Ch. 16 Endocrine

Endocrine System

A system that acts with the nervous system to coordinate and integrate the activity of body cells through hormones transported in the blood.

Endocrinology

The study of hormones and endocrine organs.

Hormones

Long-distance chemical signals produced by endocrine glands that travel in blood or lymph to exert effects on target cells.

Exocrine Glands

Glands that produce nonhormonal substances and have ducts to carry secretions to membrane surfaces.

Endocrine Glands

Glands that produce hormones and lack ducts.

Target Cells

Tissues that have specific receptors for a particular hormone and are affected by that hormone.

Autocrines

Chemicals that exert effects on the same cells that secrete them.

Paracrines

Locally acting chemicals that affect cells other than those that secrete them.

Amino Acid-Based Hormones

Hormones that include amino acid derivatives, peptides, and proteins.

Steroid Hormones

Hormones synthesized from cholesterol, including gonadal and adrenocortical hormones.

Water-Soluble Hormones

Hormones that act on plasma membrane receptors and cannot enter the cell.

Lipid-Soluble Hormones

Hormones that can enter cells and act on intracellular receptors to directly activate genes.

Cyclic AMP (cAMP)

A second messenger system used by water-soluble hormones to exert their effects.

PIP2-Calcium Signaling Mechanism

A second messenger system where phospholipase C splits PIP2 into diacylglycerol (DAG) and inositol trisphosphate (IP3).

Negative Feedback

A control mechanism where increased hormone effects inhibit further hormone release.

Humoral Stimuli

Changes in blood levels of ions and nutrients that directly stimulate hormone secretion.

Neural Stimuli

Nerve fibers that stimulate hormone release.

Hormonal Stimuli

Hormones that stimulate other endocrine organs to release their hormones.

Up-Regulation

The process where target cells form more receptors in response to low hormone levels.

Down-Regulation

The process where target cells lose receptors in response to high hormone levels.

Half-Life

The time required for the level of a hormone in the blood to decrease by half.

Anterior Pituitary

The glandular part of the pituitary that secretes hormones such as GH, TSH, ACTH, FSH, LH, and PRL.

Growth Hormone (GH)

A hormone that has direct actions on metabolism and promotes growth through insulin-like growth factors (IGFs).

Thyroid-Stimulating Hormone (TSH)

A tropic hormone that stimulates the thyroid gland's development and secretory activity.

Adrenocorticotropic Hormone (ACTH)

A hormone that stimulates the adrenal cortex to release corticosteroids.

Follicle-Stimulating Hormone (FSH)

A hormone that stimulates the production of gametes (egg or sperm).

Luteinizing Hormone (LH)

A hormone that promotes the production of gonadal hormones and triggers ovulation in females.

Prolactin (PRL)

A hormone that stimulates milk production in females.

Oxytocin

A hormone that stimulates uterine contractions and milk ejection during childbirth.