Endocrine System and Hormone Regulation Vocabulary

A comprehensive list of vocabulary terms and definitions covering the endocrine organs, hormone types, and feedback mechanisms from the Chapter 1 lecture notes.

Endocrine system

A system dealing with the release of hormones from ductless organs into the blood to maintain homeostasis.

Exocrine system

A system of organs that uses ducts to release substances, such as sweat glands or sebaceous glands.

Autocrine hormone

A hormone that acts localized in the specific area where it was released, binding back to the cell that released it.

Paracrine hormone

A short traveling hormone that is able to travel a bit longer of a distance than autocrine hormones.

Circulating hormone

A hormone that is able to travel a further distance through the blood from where it was released.

Negative feedback

A regulation mechanism that ensures balance by carrying out actions to decrease the initial stimulus.

Positive feedback

A regulation mechanism that amplifies or increases an initial stimulus until a process is completed, such as oxytocin during labor.

Hypothalamus

The structure in the brain that regulates the endocrine system by producing releasing, inhibiting, antidiuretic, and oxytocin hormones.

Infundibulum

A small spot or connection that links the hypothalamus to the pituitary gland.

Posterior pituitary gland

The lobe of the pituitary gland that does not make its own hormones but secretes ADH and oxytocin made by the hypothalamus.

Anterior pituitary gland

The lobe of the pituitary gland that produces and secretes a class of hormones known as tropic hormones.

Tropic hormones

A class of hormones that, when released, sends a signal to another organ to release its own hormone.

Trophic hormones

Hormones that allow for the growth of cells or organs.

Thyroid stimulating hormone (TSH)

A hormone produced by the anterior pituitary that targets the thyroid gland.

Follicle stimulating hormone (FSH)

A tropic hormone that targets the gonads to release inhibin, estrogens, or facilitate sperm/egg regulation.

Pineal gland

A gland in the posterior aspect of the brain that produces melatonin for sleep regulation.

Isthmus

The central portion of the thyroid gland that connects its two lobes.

Calcitonin

A hormone produced by the C cells of the thyroid gland that lowers blood calcium levels when they are too high.

Parathyroid glands

Four small dots located behind the thyroid that release parathyroid hormone ($PTH$).

Parathyroid hormone ($PTH$)

A hormone released by principal cells that increases blood calcium levels by targeting bones, intestines, and kidneys.

Antagonistic effect

An effect where two hormones have opposite actions to maintain balance, such as calcitonin and $PTH$.

Synergistic effect

An effect where two hormones work together to achieve the same goal, such as renin and aldosterone increasing blood pressure.

Thymus

An organ involved with the immune system that produces thymosins and typically atrophies as a person ages.

Erythropoietin

A hormone released by the kidney responsible for the synthesis or production of erythrocytes ($red blood cells$).

Calcitriol

A form of Vitamin $D$ released by the kidney that works synergistically with $PTH$ to increase calcium absorption.

Alpha cells

Cells in the pancreatic islets that produce glucagon to increase blood sugar.

Beta cells

Cells in the pancreatic islets that produce insulin to decrease blood sugar.

Delta cells

Cells in the pancreatic islets that produce somatostatin to regulate glucagon and insulin.

Adrenal medulla

The center portion of the adrenal gland that produces epinephrine ($adrenaline$) and norepinephrine.

Zona glomerulosa

The outermost layer of the adrenal cortex that makes mineralocorticoids for electrolyte balance.

Zona fasciculata

The middle section of the adrenal cortex responsible for making glucocorticoids involved in glucose metabolism.

Zona reticularis

The deepest layer of the adrenal cortex responsible for making androgens like testosterone.

Humoral stimulus

A trigger for hormone release related to changing levels of certain chemicals or ions in the blood, such as low calcium.

Neural stimulus

A trigger for hormone release caused by signal firing from nerve fibers, such as the sympathetic output to the adrenal medulla.

Hormonal stimulus

A trigger for hormone release where one hormone triggers the release of another hormone.