Q: Which equation best represents the relationship between cAMP and melatonin synthesis in the pineal gland?

$$\text{Melatonin} \propto \text{cAMP} \times \text{NAT}$$

Question 1

Which structure is considered the master regulator of circadian rhythms in mammals, and what evidence supports its role?

Accepted Answer

The suprachiasmatic nucleus (SCN), because it displays a circadian rhythm in neural firing rate both in vivo and in vitro.

Question 2

Which neurotransmitter is released by VLPO neurons to promote sleep, and what is its effect?

Accepted Answer

GABA, which inhibits arousal-promoting regions in the hypothalamus and brainstem.

Question 3

Which hormone is derived from tryptophan and is associated with nocturnal onset in the circadian rhythm?

Accepted Answer

Melatonin

Question 4

In the regulation of melatonin synthesis, which pathway correctly describes the sequence of neural connections from the SCN to the pineal gland?

Accepted Answer

SCN → PVN → IML → SCG → Pineal gland

Question 5

Which process in the 2-process model of sleep regulation is responsible for the homeostatic drive for sleep?

Accepted Answer

Process S

Question 6

What is the effect of increased light exposure on melatonin synthesis?

Accepted Answer

It reduces activity of sympathetic fibers, thereby reducing norepinephrine release and melatonin synthesis.

Question 7

Which of the following best describes the role of melatonin in sleep?

Accepted Answer

Melatonin decreases time to sleep onset and phase-shifts circadian rhythms.

Question 8

Which receptor types does melatonin bind to in the SCN, and what is the effect of MT1 activation?

Accepted Answer

MT1 and MT2; MT1 activation regulates REM sleep.

Question 9

Which of the following is a plausible explanation for why shift workers often fall asleep easily but have difficulty staying asleep?

Accepted Answer

Their homeostatic and circadian systems are non-additive, leading to misalignment between sleep drive and circadian rhythm.

Question 10

Which genetic disorder is characterized by progressive insomnia, hallucinations, rapid weight loss, and ultimately death, and is related to prion disease?

Accepted Answer

Fatal Familial Insomnia

Question 11

Which neurotransmitter acts as a local inhibitor via Y1 and Y2 receptors to regulate norepinephrine release in the pineal gland?

Accepted Answer

Neuropeptide Y (NPY)

Question 12

Which stage of sleep is most associated with slow wave activity and is considered deep sleep?

Accepted Answer

Stage N3 (slow wave sleep; SWS)

Question 13

Which hormone is released in a circadian pattern and is involved in promoting wakefulness, peaking in the early morning?

Accepted Answer

Cortisol

Question 14

Which experimental protocol is used to study the effects of circadian misalignment by scheduling subjects on a sleep-wake cycle outside the range of entrainment?

Accepted Answer

Forced Desynchrony (FD)

Question 15

Which equation best represents the relationship between cAMP and melatonin synthesis in the pineal gland?

Accepted Answer

$$	ext{Melatonin} \propto 	ext{cAMP} 	imes 	ext{NAT}$$

Question 16

Which of the following best describes the ethical concerns associated with sleep deprivation studies?

Accepted Answer

Chronic sleep deprivation is recognized by the UN as a form of torture, raising concerns about the origins of physiological data.

Question 17

Which of the following hormones is NOT regulated by circadian sleep regulation?

Accepted Answer

Insulin

Question 18

Which neurotransmitter is released by orexin neurons to promote arousal and wakefulness?

Accepted Answer

Orexin

Question 19

Which of the following best explains why melatonin administration can help with jet lag?

Accepted Answer

Melatonin phase-shifts circadian rhythms, helping to realign the internal clock with the new time zone.

Question 20

Which equation describes the conversion of tryptophan to melatonin?

Accepted Answer

$$	ext{Tryptophan} \xrightarrow{	ext{Trypt H}} 	ext{5-Hydroxytryptophan} \xrightarrow{	ext{AADC}} 	ext{Serotonin} \xrightarrow{	ext{NAT}} 	ext{N-Acetylserotonin} \xrightarrow{	ext{HIOMT}} 	ext{Melatonin}$$

Sleep and Circadian Rhythms: Regulation, Mechanisms, and Endocrine Connections

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