Endocrine System Overview

The endocrine system is one of the body's two major control systems, responsible for slower, long-lasting effects using hormones.

Hormones are chemical messengers that regulate various bodily functions like reproduction, growth, metabolism, and immune responses.

Endocrine glands are ductless organs that release hormones directly into the bloodstream or lymph. They are small, scattered throughout the body, and include the pituitary, thyroid, parathyroid, adrenal, and pineal glands.

Steroids are lipid-soluble hormones, while most amino acid-based hormones are water-soluble, with the exception of thyroid hormone.

Hormones interact with target cells by activating or inhibiting specific cellular processes, leading to changes in membrane permeability, enzyme activity, secretion, or cell division.

Second messenger systems, like the cyclic AMP system and calcium signaling pathway, involve a relay of signals within a cell, allowing amino acid-based hormones to indirectly influence cellular activity.

Steroid hormones and thyroid hormone enter target cells and directly activate genes, leading to the synthesis of specific proteins that influence cellular function.

Autocrines are local chemical messengers that affect the same cells that release them, while paracrines act on different cell types nearby.

A hormone produced by the parathyroid glands that increases blood calcium levels by acting on bones, kidneys, and small intestine.

A condition where the parathyroid glands produce too much PTH, leading to high blood calcium and excessive bone breakdown.

A condition where the parathyroid glands produce too little PTH, resulting in low blood calcium, muscle cramps, and potentially respiratory problems.

The outer layer of the adrenal glands that produces three types of steroid hormones: mineralocorticoids, glucocorticoids, and gonadocorticoids.

Steroid hormones produced by the adrenal cortex that regulate sodium and potassium balance in the body.

A major mineralocorticoid that helps kidneys reabsorb sodium and excrete potassium.

Steroid hormones produced by the adrenal cortex that regulate metabolism and the body's response to stress.

A major glucocorticoid that helps regulate how the body uses energy, manages stress, and controls inflammation.

Steroid hormones produced by the adrenal cortex that are related to sex hormones, but are produced in smaller amounts throughout life.

The inner layer of the adrenal glands that produces epinephrine and norepinephrine.

Hormones produced by the adrenal medulla that help the body respond to stress and activate the sympathetic nervous system.

A hormone produced by the pineal gland that helps regulate sleep-wake cycles and circadian rhythms.

A gland located in the abdomen near the stomach that acts as both an exocrine and endocrine gland.

A hormone produced by the pancreas that lowers blood glucose levels by helping cells absorb and use glucose.

A hormone produced by the pancreas that raises blood glucose levels by stimulating the liver to release stored glucose.

Hormones can be released in response to chemical changes in blood (humoral stimuli), signals from the nervous system (neural stimuli), or other hormones (hormonal stimuli).

A process where a hormone's effect is reduced as its levels rise, preventing excessive hormone activity. It's like a thermostat regulating temperature.

A target cell's response to a hormone depends on the presence of specific receptors on its surface or inside the cell.

The time it takes for half of a hormone's concentration to be eliminated from the bloodstream. This determines how long a hormone is active.

One hormone enhances or allows another hormone to exert its full effect. Think of a teacher needing a student to pass an exam.

Two or more hormones produce the same effect, and their combined effect is greater than the sum of their individual effects.

One hormone opposes the action of another hormone. Think of pushing and pulling on a door.

A small, pea-sized gland located at the base of the brain, connected to the hypothalamus. It plays a crucial role in regulating many bodily functions.

The posterior pituitary stores and releases hormones produced by the hypothalamus. Think of a storage facility for hypothalamic hormones.

A hormone that triggers powerful uterine contractions during labor and milk ejection in nursing mothers. Think of a hormone that helps babies come into the world and receive nourishment.

A hormone that regulates water balance by stimulating the kidneys to reabsorb water, reducing urine output. Think of a hormone that helps conserve water.

The anterior pituitary produces hormones that regulate other endocrine glands. Think of the 'command center' for other endocrine organs.

A hormone that promotes growth and development of all body tissues, especially bone and muscle. Think of a hormone that helps us grow taller and stronger.

A hormone that stimulates the thyroid gland to produce and release its hormones. Think of the 'starter' for the thyroid gland.

A hormone that stimulates the adrenal cortex to produce and release its hormones. Think of the 'boss' of the adrenal cortex.