Endocrine slide 1

Vocabulary terms and definitions covering general endocrine principles, chemical signaling, hormone interaction mechanisms, and hypothalamic-pituitary relationships.

Endocrine System

A major body regulatory system that uses hormones released into the bloodstream to target specific receptors, producing widespread and long-lasting effects.

Primary Endocrine Organs

Organs whose primary function is hormone secretion, including the anterior pituitary gland, thyroid gland, parathyroid gland, adrenal cortex, pancreas, and thymus.

Secondary Endocrine Organs

Organs that produce hormones as a secondary function while performing other primary physiological duties, such as the heart, liver, and kidneys.

Autocrine Signaling

A form of chemical signaling where a secreted chemical targets the cell that released it or other cells of the exact same type.

Paracrine Signaling

A form of chemical signaling where a secreted chemical targets nearby cells of a different cell type.

Endocrine Signaling

A form of chemical signaling where a hormone travels through the bloodstream to target distant cells of a different type.

Hormonal Stimuli

Regulation of hormone secretion where the release of a hormone is triggered by another hormone.

Humoral Stimuli

Regulation of hormone secretion where changes in the concentration of specific ions or nutrients in the blood or extracellular fluid trigger hormone release.

Neural Stimuli

Regulation of hormone secretion where nerve signals directly stimulate an endocrine gland to release hormones.

Hydrophilic Hormones

Water-soluble hormones that travel freely in the blood but cannot cross the lipid plasma membrane, binding instead to cell surface receptors.

Hydrophobic Hormones

Lipid-soluble hormones that require carrier proteins to travel in blood, pass freely through plasma membranes, and bind to intracellular receptors in the cytosol or nucleus.

Up-regulation

The process by which target cells increase their display of specific hormone receptors over time to increase sensitivity to that hormone.

Down-regulation

The process by which target cells decrease their display of specific hormone receptors over time to reduce sensitivity to that hormone.

Amino Acid-Based Hormones

Hormone chemical class comprising amines (single amino acid derivatives), peptides, or proteins; typically hydrophilic, with thyroid hormones as an exception.

Steroid Hormones

Lipid-soluble, hydrophobic hormones derived from cholesterol that feature a characteristic hydrocarbon ring structure.

Second Messenger System

An intracellular cascade triggered by hydrophilic hormone binding to a cell surface receptor, activating a membrane protein (like a G protein) and enzyme to produce internal signaling molecules.

cAMP (Cyclic Adenosine Monophosphate)

A common intracellular second messenger synthesized by adenylate cyclase that activates protein kinases to phosphorylate target proteins.

Synergistic Interaction

A hormone interaction where two or more hormones act together on a target cell to reinforce and amplify each other's effects.

Permissive Interaction

A hormone interaction where one hormone requires the prior or simultaneous activity of another hormone to exert its full function.

Antagonistic Interaction

A hormone interaction where the physiological action of one hormone directly opposes the action of another hormone.

Hypothalamus

A small anterior-inferior region of the diencephalon that controls body temperature, hunger, thirst, fluid balance, sleep/wake cycles, and directly regulates the pituitary gland.

Infundibulum

The connective stalk through which the pituitary gland attaches to the bottom of the hypothalamus.

Adenohypophysis

The anterior portion of the pituitary gland composed of glandular tissue that produces and releases regulatory hormones.

Neurohypophysis

The posterior portion of the pituitary gland composed of nervous tissue that stores and secretes hypothalamic neurohormones.

Hypophyseal Portal System

A vascular network of capillary beds resting on the infundibulum and pituitary gland that allows hypothalamic hormones to bypass systemic circulation to directly reach the anterior pituitary.

Antidiuretic Hormone (ADH)

Also known as vasopressin, a neurohormone synthesized in the hypothalamus and stored in the posterior pituitary that promotes water retention in kidneys and vasoconstriction.

Aquaporins

Water channels inserted into renal tubule cell membranes in response to ADH signaling to allow water reabsorption back into the cytosol and blood.

Osmoreceptors

Specialized hypothalamic cells that detect changes in blood solute concentration to regulate ADH release.

Diabetes Insipidus

An endocrine disorder caused by an abnormal deficiency of ADH, leading to excessive urination, extreme thirst, and dehydration.

Oxytocin

A hypothalamic neurohormone stored in the posterior pituitary that stimulates uterine smooth muscle contractions during birth and milk ejection from mammary glands.

Thyroid-Stimulating Hormone (TSH)

An anterior pituitary tropic hormone (thyrotropin) stimulated by TRH that promotes development of the thyroid gland and secretion of thyroid hormones.

Adrenocorticotropic Hormone (ACTH)

An anterior pituitary tropic hormone (corticotropin) stimulated by CRH that causes the adrenal cortex to develop and secrete steroid hormones like glucocorticoids.

Prolactin (PRL)

An anterior pituitary hormone stimulated by PRH and inhibited by dopamine (PIH) that promotes milk production in mammary glands.

Luteinizing Hormone (LH)

An anterior pituitary gonadotropin stimulated by GnRH that triggers ovulation in females and stimulates sex hormone production in male and female gonads.

Follicle-Stimulating Hormone (FSH)

An anterior pituitary gonadotropin stimulated by GnRH that promotes ovarian follicle maturation in females and sperm production in males.

Growth Hormone (GH)

An anterior pituitary hormone (somatotropin) stimulated by GHRH that stimulates target tissues to release insulin-like growth factors (IGFs) to promote body growth and metabolism.

Melanocyte-Stimulating Hormone (MSH)

An anterior pituitary hormone that increases melanosome activity inside melanocytes.

Endorphins

Neuropeptides produced by the anterior pituitary that block pain sensation, reduce cortisol release, and promote mood elevation.