Peripheral Clocks

Question 1

Besides the SCN, where are circadian clocks found in the body?

Answer 1

Basically all organs express clock genes

Question 2

What did scientists observe when measuring melatonin in hamster retinae?

Answer 2

Rhythmic melatonin secretion even in DD

only explanation is that there is some timing mechanism in these cells

Question 3

Are fibroblasts rhythmic in culture?

Answer 3

Yes, but need stimulation (eg serum shock) to be synchronized

Question 4

How are peripheral cells different from SCN neuronal cells?

Answer 4

They cannot form a tight network and synchronize on their own

Question 5

True/False? The SCN recovers from jetlag almost immediately, sending signals to peripheral tissues to sync everything up

Answer 5

False: The SCN recovers from jetlag almost immediately, but peripheral tissues take much longer

Question 6

How can the SCN communicate to peripheral clocks? (4)

Answer 6

Humoral signals
Autonomic Nervous system
Fasting-Feeding cycle
Body Temperature

Question 7

Is parabiosis of a wt mouse with a SCN lesioned mouse enough to restore rhythm in peripheral tissues?

Answer 7

Not in all of them

eg rescues liver but not Heart rhythm

Question 8

Why do glucocorticoids reset eg the liver clock but not the SCN clock?

Answer 8

The SCN doesn’t have glucocorticoid receptors

Question 9

How does feeding affect peripheral clocks? Central clocks?

Answer 9

Per1/2 spike during feeding in periphery

SCN expression is independent of feeding

Question 10

How does temperature rhythm affect clocks?

Answer 10

Can retrain peripheral clocks but not the SCN