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Flashcards in endocrine system Deck (54)
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Works with the NS to bring about homeostasis.

use specific communication methods and affect specific target organs.

Releases hormones into the bloodstream for distribution throughout the body

Longer periods of effect compared to the N.S.

endocrine system


secretions released into ducts opening onto epithelial surfaces

located within highly vascularized areas to ensure access to the bloodstream

Exocrine glands


: ductless organs that secrete their secretions directly into the blood

located within highly vascularized areas to ensure access to the bloodstream

Endocrine glands


Molecules that have an effect on specific organs.

Only target cells with specific receptors for the hormone respond to that hormone.

Organs, tissues, or cells lacking the specific receptor do not respond to its stimulating effects.

Three types: peptide, steroid, biogenic



most of our body’s hormones

Formed from chains of a.a., also called protein hormones

Combine with receptors on target cell’s membrane, second messenger system

Ex. growth hormone

Peptide hormones


Derived from cholesterol

Easily diffuses through membranes, form hormone-receptor complex in nucleus and can activate specific genes, transcribe mRNA and make proteins.

Ex. testosterone

Steroid hormones


Small molecules produced by altering the structure of a specific amino acid

Can either bind to receptors on membrane or in cytoplasm

Ex. thyroid hormone

Biogenic amines


A stimulus starts a process, and eventually either the hormone that is secreted or a product of its effects causes the process to slow down or turn off.

Most common control system used by body

Ex. regulation of the blood glucose levels in the body

Negative Feedback Loop


Accelerates the original process, either to ensure that the pathway continues to run or to speed up its activities.

Only a few positive feedback loops occur.

Ex. process of milk release from the mammary glands

positive feedback loop


As the master control center of the endocrine system, oversees most endocrine activity.

Special cells secrete hormones that influence the secretory activity of the ant. pit. (regulatory hormones)
releasing hormones (RH)
inhibiting hormones (IH)

Directly oversees the stimulation and hormone secretion of the adrenal medulla.

Hypothalamic Control of the Endocrine System


Produces two hormones that are transported to and stored in the posterior pituitary

antidiuretic hormone (ADH)

Some endocrine cells are not under direct control of hypothalamus.

Ex. parathyroid hormone



Lies inferior to the hypothalamus.

Small, slightly oval gland housed within the sella turcica of the sphenoid bone.

Attached to the infundibulum

Partitioned into anterior and posterior pituitary.

Controlled by regulatory hormones from the hypothalamus. Hormones reach the ant. pit. via hypothalamo-hypophyseal portal system.

Pituitary Gland (Hypophysis)


GH, growth, protein synthesis, lipid mobilization. Target: all cells

Growth hormone


TSH, stim. thyroid gland secretions. Target: thyroid gland

Thyroid-stimulating hormone


ACTH, stim. glucocorticoid secretions. Target: adrenal cortex

Adrenocorticotropic hormone


LH, ovulation, uterine lining, progesterone secretion. Target: ovary cells, uterus

Luteinizing hormone


FSH, estrogen secretion, follicle development. Target: ovary cells

Follicle stimulating hormone:


PRL, milk production. Target: mammary glands



Secretions produced by hypothalamus but released by post. pit



: ADH, reabsorption of water, increase blood volume. Target: kidney

Antidiuretic hormone


ejection of secretions from targets. Target: ductus deferens, prostate. Female: labor contractions, milk ejection. Target: uterus, mammary gland



Located immediately inferior to the thyroid cartilage (larynx) and anterior to the trachea. Palpated easily, size varies

Distinctive “butterfly” shape due to its left and right lobes, connected at the isthmus.

Regulation of thyroid hormone secretion depends upon a thyroid gland–pituitary gland negative feedback process.

Starts with hypothalamus release of TRH then ant. pit. releases TSH then thyroid gland releases T4 to body cells

Thyroid Gland


T4, follicle epithelium, regulates metabolism, O2 consumption. Target: most cells



CT, C cells, decrease Ca+ con. in body fluids, inhibits osteoclasts, stim. Ca+ excretion by kidneys. Target: bone and kidneys



Small, brownish-red glands located on the posterior surface of the thyroid gland. Usually four small nodules (range two to six)

Two different types of cells in the parathyroid gland:
chief cells
oxyphil cells: function not known.

Parathyroid Glands


PTH, chief cells,

stimulates osteoclasts to reabsorb bone and release Ca+ from bone matrix into the bloodstream

stimulates calcitriol hormone synthesis in the kidney, promotes calcium absorption in the small intestine

prevents the loss of Ca+ during the formation of urine.

Target: bone, kidney

Parathyroid hormone


Sits atop kidneys, yellow (lipids) pyramidal shape, surrounded by capsule, retroperitoneal

Synthesize more than 25 different steroid hormones, collectively called corticosteroids.

corticosteroid synthesis is stimulated by the ACTH produced by the ant. pit.

corticosteroids are vital to our survival; trauma to or removal of the adrenal glands requires corticosteroid supplementation throughout life.

Adrenal Gland


: inner core, blood vessels, with ANS

Medulla (adrenal gland)


increase HR, cardiac muscle contraction, BP, glycogen breakdown. Target most cells

Epinephrine & norepinephrine (adrenal gland)


outer sections, corticosteriod group

Cortex (adrenal gland)