Endocrine System Overview

The complex of a hormone and its receptor that binds to specific DNA regions to regulate gene expression.

A type of cellular receptor found inside the cell that directly interacts with DNA to regulate gene expression. Examples include steroid hormone receptors like estrogen, androgen, and progesterone receptors.

The process of synthesizing mRNA from DNA, which is the first step in protein production.

A mechanism where the increased effect of a hormone on its target organ inhibits further hormone release, maintaining a stable hormone level within a narrow range.

A type of stimulus that triggers hormone release in response to changes in blood levels of ions and nutrients.

Chemical messengers that act locally on cells close to the secreting cell, influencing cells of the same type.

Chemical messengers that act on cells nearby the secreting cell, but different from the secreting cell.

Chemical messengers that travel long distances in blood to act on cells far away.

Receptors located on the plasma membrane of a cell, responsible for receiving water-soluble hormones.

A signaling molecule that transmits a signal from a receptor on the cell surface to the inside of the cell, activating a cascade of events.

A crucial second messenger in many cellular processes, involved in hormone signaling and regulation.

An enzyme that converts ATP into cAMP, a key step in the cAMP second messenger system.

Proteins that act as molecular switches, adding a phosphate group to other proteins to activate or inactivate them, often triggered by cAMP.

An enzyme that breaks down cAMP, halting the cAMP signaling cascade.

The endocrine system uses hormones to coordinate and integrate activity of body cells.

Hormones are chemical messengers that travel through the bloodstream to target cells.

Endocrinology is the study of hormones and the endocrine organs.

Exocrine glands release their secretions through ducts, while endocrine glands release hormones directly into the bloodstream.

Autocrine signaling involves a cell releasing a hormone that acts on itself.

Paracrine signaling involves a cell releasing a hormone that acts on nearby cells.

Endocrine signaling involves a cell releasing a hormone that travels through the bloodstream to reach distant target cells.

The pituitary, thyroid, parathyroid, adrenal, and pineal glands are major endocrine organs.

The hypothalamus is a neuroendocrine organ, meaning it has both nervous and endocrine functions.

The pancreas, gonads (ovaries and testes), and placenta produce both hormones and other substances.

Hormones are categorized as either amino acid-based or steroid hormones, based on their chemical structure and water solubility.

Amino acid-based hormones are water-soluble, meaning they cannot cross the cell membrane. They bind to receptors on the cell surface.

Steroid hormones are lipid-soluble, meaning they can cross the cell membrane and bind to receptors inside the cell.

Hormone release is triggered by humoral, neural, or hormonal stimuli.

Target cells have specific receptors for certain hormones, making them responsive to only specific hormones.

Nerve signals stimulate the release of hormones.

Hormones from one gland stimulate the release of hormones from another gland.

The nervous system can override normal endocrine control.

Hormones can only bind to cells with specific receptors.

The amount of hormone present in the blood impacts how strongly a cell responds.

A measure of how strongly a hormone binds to its receptor, indicating the strength of their interaction.

The process where cells increase the number of receptors in response to low hormone levels, making them more sensitive to the hormone.

The process where cells decrease the number of receptors in response to high hormone levels, reducing their sensitivity to the hormone.

The time it takes for half of a hormone's concentration to be eliminated from the bloodstream.

The time it takes for a hormone to exert its effects after being released.

The duration of a hormone's effects after it has been released.

A hormone's solubility in water or lipids influences its half-life, onset, and duration.