Chp. 9 The Endocrine System 1

Endocrine system

body system that includes internal organs that secrete hormones

Endocrinology

the study of glands, tissues, and organs that create and release hormones directly into the bloodstream

Hormones

chemical substances that are secreted by cells into the extracellular fluids and regulate the metabolic activity of other cells in the body

Amino acid-based molecules

proteins, peptides and amines

steroid/lipid soluble hormones

made from cholesterol, include sex hormones of the gonads and include hormones from adrenal cortex

Prostaglandins

hormone-like lipid compounds derived from arachidonic acid, acting as local messengers to regulate inflammation, blood flow, blood clotting, and smooth muscle contraction

Target cell

specific cell that possesses functional, specialized protein receptors allowing it to recognize and respond to a particular hormone circulating in the blood or extracellular fluid

Target organ

specific organ containing cells with receptors that bind to particular hormones, causing a functional change or response

Second messenger system

(polar): intracellular signaling pathway that relays signals from membrane-bound hormone receptors to target effector proteins, causing rapid cellular responses

Negative feedback

feedback that causes the stimulus to decline or end

Positive feedback

feedback that tends to cause a variable to change in the same direction as the initial change; enhances the stimulus

pituitary gland

neuroendocrine gland located beneath the brain that serves a variety of functions including regulation of gonads, thyroid, adrenal cortex, water balance, and lactation *most important gland

Thyroid gland

one of the largest of the body’s endocrine glands; straddles the anterior trachea *has follicles which create hormones

Parathyroid gland

small endocrine glands located on the posterior aspect of the thyroid gland and regulates calcium ions in blood

Adrenal gland

hormone-producing glands located superior to the kidneys; each consists of a medulla and cortex areas *bean-shaped

Pineal gland

small, cone-shaped gland found in the brain

Ovaries

paired, almond-sized organs located in the pelvic cavity

Testes

paired; sespended in the scrotum outside the pelvic cavity *produce sperm and androgens

Hypothalamus

the region of the diencephalon forming the floor of the third ventricle of the brain; command center linking the nervous and endocrine systems to maintain homeostasis

Ductless glands

specialized organs that secrete hormones directly into the bloodstream or surrounding fluids, rather than through ducts

Tropic hormones

specialized class of hormones produced primarily by the anterior pituitary gland that target other than endocrine glands to stimulate their growth, function, and secretion of secondary hormones

Growth hormone

somatotropin; peptide hormone produced by somatotropic cells in the anterior pituitary gland, which is located at the base of the brain

Pituitary dwarfism

an endocrine disorder caused by insufficient growth hormone production by the pituitary gland, leading to slow growth and short stature with normal body proportions

Gigantism

rare; excessive linear growth (abnormally high stature) during childhood or adolescence, before the growth plates in the bones have fused

Acromegaly

rare, chronic endocrine disorder characterized by the overproduction of growth hormone in adults, typically caused by a noncancerous tumor of the pituitary gland known as a pituitary adenoma

Prolactin (PRL)

lactotropin, polypeptide hormone synthesized and secreted by specialized cells in the anterior pituitary gland, known as lactotrophs or mammotrophs

Adrenocorticotropic hormone (ATCH

regulatory pathway where the pituitary gland releases ACTH to stimulate the adrenal cortex, primarily controlling cortisol release, metabolism, and stress response

Thyroid stimulating hormone (TST) or TH

thyrotropin, glycoprotein hormone produced by the anterior pituitary gland that regulates the endocrine function of the thyroid gland

Gonadotropic hormones

hypothalamic-pituitary-gonadal axis; complex neuroendocrine network that regulates sexual development, reproduction, and gamete production

Gonads

primary reproductive organs (testes and ovaries); secrete sex hormones

Follicle stimulating hormone (FSH)

glycoprotein hormone produced by the anterior pituitary gland that plays a vital role in sexual development and reproduction

Luteinizing hormone (LH)

glycoprotein hormone produced by the anterior pituitary gland in the brain, specifically by specialized gonadotroph cells *stimulates sex hormone production

Sterility

(infertility); inability to conceive due to a hormonal imbalance that disrupts the reproductive organs, often stemming from issues in the hypothalamic-pituitary-gonadal axis

Neurosecretory hormones

specialized neurons that translate neural signals into chemical stimuli, producing neurohormones that are released into the bloodstream

Oxytocin

peptide hormone and neurotransmitter produced in the hypothalamus and released by the posterior pituitary gland *regulates social bonding, sexual reproduction, childbirth

Antidiuretic hormone (ADH)

vasopressin; peptide hormone produced in the hypothalamus and released by the posterior pituitary gland *control water retention and bp

Vasopressin

antidiuretic hormone; peptide hormone produced in the hypothalamus and released by the posterior pituitary gland that regulates water retention and bp

Diabetes insipidus

rare endocrine disorder characterized by the body’s inability to properly balance fluid levels, resulting in the production of excessive amounts of diluted urine and extreme thirst

Thyroid gland

butterfly-shaped endocrine organ located in the anterior neck that regulates metabolism, energy levels, and growth by secreting hormines T3 and T4 directly into the bloodstream

Follicles

specialized, spherical functional units responsible for the production, storage, and release of hormones

Thyroid hormone

consists of triiodothyronine (T3) and thyroxine (T4), produced by the butterfly-shaped thyroid gland located in the lower anterior neck (C5-T1) *regulates metabolic rate, heart function, and body temp.

Thyroxine (T4)

primary hormone secreted by the thyroid gland that regulates the body’s metabolic rate, heart function, digestion, and development

Triiodothyronine (T3)

highly active thyroid hormone, crucial for regulating metabolism, heart rate, body temp., and growth

Goiters

abnormal, noncancerous enlargement of the thyroid gland, resulting in swelling at the base of the neck

Cretinism

severely stunted physical and mental growth caused by untreated congenital deficiency of thyroid hormones

Myxedema

clinical state resulting from severe, long-standing hypothyroidism (under active thyroid), acting as a systemic manifestation of endocrine failure

Graves disease

chronic autoimmune disorder of the endocrine system where antibodies mistakenly stimulate the thyroid gland, located in the neck, to produce excessive thyroid hormones; results in hyperthyroidism

Exophthalmos

abnormal, anterior protrusion of one or both eyeballs out of the orbit (eye socket)

Calcitonin

32-amino acid peptide hormone, also known as thyrocalcitonin

Parathyroid

four (sometimes more) tiny, pea-sized endocrine glands located in the neck, usually embedded on the posterior surface of the thyroid gland

Parathyroid hormone (PTH)

crucial, polypeptide hormone produced by four small, pea-sized endocrine glands located in the neck, typically behind the thyroid gland