Changes

The pineal gland secretes [[Melatonin|melatonin]] in response to day length. The retina detects day length and sends an impulse via the [[Hypothalamus - Anatomy & Physiology|hypothalamus]], thoracic [[Spinal Cord - Anatomy & Physiology|spinal cord]] and cranial cervical ganglia to the pineal gland. The gland effectively acts as the body's '''biological clock''' and helps regulate the circadian rhythm, sleep and the seasonal and diurnal variations in [[:Category:Reproductive Behaviour|reproductive behaviour]]. In the horse,melatonin is inbitory on gonad function via its antigonadotrophic effects. Melatonin production is inhibited by light, therefore melatonin levels decrease in spring making horses 'long day breeders'.

The pineal gland secretes [[Melatonin|melatonin]] in response to day length. The retina detects day length and sends an impulse via the [[Hypothalamus - Anatomy & Physiology|hypothalamus]], thoracic [[Spinal Cord - Anatomy & Physiology|spinal cord]] and cranial cervical ganglia to the pineal gland. The gland effectively acts as the body's '''biological clock''' and helps regulate the circadian rhythm, sleep and the seasonal and diurnal variations in [[:Category:Reproductive Behaviour|reproductive behaviour]]. In the horse,melatonin is inbitory on gonad function via its antigonadotrophic effects. Melatonin production is inhibited by light, therefore melatonin levels decrease in spring making horses 'long day breeders'.