BIO: Exogenous Zeitgebers

Question 1

Exogenous Zeitgebers

Answer 1

external stimuli for biological rhythms

Question 2

role of light:

Answer 2

• rods and cones are chemicals called opsins to detect light
• we have a third photoreceptor cell, called intrinsically photoreceptive retinal ganglion cells (ipRGCs).

Question 3

ipRGCs:

Answer 3

these contain melatonin- a non-visual opsin used to detect intensity/wavelength of light
- the level of light detected by the ganglion cell’s melanopsin reaches the SCN through the optic nerve
- the neurons of the SCN are synchronised using this info

Question 4

setting rhythms through other factors:

Answer 4

other than light (the most powerful exogenous zeitgeber), we also use environmental stimuli to set our rhythms

Question 5

environmental stimuli (set rhythms) examples:

Answer 5

• meal times
• TV programmes
• radio programmes
• behavioural routines (e.g. reading before bed)
• regular working patterns
• clubs and hobbies