CH 16THE ENDOCRINE SYSTEM

ENDOCRINE SYSTEM FUNCTION Achieve and maintain stability of the

internal environment (_____________) Regulation through use of chemical

messengers called __________________ Communication Integration Control Can work with nervous system –

neuroendocrine system

MAJOR POINTS OF THE ENDOCRINE SYSTEM Nervous System and Endocrine System work

together to control various functions of the body.

A hormone can be released from an endocrine gland which affects behavior through the nervous system.

A few endocrine glands respond to a nervous impulse, which activate the endocrine gland to secrete a hormone which in turn affects an organ, organ system or several body systems.

Most endocrine glands respond to changes in the blood level of their own hormone or the hormone of some other endocrine gland.

ENDOCRINE SYSTEM VS. NERVOUS SYSTEM

SEE TABLE 16-1, PAGE 485Endocrine System Nervous System

Messengers are hormones Generally messengers are neural transmitters (See neurosecretion)

Message is sent in a generalized way (passively) through out the body via the circulatory system.

Message is sent along a specific route directly to the target cell via neurons. Must have complex support system

Message is slower Message can be very quick

Message affect can last for a long time Message affect is usually short

Messenger may control a wide range of target cells – most cells of the body

Message controls a small group of cells – muscles and glands

The endocrine and nervous systems overlap in the brain – the pituitary and hypothalamus. The hypothalamus stimulates the pituitary gland via a nerve, and the pituitary affects the hypothalamus with hormones.

IMPORTANT VOCABULARY Hormone – word means to excite or set in

motion. They are the chemical message (or regulators)

Target organ - Organ specifically affected by the action of a hormone. The target organ must have specific protein receptors for hormones. Can also have target tissues and target cells

Exocrine glands – secrete chemicals locally through ducts and have only local effects.

Endocrine glands – secrete chemicals (hormones) directly into the blood stream. These hormones act as chemical messengers to affect several body systems at once.

Neurosecretory tissue – modified neurons that secrete chemical messengers (hormones) that diffuse into the bloodstream not across a synapse.

GENERAL HORMONE ACTION Hormones bind to specific receptor on or

in a target cell“lock and key”

Hormone-receptor interaction produces a regulatory change in the target cellsynthesis of new proteinActivation/inactivation of enzymesOpening or closing specific ion channels

GENERAL HORMONE ACTION Different hormones can work in

combination or against each other Synergism-combinations of hormones

have a greater effect on a target cell than the sum of the effects that each hormone would have while acting alone

Permissiveness-small amount of 1 hormone allows a second hormone to have its full effect on a target cell

Antagonism-1 hormone produces the opposite effect of another hormone “fine tunes” a response

GENERAL HORMONE ACTION Hormones travel to target cells by

circulating the blood stream Endocrine glands will produce more

hormones than needed to hit the target cell.

Unused hormones are excreted by the kidneys or broken down.

HORMONES Generally they are classified by their

chemical structure. Two categories: Steroid Hormones

Steroids which are lipid soluble and made from cholesterol

Steroid type hormones produce effects that take hours or even days.

Protein Hormones (Book calls them nonsteriod hormones) Protein hormones which must interact with receptors

(other proteins) embedded the cells plasma membrane.

Protein hormones produce immediate effects. (Remember proteins are peptides made from amino acids!)

MECHANISM OF STEROID HORMONE ACTION

TYPICAL STEROID HORMONE PATHWAY

Hormone Capillary interstitial fluid into cell attach to receptor in cytoplasm nucleus attach to DNA activate gene message to ribosomesprotein production

MECHANISM OF NONSTEROID HORMONE ACTION

TYPICAL PROTEIN HORMONE PATHWAY

Hormone Capillary interstitial fluid receptor on cell surface activates adenyl

catalase convert ATP cyclic AMP activate cytoplasmic enzymesnormal cell functions

WAYS TO REGULATE HORMONES Alter rate of synthesis or release of

hormone Alter receptor number (up or down

regulation) Alter rate of degradation or excretion of

hormone Feedback loops (most are negative) Many hormones are secreted on a

rhythmic basis with periods of varying lengths.  For example, circadian rhythms are 24 hr

WHERE TO GO FROM HERE…… Rest of the chapter deals with specific

endocrine pathways…. I suggest your READ! Need to know GLANDS & HORMONES!!