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15 Cards in this Set
- Front
- Back
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What is a zeitgester? |
A stimulus which resets the biological clock. |
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What is the ticking of the biological clock dependent on? |
1. Activity 2. Temperature 3. Waking and sleeping 4. Secretion of hormones 5. Eating and drinking |
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What is the endogenous clock of the human body? |
The suprachiasmatic nucleus (SCN) |
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What are the components of the circadian system? |
1. Input - light from photoreceptors 2. Entertainment pathways |
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What are the entertainment pathways linked to? |
1. Specialised ganglion cells 2. Retinohypothalamic tract |
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What molecule is within specialised circadian rhythm cells in the eye? What does it respond to? |
1. Melanopsin 2. Sensitive to blue light |
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What is the suprachiasmatic nucleus? |
A small group of cells located in the hypothalamus which lies just above the optic chiasm. |
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What are the clock genes in the drosophila melanogaster circadian rhythm model? |
1. Per - makes period protein 2. tim - makes timeless protein 3. Vrille 4. Clock genes i) Clk (clock) ii) Cyc (cycle) |
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Describe the process of the drosophila clock gene model. |
Activation of the period and timeless protein RNAs require transcriptional activation by the Clk-Cyc promoter heterodimer. The period and timeless proteins form a heterodimer which unbinds the Clk-Cyc promoter but the heterodimers only enter the cell to do this once they have reached a certain concentration threshold. At night, the period and timeless genes are activated and the heterodimers slowly build up over night. In the middle of the night they enter the cell and unbind the Clk-Cyk promoter and subsequently degrade allowing rebinding of the Clk-Cyk promoter. This restarts the cycle anew in the morning. |
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How can the drosophila clock gene model be artificially reset? |
Clock can be artificially set using blue light which is absorbed by a protein called cryptochrome - activating it. This then allosterically binds timeless proteins causing it to unbind from the heterodimer. Thus not inhibiting the Cycle/Clock promoter and resetting the clock. |
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What are the causes of circadian rhythm disorders? |
1. Mismatch between external and internal time 2. Dysfunctional photic input to the SCN clock 3. Result of circadian dysentrainment |
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What is familial advanced sleep phase syndrome? |
A disorder which causes early waking caused by mutation in the PER2 gene (the mammalian period gene). |
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What is the consequence of a mutated PER2 gene in FASPS? |
Causes excessive build up more rapidly than usual - earlier feedback inhibition |
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What is delayed sleep phase syndrome? |
Disorder among young adults - which causes a shifted sleeping phase - genetic cause ?? - PER3 |
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What does jet lag / night shift work do to the body clock? |
Desynchronisation of the internal body clock - melatonin resets circadian rhythm |
