ultradian rhythm
b) Circadian rhythm
c) Infradian rhythm
• Circadian rhythm sleep disorder
• References

3. • Biological rhythms are internal rhythms of biological activity.
• Biological rhythms are biological processes that show cyclic variation
over time , ranging from hours to years and reflect the influence of
earths rotation upon us ..it’s living inhabitants, along with plants and
animals.
• Study of biological rhythms is known as chronobiology
Introduction

4. Pineal gland
Pine cone

5. Melatonin
• Melatonin was first isolated from the bovine pineal gland in
1958.
• In humans, it is the main hormone synthesized and secreted
by the pineal gland.
• Melatonin displays high lipid and water solubility, which
allows it to diffuse easily through most cell membranes,
including the blood-brain barrier.
• Its half-life is about 30 minutes, and it is cleared mostly
through the liver and subsequently excreted in the urine as
urinary 6-sulfatoxymelatonin.

6. Classification
B.R. Ultradian
Circadian
Infradian

7. Ultradian rhythm
• Ultra = beyond , Dian = day (Latin). A ultradian rhythm is a biological
process that repeats more frequently than once every 24 hours.
(duration: minutes/hours)
• The BRAC or Basic-Rest-Activity-Cycle of approximately 90-120
minutes. It’s probably something we are all unconsciously familiar
with e.g. in case of attention span in students or the duration of a
workout.

8. • When we need to rest, our
bodies signal to us with
either sleepiness, lack of
focus, etc.
• When you need to take a
break is to pay attention to
your body’s signals, and then
to take a break whenever you
need — using the 90/20
principle

11. Circadian rhythm
• Circa = around , Dian = day(Latin). A circadian rhythm is a biological
process that repeats approximately once every 24 hours.
• External signals, such as light, trigger the cyclical release of chemicals
that signal when to start and stop different actions.
• In humans, circadian rhythms are best known for governing our sleep
schedules.

13. • This process starts in the eye’s retina. When the retina is exposed to
light, a signal is relayed from the retina to an area of the brain, called the
suprachiasmatic nucleus, which plays a role in making us feel sleepy or
wide awake.
• The suprachiasmatic nucleus sends signals to other parts of the brain
that control hormones and body temperature. Then, signals travel from
the brain down the spinal cord and back up to the pineal gland where
melatonin production takes place.
• During the day, such signals prevent the pineal gland from producing
melatonin. But when it is dark outside, these signals are not activated,
and the pineal gland is able to produce melatonin.

14. • Exposure to light prevents melatonin release, which keeps us awake,
and lack of exposure to light causes melatonin release, which tells us
to “go to sleep!”

16. Infradian rhythm
• Infra = below , Dian = day (Latin). A Infradian rhythm is a biological
process that last longer than 24 hours and can be weekly, monthly or
annually.
• A monthly infradian rhythm is the female menstrual cycle which is
regulated by hormones that either promote ovulation or stimulate
the uterus for fertilization.
• Usual menstrual cycle is around 28 days, there is considerable
variation, with some women experiencing a short cycle of 23 days and
others experiencing longer cycles of up to 36 days.

18. • A second example of an infradian rhythm is related to the seasons.
• Research has found seasonal variation in mood, where some people
become depressed in the winter, which is known as Seasonal affective
disorder (SAD). SAD is an infradian rhythm that is governed by a yearly
cycle.
• Psychologists claim that melatonin, which is secreted by the pineal
gland during the night, is partly responsible. The lack of light during the
winter months results in a longer period of melatonin secretion, which
has been linked to the depressive symptoms.

21. Circadian rhythm sleep disorders
Delayed-sleep phase: Patients generally fall asleep in the early morning
hours; then often, especially when circumstances permit (eg, on the
weekend), they do not wake until the late morning to early afternoon.
• This is most commonly seen in adolescents and young adults. Some cannot
function during the week because they go to bed at or after midnight but
must rise at 6 AM or 6:30 AM for school. On the weekend, they often sleep
until noon or later.
Advanced-sleep phase: Patients, often older adults, typically fall asleep in
the early evening and wake earlier than desired in the morning. This occurs
because a person who goes to sleep by 8 PM, for example, will have had 8
hours’sleep by 4 AM

22. Jet lag type: Also called desynchronosis, patients temporarily have
some symptoms as a result of air travel across time zones.
• External environmental time is mismatched with the internal
circadian clock
 Symptoms: Disturbed sleep patterns
Headaches
Exhaustion
Diarrhoea or constipation

25. Shift work sleep disorder: Shift work sleep disorder (SWSD) is a sleeping
condition that is considered a circadian rhythm disorder.
• SWSD occurs when a person has trouble adjusting to the work hours
during the time period that most people sleep—such as working during a
night shift.
• This results in a conflict in the normal waking/sleeping hours.
• For example, a person with SWSD may sleep for only a few hours,
resulting in disruption of the quality as well as the length of sleep hours.

26.  Symptoms: trouble concentrating
• depression
• lack of energy
• headaches
• excessive sleepiness during waking hours (and in general)
• inability to fall asleep or stay asleep
 Shift Work Sleep Disorder Risks: mistakes at work
• frequent infections, flu, and colds
• high cholesterol levels
• breast and prostate cancer
• heart disease
• obesity

27. Treatment
1. Lifestyle Changes:creating a dark environment for sleeping
• taking naps when needed
• limiting caffeine intake
• eating a healthy diet with foods high in antioxidants (to help boost the
immune system)
2. Sleep medications can also cause serious side effects (such as
parasomnias, involve actions during sleep in which a person has no
control, such as sleepwalking).
3. Supplements. Natural supplements such as melatonin ,it can be taken
long-term & it has no side effects

28. References:
o The science of sleep (American chemical society)
o Pineal gland (biologydictionary.net)
o Consciousness and Biological Rhythms (lumenlearning.com)
o Menstruation (britannica.com)
o Circadian rhythm (nigms.nih.gov)
o The Stages of Sleep: Ultradian rhythm - Biological Psychology
(psychboost)
o The Menstrual Cycle: Infradian rhythm - Biological Psychology
(psychboost)