CHAPTER 9

ENCOCRINE SYSTEM

I. OVERVIEW

-The second great controlling system of the body

-Along with the nervous system it helps to maintain homeostasis

in the body by controlling the activity of the body’s cells.

-Endocrine system is slower than the nervous system

-Uses chemical messengers called hormones that are released into

the blood to their target cells of various organs

-Major processes controlled by hormones are:

(1)growth and development, (2)body defenses, (3) maintaining

electrolyte, water, and nutrient balance in the blood, (4) regulating

cellular metabolism and energy balance

-All hormones are amino-acid based or steroids. Amino acid-based

hormones act through second messengers. Steroid hormones (made

from cholesterol) act directly on the target cell’s DNA.

-Endocrine organs are stimulated to release their hormones into the

blood by (1) hormonal stimuli, (2) humoral stimuli, or (3) neural stimuli

Negative feedback is important in regulating hormone levels in the blood.

II. HORMONES

-Defined as chemical substances secreted by cells into the extracellular

fluids that regulate the metabolic activity of other cells in the body.

-A given hormone will affect only certain tissue cells or organs, referred

to as target cells or target organs.

-In order for a target cell to respond to a hormone, specific protein

receptors must be present on its plasma membrane or in its interior.

(only when binding occurs can a hormone influence the workings of

a cell)

III. MAJOR ENDOCRINE ORGANS

-Pituitary, thyroid, parathyroid, adrenal, pineal, thymus, pancreas, and

gonads

-The hypothalamus, which is part of the nervous system, is also a major

endocrine organ because it produces several hormones and it also

controls both the anterior and posterior pituitary.

-Endocrine glands are ductless glands.

-The pancreas along with the gonads ( testes in males and ovaries in

females) are mixed glands.

IV. PITUITARY GLAND

-Size of a grape

-Hangs from stalk (called infundibulum) from the inferior surface of

the hypothalamus of the brain.

-Fits snugly surrounded by the sella turcica of the sphenoid bone

-Anterior lobe is glandular epithelium and its secretes the hormones:

(1) prolactin, (2) Follicle Stimulating Hormone (FSH), (3) Thyroid

Stimulating Hormone (TSH), (4) Lutenizing Hormone (LH),

(5) Adrenocorticotropic Hormone (ACTH), and (6) Growth Hormone (GH)

-The posterior lobe is nervous tissue and it receives two hormones made

by the hypothalamus and stores them. (1) oxytocin (2) Antidiuretic

Hormone (ADH). When stimulated by the hypothalamus the posterior

pituitary will release one of these hormones into the blood.

V. HORMONES

-POSTERIOR PITUITARY: (controlled by hypothalamus)

ADH-will study in urinary system

Oxytocin-stimulates uterine contractions during child birth and also

Stimulates the ejection of milk in nursing mother

-ANTERIOR PITUITARY (also controlled by hypothalamus)

-(1) Growth Hormone (GH)-

-(2) Prolactin- stimulates milk production in expectant mothers

-(3) Follicle Stimulating Hormone (FSH)-reproductive system

-(4) Lutenizing Hormone (LH)- reproductive system

-(5) Thyroid Stimulating Hormone (TSH)-Stimulates the thyroid gland to

secrete the thyroid hormone into the blood

-(6) Adrenocorticotropic Hormone (ACTH)-Stimulates adrenal cortex to

secrete one or both of its hormones Cortisol (glucocorticoid) or

Aldosterone (mineralcorticoid)

Cortisol-

Aldosterone-

THYROID GLAND

-Thyroid Hormone (TH)-

-Calcitonin

PARATHYROID GLAND

-Parathyroid Hormone (PTH)

THYMUS GLAND

-Thymosin –

ADRENAL GLANDS-located superior to the kidneys

-Cortisol

-Aldosterone

PANCREAS

-Insulin (Beta Cells) Islets of Langerhans

-Glucagon (Alpha cells) Islets of Langerhans

GONADS

-Testes

-Ovaries

HUMAN CHORIONIC GONADOTROPIN (HCG)

- Secreted by the embryo (chorionic vesicle) to keep the corpus

luteum secreting progesterone to keep the uterine lining from

sloughing off so embryo can maintain it’s position in the

uterus. This is the hormone tested for to check to see if

expecting.