Biology 30 - Chapter 13

Endocrine glands

ductless glands that secrete hormones directly into the bloodstream

Hormone

chemical messenger sent to many parts of the body to produce a specific effect on a target cell or organ; examples are epinephrine and norepinephrine released from the neurons of the adrenal gland

endocrine system

in vertebrates, system that works in parallel with the nervous system to maintain homeostasis by releasing chemical hormones from various glands; composed of the hormone producing glands and tissues of the body

negative feedback mechanisms

mechanism of homeostatic response by which the output of a system suppresses or inhibits activity of the system; e.g., when a certain blood concentration of a hormone is reached, the endocrine gland releasing the hormone is inhibited by the presence of the hormone

antidiuretic hormone (ADH)

hormone regulated by the hypothalamus and released by the pituitary gland that increases the permeability of the distal tubule and the collecting duct in the nephrons of the kidneys, allowing more water to be reabsorbed into the blood from the filtrate

tropic hormones

hormone that targets endocrine glands and stimulates them to release other hormones

pituitary gland

small gland that lies just inferior to the hypothalamus; consists of the anterior and posterior pituitary, both of which produce hormones that influence metabolism, growth, development, reproduction, and other critical life functions

posterior pituitary

posterior lobe of the pituitary gland; an endocrine gland that stores and releases antidiuretic hormone (ADH) and oxytocin, which are produced in the hypothalamus and transferred to the posterior pituitary by neuronal axons

anterior pituitary

anterior lobe of the pituitary gland; an endocrine gland that synthesizes and secretes six major hormones

human growth hormone (hGH)

hormone that ultimately affects almost every body tissue, by direct stimulation or via tropic effects; stimulates the liver to secrete hormones called growth factors, which, along with hGH, influence many physiological processes, such as protein synthesis, cell division and growth, and metabolic breakdown and release of fats

thyroid gland

butterfly-shaped gland located below the larynx in the neck; produces the hormone thyroxine; helps regulate metabolism and growth

thyroxine (T4)

hormone produced by the thyroid and released into the bloodstream; controls the rate at which the body metabolizes fats, proteins, and carbohydrates for energy

Hypothyroidism

condition resulting when the thyroid produces extremely low levels of thyroxine

Hyperthyroidism

condition resulting when the thyroid produces extremely high levels of thyroxine

thyroid-stimulating hormone (TSH)

a hormone released by the anterior pituitary which causes the thyroid gland to secrete thyroxine; controlled by a negative feedback mechanism

Goitre

enlargement of the thyroid gland characterized by a large swelling in the throat, often associated with a deficiency of iodine; occurs when the thyroid gland is constantly stimulated by thyroxine-stimulating hormone (TSH), but is unable to synthesize thyroxine to create a negative feedback loop

adrenal gland

one of a pair of organs located on top of the kidneys; composed of two layers

adrenal medulla

the inner layer of the adrenal glands that produces epinephrine and norepinephrine, hormones that regulate the short-term stress response

Epinephrine

hormone produced by the adrenal cortex hormones that helps regulate the short-term stress response; also known as adrenaline

Norepinephrine

neurotransmitter released by sympathetic neurons of the autonomic system to produce an excitatory effect on target muscles; also a hormone produced by the adrenal medulla along with epinephrine to function in the short-term stress response; also known as noradrenaline

short-term stress response

the body’s acute reaction to stress in which the sympathetic nervous system is stimulated; also known as flight-or-flight response

adrenal cortex

the outer layer of the adrenal glands that produces glucocorticoids and mineralocorticoids, hormones that regulate the long-term stress response; also secretes a small amount of gonadocorticoids, female and male sex hormones that supplement the hormones produced by the gonads (testes and ovaries)

long-term stress response

sustained physiological response to stressors, characterized by increases in blood glucose and blood pressure, and decrease in inflammatory response; regulated by hormones produced by the adrenal cortex

Cortisol

a type of glucocorticoid hormone released by the adrenal cortex of the adrenal gland in a long-term stress response; triggers an increase in blood glucose levels and reduces inflammation

adrenocorticotropic hormone (ACTH)

hormone synthesized by the anterior pituitary gland to target the adrenal cortex and regulate the production of glucocorticoids

Aldosterone

a type of mineralocorticoid hormone secreted by the adrenal cortex; stimulates the distal tubule and collecting duct of the kidneys to increase the absorption of sodium into the bloodstream, which is followed by the passive absorption of water and chloride

Pancreas

small gland in the abdomen that secretes digestive enzymes into the small intestine, as well as bicarbonate to neutralize hydrochloric acid from the stomach; also secretes the hormone insulin

islets of Langerhans

cluster of endocrine cells found throughout the pancreas, consisting of glucagonproducing alpha cells and insulin-producing beta cells

beta cells

cell of the pancreas which secretes insulin to decrease the level of blood glucose

alpha cells

cell of the pancreas which secretes glucagon to increase the level of blood glucose

insulin

a hormone secreted by the beta cells of the islets of Langerhans in the pancreas to make target cells more permeable to glucose; enables the body to use sugar and other carbohydrates

Glucagon

hormone produced by the alpha cells of the islets of Langerhans in the pancreas to stimulate the liver to convert glycogen back into glucose, which is released into the blood

diabetes mellitus

a serious chronic condition that results when the pancreas does not make enough insulin or the body does not respond properly to insulin; levels of blood glucose tend to rise sharply after meals (hyperglycemia) and remain at signifi cantly elevated levels

Hyperglycemia

condition resulting from high levels of blood glucose; occurs in individuals with diabetes mellitus

type 1 diabetes

a condition in which the immune system produces antibodies that attack and destroy the beta cells of the pancreas so they are unable to produce insulin; is usually diagnosed in childhood, and patients require daily insulin injections; also known as juvenile diabetes and insulin-dependent diabetes

type 2 diabetes

a condition that develops slowly over time either because the insulin receptors on the body’s cells stop responding to insulin or because the beta cells of the pancreas produce less and less insulin over time; condition often appears in overweight adults; also known as adult-onset diabetes and non-insulin-dependent diabetes