Chapter 3A (iv) - The Endocrine System
Endocrine glands: Made of secretory cells that release their products, called hormones.
Endocrine system: Consists of endocrine glands and of organs that contain some
Major organs with endocrine tissue are:
Major glands are: - Hypothalamus
- Pituitary gland - Thymus
- Thyroid gland - Pancreas
- Parathyroid gland - Ovaries
- Adrenal gland - Heart
- Pineal gland - Placenta
- Small intestine & Kidneys
Antagonistic interaction Effect of one hormone opposes that of another hormone.
Synergistic interaction the response of a tissue to a combination of two hormones is
much greater that its response to either individual hormone.
Permissive interaction one hormone must be present for another hormone to exert its
- Suspended from the base of the brain by a short stalk.
- Stalk connects the gland to the hypothalamus
o Area of the brain that regulates physiological responses. (Body temperature,
water balance, sleeping)
- Consists of anterior and posterior lobe
- 6 hormones
o Growth hormone (GH)
o Prolactin (PRL)
o Thyroid-stimulating hormone (TSH) acts on the thyroid gland to release
o Adrenocorticotropic hormone (ACTH) tropic hormone for adrenal gland
o Follicle-stimulating hormone (FSH) promotes development of egg cells and
secretion of the hormone estrogen from the ovaries
o Luteinizing hormone (LH) causes ovulation, release of future egg cell by
the ovary in female - secretes estrogen and progesterone
Tropic hormone: A hormone produced by one endocrine gland or hormone that
influences another endocrine gland. - Anterior Lobe
o Circulatory connection
Growth Hormone (GH)
Stimulate growth through increasing in cell size and rate of cell division
Cells of bones, muscle and cartilage
Role in glucose conservation by making fats more available as a source of fuel
Too much leads to gigantism
Acromegaly - enlargement of tongue, and thickening in the bones of the hands, feet,
and face. (Happens during adulthood when bones can’t lengthen but thicken)
Dwarfism - not enough
Stimulates mammary gland to produce milk
Too much leads to sterility
- Posterior Lobe
o Neural connection
o Doesn’t produce hormone on its own
Antidiuretic hormone (ADH)
Conserve body water by decreasing urine output.
Not enough causes excessive urine production and resultant dehydration.
Stimulating the uterine contraction of childbirth.
Stimulate milk ejection
Thyroid Hormone (TH)
Regulates the body’s metabolic rate and production of heat.
Breakthrough of lipids
Use of glucose for production of ATP
Cretinism - not enough during fetal development - causes dwarfism and delayed
Too much - Graves’ disease - a person’s own immune system produced antibodies
that mimic the action of FSH.
Regulate the concentration of calcium in the blood to maintain proper functioning of
the muscles cells and neurons. Parathyroid Glands
Parathyroid Hormone (PTH)
Increases the level of calcium in the blood
Move from bone and urine into the blood
Too much causes weak bones and high levels of calcium in the blood which can cause
kidney stones, and decreased activity of the nervous system.
Outer region Adrenal Cortex
Secretes lipid-soluble hormones - steroids
Sex hormones known as Androgens and Estrogens
Affect mineral homeostasis and water balance
Aldosterone - acts on cells of kidneys to increase reabsorption of sodium ions
into the blood. - Increases water retention - Promotes secretion of K+ in urine.
Affect glucose levels
Act on liver to promote the conversion of fat and protein to intermediate substances
that are ultimately converted into glucose.
Acts on adipose tissue to breakdown fats into fatty acids
Inner region Adrenal Medulla
Secretes water-soluble hormones
Critical in the fight-or-flight response
Endocrine cells pancreatic islets
Somatosin inhibits secretion of glucagon and insulin.
Increases the level of blood sugar
Increasing conversion of glycogen to glucose
Stimulate liver to form glucose from amino acids and lactic acid Insulin
Decreases levels of glucose in the blood
Stimulates transport of glucose into muscles cells, white blood cells, and connective
Prevents conversion of amino acids and fatty acids to glucose
-Decreases in size as we age
Thymopoitein and thymosin
Promote the maturation of white blood cells called T Lymphocytes
Local signaling molecules: Act near the s