Question 1

Which of the following best describes the sequence of hormonal events leading from increased daylight to stimulation of reproductive activity in a typical long-day breeding mammal?

Accepted Answer

Increased daylight → decreased melatonin → increased TSH → increased T3 → increased kisspeptin → increased GnRH

Question 2

A researcher performs a pinealectomy (removal of the pineal gland) on a hamster. Which of the following outcomes is most likely during short-day conditions?

Accepted Answer

The hamster will show no gonadal regression, maintaining reproductive capability.

Question 3

Which hormone acts directly on tanycytes in the hypothalamus to regulate the local hormone environment during seasonal reproduction?

Accepted Answer

TSH (Thyroid Stimulating Hormone)

Question 4

In a photoperiodic species, which of the following would most likely result from chronic administration of melatonin implants during the breeding season?

Accepted Answer

Testicular atrophy and suppression of reproductive function

Question 5

A mutation blocks the function of the MT1 melatonin receptor in the pars tuberalis. Which physiological effect is most likely?

Accepted Answer

Animals will fail to exhibit seasonal reproductive shifts in response to photoperiod.

Question 6

Which of the following best explains why thyroid hormone (T3) is important for seasonal reproduction?

Accepted Answer

T3 acts in the hypothalamus to influence behavior and stimulate GnRH release via kisspeptin.

Question 7

If the enzyme Dio2 is inhibited in a long-day breeding animal, what is the most likely consequence for reproduction?

Accepted Answer

Decreased T3 production and reduced reproductive activity

Question 8

Which of the following best describes the role of the suprachiasmatic nucleus (SCN) in the regulation of biological rhythms?

Accepted Answer

The SCN receives light input and regulates melatonin secretion from the pineal gland.

Question 9

A sheep is exposed to artificially long days for several months and then continues to be exposed to long days. Eventually, the sheep stops responding reproductively to the long-day stimulus. This phenomenon is best described as:

Accepted Answer

Photorefractoriness

Question 10

Which of the following is the correct sequence for the daily and seasonal regulation of physiology by light, according to the master flow described in the study materials?

Accepted Answer

Light → ipRGC → SCN → Melatonin → Sleep (daily); Melatonin → TSH → T3 → Kisspeptin → HPG axis (seasonal)

Question 11

Which of the following would most likely occur if TSH receptors (TSHR) in the pars tuberalis are blocked in a photoperiodic animal?

Accepted Answer

The animal would fail to exhibit seasonal reproductive shifts.

Question 12

Which of the following best explains why melatonin can have opposite effects on reproduction in different species?

Accepted Answer

Melatonin's effect depends on the species and timing, either inhibiting or stimulating reproduction.

Question 13

A scientist blocks kisspeptin signaling in the hypothalamus of a long-day breeding animal. Which of the following is the most likely outcome?

Accepted Answer

Decreased GnRH and LH secretion, leading to reduced reproductive activity

Question 14

Which of the following is a direct effect of increased melatonin secretion during short days in a photoperiodic mammal?

Accepted Answer

Suppression of the reproductive axis via GnIH

Question 15

A farmer wants to maximize the reproductive output of his sheep flock. Which of the following strategies would most likely be effective based on the photoperiodic control of reproduction?

Accepted Answer

Expose sheep to long days to decrease melatonin secretion and stimulate the reproductive axis.

Question 16

Which of the following best describes the role of GnIH in the seasonal regulation of reproduction?

Accepted Answer

GnIH inhibits the reproductive axis, especially during periods of high melatonin.

Question 17

Which of the following is the correct order of events for the seasonal regulation of the HPG axis in response to light?

Accepted Answer

Light → Melatonin → TSH → T3 → Kisspeptin → GnRH → LH/FSH → Gonads

Question 18

Which of the following best describes the effect of blocking the enzyme Dio2 in the hypothalamus during the breeding season?

Accepted Answer

Decreased conversion of T4 to T3, suppressing reproduction

Question 19

Which of the following is a function of the biological clock in photoperiodic species?

Accepted Answer

It provides endogenous timing mechanisms that regulate physiology and behavior.

Seasonal Reproduction and Photoperiodism: Endocrine and Neural Regulation

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