Functional Organization of the Endocrine System Flashcards

A comprehensive set of vocabulary flashcards covering the functional organization of the endocrine system, signaling mechanisms, chemical classes, and receptor types.

Paracrine

A form of local signaling that occurs through diffusion over short distances.

Autocrine

A type of cell signaling where cells respond to signals secreted by themselves.

Endocrine system

A system comprised of glands, tissues, and cells that secrete hormones directly into the blood.

Endocrine glands

Ductless glands that secrete chemicals directly into the blood.

Exocrine glands

Glands that have ducts which empty into open areas and are not considered part of the endocrine system.

Norepinephrine

A chemical messenger that acts as both a neurotransmitter in the nervous system and a hormone in the endocrine system.

Amplitude-modulated signals

Signals where the concentration of the hormone determines the strength of the signal and the magnitude of the response.

Frequency-modulated signals

Signals where the strength depends on the frequency, rather than the size, of action potentials.

Humoral Stimuli

Control of hormone release caused by changes in body fluids, such as low calcium levels stimulating parathyroid hormone release.

Neural Stimuli

Control of hormone release where an action potential triggers the release of neurotransmitters that then cause endocrine cells to secrete hormones.

Hormonal Stimuli

A control mechanism where hormones from one gland cause endocrine cells in another gland to release hormones.

Tropic hormones

Hormones that act specifically on other endocrine cells to regulate their function.

Negative feedback

A regulatory mechanism where a hormone exerts feedback to stop the secretion of preceding hormones in its pathway.

Positive feedback

A regulatory mechanism where a hormone further stimulates the secretion of the hormones that triggered its own release.

Steroid hormones

Lipid-soluble hormones derived from cholesterol, including sex steroids like testosterone and corticosteroids like cortisol.

Thyroid hormones

Lipid-soluble hormones derived from the amino acid tyrosine, such as thyroxine ($C_{15}H_{11}I_4NO_4$).

Eicosanoids

Fatty acid derived hormones, such as prostaglandins.

Water-soluble hormones

Hydrophilic hormones, including protein, peptide, and amino acid derivatives, that travel in blood plasma and have relatively fast clearance rates.

Peptide hormones

Water-soluble hormones consisting of short chains of amino acids, such as Oxytocin and Antidiuretic hormone (ADH).

Catecholamines

Amino acid derivatives made from tyrosine, including Dopamine, Epinephrine, and Norepinephrine.

Transport proteins

Proteins such as albumins and globulins that bind to hydrophobic hormones like steroids and thyroid hormones in the blood.

Unbound hormones

Free hormones that are not attached to transport proteins; only these can leave the bloodstream or be cleared.

Nuclear Receptors

Receptors for lipid-soluble hormones that pass through the plasma membrane to control transcription, resulting in a relatively slow response.

Membrane-Bound Receptors

Cell surface receptors for water-soluble hormones that often activate G proteins and second messengers to produce quick cellular responses.

Kinases

Enzymes that add phosphates to inactive molecules to activate them within signal transduction pathways.

Agonist

A drug or chemical that binds to a receptor and activates it, mimicking the action of a natural hormone.

Antagonist

A drug or chemical that binds to a receptor and inhibits it, stopping the action of a hormone.