Human Physiology Quiz

The active form of vitamin D, produced by the kidneys under the influence of PTH, crucial for calcium absorption and bone health.

A hormone produced by the thyroid gland that lowers blood calcium levels by promoting calcium deposition in bones and inhibiting calcium absorption.

Hormone produced by the parathyroid glands, primarily involved in increasing blood calcium levels by stimulating bone resorption, enhancing calcium reabsorption in the kidneys, and promoting vitamin D activation.

A disorder characterized by low blood calcium levels, often leading to muscle spasms, seizures, and cardiac problems.

A disorder characterized by high blood calcium levels, often leading to kidney stones, bone weakening, and fatigue.

The master clock of the circadian rhythm, located in the hypothalamus, responsible for synchronizing the body's internal clock with the external light-dark cycle.

The pathway that carries light signals from the retina to the SCN, playing a crucial role in entraining the circadian rhythm to the external environment.

Biological rhythms that operate on a roughly 24-hour cycle, driven by internal clocks and influenced by environmental cues.

The central pacemaker of the circadian rhythm, located in the hypothalamus of the brain. It regulates hormone release, body temperature, and sleep-wake cycles.

A group of genes that control the timing of biological processes, operating on a 24-hour cycle.

Two key clock genes, CLOCK and BMAL1, form a complex that activates the expression of other clock genes, like PER and CRY.

PER and CRY form a complex that inhibits the activity of CLOCK/BMAL1, completing the feedback loop.

The monarch butterfly uses its circadian clock to navigate during migration, combining the sun compass and internal clock to determine direction.

Light resets the monarch's clock daily, ensuring precise navigation over long distances.

Climate change has caused shifts in migration timing in birds, mainly due to changes in temperature and photoperiod.

Disruptions in environmental cues, like temperature and photoperiod, can lead to mistimed breeding in birds, affecting population dynamics.

The master control center for the process of sexual development, where GnRH (gonadotropin-releasing hormone) is produced, driving the pituitary gland to release FSH (follicle-stimulating hormone) and LH (luteinizing hormone).

The 'middle man' that responds to the hypothalamus and releases FSH and LH, which then travel to the gonads (testes or ovaries) to control sexual development.

The reproductive organs (testes in males, ovaries in females) that produce sex hormones and gametes (sperm or eggs).

The process where hormones produced by the gonads feedback to the hypothalamus and pituitary gland, influencing the production of GnRH, FSH, and LH. This regulates the levels of sex hormones in the body.

The process where high levels of estrogen trigger a surge in LH production, leading to the release of an egg from the ovary (ovulation).

An individual's biological characteristics related to reproduction, determined by chromosomal sex (XX or XY), gonadal sex (testes or ovaries), and phenotypic sex (external genitalia).

An individual's sense of self, not necessarily aligned with their biological sex, influenced by social and psychological factors.

Situations where an individual's chromosomal, gonadal, or phenotypic sex don't align, leading to variations from typical sex development.

The phase of the menstrual cycle after ovulation where the endometrium prepares for implantation. Progesterone, produced by the corpus luteum, plays a crucial role in this process.

The process of shedding the endometrium when implantation doesn't occur, leading to menstruation.

The complex process of labor and delivery, involving coordinated contractions of the uterus and abdominal muscles.

The first stage of labor, characterized by cervical dilation (opening) due to uterine contractions.

The second stage of labor, where the baby is expelled from the uterus through the birth canal.

The third stage of labor after the delivery of the fetus, where the placenta detaches from the uterine wall and is expelled.

The process of producing milk in the mammary glands, initiated after childbirth and sustained by hormonal changes.

A natural form of birth control where the act of breastfeeding suppresses ovulation, delaying a woman's return to fertility.

The pancreas in teleosts is dispersed, with endocrine and exocrine cells scattered in the mesentery, liver, or intestines, unlike the centralized organ in mammals.

Teleosts primarily rely on protein metabolism for gluconeogenesis, leading to a higher proportion of A-cells (glucagon producers) in their pancreatic islets compared to mammals.

In teleosts, pancreatic islets (Brockmann bodies) are separate structures located near blood vessels, facilitating efficient hormone distribution.

Parathyroid hormone (PTH) increases blood calcium levels by stimulating bone resorption, enhancing calcium reabsorption in the kidneys, and activating vitamin D.

Vitamin D, in its active form (calcitriol), promotes calcium and phosphate absorption in the gut, contributing to bone health and calcium regulation.

Maintaining a balance between calcium and phosphate is crucial for bone health, neuromuscular function, and energy metabolism.

High phosphate levels can bind to calcium, reducing its availability in the bloodstream. This highlights the interconnection between these two mineral ions.

Hormonal regulation of calcium and phosphate ensures their optimal levels in the body, supporting various physiological functions.

A hormone produced by the thyroid gland, calcitonin acts to lower blood calcium levels by inhibiting bone resorption, effectively putting the brakes on calcium release from bones. It's like a 'calcium saver' that helps maintain the balance of calcium in your blood.

99% of the body's calcium reserves are stored in bones as hydroxyapatite, a mineral that strengthens bone structure. This acts as a calcium reservoir, releasing calcium into the bloodstream when blood calcium levels drop.

Osteoblasts are bone-forming cells, like builders that deposit calcium and phosphate into the bone matrix, strengthening bones. They're stimulated by calcitonin, the calcium-lowering hormone.

Osteoclasts, on the other hand, act as 'bone breakers.' They break down bone matrix, releasing calcium and phosphate into the bloodstream. They are stimulated by PTH when blood calcium levels are low.

This hormone is produced by the parathyroid glands when blood calcium levels drop. It triggers a chain reaction to increase blood calcium: stimulating osteoclasts to break down bone and release calcium, enhancing calcium reabsorption in the kidneys, and indirectly boosting calcium absorption in the intestines.

The kidneys play a vital role in regulating calcium and phosphate levels. They filter calcium from the blood and reabsorb 98% of it. PTH increases calcium reabsorption in the distal tubules, helping to conserve calcium within the body.

Enterocytes, located in the small intestine, are responsible for absorbing dietary calcium and phosphate, aided by vitamin D. This process is crucial for maintaining adequate levels of calcium and building strong bones.

Vitamin D, synthesized from cholesterol, plays a crucial role in calcium absorption. UV light converts 7-dehydrocholesterol in the skin to vitamin D3, which is then converted to its active form in the liver and kidneys.