Copy of 10.1 Hormones Chemical Regulators.docx

Endocrine glands

Ductless glands that secrete hormones directly into the bloodstream or extracellular fluid, allowing the signals to reach target organs with appropriate receptors.

Steroids

Lipid-soluble hormones derived from cholesterol, secreted by gonads, adrenal cortex, and placenta, passing through cell membranes to bind to protein receptors and activate gene expression.

Protein hormones

Water-soluble hormones that bind to receptors on the surface of target cells, triggering specific chemical reactions within the cell without entering it, leading to various cellular responses.

Endorphins

Protein hormones present during exercise, excitement, or pain, producing analgesia and a sense of well-being, acting as natural pain relievers.

Epinephrine (adrenaline)

Protein hormone secreted from the thyroid and adrenal medulla, increasing heart rate, constricting blood vessels, dilating air passages, and participating in the "fight or flight" response of the sympathetic nervous system.