T3: Seasonal Ovulatory

Question 1

What season is long photoperiods (long day breeders)

Answer 1

spring/summer

Question 2

What season has short photoperiods (short day breeders)

Answer 2

fall/ winter

Question 3

During short photoperiods the excitatory pathways are

Answer 3

less active

Question 4

what species are short day breeders

Answer 4

ewe

Question 5

what species are long day breeders

Answer 5

mare

Question 6

Describe the pathway for long day breeders

Answer 6

• long photoperiods/ more light is sensed by the retina of the eye
  -with more light being sensed, there is a retinal nerve firing an excitatory signal to the brain
  -the retinal nerves act on the suprachiasmatic nucleus (surge center of the hypothalamus)
  -this signal received from the nucleus is then acting on the superior cervical ganglion
  -this inhibitory neuron is excited/activated, which then inhibits the pineal gland
  -this inhibitory signal is acting on the pinealocyte of the “cells”
  -causing low norepinephrine (NT) secretion and low melatonin release
  -low melatonin release stimulates/acts on RFRP neuron, increasing RFRP-3 production
  -this increase acts on LONG DAY kiss neurons(STIMULATED), now stimulated, acts on High kiss -10
  -stimulates high production of GNRH, FSH/LH and generated cyclicity

Question 7

What do pinealocytes do

Answer 7

make melatonin

Question 8

what does the inhibitory signal have an effect on in the pineal gland and where is it coming from? (long day breeder)

Answer 8

the inhibitory signal makes low norepinephrine secretion and low melatonin

Question 9

describe what happens in a long day period but on a short day breeder

Answer 9

• long photoperiods/ more light is sensed by the retina of the eye
  -with more light being sensed, there is a retinal nerve firing an excitatory signal to the brain
  -the retinal nerves act on the suprachiasmatic nucleus (surge center of the hypothalamus)
  -this signal received from the nucleus is then acting on the superior cervical ganglion
  -this inhibitory neuron is excited/activated, which then inhibits the pineal gland
  -this inhibitory signal is acting on the pinealocyte of the “cells”
  -causing low norepinephrine (NT) secretion and low melatonin release
  -low melatonin release stimulates/acts on RFRP neuron, increasing RFRP-3 production (inhibiting)
  -this increase acts on SHORT DAY kiss neurons (INHIBITED), acts on low kiss -10
  -stimulates low production of GNRH, FSH/LH and generates no cycles (period of anestrus)

Question 10

what does increasing daylength do (long day breeder)

Answer 10

receptors in the eye act on pineal gland, decreasing melatonin, increasing GNRH/LH

Question 11

what does decreasing daylength do (short day breeder)

Answer 11

increases melatonin, decreasing GNRH/ LH

Question 12

Silent ovulation

Answer 12

in the ewe, the first ovulation after seasonal anestrus is not accompanied by a behavioral estrus

Question 13

When does the mare cycle and not

Answer 13

long day breeder: Spring =cycles
Fall= anestrus

Question 14

when does the ewe cycle and not

Answer 14

short day breeder: Fall= cycles
Spring= anestrus

Question 15

What are the two primary factors that influence the onset of the breeding system

Answer 15

photoperiod and temperature

Question 16

What specifically causes the decrease in melatonin

Answer 16

reduced norepinephrine results in low melatonin secretion from the pineal gland

Question 17

when days are short

Answer 17

melatonin increases, decreases RFRP-3 inhibition on kisspeptin neurons (in short day breeding females; this signals elevates levels of GnRH, FSH,LH to initiate cycles

High melatonin during short days(long day breeders) reduce levels of GNRH, FSH, LH and terminates cycles

Question 18

what is the fundamental reason that differences between seasonal breeders exist

Answer 18

related to genetic differences in the responsiveness of certain groups of kisspeptin neurons to RFRP-3