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The Endocrine System Notes
I. Major Endocrine Organs
Gland
Pineal
Hormone Released
Melatonin
Hypothalamus
Hypothalamic-releasing &
release-inhibiting
hormones
Anterior
Pituitary
Growth hormone (GH)
Soft tissues, bones
Stimulates protein synth. & bone growth
______________________
Mammary glnds
Reg. Oogenesis & spermatogenesis
Luteininzing Hormone;
______________________
________________________________________________
Follicle stimulating
hormone (FSH);
_______________________
Stimulate secretion of gluco-corticoids
Adrenocorticotropic
hormone (ACTH)
_______________________
Posterior
Pituitary
Thyroid
Target Tissue / Organ
Chief Function of Hormone
Involved in daily rhythms; possibly involved in maturation of sex
organs
Regulate anterior pituitary hormones
Stimulates milk production & secretion
Stimulate secretion of ______________________________________
Thyroid stimulating
(TSH)
_______________________
______________________
Uterus,mammary glands
Uterine contractions, release of milk
____________________
All tissues
_____________________
Bones, kidneys, intestine
______________________________
Increases metabolic rate; helps to reglt. growth & development
______________________________________________
Antidiuretic Hormone
(ADH);
Kidneys, sweat glands
_______________________
Increases rate of cellular metabolism
Triiodothyronine (T3)
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Parathyroid
Parathyroid hormone
(PTH)
Bones, kidneys, intestine
__________________________________________________
Thymus
Thymosin
_________________
Stimulates maturation of T lymphocytes
Adrenal Gland
Adrenal
Medulla
Epinephrine &
Norepinephrine
Cardiac & other muscles
Stimulate ____________________ reaction; raise blood
_______________________________________________
Glucocorticoids ex.
Cortisol
________________
______________________________
Mineralcorticoids ex.
________________
Increase reabsorption of ______ & to excrete __________
Adrenal Cortex
Aldosterone
Androgens ex. DHEA
Pancreas
Gonads
Ovaries
Testes
_____________________
Stimulate onset of ___________, female sex drive
________________
Lowers blood ________________
Glucagon
Liver, muscles, adipose
tissues
_______________
____________________
Uterus
Regulates menstrual cycle, secondary sex characteristics.
_____________________
_____________________
______________________
Uterus
Pelvis, cervix
Dilates cervix & birth canal
Inhibits ____________________
_____________________
Testes
Regult. spermatogenesis, secondary sex characteristics
Inhibin
_______________
Ant. Pituitary
___________blood glucose levels
Reg.menstrual cycle, pregnancy
inhibits FSH release
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The Endocrine System Notes
I. Hormones:
A. Endocrine system produces hormones that are important in maintaining homeostasis & regulating reproduction &
development.
B. A Hormone is a chemical messenger produced by a cell that effects specific change in the cellular activity of other cells
(target cells).
C. Unlike exocrine glands that release their products at the body’s surface or into body cavities through ducts, the endocrine
glands do not secrete substances into ducts instead their hormones are secreted directly into the surrounding extracellular
space & then diffuse into nearby capillaries & are transported throughout the body in the blood.
D. The endocrine & nervous systems often work together to maintain homeostasis.
E. The nervous system uses neurotransmitters to act on cells (which is usually short-lived) to maintain homeostasis
F. The endocrine system uses hormones (which effects last longer) to produce homeostasis.
G. Hormones are classified into 2 basic categories: peptides (including amino acids, polypeptides, & proteins) & steroids
(complex rings of carbon & hydrogen atoms) synthesized by cholesterol. Ex. Gonadal hormones adrenocortical hormones
H. Pituitary – found in sella turcia pea-size, master gland. The Anterior pituitary has hormone production glandular portion.
The Posterior pituitary neural portion & extension of hypothalamus. Ex. GH (bone & muscle) & TSH (growth of thyroid)
I. Thyroid-Found in anterior throat overlying inferior border of larynx. One of the largest endocrine glands & has a heavy
blood supply. Ex. Thyroid hormone T3 & T4 contain iodine.
J. T3-T4 Function to 1) accelerate cellular metabolism, 2) tissue growth, 3) skeletal reproductive & nervous system
development.
K. Thyroid gland unique because it can store & slowly release its hormones (up to 3 months worth)
L. Over active & uner active thyroid can cause severe disturbances. Ex. Hypothroid syndrome – goiter; Severe hypothyroidism
– cretinism; Graves disease-most common.
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M. Parathyroid – 4 to 8 embedded in posterior aspect of thyroid gland. Ex. PTH important in controlling level of calcium in
blood.
N. Hyperparathyroidism-rare result of PTH defiency untreated death may occur. Kidney stones, reflexes & skeletal muscle
weakness.
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O. Adrenal glands almond size atop the kidneys.
1. Adrenal Medulla- epinephrine & norepinephrine
2. Adrenal cortex- corticosteroids
P. Pancreas- located partially behind the stomach. Endocrine & exocrine – Islets of Langerhans-minute clusters of cells that
produce pancreatic hormones. Ex. Insulin-lowers blood sugar levels: hypoglycemic; Glucagon-causes release of glucose into
blood-major target cell are liver cells: hyperglycemic
Q. Pineal located in brain secretes melatonin fuction is unclear.
II. Hormone Action
A. Hormones activate target cells by 1 of 2 methods, depending upon the chemical nature of the hormone:
1) peptide hormones {water soluble} that bind to a receptor protein on the plasma membrane of the cell. The receptor
protein, then stimulates the production of a second messenger (either cAMP or calcium.)
2) steroid hormones {lipid soluble} that diffuse through the plasma membrane of the target cell & bind to receptor protein
present in the cytoplasm that activates a DNA segment that turns on specific genes.
III. Control of Hormone Production
A. Endocrine glands release hormones in response to 1 or more of the following stimuli:
1. Hormones form other endocrine glands
2. Chemical characteristics of the blood
3. Neural stimulation
4. most hormone production is regulated by negative feedback system.
a. negative feedback: hormones secretion is triggered by some internal or external stimulus, then rising hormones
levels inhibit further hormone release resulting in blood levels of many hormones varying only within a very narrow margin.
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IV. Communication b/w the Hypothalamus & Pituitary Glands
A. Communication b/w the hypothalamus & the Anterior Pituitary Gland occurs through chemicals that are produced by the
hypothalamus & delivered to the ant. pituitary through blood vessels.
B. Communication b/w the hypothalamus & the Posterior Pituitary Gland occurs through neurosecretory cells that connect the
2 glands.
V. Antagonistic Hormones
A. When the body hormone levels drop below normal homeostasis levels the antagonistic hormones are secreted to bring the
body back to homeostasis.
B. Ex. Bundles of cells in the pancreas called the islets of Langerhans contain 2 kinds of cells alpha (secrete glucagons) & beta
(secrete insulin) cells, that control blood glucose concentrations by producing the antagonistic hormones insulin & glucagon
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VI. Major Endocrine Organs
Gland
Hormone Released
Pineal
Melatonin
Hypothalamus
Hypothalamic-releasing Anterior
& release-inhibiting
pituitary
hormones
Anterior
Pituitary
Growth hormone (GH)
Soft tissues,
bones
Stimulates protein synth. &
bone growth
Prolactin;
Mammary glnds
Stimulates milk production &
secretion
Luteininzing Hormone;
Ovary, testes
Follicle stimulating
hormone (FSH);
Gonads
Reg. Oogenesis &
spermatogenesis
Adrenocorticotropic
hormone (ACTH)
Adrenal cortex
Thyroid stimulating
(TSH)
Thyroid
Posterior
Pituitary
Oxytocin
Uterus,mammary Uterine contractions, release of
glands
milk
Thyroid
Parathyroid
Antidiuretic Hormone
(ADH);
Target Tissue /
Organ
Various Tissues
Chief Function of Hormone
Involved in daily rhythms;
possibly involved in maturation
of sex organs
Regulate anterior pituitary
hormones
Same as LH
Stimulate secretion of glucocorticoids
Stimulate secretion of T3 & T4
Kidneys, sweat
glands
Increases water retention
Thyroxin (T4)
All tissues
Calcitonin
Bones, kidneys,
intestine
Bone
Increases metabolic rate; helps
to reult. growth & development
Triiodothyronine (T3)
Parathyroid hormone
(PTH)
Bones, kidneys,
intestine
Lowers blood calcium levels
Increases rate of cellular metabolism
Raises blood calcium levels
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Thymus
Thymosins
T lymphocytes
Stimulates maturation of T
lymphocytes
Epinephrine &
Norepinephrine
Glucocorticoids ex.
Cortisol
Mineralcorticoids ex.
Aldosterone
Androgens ex. DHEA
Cardiac & other
muscles
All tissues
Stimulate “fight-or-fight”
reaction; raise blood glucose lvl.
Raises blood glucose level
Kidneys
Increase reabsorption of Na+ &
to excrete K+
Stimulate onset of puberty,
female sex drive
Gland
Hormone Released
Chief Function of Hormone
Pancreas
Insulin
Glucagon
Target Tissue /
Organ
Liver, muscles,
adipose tissues
Liver
Gonads
Ovaries
Estrogen
Uterus
Testes
Progesterone
Relaxin
Inhibin
Testosterone
Uterus
Pelvis, cervix
Ant. pituitary
Testes
Inhibin
Ant. Pituitary
Regulates menstrual cycle,
secondary sex characteristics.
Reg.menstrual cycle, pregnancy
Dilates cervix & birth canal
Inhibits FSH release
Regult. spermatogenesis,
secondary sex characteristics
inhibits FSH release
Adrenal Gland
Adrenal
Medulla
Adrenal
Cortex
Sex organs, skin,
muscles
Lowers blood glucose levels
Increases blood glucose levels
VII 2 kinds of Glands
Endocrine
&
Exocrine
-ductless
ducts
-release hormones in blood
-nonhormonal products
-rich vascular & lymph drainage
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ex. Pituitary & Thymus
ex. Pancreas
thyroid & parathyroid
gonads
adrenal & pineal
*Note: Hypothalamus is a neuroendocrine organ.
*hormones also produced by small intestine, stomach, kidneys, heart, placenta
VIII Process controlled by hormones:
Reproduction
Growth & development
Mobilization of body defenses
Energy Balance
Maintenance of electrolyte, water & nutrient balance of blood
Cellular metabolism
VIX,
There are 2
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