AP® Biology - Endocrine and Development Part 2

In keeping with its name, FSH promotes the development of mature follicles (structures that contain egg cells). Its levels are highest before ovulation and low during pregnancy.

Both FSH and LH are peptide hormones secreted from the anterior pituitary.

FSH facilitates spermatogenesis, or sperm production, by stimulating Sertoli cells in the testes.

Both FSH and LH are peptide hormones secreted from the anterior pituitary.

LH promotes ovulation with a peak in concentration known as the LH surge. It also facilitates the development of the corpus luteum.

Both FSH and LH are peptide hormones secreted from the anterior pituitary.

LH increases the production of testosterone by stimulating Leydig cells in the testes.

Both FSH and LH are peptide hormones secreted from the anterior pituitary.

Tropic hormones

One example is TSH, or thyroid-stimulating hormone. Instead of directly altering a cellular process on its own, it stimulates the thyroid to produce its own hormones.

ADH stimulates the kidneys to increase water reabsorption, especially in dehydrated individuals.

This function limits water loss, preventing blood pressure from becoming too low.

Oxytocin is secreted by the posterior pituitary. Its main role is to facilitate labor contractions during childbirth. ## Footnote Oxytocin is also involved in other childbirth-related functions, including facilitating nursing and promoting mother-infant bonding.

The pancreas produces and secretes insulin and glucagon, two hormones that have opposite effects on plasma glucose levels. These hormones are produced in structures termed islets of Langerhans.

A third hormone released by the pancreas is somatostatin, but the AP Biology exam is unlikely to mention it.

Insulin removes glucose from the blood and facilitates its storage in the tissues as glycogen. It is released when plasma glucose levels are high, such as after a meal.

Insulin is secreted by pancreatic beta cells.

Glucagon facilitates the conversion of stored glycogen to glucose. This process increases plasma glucose levels.

Glucagon is secreted by pancreatic alpha cells.

The thyroid gland releases thyroid hormones, known as T3 and T4 (thyroxine), which control metabolism. It also secretes calcitonin.

The endocrine activity of the thyroid is determined by thyroid-stimulating hormone (TSH), which is secreted from the anterior pituitary.

The parathyroid glands produce parathyroid hormone (PTH). This hormone increases plasma calcium levels by stimulating the breakdown of bone.

Make sure to be familiar with the difference between PTH and calcitonin, which have opposite functions.

Plasma calcium levels would increase.

PTH is released from the parathyroid glands when plasma calcium is low. Among other functions, it stimulates the breakdown of bone, which releases calcium into the extracellular fluid.

Plasma calcium levels would decrease.

Calcitonin is released from the thyroid when plasma calcium levels are high. It stimulates specialized cells to increase bone formation, taking calcium out of the blood in the process.

Plasma concentrations of calcium ion (Ca2+) are controlled by both of these glands.

The parathyroid glands secrete parathyroid hormone (PTH), which increases plasma calcium levels. Calcitonin, a product of the thyroid, has the opposite effect.

The two main parts are the cortex, or outer region, and the medulla, or inner region.

The adrenal cortex secretes aldosterone and cortisol.

More broadly, the cortex produces glucocorticoids (such as cortisol and cortisone) and mineralocorticoids (such as aldosterone). It also synthesizes some sex hormones.

The adrenal medulla secretes epinephrine and norepinephrine, both catecholamines.

Notably, these products can function as either hormones or neurotransmitters, depending on the location of release.

The products of the adrenal cortex are steroid hormones.

For the AP Biology exam, this can be remembered by recalling their broad classification: corticosteroids.

Aldosterone stimulates the kidneys to increase sodium reabsorption; water follows and is passively reabsorbed as well.

This function results in water retention, preventing blood pressure from becoming too low.

Estrogen and progesterone

These hormones play major roles in the development of secondary sex characteristics, regulation of the menstrual cycle, and pregnancy.

The pineal gland produces melatonin, which helps regulate circadian rhythms.

This pathway is a second messenger system.

The first messenger is the hormone itself; the second is an intracellular ion or molecule, like Ca2+ or cAMP. These systems commonly involve G protein-coupled receptors, or GPCRs.

A lowered consumption of iodine might affect the thyroid gland.

Iodine is required for thyroid hormone synthesis. Most table salt is iodized to protect against goiter, a condition in which the thyroid gland becomes enlarged to compensate for an iodine deficiency.

Parathyroid hormone (PTH)

It is important to know alternative ways that the AP Biology exam can phrase common terms. "Bone resorption" simply describes the breakdown of bone, which is promoted by PTH.