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Endocrine System

system of ductless glands that release hormones into the circulation


messenger molecules that travel in the circulatory vessels and signal physiological changes in target cells

True Endocrine Organs (5)

Pituitary Gland
Pineal Gland
Thyroid Gland
Parathyroid Glands
Adrenal Glands

Other Endocrine Glands (4)


Types of Hormones (2)

Steroids- lipid molecules derived from cholesterol
Amino Acid Based Hormones- peptides, proteins, and modified amino acids

Target Cells

-have specific receptors which bind to specific hormones and then react in a pre-programmed response

Path of Hormones

secreted from particular gland ----(neural/blood pathway)----> target cell ---->physiological response

Types of Hormone Stimuli


Humoral Stimuli

endocrine glands secrete hormone in direct response to change in the blood

Neural Stimuli

nerve fibers stimulate cells within endocrine gland to release hormones

Hormonal Stimuli

hormones from certain endocrine glands secrete hormones that stimulate other endocrine glands so that they released their hormone

Negative Feedback

Hormone secretion is started/stopped based on a set blood concentration level. Once the blood concentration achieves homeostasis hormone secretion stops.

Positive Feedback

As blood concentration of hormone increases, the effector organ secretes more hormone ex:oxytocin

Divisions of the Pituitary Gland

Anterior Lobe (composed of glandular tissue)
pars distalis
pars intermedia
pars tuberalis
Posterior Lobe (composed of neural tissue)
pars nervosa

Pituitary Anterior Lobe Hormones

-Thyroid Stimulating Hormone
-Adrenocorticotropic Hormone
-Follicle Stimulating Hormone
-Luteinizing Hormone

-Growth Hormone
-Melanocyte Stimulating Hormone

Growth Hormone (GH)

type of cells: somotropic
target organ: liver, muscle, bone, etc.
response: stimulated protein synthesis, somatic growth

Thyroid Stimulating Hormone (TSH)

type of cells: thyrotroph
target organ: thyroid gland
response: stimulates thyroid to release TH

Adrenocorticotropic Hormone (ACTH)

type of cells: corticotroph
target organ: adrenal cortex
response: release of adrogens

Follicle Stimulating Hormone (FSH)

type of cells: gonadotropic cells
target organ: gonads
response: stimulates estrogen/testosterone production

Prolactin (PRL)

type of cells: prolactin
target organ: breast tissue
response: lactation

Posterior Lobe Hormones

Neural Stimuli
-Antidiuretic Hormone (ADH)

Antidiuretic Hormone (ADH)

target: kidneys
response: kidney cells resorb water and return it to blood


target: uterus, breasts
response: uterine contractions, milk ejection

Thyroid Gland

location: anterior neck
thyroid hormone (TH)

Thyroid Hormone (TH)

target: all cells
response: increased basal metabolic rate


target: kidneys
response: lowers blood calcium level

Parathyroid Gland/Hormone

location: posterior surface of thyroid gland
Parathyroid Hormone (PTH)
produced by chief cells
target: kidneys
effect: increases blood calcium level

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