Edit · Endocrine System: Hormones, Glands, Feedback, and Regulation

Endocrine vs. Nervous System

Endocrine: slower hormone signals through blood, longer effects. Nervous: fast electrical signals, usually shorter effects.

Endocrine Gland

Organ that produces and releases hormones into the blood.

Hormone

Chemical messenger that travels through blood and affects target cells.

Receptor

Protein that recognizes and binds a specific hormone.

Target Cell

Cell containing the correct receptor to respond to a hormone.

Water-Soluble Hormones

Cannot easily cross cell membrane; bind surface receptors and often use second messengers.

Lipid-Soluble Hormones

Pass through cell membrane and bind internal receptors; often change gene activity.

Second Messenger

Molecule inside a cell that carries a hormone's signal; example: cAMP.

Gene Activation

Hormonal signals can turn genes on or off, changing protein production.

Hypothalamus

Brain region that regulates the pituitary gland and connects nervous and endocrine systems.

Pituitary Gland

Gland below brain that releases hormones controlling growth, reproduction, and other glands.

Anterior vs. Posterior Pituitary

Anterior: produces and releases several hormones. Posterior: stores and releases ADH and oxytocin made by hypothalamus.

Growth Hormone (GH)

Stimulates growth of bones and body tissues.

Prolactin

Stimulates milk production.

TSH

Stimulates thyroid gland to release thyroid hormones.

ACTH

Stimulates adrenal cortex to release cortisol.

FSH

Helps stimulate egg development and sperm production.

LH

Triggers ovulation and stimulates testosterone production.

Endorphins

Natural chemicals that help reduce pain.

ADH

Helps kidneys retain water and reduce urine output.

Oxytocin

Stimulates uterine contractions and milk release; involved in social bonding.

Hormonal Negative Feedback

High enough hormone levels reduce further hormone release, helping maintain balance.

Thyroid Gland

Located in neck; produces T3 and T4 to regulate metabolism and calcitonin to help lower blood calcium.

Parathyroid Glands

Located behind thyroid; release PTH to raise blood calcium.

Adrenal Cortex

Outer adrenal gland; produces cortisol for stress responses and aldosterone for sodium balance.

Adrenal Medulla

Inner adrenal gland; releases epinephrine for fight-or-flight responses.

Pancreas

Located in abdomen; produces insulin and glucagon to regulate blood glucose.

Pineal Gland

Located in brain; produces melatonin to regulate sleep-wake cycles.

Insulin

Released when blood glucose rises; helps lower blood sugar.

Glucagon

Released when blood glucose falls; helps raise blood sugar.

Diabetes Mellitus

Condition involving impaired blood glucose regulation, commonly causing high blood sugar.

Hypoglycemia

Abnormally low blood glucose.

Estrogen

Supports female reproductive development and menstrual cycle regulation.

Progesterone

Prepares and maintains uterine lining for pregnancy.

Testosterone

Supports male reproductive development and sperm production.

Prairie Vole Study

Oxytocin, vasopressin, and brain receptors influence social bonding and pair-bond formation.