The scientific study of hormones and endocrine organs.

(a)  

Are chemical substances that are secreted by endocrine cells into the extracellular fluids and regulate the metabolic activity of other cells in the body.

(a)  

Including proteins, peptides and amines.

(a)  

Are made from cholesterol.

Include the sex hormones made by the gonads (ovaries and testes) and the hormones produced by the adrenal cortex.

(a)  

Local hormones made from highly active lipids released from nearly all cell membranes.

(a)  

Although the bloodborne hormones circulate to all the organs of the body, a given hormone affects only certain tissue cells or organs, referred to as its _____ or _____

(a)  

The term (a)   comes from a Greek word meaning “to arouse.”

Hormones “arouse” or bring about their effects on the body’s cells primarily by altering cellular activity—that is, by _____ or _____ the rate of a normal, or usual, metabolic process rather than by stimulating performance of a new one.

(a)  

The action of your hormone is either to _____ or to _____.

(a)  

The precise changes that follow hormone binding depend on the specific hormone and the target cell type, but typically one or more of the following occurs:

(a)  

✓ ALL steroids’ mechanism of action is gene activation which interferes with genetic activity.

✓ Steroidal hormones (and thyroid hormone) use the mechanism of direct gene activation.

✓ Being lipid-soluble molecules, the steroid hormones can

1.) diffuse through the plasma membranes of their target cells. Once inside, the steroid hormone

2.) enters the nucleus and

3.) binds to a specific hormone receptor there. The hormone-receptor complex then

4.) binds to specific sites on the cell’s DNA,

5.) activating certain genes to transcribe messenger RNA (mRNA). The mRNA then

6.) is translated in the cytoplasm, resulting in the synthesis of new proteins.

(a)  

✓ Water-soluble, nonsteroidal hormones (protein and peptide hormones) are unable to enter the target cells. Instead they bind to hormone receptors situated on the target cell’s plasma membrane and utilize a second-messenger system.

✓ There is a variety of possible second messengers (including cyclic guanosine monophosphate (cGMP) and calcium ions) and many possible target cell responses to the same hormone, depending on the tissue type stimulated.

✓ Common second-messengers: cyclic GMP, cyclic AMP, and calcium-based second-messenger (concerned with IP3 or inositol triphosphate)

✓ In these cases,

1.) the hormone (first messenger) binds to the membrane receptor and

2.) the activated receptor sets off a series of reactions (a cascade) that activates an enzyme. In turn,

3.) the enzyme catalyzes reactions that produce second-messenger molecules (in this case, cyclic AMP, also known as cAMP or cyclic adenine monophosphate) that

4.) oversee additional intracellular changes that promote the typical response of the target cell to the hormone.

*With direct gene activation, it is the hormone that directly affects the organ, tissue or cell. Whereas the second-messenger system uses another substance to act in lieu of the primary hormone.

(a)  

✓ chief means of regulating blood levels of nearly all hormones

✓ in such systems, some internal or external stimulus triggers hormone secretion; then rising hormone levels inhibit further hormone release (even while promoting responses in their target organs). As a result, blood levels of many hormones vary only within a very narrow range.

✓ simply put, “kung unsay kulang, dugangan; kung unsay daghan, i-decrease”. For example, when hormones are in excess, a signal will be sent to the brain in order to stop the production of hormones. Likewise, if the hormones are insufficient, a signal will be sent to brain in order for it to signal the lower system or glands to produce hormones

(a)  

The three mechanisms (hormonal, humoral and neural) typify most systems that control hormone release, but they by no means explain all of them, and some endocrine organs respond to many different stimuli.

(a)  

✓ the most common stimulus

✓ the endocrine organs are prodded into action by other hormones

✓ refers to the release of a hormone in response to another hormone

✓ hormone release promoted by this mechanism tends to be rhythmic, with hormone blood levels rising and falling again and again.

✓ Examples: hypothalamic and pituitary hormones

(a)  

✓ humor = body fluids (blood, bile, and others)

✓ changing blood levels of certain ions and nutrients to stimulate hormone release.

✓ refers to the control of hormone release in response to changes in extracellular fluid; body responds to changes in the electrolytes or ions in blood

✓ hormones released in response to humoral stimuli: PTH produced by parathyroid, calcitonin produced by thyroid, and insulin produced by pancreas.

(a)  

✓ in isolated cases, nerve fibers stimulate hormone release, and the target cells are said to respond to neural stimuli.

✓ The classic example is sympathetic nervous system stimulation of the adrenal medulla to release norepinephrine and epinephrine during periods of stress.

(a)  

The endocrine system’s mechanism which controls the release of hormones is the (a)   .

Then, either _____ acts on the system or the organ or it goes by way of _____. Best examples are: cyclic AMP, cyclic GMP and calcium.

(a)  

Most common form of stimuli that causes the release of hormones; one hormone would cause the release of another hormone because that hormone does not act directly. Best examples are: hypothalamic hormones; pituitary hormones. Hypothalamic hormones will stimulate pituitary gland to release another hormone. Hormone stimulates another gland to secrete another hormone.

(a)  

Body responds to changes in the electrolytes or ions in blood. For example, calcium levels in the blood is low, it will send a signal to the brain asking for calcium then the hypothalamus will send a signal to the pituitary which will release a hormone that would send a signal to the parathyroid gland. Then, the parathyroid gland would release PTH which supplies calcium to blood from bone.

(a)  

Overproduction of (a)   will result to breaking of bones.

#1 source of calcium for blood is the (a)   .

Under stress, your body will respond by increasing the sympathetic activity which stimulates the adrenal medulla to secrete the stress hormone: epinephrine.

(a)