Unit XI (Book Notes) Flashcards
The ___ system is composed of endocrine glands and specialized endocrine cells located throughout the body.
endocrine
Endocrine glands and cells secrete very small amounts of chemical messengers called ___ into the extracellular fluid.
hormones
Hormones circulate through the bloodstream to specific sites called ___ or ___
target tissues or effectors
At their target tissues, hormones stimulate a specific response. Thus, the term endocrine derived from the Greek words endo, meaning “___,” and krino, “___“-appropriately describes this system.
within
to secrete
Endocrine glands and cells secrete very small amounts of chemical messengers called hormones into the ___ fluid.
extracellular
___ glands have ducts that carry their secretions to the outside of the body, or into a hollow organ, such as the stomach or intestines.
Exocrine
Examples of exocrine secretions are:
saliva, sweat, breast milk, and digestive enzymes.
The study of the endocrine system is known as ___.
endocrinology
The major endocrine glands are:
pineal gland, pituitary, thyroid, parathyroids, thymus, adrenals, pancreas, ovaries, and testes.
___ allows cells to communicate with each other to regulate body activities.
Chemical messengers
A ___ is an organ consisting of epithelial cells that specialize in secretion, which is the controlled release of chemicals from a cell.
gland
An ___ chemical messenger stimulates the cell that originally secreted it. Good examples of this are those secreted by white blood cells during an infection.
autocrine (auto-, self)
Good examples of this are those secreted by white blood cells during an infection.
autocrine chemical messenger
___ chemical messengers act locally on neighboring cells. These chemical messengers are secreted by one cell type into the extracellular fluid and affect surrounding cells. An example of this is histamine, released by certain white blood cells during allergic reactions. Histamine stimulates vasodilation in nearby blood vessels.
Paracrine (para-, next to)
An example of this is histamine which is released by certain white blood cells during allergic reactions. Histamine stimulates vasodilation in nearby blood vessels.
paracrine chemical messenger
___ are chemical messengers secreted by neurons that activate an adjacent cell, whether it is another neuron, a muscle cell, or a glandular cell.
Neurotransmitters
A good example of this is paracrine chemical messengers.
Neurotransmitters
___ chemical messengers are secreted into the bloodstream by certain glands and cells, which together constitute the endocrine system. These chemical messengers travel through the blood to their target cells.
Endocrine (endo-, within)
Secreted by cells in a local area; influences the activity of the same cell or cell type from which it was secreted
Autocrine
Produced by a wide variety of tissues and secreted into the extracellular fluid; has a localized effect on other tissues
Paracrine
Somatostatin, histamine, eicosanoids
Paracrine
Produced by neurons; secreted into a synaptic cleft by presynaptic nerve terminals;
travels short distances; influences postsynaptic cells
Neurotransmitter
Acetylcholine, epinephrine
Neurotransmitter
Secreted into the blood by specialized cells; travels some distance to target tissues; results in coordinated regulation of cell function
Endocrine
Eicosanoids (prostaglandins, thromboxanes, prostacyclins, leukotrienes)
Autocrine
The main regulatory functions of the endocrine system are the following:
- Regulation of metabolism.
2. Control of food intake and digestion. - Modulation of tissue development.
- Regulation of ion levels.
- Control of water balance.
- Regulation of cardiovascular functions.
- Control of blood glucose and other nutrients.
- Control of reproductive functions.
- Stimulation of uterine contractions and milk release.
- Modulation of immune system function.
The word hormone is derived from the Greek word ___, which means to “set into motion.”
hormon
Hormones fit into one of two chemical categories:
(1) lipid-soluble Hormones
(2) water-soluble hormones
___ hormones are nonpolar and include steroid hormones, thyroid hormones, and fatty acid derivative hormones, such as certain eicosanoids.
Lipid-soluble
There are at least three mechanisms that could potentially result in the removal of unprotected lipid-soluble hormones from the body:
(1) breakdown by enzymes in the liver or enzymes in the lungs
(2) excretion into urine by the kidneys
(3) breakdown by enzymes in the bloodstream
Fortunately, lipid-soluble hormones are not unprotected. Instead, they travel in the bloodstream bound to ___. They “chaperone” the hormone.
binding proteins
The life span of lipid-soluble hormones in the blood typically ranges from a ___ to ___
few days to several weeks.
___ hormones are polar molecules; they include protein hormones, peptide hormones, and most amino acid derivative hormones.
Water-soluble
Because water-soluble hormones can dissolve in blood, many circulate as ___ hormones, meaning that most of them dissolve directly into the blood and are delivered to their target tissue without attaching to a binding protein.
free
Are many water-soluble hormones quite large or small?
Do they readily diffuse through the walls of all capillaries?
What does it mean for its diffusion into the blood and tissue space?
Large
No
It diffuses more slowly.
Organs regulated by some protein hormones have very porous, or fenestrated, capillaries to aid in the delivery of these hormones to individual cells. On the other hand, other water-soluble hormones are quite small and are attached to a ___ to avoid being filtered out of the blood.
binding protein
Do water-soluble hormones have relatively short or long half-lives?
Short
hormones that circulate freely in the blood
Free hormones
There are many modifications made to hormone molecules that help protect them from being destroyed. Three important modifications include:
- Having a carbohydrate attached to them.
- Having a terminal end protected from protease activity.
- Having binding proteins. Bound hormones circulate in the plasma longer than free water-soluble hormones do.
Three types of stimuli regulate hormone release:
(1) humoral
(2) neural
(3) hormonal
No matter what stimulus causes the release of the hormone, the blood level of hormones fluctuates within a homeostatic range through ___ feedback mechanisms.
negative
Molecules and ions in the bloodstream can directly stimulate the release of some hormones. These chemicals are referred to as ___ stimuli.
humoral
The word ___ refers to body fluids, including blood. The cells that secrete these hormones have receptors for certain substances in the blood.
humoral
The second type of hormone regulation involves ___ stimuli of endocrine glands.
For example, the sympathetic nervous system stimulates the secretion of epinephrine and norepinephrine, from the adrenal gland during exercise.
neural
Specialized neuropeptides stimulate hormone secretion from other endocrine cells and are called ___ hormones, a term usually reserved for hormones from the hypothalamus
releasing
The third type of regulation uses ___ stimuli. It occurs when a hormone is secreted that, in turn, stimulates the secretion of other hormones.
hormonal
The most common examples of hormonal stimuli are hormones from the anterior pituitary gland, called ___ hormones. They are hormones that stimulate the secretion of another hormone.
tropic
Often when a hormone’s release is sensitive to the presence of a humoral stimulus, there exists a ___ hormone whose release is inhibited by the same humoral stimulus. Usually, this hormone’s effects oppose those of the secreted hormone and counteract the secreted hormone’s action.
companion
Some hormones prevent the secretion of other hormones, which is a common mode of hormone regulation. For example, hormones from the hypothalamus that prevent the secretion of tropic hormones from the anterior pituitary gland are called ___ hormones.
inhibiting
Two major mechanisms maintain hormone levels in the blood within a homeostatic range:
(1) negative feedback
(2) positive feedback
Most hormones are regulated by a ____ mechanism, whereby the hormone’s secretion is inhibited by the hormone itself once blood levels have reached a certain point and there is adequate hormone to activate the target cell.
The hormone may inhibit the action of other, stimulatory hormones to prevent the secretion of the hormone in question. Thus, it is a self-limiting system.
negative feedback
Some hormones, when stimulated by a tropic hormone, promote the synthesis and secretion of the tropic hormone in addition to stimulating their target cell. In turn, this stimulates further secretion of the original hormone.
This is known as a ___ mechanism
positive feedback
Hormones exert their actions by binding to target cell proteins called ___.
receptors
Can a hormone can stimulate only the cells that have the receptor for that hormone?
Yes
___ hormones diffuse through the cell membrane of its target cell and bind to a cytoplasmic receptor or a nuclear receptor. In the nucleus, the combination of the hormone and the receptor initiates protein synthesis.
Lipid-soluble
___ hormones bind to the external portion of membrane-bound receptors, which are integral membrane proteins on its target cell.
Water-soluble
These intracellular pathways elicit specific responses in cells. including the production of molecules called ___ messengers. These are molecules produced inside a cell once a hormone or another chemical messenger binds to certain mem-brane-bound receptors.
second
the enlarging of the prostate gland.
benign prostatic hyperplasia
___ are triangular-shaped glands located on top of each kidney.
Adrenal glands
The adrenal glands are made up of two parts:
(adrenal cortex and adrenal medulla).