Chapter 9: BIOLOGICAL CLOCKS Flashcards
What is the circadian rhythm?
Daily rhythmical change in behaviour or physiological processes
What is a Zeitgeber?
- German for “time giver”
- Stimulus (usually the light of dawn) that resets biological clocks that is responsible for circadian rhythms.
How long is a circadian rhythm cycle?
approximately 24h
What keeps the clock adjusted to 24h?
Regular daily variation in the level of illumination (sunlight and darkness)
What does the suprachiasmatic nucleus (SCN) do?
Contains biological clock that is responsible for organizing many of the body’s circadian rhythms.
What is melanopsin?
Photopigment in retinal ganglion cells.
Where do the axons of melanopsin transmit information to?
SCN, thalamus, olivary pretectal nuclei
According to evidence, what are the two means by which SCN controls cycles of sleep and waking?
- Direct neural connections
- Secretion of chemicals that affect the activity of neurons in other regions of the brain
Retinohypothalamic pathway diagram
See slide 70
What makes SCN neurons tick? see diagram slide 71
- Protein enters nucleus, suppressing the gene responsible for its production, no more messenger RNA is made
- The level of protein falls so the gene is active again
- The gene is active: messenger RNA leaves the nucleus and causes the production of the protein
What is the advanced sleep syndrome?
-4hours advance in rhythms of sleep and temperature cycles
What is advanced sleep phase syndrome caused by?
-mutation of a gene (per2) involved in rhtythmicity of neurons of SCN
What is delayed sleep phase syndrome?
- Same than advanced sleep phase syndrome but delayed instead
- Caused by the same thing
Control of Circadian rhythms diagram
See slide 73
What is the pineal gland?
-Gland attached to the dorsal tectum
