AP PSYCHOLOGY

Detailed explanation-1: -The suprachiasmatic nuclei (SCN) of the hypothalamus contain a pacemaker that generates circadian rhythms in many functions. Light is the most important stimulus that synchronizes the circadian pacemaker to the environmental cycle.

Detailed explanation-2: -Many SCN neurons are sensitive to light stimulation via the retina, and sustainedly firing action potentials during a light pulse ( 30 seconds) in rodents. The photic response is likely linked to effects of light on circadian rhythms.

Detailed explanation-3: -Inputs to the SCN The SCN receives two types of input: photic and non-photic. The photic input comes from intrinsically photosensitive retinal ganglion cells (ipRGCs), which project through the retino-thalamic tract via glutamatergic synapses to neurons in the SCN. This helps to synchronise the circadian clock.

Detailed explanation-4: -Our circadian pacemaker, the suprachiasmatic nuclei (SCN) in the hypothalamus, is entrained to the 24-hour solar day via a pathway from the retina and synchronises our internal biological rhythms.

Detailed explanation-5: -The SNC contains receptors that are sensitive to light and this external cue is used to synchronise the body’s internal organs and glands. Melanopsin, which is a protein in the eye, is sensitive to light and carries the signals to the SCN to set the 24-hour daily body cycle.