Biological Clocks Flashcards
What are the 5 types of biological clocks?
Circadian, circatidal, circalunar,circaannual and semicircalunar
What is the circadian clock?
Daily - every 24 hours
What is the circatidal clock?
12.4 cycle, involves flow of tides
What is the circa lunar
Occurs every 28-29 day cycles
Affects arise and terrestrial organisms and involves the lunar phase
What is the circa-annual phase?
Yearly rhythms - drove by geogphysical cycles
What is semi-circulunarphase?
15 day cycle which corresponds to a full moon affecting amplitude tide
What is a biological clock in a human?
It is a block of sells called the supraschismatuc nucleus
What is a biological clock in the drosophilia fly?
It is a group of cells in the lamina of the eye which create the basis of the clock
What animals have biological clocks and why are they important?
They are found in organisms - and must be evolutionary important
What do biological clocks allow organisms to do?
They anticipate regular changes in the environment such as night and day
They prepare for activity changes in metabolism
It coordinates internal events such as hormone release
Does the biological clock compensate temperature?
They dont regulate body temperature, if temperature gets too high or low it will cause the clock to go outside of time
Does the biological clock entrain itself to external stimuli?
It has to synchronise to external stimuli
If your ravel to and from different time differences the external clock cycle trains the body clock
This is known as retrainment of the body clock to its original time
How do clocks work?
There are 3 input pathways known as:
Envrionemental change
Light
Temperature
These feed into clock cells (nuerons). The clock cells have cyclic intracellular mechanisms which have output pathways to drive rhythmic phenotypes which are:
Behaviour
Physiolocailly
Biochemistry
How do you monitor behaviour in uridessy
Put them in 5ml tubes with 2 ml water and sand in the tube
Uridissey burrows into the sand when tides go out and when it comes in they swim in the top parts of the water before burrowing down
An infrared beam is passed across the tube and it records each time the urididessy passes the beam
What are the results from changing the day and night cycles to rats that run on wheels?
First 8 days: animal was under 12 hour light basis and there is tight rhythmicity between the wheel running times
16 days: the lights get switched off - they are still rhyming but the rats clock runs less than 24 hours
Why does the rats clock run less than 24 hours after 16 days?
This is due to the activity occurring earlier each day to when the biological clock would usually start
It also tells us its a nocturnal animal as its internal clock mechanism is not the same as a 24 circadian clock
How do record clock cell activity in the rat brain?
Attatches a luminescent reporter to a gene involved in circadian mechanism
Each time the cell/gene is active it produces light
Each time PER protein is made it illuminates
Why would you record clock cell activity in the brain?
You can see when the cells are active
What do monarch use as a compass?
Monarch butterflies use the sun as a compass
They do this by compensating their flight direction according to the position of the sun
How many chryptomes are present in a monarch butterfly clock cell?
2.
What to the chryptochromes do in the monarch clock cells?
There are 2 of these known as chrptochrome 1 and 2
They form part of the negative regulatory part of the clock cell - mostly chyptochrome 2 though
What is the antennae used for in monarch clocks?
Antennae are required for time compensated sun compass orientation
What happens if you chop off the monarchs antennae
The butterfly will lose orientation and compensation occurs
How does the monarch’s antennae work?
The antennae contain clocks independent from the central brain
The chopped of antennae showed that the clock genes have rhythmic and self sustaining gene expression
Is the monarch’s antennae is controlled by the brain?
No, because when you chop it off the clock still works meaning that the antennae is independent to the brain
How does the monarch’s time compensated compass work?
Main retina senses sunlight and the dorsal rim of the eye detects polarised light
The inputs are integragated and processed in the central complex of the brain
Blue light entrains the clock in the brain and antennae via chryptochrome 1.
Clock provide temporal information that is integrated by neural circuits.
What do sand hoppers use to navigate?
The sun and moon
How do they use their clocks?
They use their clocks to compensate the movement of the celestial markers- sun and moon
What do lunar-ticks do when they get disturbed
They hop backwards from where they have been disturbed
Are antennae required in solar orientation talitrus?
Yes, the talitrus is deficient or has no antennae they will lose their lunar orientation.
How does the brain and antennae work in the talitrus
The antennae are independed in a certain time of the clock phase due to a different rhythmic expression
