The Endocrine System Lecture Flashcards

Comprehensive vocabulary flashcards covering the processes, hormones, glands, and disorders of the endocrine system based on the lecture transcript.

Endocrine System

A system for intercellular communication using chemical signaling via hormones that generally acts over greater distances and more slowly than the nervous system.

Hormones

Chemical messengers of the endocrine system released into the extracellular fluid and transported primarily via the bloodstream to bind to receptors on target cells.

Target cells

Any cells that possess a specific receptor for a particular hormone.

Amino acid-derived hormones

Hormones such as amines, peptides, and proteins (e.g., melatonin, epinephrine) that cannot pass through the plasma membrane and must attach to receptors on the outside of the cell.

Lipid-derived hormones

Hormones such as steroids (e.g., testosterone, cortisol) that are soluble in the plasma membrane and attach to receptors inside the cell.

Intracellular Hormone Receptor Pathway

The pathway of hormone action used by steroid and thyroid hormones where the hormone-receptor complex enters the nucleus to trigger gene transcription.

Cell Membrane Receptor Pathway

The pathway of action for amino acid-derived hormones where receptors are on the outside of the plasma membrane, often utilizing cAMP as a second messenger.

Positive feedback loop

A mechanism characterized by the release of additional hormone in response to an original hormone release, such as oxytocin during childbirth or blood clotting.

Negative feedback

The most common feedback mechanism in the body, characterized by the inhibition of further secretion of a hormone in response to adequate levels of that hormone.

Humoral stimuli

A type of stimulus where an endocrine gland secretes a hormone in response to changes in blood levels of an ion or nutrient, such as $Ca^{+2}$ levels.

Hormonal stimuli

A type of stimulus where an endocrine gland secretes a hormone in response to the presence of another hormone produced by a different endocrine gland.

Neural stimuli

A type of stimulus where an endocrine gland is signaled to secrete a hormone by neurons, such as the release of epinephrine during danger.

Hypothalamus-pituitary complex

Considered the "command center" of the endocrine system because it coordinates the production and release of many hormones.

Infundibulum

A stem that suspends the pituitary gland (hypophysis) from the hypothalamus.

Neurohypophysis

The posterior pituitary gland, made of neural tissue, which stores and secretes hormones like ADH and oxytocin produced by the hypothalamus.

Adenohypophysis

The anterior pituitary gland, made of glandular tissue, which manufactures its own hormones such as GH, TSH, and ACTH.

ADH (Anti-diuretic Hormone)

A hormone that stimulates water reabsorption by the kidneys; its inhibition by alcohol leads to increased urine production.

Diabetes insipidus

A condition characterized by chronic underproduction of ADH leading to chronic dehydration and electrolyte imbalances.

Growth Hormone (GH)

A hormone that stimulates long bones and skeletal muscles to grow or undergo mitosis.

Gigantism

A disorder caused by excess GH production in children while growth plates are still open, resulting in extreme height.

Acromegaly

A disorder caused by excess GH production in adults, leading to increased growth of bones in the hands, face, and feet.

Thyroid Stimulating Hormone (TSH)

A hormone produced by the anterior pituitary that stimulates the thyroid gland to secrete thyroid hormone.

Tropic hormone

A hormone that has another endocrine gland as its target tissue.

Thyroid Hormone ($T_3$ and $T_4$)

The major metabolic hormones (triiodothyronine and thyroxine) produced in the colloid center of thyroid follicles that require iodine.

Calcitonin

A hormone produced by the thyroid gland that lowers calcium levels in the blood.

Goiter

An enlarged thyroid gland often caused by iodine deficiency leading to the overproduction of TSH.

Cretinism

Neonatal hypothyroidism in children resulting in cognitive deficits, short stature, and potentially deafness or muteness.

Graves disease

An autoimmune disease causing hyperthyroidism, often characterized by exophthalmos (protruding eyes).

Parathyroid hormone (PTH)

A hormone that increases blood calcium by stimulating osteoclasts and increasing membrane permeability to sodium.

Adrenal Cortex

The outer region of the adrenal gland consisting of the zona glomerulosa, zona fasciculata, and zona reticularis.

Aldosterone

A mineralocorticoid produced in the zona glomerulosa that causes the kidneys to reabsorb sodium, increasing blood volume and pressure.

Cortisol

A glucocorticoid produced in the zona fasciculata that acts as an anti-inflammatory steroid and increases blood glucose.

Catecholamines

A chemical class of hormones including epinephrine and norepinephrine secreted by the adrenal medulla during the "fight or flight" response.

Cushing’s Disease

A disorder caused by overproduction of corticosteroids, featuring symptoms like moon facies, buffalo hump, and weight gain.

Addison’s Disease

A disorder caused by hyposecretion of corticosteroids, causing bronzing of the skin and low blood glucose and sodium levels.

Melatonin

A hormone secreted by the pineal gland that regulates biological rhythms and sleep-wake cycles.

Human Chorionic Gonadotropin (hCG)

A hormone produced by the placenta that promotes progesterone synthesis and is detected by pregnancy tests.

Islets of Langerhans

Cell clusters in the pancreas containing alpha cells (glucagon) and beta cells (insulin).

Type 1 diabetes mellitus

An autoimmune disease affecting beta cells so no insulin is produced; accounts for $5\%$ of diabetes cases.

Type 2 diabetes mellitus

A condition where cells become resistant to insulin; accounts for $95\%$ of diabetes cases and is often associated with weight.

Thymosin

A hormone produced by the thymus gland that contributes to the maturation of T lymphocytes (T cells).

Atrial natriuretic peptide

A hormone produced by heart cells that reduces sodium and water reabsorption in the kidneys to reduce blood pressure.

Renin

A kidney secretion released during low blood pressure that triggers the RAAS and the release of aldosterone.

Erythropoietin (EPO)

A hormone released by the kidneys that triggers erythrocyte production in the red bone marrow when low blood oxygen is detected.