Endocrine System

Coordinates and directs the activity of the body’s cells through the release of

hormones into the bloodstream

What does this system do?

-regulates mood-regulates growth and development-regulates tissue function-regulates metabolism-regulates sexual function-regulates reproduction

Characteristics

-uses hormones to send messages-hormones secreted by glands-hormones transported through blood-organs/glands are small compared to other

systems

Chemistry of Hormones

1. Amino acid-based hormone (protein and peptide based)peptide -2 or more amino acidsproteins-10 or more amino acids

2. Steroid hormones(made from cholesterol)-consist of sex hormones made by gonads (ovaries

and testes) and hormones made by adrenal gland

How Hormones Work?

General Info-hormones affect only certain tissue cell or organs called

target cells or target organs-target cells must have protein receptors present on the

cell membrane to allow the hormone to attach -hormone must bind to the target cell to influence the

cell

How do hormones work?Second Messenger System (amino acid-based)

1. Hormone binds to receptor on the target cell membrane

2. Receptor with the hormone activates an enzyme inside the cell

3. Enzyme activates various reactions inside the cell

How do hormones work?Direct Gene Activation (Steroid hormones)1. Diffuse through the cell membrane of the target cell2. Enters the nucleus of the cell3. Binds to a protein receptor inside the nucleus4. Hormone and receptor attach to the DNA5. Activates mRNA6. mRNA leaves nucleus and makes new proteins

How are the endocrine organs activated to release hormones?

Hormone release is triggered through negative feedback mechanisms

3 ways hormones are released1. Hormonal stimuli2. Humoral stimuli3. Neural stimuli

Hormonal stimuli

-most common-endocrine organs are activated by other

hormones

Neural stimuli-nerve fibers stimulate hormone releaseExample: sympathetic nervous system stimulates

adrenal gland to release hormones(fight or flight: adrenaline rush)

Humoral Stimuli-hormone release is activated by changing blood levels of certain

nutrients-word humor indicates the various body fluids (blood, bile, and others)Example: 1. Calcium levels trigger parathyroid hormone2. Glucose levels trigger release of insulin from pancreas

Major organs of Endocrine System

Pituitary Gland

-approximately the size of a pea-hangs on inferior surface of hypothalamus on the brain-has 2 lobes 1) anterior pituitary (gland tissue)2) posterior pituitary (nervous tissue)

Anterior lobe of Pituitary GlandRelease 6 hormones

2 stimulate nonendocrine target1. Growth hormone (GH)-bone/muscle growth2. Prolactin-milk production in breast4 stimulate endocrine glands (tropic hormones)1) Adrenocorticotropic (ACTH) –adrenal gland2) Thyroid-stimulating hormone (TH)-thyroid 3 & 4) Gonadotropic hormone –gonads (testes and ovaries)

3. follicle-stimulating hormone (FSH)-sex cell production4. Luteinizing hormone-ovulation of egg