Reproductive Seasonal Cyclicity & Menstrual Cycle

Menstrual Cycle

events between 2 successive menstrual periods

Menses

sloughing of the endometrium

What are the Menstrual Cycle Events?

1. Menses

2. Follicle Growth 

3. Ovulation

4. Corpus Luteum 

5. Endometrial Growth 

6. Luteolysis 

Does luteolysis in primates require a uterus?

No. 

When will seasonal cyclers typically cycle?

when there is the least amount of stress

Obligatory Seasonal Breeders

rely on seasonal cues to predict when conditions are favorable to reproduction and bearing young.

Opportunistic Seasonal Breeders

react directly to changes in environment — NOT linked to seasonal cues (ex. house mouse)

What are the steps of Photoperiod Regulation in seasonal breeders?

1. Light and darkness are detected by the retina 

2. Info is sent to the suprachiasmatic nucleus (SCN) through the optic nerve

3. Info is sent to the superior cervical ganglion (SCG). 

4. Neurons transmit info to the pineal glans to regulate melatonin release 

Does Melatonin directly regulate GnRH release?

No. Melatonin work through other intermediates which release GnRH.

What happens during menstruation?

1. P4 and E2 drop 

2. Menses 

3. There is variation as to when it will happen and for how long (depends on the follicular phase)

Draw and explain a graph depicting the hormonal changes in the menstrual cycle

1. Proliferative Phase = Menses & Follicular phase

2. Endometrial Thickness = Ovulation

3. Secretory Phase = Luteal Phase

Draw a table depicting the differences between the menstrual cycle and the estrus cycle

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