Non-image forming pathway
Module B, Basis of light and light perception
Circadian rhythms
- various metabolic processes cycle alternately through high and low activity phases
with a periodicity of app. 24 hrs.
- derived from the latin ‘circa diem’ = approximately a day
- oscillator = internal pacemaker - coupled to variety of physiological processes
Physiological and hormonal systems during a day:
Melatonin = causes you to sleep
- synthesized and secreted by the pineal gland
- secreted ONLY at night
- is NOT dependent on sleep
- is influenced by bright light
Serotonin = well being and happiness
Cortisol = adrenaline-like
SCN process
S → Sleep, a homeostatic “sleep propensity” that determines the recent amount
of sleep and wakefulness accumulated
, C → Circadian, and endogenous “clock” that drives the rhythm of the sleep-wake
cycle. Functions like a sinewave.
Zeitgebers: periodic stimuli acting on the internal clock of a human being.
Most important zeitgeber is light.
All photoreceptors and their wavelength peaks:
Max wavelengths:
Rods = 498
Cones:
- Blue = 420
- Green = 534
- Red = 564
Module B, Basis of light and light perception
Circadian rhythms
- various metabolic processes cycle alternately through high and low activity phases
with a periodicity of app. 24 hrs.
- derived from the latin ‘circa diem’ = approximately a day
- oscillator = internal pacemaker - coupled to variety of physiological processes
Physiological and hormonal systems during a day:
Melatonin = causes you to sleep
- synthesized and secreted by the pineal gland
- secreted ONLY at night
- is NOT dependent on sleep
- is influenced by bright light
Serotonin = well being and happiness
Cortisol = adrenaline-like
SCN process
S → Sleep, a homeostatic “sleep propensity” that determines the recent amount
of sleep and wakefulness accumulated
, C → Circadian, and endogenous “clock” that drives the rhythm of the sleep-wake
cycle. Functions like a sinewave.
Zeitgebers: periodic stimuli acting on the internal clock of a human being.
Most important zeitgeber is light.
All photoreceptors and their wavelength peaks:
Max wavelengths:
Rods = 498
Cones:
- Blue = 420
- Green = 534
- Red = 564
