Animal Physiology ( Biological Clock)

The way your body system works, in response to time zone.

1. ANIMAL PHYSIOLOGY SEMINAR PRESENTATION BY U.ID

2. ON: “THE BIOLOGICAL CLOCK”

3. POINTS COVERED …. # BASIC CONCEPT OF BIOLOGICAL CLOCK * CIRCADIAN RHYTHMS = LUNAR & TIDAL RHYTHM = CIRCA ANNUAL RHYTHM # PHOTOPERIODISM

4. BIOLOGICAL CLOCK….(a life clock ) DEF: an innate timing mechanism in living organism that controls the periodicity of various functions or activities, such as metabolic changes, sleep cycles, or photosynthesis etc,is termed as BIOLOGICAL CLOCK. = The study related to biological clock and its regulation is compiled in a branch of science called as CHRONOBIOLOGY.. which simply means chrono -time & biology-study of life.

5. What is the master clock? A master clock in the brain coordinates all the biological clocks in a living body , keeping the clocks in sync. In vertebrate animals, including humans, the master clock is a group of about 20,000 nerve cells (neurons) that form a structure called the suprachiasmatic nucleus, or SCN. The SCN is located in a part of the brain called the hypothalamus and receives direct input from the eyes.

6. Physiology of biological clocks #In mammals, cells for biological clock are located in the hypothalamus, in two clusters of nerve cells called the suprachiasmatic nuclei (SCN). #Light receptors in the retina are connected by nerves to the SCN. #SCN & mammalian pineal gland are linked. #Thus, light is detected by eye, which passes this information on to the SCN, which in turn passes the information on to the pineal gland, controlling melatonin production. * (, a hormone that is produced by the pineal gland in animals and regulates sleep and wakefulness which is produced in high levels at night and low levels during the day)

7. #As SCN generates a rhythm that lasts longer than 24 hours, it needs to be reset each day. - Reset or adjusted by a number of factors called phase setters or synchronizers or daily clues light, darkness, temperature ,sound ,feeding time,etc . EX : a nocturnal animal uses darkness for resetting its biological clock and a diurnal animal uses light for resetting its biological clock …

8. #It is an automatic clock which is capable of producing biological rhythms in both plants and animals… …….. rhythms ???......

9. BIOLOGICAL RHYTHMS-( periodic physiological fluctuation) a sequence of bodily activities that repeat themselves through time in the same order & at the same interval. -These activities are cyclic in nature and are repeating at regular intervals. -Such as sleeping & awakening ,menstrual cycle, breeding behaviour ,migration in birds are some good examples of biological rhythms..

10. FORMS:… ENDOGENOUS (biological clock control EXOGENOUS (direct control) Endogenous Biological Rhythms are naturally occurring cycles within our bodies. They are 'built in' and naturally occurs within our body. Endogenous biological rhythms are regulated by the organism and are not dependent on external stimuli. Examples: are circadian rhythms, body temperature regulation, menstrual cycle, etc  Exogenous biological rhythms are driven directly by the environment or another external influence. Another term for this type of biological rhythm is a direct effect. An example of an exogenous biological rhythm is the hopping of sparrows on a perch when a light is turned on. Such rhythms are said to have a geophysical counterpart; in this case, the presence of light.

11. TYPES OF BIOLOGICAL RHYTHM… CIRCADIAN RHYTHM CIRCANNUAL RHYTHM LUNAR & TIDAL RHYTHM

12. CIRCADIAN RHYTHM…. These are the daily biological rhythm which occurs on a 24hr cycle ,and co-relates to the dark (night)- light (day)cycle . The common physiologies under circadian rhythm are… *the sleeping & awakening in humans *flowering in lily and jasmine *laying of eggs in hen..etc

13. Physically, the circadian clock is located in the  suprachiasmatic nucleus (SCN) in the hypothalamus of the brain. { The SCN is a tiny pinhead-sized area, containing just 20,000 or so very small neurons , but it has the responsibility for sending signals to several other parts of the brain to regulate the daily sleep-wake cycle, body temperature, hormone production and other functions The sleeping & awakening in humans

14. PHYSIOLOGY : Exposure to natural daylight -stimulates a nerve pathway from special photoreceptive ganglion cells in the retina of the eye. - These cells contain a unique light-sensitive pigment called  melanopsin , and are most sensitive to short wavelength “blue light”. - The light-dark signals are sent via the optic nerve to the  suprachiasmatic nucleus, which uses them to reset its own circadian clock each day.

15. LUNAR & TIDAL RHYTHM The cyclical activities exhibited by organisms in relation to the 29day lunar month are called as lunar rhythms…   -Most obvious environmental variables affected by the moon(lunar) are light and tide, and of these the tide appears to have the greatest impact. For this reason lunar rhythms seem to occur mostly in marine species. -During full moon and new moon days= tides are greatest are called spring tides , caused by the cooperative gravitational attractions of sun and the moon. -At the moons’s quarters ,the sun and moon oppose each other resulting in smallest tides called ebb tides . -The spring and ebb tides occurs at an interval of 14.5days.Hence this rhythm has a duration of 29dys.

16. Certain animals’s activities are adapted to lunar cycles and they exhibits lunar rhythms . The best studied lunar.R are the monthly reproductive rhythms of # palolo worms #fire worms #sea lily #may fly swarming The breeding rhythms of these animals are in relation to the phases of moon. Example : classical ex palolo worm( leodice ), -a tube dweller in coral reefs,its west indian species leodice fucata - spawns only during 3 rd quarter of june-july moon. -The anterior part remains in its burrow beneath sea ,but the posterior ends distended with ripe gamets ,break off and wriggle to surface in such wast number that water is milky for an hr or two with the eggs and sperms. ,this swarming occurs at dawn.

17. The  palolo worm,- exhibits a mixed rhythm, mixed between annual and lunar.

18. CIRCANNUAL RHYTHM (circa- approximately   , annual-yearly) The biological activities exhibited by organisms repeated year by year is termed as circannul rhythm. There are certain physiological events occuring in many organisms with an interval of 1yr or 365.   Example , migratory birds. Every year they fly, without fail. Experiments have been carried out in which the birds have been kept in a controlled environment, without the chance of a disease or any situation that might cause them to migrate. But still, the birds showed migratory behavior at the same time as they did every year.  *Then there is the breeding cycles of different organisms. They repeat the same cycle every year, at the same time. *Another example could be the the hibernation cycle. It is repeated even if the conditions do not require hibernation.

19. Types of biological rhythm disorders? Disorders may develop when natural biological rhythms are disturbed. These disorders include: sleep disorders : The body is “wired” to sleep at night. Disruptions in the body’s natural rhythms can lead to affected sleep, including insomnia. jet lag : A disruption in circadian rhythms when traveling across time zones or overnight. shift work disorders : When a person works outside the typical work day it causes changes in typical circadian rhythms . - excessive sleepiness affecting people whose  work hours overlap with the typical sleep period .

20. Photoperiodism (photos-light ,periods-length of time)   It is the functional or behavioral  response  of an organism to changes of duration in daily, seasonal, or yearly cycles of light and darkness. ……….It occurs in both plants and animals as well…… The response of plants to the photoperiod(period of time each day during which an organism receives illumination) expressed in the form of flowering is called as photoperiodism …. When stimulated by light, an  animal’s pituitary gland will release hormones that affect reproduction. Thus, mating season of a species can be made to occur at an unusual time by manipulating daylight. ------Long periods of light followed by short periods = induce mating behaviour in species that normally breed in autumn ( e.g.,  goats and sheep), while spring breeders ( e.g.,  mink) will start the reproductive process when daylight is increased.

21. Application of photoperiodism is common in the poultry industry, as daylight affects egg-laying, mating . *Reproduction in many species occurs at specific times of the year. Plants produce pollen at the times of year when pollinators will be active, *while animals often reproduce in the spring and summer to take advantage of the warmer temperatures. *Often reproduction is triggered by a critical photoperiod. In many male animals, testis size is affected by photoperiod. In both hamsters and some birds for example the testes are small in short days (i.e. in winter) but grow dramatically in long days.

22. THANK YOU