Chapter 11 Endocrine System
Endocrine System:
The endocrine system is made up of the cells, tissues, and organs that secrete hormones into body fluids
such as the blood stream. What is its function? To control certain physiological activities and help
maintain homeostasis
What is the difference between an endocrine gland and an exocrine gland? Endocrine glands secrete hormones which
circulate in the blood, while exocrine glands secrete substances into ducts leading to a body surface
hormone:
What types of chemicals can hormones be? Steroids, amines, peptides, proteins, or glycoproteins
What is the tissue called that hormones affect? Target tissues
hormonal mechanisms:
___Steroid_____ hormones are lipid-soluble and can pass through cell membranes.
Their receptors are located in the target cell's __nucleus___.
The hormone-receptor complex binds with the _DNA__ and activates specific __genes___ that, in
turn, direct the synthesis of specific ___proteins__.
__non-steroid__ hormones combine with receptors in target cell __membranes__; the receptors have a
___binding_____ site and a/an __activity_______ site.
The hormone-receptor complex (as first messenger) triggers a cascade of biological activity. What happens after the
complex forms? Generally activates a G-protein, which then activates an enzyme on the inner surface of the cell
membrane.. This produces a second messenger inside the cell that then activates prteins to
induce changes within the cell
What is the name of the second messenger? The most common second messenger is cAMP
Prostaglandins are locally-produced lipids that affect the organ in which they are produced with a variety of effects.
What are some of these effects? Relax or contract smooth muscle, stimulate secretion, influence blood pressure
hormone control:
There are several ways in which hormone release is very closely regulated. All of these mechanisms use negative
feedback.
Release of __tropic_ hormones from the hypothalamus controls secretions of the _anterior pituitary_.
The __nervous____ system influences certain endocrine glands directly with impulses.
Other glands respond directly to changes in the __internal_____ fluid composition.
Negative Feedback Systems – Explain in general how negative feedback works.
When the concentration of a regulated substance reaches a certain level, the gland is inhibited from secreting more
hormone. How would this function in the above three situations?
Pituitary Gland:
The pituitary gland is attached to the base of the brain and has a front lobe called the __anterior pituitary__
and a rear lobe called the ___posterior pituitary___.
The brain controls the activity of the pituitary gland in two ways.
Releasing hormones from the _hypothalamus____ control the secretions of the anterior pituitary and are
carried in the bloodstream by ___hypophyseal portal____ veins.
The posterior pituitary releases hormones into the bloodstream in response to nerve impulses from the
___hypothalamus___.
Anterior pituitary:
The anterior pituitary consists mostly of __epithelial __ tissue arranged around blood vessels and
enclosed in a capsule of collagenous ___connective__tissue.
How many hormones does it secrete? Six
What function do most of them have in common? Several stimulate other endocrine glands
growth hormone GH:
What is the function of GH? Stimulates body cells to grow and reproduce
What factors influence growth besides GH? Nutritional status
What hormones from the hypothalamus control the levels of GH? GH-Releasing Hormone and GH_ReleaseInhibiting Hormone
What disorders may result from a lack of or too much GH? Too little: pituitary dwarfism. Too much: giantism
prolactin PRL:
What is the function of PRL? Promotes milk production in lactating women
What is its target tissue? The breasts
What hypothalamic hormones affect it? PR- Releasing Hormone
thyroid stimulating hormone TSH:
What is the function of TSH? (what is its target organ?)
What hypothalamic hormones affect its release? Thyrotropin-Releasing Hormone (TRH)
How are these hormones from the hypothalamus regulated? As the level of circulating thyroid hormones fall, the
hypothalamus puts out TRH. When the levels of circulating thyroid hormones are at correct level, the
hypothalamus stops putting out TRH.
adrenocorticotropic hormone ACTH:
What is the target organ for ACTH? Adrrenal Cortex
What hormones does it affect the release of? Cortisol
What is the name of the hormone from the hypothalamus that controls ACTH’s release? Corticotropin-releasing
Hormone (CRH)
follicle stimulating hormone FSH:
What are the target organs for FSH? Gonads
What effect does it have on the males? Testes start to produce sperm
On females? Ovaries begin to produce eggs and to produce and release estrogens
What hormone from the hypothalamus affects its release? Gonadotropin-Releasing Hormones
luteinizing hormone LH:
What does it do? Causes ovulation and formation of corpus luteum in the ovary which then begins to release
estrogen and progesterone
How is it different in males than in females? In males it stimulates the testes to release testosterone
What is its controlling hormone from the hypothalamus called? Gonadotropin-releasing hormone
Posterior pituitary:
The posterior lobe consists of __nerve__ fibers and supporting _neuroglial cells arising in the
hypothalamus.
What structure actually produces the hormones released by the posterior pituitary?hypothalamus
antidiuretic hormone ADH:
What is the function of this hormone? Causes the kidneys to conserve water
What disorder may result if enough ADH isn’t secreted? Diabetes insipidus
oxytocin:
What are the functions of this hormone ? causes contraction of the uterus walls during childbirth and milkletdown during breast feeding
Thyroid Gland:
The thyroid gland is located below the _larynx___ and consists of two broad __lobes_____ connected by an
___isthmus__.
The thyroid consists of secretory parts called _follicles___ filled with hormone-storing
__colloid__.
thyroxine T4: How many iodines does it contain? four
triiodothyronine T3: How many iodines? three
What is the function of these two hormones? They regulate metabolism
How does TSH affect their release? TSH stimulates the thyroid to release T3 and T4
How do they affect the release of TSH? When these hormones are at the correct level, the release of TSH is
inhibited
What is a goiter and what may cause one? A goiter is an enlarged thyroid gland that is usually caused by lack of
iodine. Without iodine, the thyroid cannot make T3 and T4, and thus nothing inhibits the release of TSH which
continues to over stimulate the thyroid
calcitonin:
What is the function of this hormone? Lowers blood levels of calcium and phosphate ions
What part of the thyroid secretes it? It is secreted by extrafollicular cells of the thyroid
Parathyroid Glands:
How many are there and where are they found? Four: located on the back of the thyroid gland
parathyroid hormone PTH:
What is the function of this hormone? Increases blood calcium levels
How does it achieve this function?
Stimulates osteoclasts in bone which break down bone tissue and rlease
calcium into the blood: it also influences the kidneys to conserve calcium
How is it related to calcitonin from the thyroid? PTH and Calcitonin have opposite effects and work together to
maintain the correct levels of calcium ions in the blood
Adrenal Gland:
The adrenal glands sit atop the __kidneys_____ enclosed in a layer of ___fat__.
Adrenal medulla:
The adrenal medulla is made up of modified __post-ganglionic neurons__ that are connected to the _sympathetic___
nervous system. The hormones secreted are the same as neurotransmitters of this system but are called hormones
because they are secreted into the __body fluids and blood stream_____.
epinephrine & norepinephrine:
What affect do these have on the body? Similar effects to those of the sympathetic division of the autonomic
nervous system
What are they secreted in response to? Stress and “fight or flight” situations
adrenal cortex:
The adrenal cortex makes up most of the adrenal glands and consists of ___epithelial_____ cells in three layers—
an outer, middle, and an inner zone. Several groups of hormones are secreted by the cortex.
mineralocorticoids - aldosterone:
This hormone controls the levels of _sodiun__ ions by conserving them in the __kidneys____.
Why is this important? Important in homeostasis of the body
Which zone secretes mineralocorticoids? Outer zone
glucocorticoids:
These hormones influence the metabolism of glucose, protein, and fat in response to conditions that __stress__
the body and require a greater supply of __glucose___ in the bloodstream.
How does negative feedback control the release of these hormones? CRH from hypothalus causes pituitary to
release ACTH. ACTH in turn stimulates release of glucocorticoids. Glucocorticoids inhibit further release of CRH
What else can trigger their release? Stress , injury, or disease
Name an important Gluccocorticoid. cortisol
Which zone secretes these hormones? Middle zone
sex hormones:
Sex hormones, produced in the ___inner____zone, are mostly of the _male_____ type but can be
converted to __female___ hormones in the skin, liver, and adipose tissues.
b.
These hormones supplement those released by the gonads and may stimulate early
development of reproductive organs.
pancreas:
The pancreas secretes hormones as an _endocrine__ gland, and digestive juices to the digestive tract as an
___exocrine___ gland.
Where is the pancreas located? Behind and beneath the stomach
Its endocrine portions are the islets of __langerhans__ that include two cell types--_alpha__
cells that secrete glucagon, and __beta___ cells that secrete insulin.
Glucagon __increases__ the blood levels of glucose by stimulating the breakdown of
_glycogen____and the conversion of noncarbohydrates into ___glucose___.
What controls the levels of glucagon in the blood? Declining blood sugar levels
Insulin __decreases___ the blood levels of glucose by stimulating the liver to form __glycogen___
increasing __protein__ synthesis, and stimulating adipose cells to store _fat_.
What controls the blood levels of insulin? High blood sugar levels
Pineal gland:
The pineal gland, near the upper portion of the thalamus, secretes _melatonin___-, which is involved in the
regulation of __circadian_______________________ rhythms of the body.
Thymus gland:
The thymus gland, lying between the lungs under the __sternum____, secretes _thymosin______ that
affect production and differentiation of T lymphocytes that are important in _immunity_______________________.
Reproductive Glands
The ovaries produce what two hormones? Estrogen and progesterone
What does the placenta produce? Estrogen, progesterone, and gonadotropin
The testes produce __testosterone____.
Digestive Glands Other Hormone Producing Organs
The digestive glands secrete hormones associated with the processes of digestion.
The __heart___ secretes atrial natriuretic peptide affecting sodium and the kidneys secrete
__erythropoietin_____ for blood cell production.
Stress:
Factors that serve as stressors to the body produce stress and threaten ___homeostasis_______________.
Stress may be physical, psychological, or some combination of the two.
What effects on the body does physical stress have? Threatens the survival of tissues
What does psychological stress result from ? real or perceived dangers
Responses to stress are designed to maintain homeostasis.
The _hypothalmus____ controls the general stress syndrome, which involves increased sympathetic
activity and increased secretion of which hormones? Cortisol, glucagon, growth hormone, and antidiuretic
hormone.