Biol2302_Chapter16__1_

Endocrine System

A system of glands that secrete hormones directly into the bloodstream to regulate various functions in the body.

Autocrine signaling

A type of signaling in which a cell signals to itself by releasing a ligand that binds to receptors on its own cell surface.

Paracrine signaling

A form of cell signaling in which cells communicate with nearby cells through the release of chemical messengers.

Endocrine signaling

Signaling in which hormones produced in one part of the body travel through circulation to affect distant target cells.

Exocrine Glands

Glands that secrete non-hormonal substances through ducts to the surface of membranes, such as sweat and salivary glands.

Endocrine Glands

Ductless glands that release hormones directly into the surrounding extracellular fluid.

Neuronal Signaling

The signaling process in the nervous system that involves the quick transmission of electrical impulses and the release of neurotransmitters.

Hormones

Chemical messengers released into the extracellular fluids that regulate metabolic processes in target cells.

Receptor

A protein molecule on the surface or inside of a cell that binds to a specific hormone, initiating a cellular response.

Half-life of Hormones

The time required for the level of a hormone in the blood to decrease by half, which varies among different hormones.

Pituitary Gland

A gland located at the base of the brain that secretes various hormones regulating other endocrine glands.

Thyroid Hormone

A hormone produced in two forms, T4 (thyroxine) and T3 (triiodothyronine), which regulate metabolism and development.

Calcitonin

A hormone produced by parafollicular cells of the thyroid gland that lowers blood calcium levels by inhibiting osteoclast activity.

Parathyroid Hormone (PTH)

The primary hormone responsible for regulating calcium levels in the blood by acting on bones, kidneys, and the intestine.

Aldosterone

A mineralocorticoid hormone produced by the adrenal cortex that regulates sodium and potassium levels in the blood.

Cortisol

A glucocorticoid hormone produced by the adrenal cortex that influences glucose metabolism and helps the body respond to stress.

Insulin

A hormone secreted by the pancreatic beta cells that lowers blood glucose levels by facilitating its uptake into tissues.

Glucagon

A hormone secreted by the pancreatic alpha cells that increases blood glucose levels by promoting glycogenolysis and gluconeogenesis.

Melatonin

A hormone produced by the pineal gland that regulates sleep-wake cycles and has antioxidant properties.

Hypothalamus

A brain region that regulates the endocrine system by sending signals to the pituitary gland and controlling hormone release.