ORGB 364 FINAL EXAM NOTES COMPLETE
STUDY A-HEAD SOLUTION GUIDE
ATHABASCA UNIVERSITY EXAM SCRIPT
2026 COMPREHENSIVE QUESTIONS WITH
SOLUTIONS GRADED A+
⩥ Long day breeders. Answer: hamster
horse
⩥ Ewes photoperiod. Answer: short day breeders - naturally start cycling
in late summer and fall
neuronal pathway monitors photoperiod
⩥ Anestrus. Answer: female does not come into heat or ovulate
⩥ Ewe seasonal anestrus. Answer: during spring/ early summer
⩥ Steroidogenic hormones during anestrus. Answer: low E2 and P4 due
to no ovulation and no follicular growth
E2 still provides negative feedback loop and inhibits LH pulse frequency
brain is more sensitive to negative feedback during this time
, ⩥ Steroidogenic hormones during breeding season. Answer: P4 is high
in CL after ovulation and suppresses LH to inhibit another round of
ovulation
E2 during the follicular phase - suppresses amplitude of LH pulses
E2 during late follicular phase - high sustained levels of E2 triggers LH
surge to induce ovulation
⩥ E2 effect on LH pulses. Answer: inhibits pulse amplitude
⩥ P4 effect on LH pulses. Answer: inhibits pulse frequency
⩥ Pineal gland effect on ewes during breeding season. Answer: acts as a
seasonal clock in ewes
1. secretes melatonin when it is dark
2. melatonin acts on hypothalmus
3. reduces E2 sensitivity and increases LH and follicular growth to
induce ovulation
⩥ Pineal gland effect on ewes during anestrus. Answer: 1. Longer days,
shorter nights
2. Lessened secretions of melatonin
3. brain remains sensitive to E2
4. low production of GnRH and LH - no ovulation
STUDY A-HEAD SOLUTION GUIDE
ATHABASCA UNIVERSITY EXAM SCRIPT
2026 COMPREHENSIVE QUESTIONS WITH
SOLUTIONS GRADED A+
⩥ Long day breeders. Answer: hamster
horse
⩥ Ewes photoperiod. Answer: short day breeders - naturally start cycling
in late summer and fall
neuronal pathway monitors photoperiod
⩥ Anestrus. Answer: female does not come into heat or ovulate
⩥ Ewe seasonal anestrus. Answer: during spring/ early summer
⩥ Steroidogenic hormones during anestrus. Answer: low E2 and P4 due
to no ovulation and no follicular growth
E2 still provides negative feedback loop and inhibits LH pulse frequency
brain is more sensitive to negative feedback during this time
, ⩥ Steroidogenic hormones during breeding season. Answer: P4 is high
in CL after ovulation and suppresses LH to inhibit another round of
ovulation
E2 during the follicular phase - suppresses amplitude of LH pulses
E2 during late follicular phase - high sustained levels of E2 triggers LH
surge to induce ovulation
⩥ E2 effect on LH pulses. Answer: inhibits pulse amplitude
⩥ P4 effect on LH pulses. Answer: inhibits pulse frequency
⩥ Pineal gland effect on ewes during breeding season. Answer: acts as a
seasonal clock in ewes
1. secretes melatonin when it is dark
2. melatonin acts on hypothalmus
3. reduces E2 sensitivity and increases LH and follicular growth to
induce ovulation
⩥ Pineal gland effect on ewes during anestrus. Answer: 1. Longer days,
shorter nights
2. Lessened secretions of melatonin
3. brain remains sensitive to E2
4. low production of GnRH and LH - no ovulation
