MODULE 9

Endocrine system

system of glands that releases hormones into blood

Hormone

chemical messenger that affects target cells

Target cell

cell with the correct receptor for a hormone

Hormone receptor

protein that allows a cell to respond to a hormone

Homeostasis

maintenance of internal balance

Endocrine signaling

hormones travel through blood to distant cells

Autocrine signaling

cell releases a signal that affects itself

Paracrine signaling

signal affects nearby cells

Synaptic signaling

neurons release neurotransmitters across a synapse

Direct signaling

neighboring cells communicate through gap junctions

Endocrine gland

ductless gland that releases hormones into blood

Exocrine gland

gland that releases substances through ducts

Hypothalamus

controls endocrine activity and links nervous and endocrine systems

Pituitary gland

controls many other endocrine glands

Pineal gland

produces melatonin and controls sleep cycles

Thyroid gland

produces T3 T4 and calcitonin

Parathyroid glands

produce PTH and raise blood calcium

Adrenal glands

produce hormones involved in stress and blood pressure

Pancreas

regulates blood glucose using insulin and glucagon

Water-soluble hormone

hormone that travels freely in blood

Lipid-soluble hormone

hormone that requires transport proteins

Amino acid derivative

hormone made from an amino acid

Peptide hormone

hormone made from amino acid chains

Glycoprotein hormone

peptide hormone containing carbohydrates

Eicosanoid

lipid-derived hormone made from arachidonic acid

Steroid hormone

hormone made from cholesterol

Catecholamines

epinephrine norepinephrine and dopamine

Melatonin

hormone made from tryptophan that controls circadian rhythm

Intracellular receptor

receptor located inside the cell

Cell membrane receptor

receptor located on the cell membrane

Second messenger system

pathway used by hormones that cannot cross the membrane

First messenger

hormone that starts a signaling pathway

Second messenger

intracellular molecule that carries the signal

cAMP

second messenger that activates protein kinase A

Downregulation

decrease in receptors caused by high hormone levels

Upregulation

increase in receptors caused by low hormone levels

Permissive effect

one hormone allows another hormone to work

Synergistic effect

two hormones produce a stronger effect together

Antagonistic effect

two hormones produce opposite effects

Negative feedback

response decreases the original stimulus

Positive feedback

response increases the original stimulus

Humoral stimulus

hormone release caused by changes in blood chemicals

Hormonal stimulus

one hormone causes another gland to release hormones

Neural stimulus

nervous system triggers hormone release

HPA axis

hypothalamus pituitary and adrenal control pathway

Infundibulum

structure connecting hypothalamus to pituitary

Posterior pituitary

stores and releases ADH and oxytocin

Anterior pituitary

produces and releases several hormones

Hypophyseal portal system

blood vessel system connecting hypothalamus to anterior pituitary

ADH

increases water reabsorption by kidneys

Vasopressin

another name for ADH

Oxytocin

causes uterine contractions and milk let-down

TSH

stimulates the thyroid gland

ACTH

stimulates the adrenal cortex

GH

promotes growth and protein synthesis

FSH

stimulates gamete production

LH

stimulates ovulation and sex hormone production

PRL

stimulates milk production

MSH

stimulates melanin production

TRH

hypothalamic hormone that stimulates TSH

GHRH

hypothalamic hormone that stimulates GH

GHIH

hypothalamic hormone that inhibits GH

PRF

hypothalamic hormone that stimulates PRL

PIH

hypothalamic hormone that inhibits PRL

T3

thyroid hormone that increases metabolism

T4

thyroid hormone that increases metabolism

Calcitonin

hormone that lowers blood calcium

PTH

hormone that raises blood calcium

Iodine

substance required to produce T3 and T4

Thyroglobulin

protein that binds iodine during thyroid hormone production

Colloid

material where thyroid hormones are stored

Hyperthyroidism

condition with excessive thyroid hormone

Hypothyroidism

condition with insufficient thyroid hormone

Graves disease

disorder that causes hyperthyroidism

Goiter

enlarged thyroid gland often caused by iodine deficiency

Hyperparathyroidism

condition with excessive PTH

Hypoparathyroidism

condition with insufficient PTH

Tetany

muscle spasms caused by low calcium

Adrenal medulla

inner adrenal region that produces epinephrine and norepinephrine

Adrenal cortex

outer adrenal region that produces cortisol and aldosterone

Epinephrine

hormone that produces the fight-or-flight response

Norepinephrine

hormone involved in the fight-or-flight response

Cortisol

hormone that increases blood glucose and suppresses inflammation

Aldosterone

hormone that causes sodium and water retention

RAAS

system that increases blood pressure

Renin

enzyme released by kidneys when blood pressure is low

Angiotensinogen

substance converted into angiotensin I

Angiotensin I

substance converted into angiotensin II