The Endocrine System Notes

I. Major Endocrine Organs

Gland

/

Hormone Released

/ Target Tissue / Organ / Chief Function of Hormone

Pineal

/ Melatonin / Involved in daily rhythms; possibly involved in maturation of sex organs

Hypothalamus

/ Hypothalamic-releasing & release-inhibiting hormones / Regulate anterior pituitary hormones
Anterior Pituitary / Growth hormone (GH)
______
Luteininzing Hormone;
Follicle stimulating hormone (FSH);
Adrenocorticotropic hormone (ACTH)
Thyroid stimulating (TSH) / Soft tissues, bones

Mammary glnds

______

______

______

______

/ Stimulates protein synth. & bone growth
Stimulates milk production & secretion
Reg. Oogenesis & spermatogenesis

______

Stimulate secretion of gluco-corticoids

Stimulate secretion of ______

Posterior Pituitary / ______
Antidiuretic Hormone (ADH); / Uterus,mammary glands
Kidneys, sweat glands / Uterine contractions, release of milk

______

Thyroid / ______

______

Triiodothyronine (T3) / All tissues
Bones, kidneys, intestine

______

/ Increases metabolic rate; helps to reglt. growth & development
______
Increases rate of cellular metabolism
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 ______
Adrenal Cortex / Glucocorticoids ex. Cortisol
Mineralcorticoids ex. Aldosterone
Androgens ex. DHEA / ______
______
______/ ______
Increase reabsorption of ______& to excrete ______
Stimulate onset of ______, female sex drive
Pancreas / ______

Glucagon

/ Liver, muscles, adipose tissues
______/ Lowers blood ______
______blood glucose levels
Gonads
Ovaries / ______
______
______
______/ Uterus

Uterus

Pelvis, cervix

Ant. Pituitary

/ Regulates menstrual cycle, secondary sex characteristics.

Reg.menstrual cycle, pregnancy

Dilates cervix & birth canal

Inhibits ______

Testes / ______

Inhibin

/ Testes
______ / Regult. spermatogenesis, secondary sex characteristics
inhibits FSH release


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.

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.

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.

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

VI. Major Endocrine Organs

Gland

/

Hormone Released

/ Target Tissue / Organ / Chief Function of Hormone

Pineal

/ Melatonin / Various Tissues / Involved in daily rhythms; possibly involved in maturation of sex organs

Hypothalamus

/ Hypothalamic-releasing & release-inhibiting hormones / Anterior pituitary / Regulate anterior pituitary hormones
Anterior Pituitary / Growth hormone (GH)
Prolactin;
Luteininzing Hormone;
Follicle stimulating hormone (FSH);
Adrenocorticotropic hormone (ACTH) Thyroid stimulating (TSH) / Soft tissues, bones

Mammary glnds

Ovary, testes

Gonads

Adrenal cortex

Thyroid

/ Stimulates protein synth. & bone growth
Stimulates milk production & secretion
Reg. Oogenesis & spermatogenesis

Same as LH

Stimulate secretion of gluco-corticoids
Stimulate secretion of T3 & T4
Posterior Pituitary / Oxytocin
Antidiuretic Hormone (ADH); / Uterus,mammary glands
Kidneys, sweat glands / Uterine contractions, release of milk

Increases water retention

Thyroid / Thyroxin (T4)

Calcitonin

Triiodothyronine (T3) / All tissues
Bones, kidneys, intestine

Bone

/ Increases metabolic rate; helps to reult. growth & development
Lowers blood calcium levels
Increases rate of cellular metabolism
Parathyroid / Parathyroid hormone (PTH) / Bones, kidneys, intestine / Raises blood calcium levels
Thymus / Thymosins / T lymphocytes / Stimulates maturation of T lymphocytes
Adrenal Gland
Adrenal Medulla / Epinephrine & Norepinephrine / Cardiac & other muscles / Stimulate “fight-or-fight” reaction; raise blood glucose lvl.
Adrenal Cortex / Glucocorticoids ex. Cortisol
Mineralcorticoids ex. Aldosterone
Androgens ex. DHEA / All tissues
Kidneys
Sex organs, skin, muscles / Raises blood glucose level
Increase reabsorption of Na+ & to excrete K+
Stimulate onset of puberty, female sex drive

Gland

/

Hormone Released

/ Target Tissue / Organ / Chief Function of Hormone
Pancreas / Insulin
Glucagon / Liver, muscles, adipose tissues
Liver / Lowers blood glucose levels
Increases blood glucose levels
Gonads
Ovaries / Estrogen
Progesterone
Relaxin
Inhibin / Uterus
Uterus
Pelvis, cervix
Ant. pituitary / Regulates menstrual cycle, secondary sex characteristics.
Reg.menstrual cycle, pregnancy
Dilates cervix & birth canal
Inhibits FSH release
Testes / Testosterone
Inhibin / Testes
Ant. Pituitary / Regult. spermatogenesis, secondary sex characteristics
inhibits FSH release

VII 2 kinds of Glands

Endocrine & Exocrine

-ductless ducts

-release hormones in blood -nonhormonal products

-rich vascular & lymph drainage -

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 Energy Balance

Mobilization of body defenses Maintenance of electrolyte, water & nutrient balance of blood

Cellular metabolism

VIX,

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