endocrine Flashcards
As the second control
system of the body, the
endocrine system releases
chemicals called hormones that
regulate complex body
processes.
endocrine system
the endocrine system acts more
slowly by using chemical messengers, which are released into the blood to be
transported throughout the body called
hormones
hormones have widespread effects, the
major processes they control are
- reproduction
- mobilizing body defenses against stressors
- regulating cellular metabolism and energy balance
scientific study of hormones and endocrine organs
endocrinology
are chemical substances secreted by
endocrine cells into the extracellular fluids that
regulate the metabolic activity of other cells in the body
Hormones
Although the body produces many different
hormones, nearly all of them can be classified
chemically as either
amino acid–based molecules and steroid hormones
hormones that is made from cholesterol
Steroid hormones
Steroid hormones include the sex hormones made by the
gonads
the hormones that act locally, are made from highly active lipids released from nearly all cell membranes.
prostaglandins
a given hormone affects only certain tissue cells or organs, referred to as its
target cells or target organs
Hormone “arouse,” or bring about their
effects on, the body’s cells primarily by altering
cellular activity
by increasing or decreasing the rate of a normal
Hormone can change plasma membrane permeability or membrane potential (electrical state) by
opening or closing ion channels
can use the mechanism of direct gene activation
Steroid hormones
Steroid hormones can use the mechanism of
direct gene activation
Direct gene activation
- the steroid hormone enters the nucleus
- binds to a specific hormone receptor
- hormone-receptor complex then binds to specific sites on the cell’s DNA
- activating certain genes to transcribe messenger RNA (mRNA)
- mRNA is translated in the cytoplasm
- resulting in the synthesis of new proteins
Alternatively, the steroid hormone may bind to receptors in thecytoplasm, and then the complex moves into the nucleus to activate certain genes.
True
the steroid hormone may bind to receptors in the
cytoplasm
the complex moves into the nucleus to
activate certain genes.
not water-soluble and unable to enter target cells directly
Protein and peptide hormones
Protein and peptide hormones bind to hormone receptors situated on the target cell’s plasma membrane and use a
second-messenger system
second-messenger system
- the hormone (first messenger) binds
to the receptor protein on the membrane - the activated receptor sets off a series of reactions (a cascade) that activates an enzyme
- The enzyme, in turn, catalyzes reactions that produce second-messenger molecules
- cyclic AMP, also known as cAMP, or cyclic adenosine monophosphate that oversee additional intracellular changes that promote the typical response of the target cell to the hormone
are the chief means of regulating blood levels of nearly all hormones
negative feedback mechanisms
The stimuli that activate endocrine glands fall into three major categories
—hormonal, humoral, and neural
These three mechanisms represent the most common systems that control hormone release, but they by no means explain all of them. Some endocrine organs respond to many different stimuli.
—hormonal, humoral, and neural
The most common stimulus, in which endocrine organs are prodded into
action by other hormones
hormonal stimulus
Changing blood levels of certain ions and nutrients may also stimulate hormone release
humoral stimuli
which are also bloodborne chemicals
hormonal stimuli
a decreasing blood calcium ion level in the capillaries serving the parathyroid glands prompts the release of
parathyroid hormone (PTH).
In isolated cases, nerve fibers stimulate hormone release, and the endocrine cells are said to respond to
neural stimuli
The classic example of neural stimuli is sympathetic nervous system stimulation of the adrenal medulla
to release the ( during periods of stress)
catecholamines norepinephrine and
epinephrine
major endocrine organs of the body include
the
pituitary, pineal, thyroid, parathyroid, thymus
and adrenal glands, pancreas, and gonads (ovaries and testes)
is also recognized as a major endocrine organ because it pro duces several hormones
hypothalamus
hormone-producing glands, have purely endocrine
functions
(the anterior pituitary, thyroid, parathyroids, and adrenals)
