Chapter 17: Endocrine System Anatomy & Physiology

Vocabulary practice flashcards covering terms, anatomical structures, hormones, and clinical conditions detailed in Chapter 17 Endocrine System.

Endocrine system

A body control system composed of ductless endocrine glands that synthesize and secrete hormones directly into the blood to be transported throughout the body.

Target cells

Cells containing specific receptors for a hormone that bind the hormone and initiate a cellular response.

Ligands

Chemical messengers released by both the endocrine and nervous systems that bind to specific cellular receptors on target cells.

Hormonal stimulation

A mechanism of hormone release where an endocrine gland cell releases its hormone in response to the binding of another hormone.

Humoral stimulation

A mechanism of hormone release where an endocrine gland cell releases its hormone in response to changing levels of a nutrient or ion in the blood.

Nervous system stimulation

A mechanism of hormone release where an endocrine gland cell releases its hormone in response to direct neural stimulation.

Steroid hormones

Lipid-soluble hormones synthesized from cholesterol, including gonadal steroids (such as estrogen) and corticosteroids (such as cortisol).

Biogenic amines

Modified amino acids (monoamines) that are water-soluble (except for thyroid hormone), including catecholamines, thyroid hormone, and melatonin.

Protein hormones

Water-soluble molecules composed of chains of amino acids, representing the majority of hormones in the body.

Local hormones

Signaling molecules that do not circulate in the blood, instead acting locally by binding to the cell that released them or to neighboring cells.

Autocrine stimulation

A pattern of local hormone signaling where molecules bind to and affect the same cell that secreted them.

Paracrine stimulation

A pattern of local hormone signaling where molecules bind to and affect neighboring target cells.

Eicosanoids

A class of local hormones formed from 20-carbon fatty acids (such as arachidonic acid) within the phospholipid bilayer of the plasma membrane.

Prostaglandins

A type of eicosanoid local hormone that stimulates pain and inflammatory responses, whose formation is inhibited by aspirin and other NSAIDs.

Biological half-life

The time required to reduce a hormone's concentration in the blood to half of its original level.

Hormone-response element (HRE)

A specific sequence of DNA in the nucleus to which a lipid-soluble hormone-receptor complex binds to initiate transcription of mRNA.

Up-regulation

An increase in the number of receptors on a target cell, which increases the cell's sensitivity to a hormone.

Down-regulation

A decrease in the number of receptors on a target cell, which decreases the cell's sensitivity to a hormone.

Synergistic interaction

A hormone interaction where two or more hormones work together to reinforce each other's activity and produce a greater effect.

Permissive interaction

A hormone interaction where the activity of one hormone requires the prior or concurrent action of a second hormone.

Antagonistic interaction

A hormone interaction where one hormone opposes the physiological activity of another hormone.

Infundibulum

The stalk-like anatomic structure that connects the pituitary gland to the hypothalamus.

Posterior pituitary

The neural portion of the pituitary gland (neurohypophysis) that stores and releases antidiuretic hormone (ADH) and oxytocin produced by the hypothalamus.

Hypothalamo-hypophyseal portal system

A specialized vascular network of primary capillaries, hypophyseal portal veins, and secondary capillaries that transports regulatory hormones directly from the hypothalamus to the anterior pituitary.

Tropic hormones

Hormones secreted by the anterior pituitary (except prolactin) that stimulate other endocrine glands to synthesize and release their hormones.

Acromegaly

A clinical condition in adults resulting from excessive growth hormone production, characterized by enlargement of the bones of the face, hands, and feet.

Pituitary dwarfism

A disorder caused by inadequate growth hormone production, resulting in short stature and hypoglycemia.

Pituitary gigantism

A condition caused by hypersecretion of growth hormone during childhood, leading to excessive growth, hyperglycemia, and enlarged internal organs.

Follicular cells

Simple cuboidal epithelial cells that enclose the follicle lumen in the thyroid gland and synthesize thyroglobulin (TGB).

Colloid

A viscous, protein-rich fluid housed within the follicle lumen of the thyroid gland containing thyroglobulin and precursor molecules.

Parafollicular cells

Cells located between the thyroid follicles that synthesize and release the hormone calcitonin.

Calcitonin

A hormone secreted by parafollicular cells in response to elevated blood calcium levels that acts to decrease blood calcium by inhibiting osteoclasts and increasing urinary calcium excretion.

Graves disease

An autoimmune cause of hyperthyroidism resulting from a loss of feedback control in the thyroid gland.

Hashimoto thyroiditis

An autoimmune cause of hypothyroidism resulting from immune system destruction of the thyroid gland.

Zona glomerulosa

The thin, outer cortical layer of the adrenal gland that synthesizes mineralocorticoids such as aldosterone.

Zona fasciculata

The thick, middle cortical layer of the adrenal gland that synthesizes glucocorticoids such as cortisol.

Zona reticularis

The thin, inner cortical layer of the adrenal gland that synthesizes gonadocorticoids (adrenal androgens).

Aldosterone

A mineralocorticoid produced by the zona glomerulosa that fosters $Na^+$ retention and $K^+$ secretion in the kidneys.

Cortisol

A glucocorticoid produced by the zona fasciculata that increases blood levels of nutrients, particularly glucose, during stress.

Cushing syndrome

A condition caused by chronic exposure to excessive glucocorticoid hormones, characterized by obesity, hypertension, hirsutism, and kidney stones.

Addison disease

A form of adrenal insufficiency characterized by a chronic shortage of glucocorticoids and mineralocorticoids due to adrenal gland failure.

Pancreatic islets

Microscopic clusters of endocrine cells (also known as islets of Langerhans) within the pancreas containing alpha, beta, delta, and F cells.

Alpha cells

Endocrine cells within pancreatic islets that detect decreases in blood glucose and secrete glucagon.

Beta cells

Endocrine cells within pancreatic islets that detect increases in blood glucose and secrete insulin.

Type 1 diabetes

A metabolic disease characterized by absent or diminished release of insulin due to autoimmune destruction of pancreatic beta cells.

Type 2 diabetes

A metabolic disease characterized by decreased insulin release or reduced insulin sensitivity in target cells, strongly associated with obesity.

Hypoglycemia

A state of abnormally low blood glucose concentration, specifically defined as levels falling below $60\,mg/dL$.

Pineal gland

An unpaired endocrine structure located in the epithalamus of the diencephalon that secretes melatonin at night to regulate circadian rhythms.

Parathyroid hormone (PTH)

A hormone produced by chief cells in the parathyroid glands that acts to increase blood calcium levels.

Erythropoietin (EPO)

A hormone released by kidney endocrine cells in response to low blood oxygen that stimulates red blood cell production in bone marrow.

Leptin

A hormone secreted by adipose connective tissue that binds to neurons in the hypothalamus to regulate appetite.