Systems Physiology - AP Biology

The hormone responsible for the reduction of calcium in the blood is calcitonin. This hormone promotes the assimilation of calcium ions into the bone matrix from the blood. This reduces the concentration of calcium ions in the blood and increases the concentration found in the bone. Meanwhile, PTH has the opposite effect by taking calcium ions from the bone matrix and releasing them into the blood.

The correct answer is oxytocin because this hormone is produced in the posterior pituitary gland along with antidiuretic hormone (ADH). Oxytocin is responsible for uterine contraction during labor in a positive feedback look mechanism.

Melatonin is produced in the pineal gland which is a gland in the brain responsible for the body’s circadian rhythms and sleep/wake cycle. The concentration of melatonin peaks at night and causes us to fall asleep. Melatonin is degraded while we sleep so that when we wake up in the morning we start to produce it again throughout the day.

Cortisol is a hormone secreted by the adrenal cortex. The adrenal cortex is first stimulated by adrenocorticotropic hormone, which is secreted from the anterior pituitary gland.

The hypothalamus releases hormones that control the release of hormones from the anterior pituitary, which in turn controls the release of hormones from other endocrine glands. The anterior pituitary is also controlled by several negative feedback systems based on hormones released throughout the body and their effects.

Gonadotropin-releasing hormone (GnRH), released from the hypothalamus, is responsible for regulating follicle-stimulating hormone and luteinizing hormone release. Growth-hormone-releasing hormone (GHRH) regulates release of growth hormone (GH), and corticotropin-releasing factor (CRF) regulates adrenocorticotropic hormone (ATCH) release from the anterior pituitary. Thyroid-stimulating hormone (TSH) is released from the anterior pituitary and stimulates release of T3 and T4 from the thyroid.

Signals from the hypothalamus go to the posterior pituitary gland, which is located at the base of the hypothalamus. The pituitary consists of two lobes (anterior and posterior), which function independently. The anterior and posterior pituitary produce a collection of hormones that are key to endocrine signaling throughout the body.

The posterior pituitary stores and secretes two hormones (oxytocin and vasopressin), while the anterior pituitary produces six different hormones (growth hormone, prolactin, follicle-stimulating hormone (FSH), luteinizing hormone (LH), thyroid-stimulating hormone (TSH) and adrenocorticotropic hormone (ACTH). The posterior pituitary will only secrete hormones when stimulated by the hypothalamus.

The anterior pituitary gland contains endocrine cells that release hormones through the hypothalamic-hypophyseal axis. Prolactin controls milk production and contributes to regulation of the immune system. Of the listed hormones, prolactin is the only hormone released from the anterior pituitary.

Insulin and glucagon are secreted by the pancreas. Cortisol is released by the adrenal cortex; epinephrine is released by the adrenal medulla.

Melatonin is secreted by the pineal gland, which is also in the brain. The function of melatonin is not yet certain, but current research hints that it plays functions in regulation of the circadian rhythm. All other hormones are indeed secreted by the pituitary gland.

The posterior pituitary only secretes oxytocin and vasopressin (antidiuretic hormone). The hypothalamus actually creates these hormones and stores them in the posterior pituitary.

The anterior pituitary releases the growth hormone (GH), adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin. You can remember all of these hormones by using the acronym FLATPEG, where:

F- FSH

L- LH

A- ACTH

T- TSH

P- Prolactin

E- Endorphins

G- GH

The hypothalamus is a structure in the brain responsible for homeostatic control over much of the body. It is responsible for maintaining core body temperature within normal levels. There are special neurons located within the hypothalamus that respond to changes in body temperature. The hypothalamus then sends out signals to the result of the body in response to changes in temperature.

The villi are helpful in increasing the surface area of the small intestine. This greatly increases the absorptive capabilities of the small intestine. The stomach has no villi, and does not contribute to absorption of macromolecules.

The hepatic portal system involves the capillaries of the small intestine and capillaries of the liver. A portal system refers to two different capillary beds, connected by arterioles, that both receive blood before it returns to the heart for reoxygenation. The prefix "hepa-" refers to the liver.

The pancreatic duct transfers digestive enzymes from the pancreas into the lumen of the small intestine. Lacteal vessels receive fats from the small intestine and carry them into the lymphatic system. The pulmonary circuit refers to the region of the circulatory system that carries blood from the right ventricle to the lungs, and back to the left atrium.

When digested food exits the stomach, it passes through the pyloric sphincter and enters the duodenum, the first region of the small intestine. The duodenum is the introduction point for the pancreatic digestive enzymes, as well as the neutralization of stomach acid. The majority of chemical digestion occurs in the duodenum. The middle region of the small intestine is the jejunum, and the final region is the ileum. These regions are primarily responsible for nutrient absorption and have the largest concentration of microvilli. After passing through the ileum, the digested matter enters the large intestine.

Food is converted into a bolus upon swallowing, then into chyme in the stomach. The chyme travels from the stomach into the first part of the small intestine, the duodenum. The chyme then moves through the jejunum, then through the ileum before entering the large intestine. Villi are finger-like projections of the small intestine that increase the surface area of the epithelium to maximize nutrient absorption. The ilium is a part of the hip bone.

Pepsin is a protein degrading enzyme that is released by the stomach. All the other choices are released by the pancreas into the duodenum.

Microvilli are found at the microscopic level within the digestive tract to help increase surface area. The increased surface area aids in the absorption of nutrients as they pass through the small intestine. Microvilli allow for folds in the digestive tract, which in turn, increase the amount of area available for nutrient absorption.

The esophagus is responsible for transporting food from the mouth to the stomach via peristalsis, which consists of smooth muscle contractions, but does not help digest the food content in the process. The mouth, stomach, and small intestine, however, all help in the process of food digestion. The mouth introduces enzymes in the saliva, the stomach introduces pepsin, and the small intestine introduces a number of other enzymes for digestion of macromolecules.

Cholecystokinin (CCK) is a hormone released by the duodenum to signal and stimulate accessory organs for digestive enzymes. Salivary amylase digests starch in the mouth, while pepsin is used to digest proteins in the stomach.