Endocrine-Parathyroid: Cellular Biology & Homeostasis

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Where are the parathyroid glands usually located in most species?

Within the liver

Near the kidneys

On the lobes of the thyroid glands (correct)

Attached to the spinal cord

What is the function of a preprohormone in hormone synthesis?

Stored in secretory granules after cleavage

Immediate release into the bloodstream

Active form in the Golgi apparatus

Inactive molecule in the endoplasmic reticulum (correct)

Which cells are responsible for synthesizing parathyroid hormone (PTH)?

Osteoclasts

Osteocytes

Osteogenic cells

Parathyroid chief cells (correct)

In which organelle is a prohormone cleaved into its active form?

Golgi apparatus Signup and view all the answers

What is the primary target tissue or organ affected by parathyroid hormones?

Kidneys Signup and view all the answers

Which type of gland is the parathyroid gland classified as?

Endocrine gland Signup and view all the answers

What is the role of calcitriol in calcium metabolism?

Enhances calcium absorption in the intestines Signup and view all the answers

What is the primary function of Parathyroid Hormone (PTH) on target tissues?

Increase calcium reabsorption in kidneys Signup and view all the answers

What is the primary stimulus for the release of PTH from the parathyroid gland?

Decrease in blood ionized calcium levels Signup and view all the answers

What is the role of the oxyphil cells in the parathyroid gland?

Unknown, but they are larger than the chief cells and have oxidative and hydrolytic enzyme activity Signup and view all the answers

How is PTH synthesized in the parathyroid gland?

Prepro-PTH is synthesized in the rough endoplasmic reticulum (rER) and then cleaved to pro-PTH, which is then secreted Signup and view all the answers

What is the primary role of calcium and phosphate in the body?

They play a major role in physiological homeostasis, including muscle contraction, nerve cell activity, and the structural integrity of bones and teeth Signup and view all the answers

What is the half-life of parathyroid hormone (PTH) in the body?

5-10 minutes Signup and view all the answers

How are the calcium-sensing receptors on the parathyroid gland membrane involved in PTH regulation?

They are G-protein coupled receptors that activate the cAMP-PKA pathway, which stimulates PTH release Signup and view all the answers

Where is PTH primarily metabolized in the body?

Primarily in the liver Signup and view all the answers

What is the approximate percentage of calcium found in the bones?

99% Signup and view all the answers

Which of the following is not a major function of calcium and phosphate in the body?

Regulation of body temperature Signup and view all the answers

What is the usual number of parathyroid glands pairs found in most species?

Two pairs Signup and view all the answers

What is the primary chemical structure of parathyroid hormone (PTH)?

Protein Signup and view all the answers

Which organelle is responsible for cleaving a prohormone into its active hormone form?

Golgi apparatus Signup and view all the answers

What is the usual type of molecule in which hormones are synthesized initially before being activated into hormones?

Pre-prohormone Signup and view all the answers

What is the primary role of the calcium-sensing receptors on the parathyroid gland membrane?

To detect changes in blood ionized calcium levels and regulate PTH release Signup and view all the answers

Which of the following statements about the synthesis of PTH is true?

Prepro-PTH is synthesized in the rough endoplasmic reticulum and then cleaved to pro-PTH Signup and view all the answers

Which of the following is the primary stimulus for the secretion of aldosterone?

Increased plasma potassium concentration Signup and view all the answers

Which of the following stimuli is the primary trigger for renin secretion from the juxtaglomerular apparatus?

Reduced blood pressure in the kidney Signup and view all the answers

How does ACTH (adrenocorticotropic hormone) influence aldosterone secretion?

ACTH has no significant effect on aldosterone synthesis and secretion Signup and view all the answers

What is the primary anatomical location of the zona glomerulosa, the site of aldosterone synthesis?

The outer cortex of the adrenal gland Signup and view all the answers

Which of the following is a key function of the renin-angiotensin-aldosterone system (RAAS) in regulating aldosterone secretion?

Detecting changes in blood pressure in the kidney Signup and view all the answers

How does an increase in plasma potassium concentration influence aldosterone secretion?

It stimulates aldosterone secretion independently of the RAAS Signup and view all the answers

What is the primary target tissue for the actions of aldosterone?

The distal renal tubules Signup and view all the answers

Which of the following is a key function of the macula densa in the regulation of aldosterone secretion?

Detecting changes in plasma sodium concentration Signup and view all the answers

What is the primary role of the afferent arteriole baroreceptors in the regulation of aldosterone secretion?

They detect changes in blood pressure in the kidney Signup and view all the answers

What is the primary function of the Zona Glomerulosa in the adrenal gland?

Secretion of mineralocorticoids Signup and view all the answers

How are steroid hormones primarily transported in the blood after being synthesized?

By binding to specific carrier proteins Signup and view all the answers

Which enzyme is mainly involved in the conversion of cholesterol to pregnenolone in steroidogenesis?

ACTH Signup and view all the answers

In steroid hormone metabolism, what process mainly occurs in the liver to prepare them for excretion?

Conjugation to sulfates and glucuronides Signup and view all the answers

What is the approximate clearance half-life of aldosterone in the body?

20 minutes Signup and view all the answers

Which glandular axis regulates the synthesis of steroid hormones in the adrenal cortex?

Hypothalamic-Pituitary-Adrenal (HPA) axis Signup and view all the answers

What is the main role of mineralocorticoids synthesized by the adrenal gland?

Control of salt and water balance Signup and view all the answers

How do steroid hormones trigger a response in target cells?

By binding to intracellular receptors and controlling gene transcription Signup and view all the answers

Where do Androgen hormones primarily bind in target cells to trigger a rapid cellular response?

Cell membrane receptors Signup and view all the answers

Which layer of the adrenal gland produces glucocorticoids?

Zona Fasciculata Signup and view all the answers