Biological Rhythms and energy balance L6

What is the primary function of the pineal gland?

The pineal gland produces melatonin, which regulates biological rhythms such as sleep/wake cycles.

Where is the pineal gland located?

The pineal gland is located between the hemispheres of the brain, behind the thalamus.

How does light affect melatonin production?

Light inhibits the pineal gland, leading to less melatonin production, while darkness stimulates its secretion.

What is the effect of blue light on melatonin production?

Blue light interferes with melatonin production, disrupting the circadian rhythm.

What is jet lag in relation to melatonin secretion?

Jet lag occurs when the melatonin cycle is aligned with the original time zone while the external environment shifts to a new location, causing delayed or advanced melatonin secretion.

What are biological rhythms?

Biological rhythms are reoccurring cycles in biological processes that help organisms adapt to daily, monthly, or seasonal changes.

What are circadian rhythms and what do they regulate?

Circadian rhythms are 24-hour cycles that regulate processes such as sleep-wake cycles, body temperature, and cortisol levels.

What hormonal mechanism controls circadian rhythms?

The retina detects light, sends a signal to the suprachiasmatic nucleus (SCN) in the hypothalamus, which then signals the pineal gland to suppress or release melatonin.

What are ultradian rhythms and give an example?

Ultradian rhythms are cycles shorter than 24 hours, such as REM sleep cycles, which occur approximately every 90 minutes.

What hormonal mechanisms regulate ultradian rhythms?

Ultradian rhythms are often regulated by neurotransmitters and hormones like ghrelin and leptin.

What is an example of an infradian rhythm?

The menstrual cycle, which lasts about 28 days, is an example of an infradian rhythm.

What hormonal mechanisms are involved in infradian rhythms?

Infradian rhythms involve the release of FSH, LH, oestrogen, and progesterone from the hypothalamus, pituitary gland, and ovaries.

What are circannual rhythms?

Circannual rhythms are yearly cycles that can affect behaviors such as seasonal affective disorder and animal migration or reproduction.

How does day length influence circannual rhythms?

Changes in day length influence melatonin duration, which affects reproductive hormones and mood regulation.

What is homeostasis?

Homeostasis is the regulation of internal conditions such as temperature, pH, and blood sugar to maintain a stable internal environment despite external changes.

What are the key systems involved in homeostasis?

The nervous system (fast-acting responses), endocrine system (hormonal regulation), and excretory system (water and ion balance) are key to homeostasis.

What is the role of the pancreas in homeostasis?

The pancreas has exocrine functions (digestive enzymes) and endocrine functions (secreting glucagon, insulin, and somatostatin).

What do alpha cells in the pancreas secrete?

Alpha cells secrete glucagon, which raises blood sugar levels.

What do beta cells in the pancreas secrete?

Beta cells secrete insulin, which lowers blood sugar levels.

What is C-peptide and its significance?

C-peptide is cleaved from proinsulin and secreted alongside insulin; it serves as a proxy for energy balance and nutritional status.

How does physical activity affect urinary C-peptide levels?

Physical activity can lower urinary C-peptide levels in the short term, indicating a relationship between energy expenditure and metabolic processes.

What are recent advances in non-invasive endocrinological techniques?

Recent advances include salivary and sweat-based detection of thyroid hormones, which provide stress-free and repeatable monitoring methods.

What do urinary iodine levels indicate?

Urinary iodine levels reflect thyroid hormone production potential, as iodine is essential for the synthesis of T3 and T4.