Chapter 45 Flashcards
What are the four mechanisms of cell communication?
direct contact; synaptic signaling; endocrine signaling; paracrine signaling
What is a hormone?
regulatory chemical secreted into extracellular fluid and carried by the blood
What is the main advantage of hormones?
they can act at a distance from its source
Specialized organs that secrete hormones are called
endocrine glands
What are two organs that additionally secrete hormones?
kidney; liver
What is the endocrine system?
collectively refers to organs, tissues that produce hormones
(T/F) The blood carries hormones to every cell in the body.
true
What must a cell have to be able to respond to a hormone?
A cell must have the appropriate receptor to respond.
The highly specific interactions between hormones and their receptors enable hormones to be active at
remarkably small concentrations, such as 1e-8 or 1e-9 M
What is the name for the chemical messengers that are not neurotransmitters or hormones, and where do they act?
paracrine regulators; released and act within an organ on nearby cells as local regulators
Do paracrine regulators travel through the blood?
no
What is autocrine signaling?
when cells release signaling molecules that affect their own behavior
Autocrine signaling is common in (2)
the immune system; cancer cells that release growth factors that stimulate their own growth
What are pheromones?
chemicals released into the environment to communicate among individuals of a single species
What do pheromones change?
may alter the behavior or physiology of the receiver, but are not involved in the normal metabolic regulation of an animal
Molecules aren’t just limited to acting as hormones; they can also act as
neurotransmitters
Give an example of a molecule that functions as a hormone and as a neurotransmitter that is secreted by the adrenal glands.
norepinephrine
Neurons secrete a class of hormones carried by the blood that are called
neurohormones
What secretes antidiuretic hormone?
neurons in the brain
How can neurons deliver chemical messages beyond the nervous system itself?
some specialized regions of the brain contain not only neurotransmitting neurons, but also clusters of neurons producing neurohormones
What controls endocrine glands’ secretory activities?
nervous system
What controls the hormonal secretions of the anterior pituitary gland?
hypothalamus
What produces the hormones of the posterior pituitary?
hypothalamus
Is the secretion of hormones always under neural control?
No, it can be independent of neural control
Give an example of two hormones that are secreted outside of neural control.
insulin from pancreas; aldosterone by adrenal cortex
What stimulates the release of insulin from the pancreas?
stimulated by increases in the blood concentrations of glucose
What stimulates the release of aldosterone from the adrenal cortex?
stimulated by increases in the blood concentrations of K+
Cells in the organs that are part of the endocrine system secrete hormones after synthesis into what?
the extracellular fluid, where it diffuses into surrounding blood capillaries
Contrast endocrine and exocrine glands.
Exocrine glands secrete their product into a duct to outside the body or into the gut
What are the two basic characteristics of hormones?
must be sufficiently complex to convey regulatory information to targets; must be adequately stable to resist destruction prior to reaching target cells
What are the three primary categories of hormones?
peptides and proteins; amino acid derivatives; steroids
How many AAs long is antidiuretic acid?
9 amino acids
How many AAs long is insulin?
51 amino acids
How many AAs long is growth hormones?
191 amino acids
Peptides and proteins are composed of
chains of amino acids
Amino acid derivatives are hormones manufactured by
enzymatic modification of specific amino acids
Amino acid derivatives include hormones secreted by what three structures?
adrenal medulla; thyroid; pineal glands
The amino acid derivatives secreted from the adrenal medulla are derived from
tyrosine.
What is the name for the group of amino acid derivatives secreted from the adrenal medulla that are derived from tyrosine?
catecholamines
Catecholamines include what two classes of hormones?
epinephrine (adrenaline) and norepinephrine (noradrenaline)
What are thyroid hormones? (2)
hormones that are derived from tyrosine; secreted by thyroid gland
What are two groups of hormones that are derived from tyrosine?
catecholamines; thyroid hormones
What secretes melatonin?
pineal gland
Melatonin is derived from which amino acid?
tryptophan
Describe steroids.
lipids manufactured by enzymatic modifications of cholesterol
Steroids are primarily derived from
cholesterol
Steroid hormones can be divided into what two classes?
sex steroids; corticosteroids
Sex steroids are secreted by (4)
the testes, ovaries, placenta, adrenal cortex
Corticosteroids are secreted by
only the adrenal cortex
Give 5 examples of steroid hormones.
testosterone; estradiol; progesterone; aldosterone; cortisol
Broadly speaking, hormones can be organized into what two categories?
lipophilic; hydrophilic
Which two categories/classes of hormones are lipophilic?
steroid hormones; thyroid hormones
Which categories/classes of hormones are hydrophilic?
almost everything except steroid hormones, thyroid hormones
Hydrophilic hormones are freely soluble in (2)
water; blood
The hypothalamus secretes what two hormones?
releasing hormones; inhibiting hormones
What is the the target tissue for releasing hormones?
adenohypophysis
What is the principal action of releasing hormones?
activates release of adenohypophyseal hormones
What is the chemical nature of releasing hormones?
peptides
What is the target tissue of inhibiting hormones?
adenohypophysis
What is the principal action of inhibiting hormones?
inhibit release of adenohypophyseal hormones
What is the chemical nature of inhibiting hormones?
peptides (except prolactin-inhibiting factor, which is dopamine)
What is another name for the posterior-pituitary gland?
neurohypophysis
What is another name for the neurohypophysis?
posterior-pituitary gland
What are the two hormones secreted by the neurohypophysis?
antidiuretic hormone (ADH); oxytocin (OT)
What is the target tissue of the antidiuretic hormone?
kidneys
What is the principal action of the antidiuretic hormone?
conserves water by stimulating its reabsorption from urine
What is the chemical nature of the antidiuretic hormone?
peptide (9 amino acids)
What are the target tissues of oxytocin?
uterus; mammary glands
What are the principal actions of oxytocin?
in the uterus, stimulates contractions; in the mammary glands, stimulates milk ejection
What is the chemical nature of oxytocin?
peptide (9 amino acids)
What is another name for the anterior-pituitary gland?
adenohypophysis
What is another name for the adenohypophysis?
anterior-pituitary gland
What 7 hormones are secreted by the adenohypophysis?
adrenocorticotropic hormone (ACTH); melanocyte-stimulating hormone (MSH); growth hormone (GH); prolactin (PRL); thyroid-stimulating hormone (TSH); luteinizing hormone (LH); follicle-stimulating hormone (FSH)
What is the target tissue of the adrenocorticotropic hormone?
adrenal cortex
What is the principal action of the adrenocorticotropic hormone?
stimulates secretion of adrenal cortical hormones such as cortisol
What is the chemical nature of the adrenocorticotropic hormone?
peptide (39 amino acids)
What is the target tissue of the melanocyte-stimulating hormone?
skin
What are the principal actions of the melanocyte-stimulating hormone?
stimulates color change in reptiles and amphibians; various functions in mammals
What is the chemical nature of the melanocyte-stimulating hormone?
peptide (2 forms: 13 and 22 amino acids)
What is the target tissue of the growth hormone?
many organs
What is the principal action of the growth hormone?
stimulates growth by promoting bone growth, protein synthesis, and fat breakdown
What is the chemical nature of the growth hormone?
protein
What is the target tissue of prolactin?
mammary glands
What is the principal action of prolactin?
stimulates milk production
What is the chemical nature of prolactin?
protein
What is the target tissue of the thyroid-stimulating hormone?
thyroid gland
What is the principle action of the thyroid-stimulating hormone?
stimulates thyroxine secretion
What is the chemical nature of the thyroid-stimulating hormone?
glycoprotein
What is the target tissue of the luteinizing hormone?
gonads
What are the principal actions of the luteinizing hormone? (2)
in females, stimulates ovulation and corpus luteum formation; in males, stimulates secretion of testosterone
What is the chemical nature of the luteinizing hormone?
glycoprotein
What is the target tissue of the follicle-stimulating hormone?
gonads
What are the principal actions of the follicle-stimulating hormone?
in females, stimulates development of ovarian follices; in males, stimulates spermatogenesis
What is the chemical nature of the follicle-stimulating hormone?
glycoprotein
What two hormones does the thyroid gland secrete?
thyroid hormones (thyroxine + triiodothyronine); calcitonin
What is the target tissue of the thyroid hormones?
most cells
What are the principal actions of the thyroid hormones? (2)
stimulates metabolic rate; essential to normal growth and development
What is the chemical nature of the thyroid hormones?
amino acid derivative (iodinated)
What is the target tissue of calcitonin?
bone
What is the principal action of calcitonin?
inhibits loss of calcium from bone
What is the chemical nature of calcitonin?
peptide (32 amino acids)
What hormone does the parathyroid gland secrete?
parathyroid hormone (PTH)
What are the target tissues of the parathyroid hormone? (3)
bone; kidneys; digestive tract
What are the principal actions of the parathyroid hormone? (2)
raises blood calcium level by stimulating bone breakdown; stimulates calcium reabsorption in kidneys; activates vitamin D
What is the chemical nature of the parathyroid hormone?
peptide (34 amino acids)
What two hormones are secreted by the adrenal medulla?
epinephrine (adrenaline); norepinephrine (noradrenaline)
What are the target tissues of epinephrine and norepinephrine? (3)
smooth muscle; cardiac muscle; blood vessels
What are the principal actions of epinephrine and norepinephrine? (5)
initiates stress responses; raises heart rate, blood pressure, metabolic rate; dilates blood vessels; mobilizes fat; raises blood glucose level
What is the chemical nature of epinephrine and norepinephrine?
amino acid derivatives
What two hormones does the adrenal cortex secrete?
glucocorticoids (like cortisol); mineralocorticoids (like aldosterone)
What is the target tissue of the glucocorticoids?
many organs
What are the principal actions of the glucocorticoids? (3)
adaptation to long-term stress; raises blood glucose level; mobilizes fat
What is the chemical nature of the glucocorticoids?
steroids
What is the target tissue of the mineralocorticoids?
kidney tubules
What is the principal action of the mineralocorticoids?
maintains proper balance of Na+ and K+ in blood
What is the chemical nature of the mineralocorticoids?
steroid
What two hormones are secreted by the pancreas?
insulin; glucagon
What are the target tissues of insulin? (3)
liver; skeletal muscles; adipose tissue
What are the principal actions of insulin? (2)
lowers blood glucose level; stimulates glycogen, fat, protein synthesis
What is the chemical nature of insulin?
peptide (51 amino acids)
What are the target tissues of glucagon? (2)
liver; adipose tissue
What are the principal actions of glucagon? (2)
raises blood glucose level; stimulates breakdown of glycogen in liver
What is the chemical nature of glucagon?
peptide (29 amino acids)
What are the two hormones secreted by the ovaries?
estradiol; progesterone
What are the target tissues of estradiol? (2)
general; female reproductive structures
What are the principal actions of estradiol? (2)
generally, stimulates development of female secondary sex characteristics; in female reproductive structures, stimulates growth of sex organs at puberty and monthly preparations of uterus for pregnancy
What is the chemical nature of estradiol?
steroid
What are the target tissues of progesterone? (2)
uterus; mammary glands
What are the principal actions of progesterone? (2)
in the uterus, completes preparation for pregnancy; in mammary glands, stimulates development
What is the chemical nature of progesterone?
steroid
What hormone is secreted by the testis?
testosterone
What are the target tissues of testosterone?
many organs; male reproductive structures
What are the principal actions of testosterone? (2)
in many organs, stimulates development of secondary sex characteristics in males and growth spurt at puberty; in male reproductive structures, stimulates development of sex organs and spermatogenesis
What is the chemical nature of testosterone?
steroid
What hormone is secreted by the pineal gland?
melatonin
What are the target tissues of melatonin? (3)
gonads; brains; pigment cells
What is the principal action of melatonin?
regulates biological rhythms
What is the chemical nature of melatonin?
amino acid derivative
How do hydrophilic hormones activate target cell receptors?
because hydrophilic hormones cannot cross a cell membrane, they must activate target cell receptors from outside the cell membrane
How do lipophilic hormones travel in the blood?
lipophilic hormones travel in the blood attached to transport proteins
How do lipophilic hormones activate target cell receptors?
they cross the cell membrane and bind to intracellular receptors
Eventually, what happens to hydrophilic and lipophilic hormones?
they are destroyed/deactivated after use and are excreted in bile or urin
Which hormone is deactivated more rapidly?
hydrophilic hormones are deactivated more rapidly than lipophilic hormones
Describe the longevity of hydrophilic and lipophilic hormones.
hydrophilic hormones act over brief periods of time whereas lipophilic hormones act over prolonged periods
Where does paracrine regulation occur?
occurs in most organs and among the cells of the immune system
What are growth factors?
proteins that promote growth and cell division in specific organs
What does the epidermal growth factor do?
activates mitosis of skin and development of connective tissue cells
What does the nerve growth factor do?
stimulates growth and survival of neurons
What does the insulin-like growth factor do? (2)
stimulates cell division in developing bone; protein synthesis in many other tissues
What are cytokines?
growth factors specialized to control cell division and differentiation in the immune system
What are neurotropins?
growth factors that regulate the nervous system
Damage to the genes coding for growth factors or their receptors can lead to
unregulated cell division and the development of tumors
NO can function as a
neurotransmitter
NO is produced by
the endothelium of blood vessels
How does NO function as a paracrine regulator?
it diffuses to the smooth muscle layer of the blood vessel and promotes vasodilation
What is one of the major roles of NO?
control of blood pressure by dilating arteries
What does endothelin do?
stimulates vasoconstriction
What does bradykinin do?
promotes vasodilation
Why is paracrine regulation important in the context of blood vessels?
supplements the regulation of blood vessels by autonomic nerves, enabling vessels to respond to local conditions
Describe the structure of a prostaglandin.
20-carbon-long fatty acid that contains a five-membered carbon ring
Prostaglandins are derived from
arachidonic acid
When is arachidonic acid released?
released from phospholipids in the cell membrane under hormonal or other stimulation
(T/F) Prostaglandins are produced in a small number of organs.
False, prostaglandins are produced in almost every organ and participate in a variety of regulatory functions
Excessive prostaglandin production may be involved in (3)
premature labor; endometriosis; dysmenorrhea
Prostaglandins are involved in (3)
regulating reproductive functions; promoting smooth muscle contractions; lung + kidney regulation
In fish, prostaglandins have been found to function as
both a hormone and a paracrine regulator
How are prostaglandins involved in pain?
they’re produced at locations of tissue damage, where they promote inflammation, swelling, pain, or fever
Prostaglandins produced in a fish’s ovary can travel to what structure?
can travel to the brain to synchronize associated spawning behavior
Give an example of a drug that inhibits prostaglandin synthesis.
aspirin
To what class of drugs does aspirin belong to?
nonsteroidal anti-inflammatory drugs (NSAIDs)
Give two examples of NSAIDs, other than aspirin.
indomethacin; ibuprofen
NSAIDs act to inhibit what two enzymes?
cyclooxygenase-1 and cyclooxygenase-2
The inhibition of which enzyme contributes to anti-inflammatory effects?
cyclooxygenase-2, which is necessary for the production of prostaglandins from arachidonic acid
What are the side effects of the inhibition of cyclooxygenase-1? (2)
gastric leeding; prolonoged clotting time
How do recently-developed pain relievers inhibit COX-1 and COX-2?
they selectively inhibit COX-2 but not COX-1
Are COX-2 inhibitors more effective for pain than other NSAIDs?
no
What is another lipophilic hormone, other than steroid or thyroid hormones?
the retinoids (vitamin A)
Broadly speaking, prostaglandins are what type of regulator?
prostaglandins are a diverse group of paracrine regulators
Ultimately, hormones that enter the cell are ultimately destined for what structure?
the nucleus
What are two ways that hormones entering the cell go to the nucleus?
they can bind to receptors in the cytoplasm and move as a complex into the nucleus; they can directly travel into the nucleus and then bind to a receptor
The hormone-receptor complex, once in the nucleus, undertakes what task?
binds to specific regions of DNA called hormone response elements
What are hormone response elements?
specific regions of DNA to which hormone-receptor complexes bind
Receptors that bind to hormones and facilitate DNA transcription are known as
hormone-activated transcription factors
Describe the proteins that result from hormone-activated transcription.
often have activity that changes the metabolism of the target cell in a specific fashion
What happens when estrogen binds to its receptors in the liver cells of chickens?
the protein vitellogenin is produced, which is transported to the ovary to form the yolk of eggs
What happens when thyroid hormones bind to its receptors in the anterior pituitary of humans?
inhibition of the expression of the gene for thyrotropin (a negative feedback mechanism)
How often can it take for the effect of lipophilic hormone stimulation to be apparent in target cells?
it can take several hours
Which classes of hormones are too large or too polar to cross the plasma membrane of their target cells? (2)
peptides/protein/glycoprotein hormones; catecholamine hormones
Where do large or hydrophilic hormones bind to the cell?
they bind to receptor proteins located on the outer surface of the plasma membrane
The cellular response of a hydrophilic/large hormone binding to a surface receptor is called
signal transduction
The cellular response of a hydrophilic/large hormone binding to a surface receptor is made possible by
intracellular enzymes called protein kinases
What are protein kinases?
critical regulatory enzymes that activate or deactivate intracellular proteins by phosphorylation
For which hormone is its receptor itself a kinase?
insulin
What happens when insulin binds to its receptor that is itself a kinase?
results in the placement of glucose transport proteins in the plasma membrane, which enables glucose to enter cells
In other peptide hormones, such as the growth hormone, how are receptors activated?
The receptor itself is not a kinase, but the hormone-bound receptor recruits and activates intracellular kinases, which then initiate cellular response
Hydrophilic hormones, in addition to activating receptors on target cells and activating protein kinases, can also initiate cellular response through what system?
second-messenger systems
Give an example of a hydrophilic hormone that makes use of the second messenger system.
epinephrine
How does the second-messenger system work?
the interaction between the hormone and its receptor activates mechanisms in the plasma membrane that increase the concentration of second messengers within the target cell cytoplasm
In the 1960s, Earl Sutherland showed
that activation of epinephrine receptors on liver cells increases intracellular levels of cAMP (a second messenger)
What was the first second messenger system to be described?
the epinephrine-cAMP second messenger system
What are two additional lipid messengers other than cAMP?
inositol triphosphate (IP3) and diacylglycerol (DAG)
Do receptors that activate second messengers manufacture the second messenger themselves?
No, they don’t
How do receptors that activate second messengers induce production of second messengers?
The binding of the hormone to its receptor causes G proteins to shuttle within the plasma membrane from the receptor to the second-messenger-generating enzyme
How do G proteins work in the context of epinephrine? (2)
G proteins activate an enzyme called adenylyl cyclase, which catalyzes the formation of the second messenger cAMP from ATP; cAMP then diffuses within the cytoplasm and binds/activates protein kinases
What is the effect of cAMP dependent protein kinases in liver cells?
activates enzymes that convert glycogen into glucose
What is the effect of cAMP dependent protein kinases in cardiac muscle cells?
increase in the rate and force of cardiac muscle contraction
The cellular response to a hormone primarily depends on
the type of G protein activated by the hormone’s receptor
Can a single hormone have distinct actions in two different cell types?
Yes, if the receptors in those two cells are linked to different G proteins
T/F: the binding of a hydrophilic hormone is irreversible.
False, the binding of a hydrophilic hormone is reversible and very brief
What deactivates hydrophilic hormones following binding?
The target cell deactivates the hormone and also contains specific enzymes that rapidly deactivate second messengers and protein kinases
What are the enzymes involved in the cAMP-dependent protein kinase stimulation of cardiac muscle cells?
a G protein is linked to the IP-3 generating enzyme phospholipase C, and IP-3 regulates the release of Ca2+ ions, which causes muscle contractions
What is another name for the pituitary gland?
hypophysis
What is another name for the hypophysis?
pituitary gland
Describe the location of the pituitary gland.
hangs by a stalk from the hypothalamus at the base of the brain posterior to the optic chasm
The pituitary gland is composed of which two parts?
anterior pituitary (adenohypophysis) and posterior pituitary (neurohypophysis)
What are the fibrous and glandular parts of the pituitary gland?
the fibrous part is the posterior pituitary and the glandular part is the anterior pituitary
T/F: The anterior pituitary and posterior pituitary glands have different embryonic origins.
True: the anterior pituitary and the posterior pituitary have different embryonic origins.
T/F: The anterior pituitary and posterior pituitary glands are regulated by different control system.s
True: the anterior pituitary and the posterior pituitary are regulated by different control systems
Why does the posterior pituitary appear fibrous?
because it contains axons that originate in cell bodies within the hypothalamus and that extend along the stalk of the pituitary as fibers
How does the fibrous nature of the posterior pituitary form during development?
As the floor of the third ventricle of the brain forms the hypothalamus, part of the neural tissue grows downward to produce the posterior pituitary
What is diuresis?
urine production
What is the relationship between ADH and diuresis?
ADH inhibits diuresis
What is the relationship between alcohol and ADH?
alcohol inhibits ADH secretion, which leads to frequent urination
In mammals, oxytocin is responsible for what ejection reflex?
oxytocin is responsible for the milk ejection reflex, in which sensory receptors in the nipples send impulses to the hypothalamus and trigger the release of oxytocin
T/F: Does oxytocin secretion continue after childbirth in women?
True, continues after childbirth in women who are breastfeeding
What is a related posterior pituitary hormone to oxytocin?
arginine vasotocin
What does arginine vasotocin do? (2)
acts like oxytocin but in nonmammalian species; in chickens and sea turtles, arginine vasotocin activates oviduct contraction during egg laying
Beyond reflexes, how is oxytocin involved in behavior?
it is an important regulator of reproductive behavior in men and women
Give two examples of how oxytocin regulates reproductive behavior.
promotes pair bonding; regulates sexual responses like arousal and orgasm
For reproductive behavior, oxytocin behaves much like a
a neurotransmitter in a paracrine fashion inside the CNS
Where are ADH and oxytocin actually produced, and why is this confusing?
ADH and oxytocin are actually produced by neuron cell bodies located in the hypothalamus; they’re transported along the axon tract between the hypothalamus and the posterior pituitary and are stored in the posterior pituitary
What kind of reflex secretes ADH and oxytocin?
neuroendocrine reflex, because both the nervous and endocrine systems are involved
How many hormones does the anterior pituitary produce?
seven
Where does the anterior pituitary develop from?
develops from a pouch of epithelial tissue that pinches off from the roof of the embryo’s mouth
T/F: the anterior pituitary is part of the nervous system.
FALSE, the anterior pituitary is NOT part of the nervous system
Several hormones of the anterior pituitary are collectively referred to as
tropic hormones (tropins)
What do tropic hormones do?
tropic hormones act on other endocrine glands to stimulate secretion of hormones produced by the target gland
The anterior pituitary secretes what three structurally similar families of hormones?
peptide hormones; protein hormones; glycoprotein hormones
What is another name for the growth hormone?
somatotropin
Does the growth hormone stimulate bone growth directly?
No, it stimulates bone growth indirectly
How many amino acids long are protein hormones?
a single chain of approximately 200 amino acids
Other than stimulating milk production, what else does prolactin do? (3)
regulation of water/ion transport across epithelia; stimulation of organs that nourish the young; activation of parental behaviors
What are the largest and most complex hormones known?
glycoprotein hormones
Describe the structure of glycoprotein hormones.
dimers, containing alpha/beta subunits each 100 amino acids in size with covalently linked sugar residues
Which subunit of the glycoprotein hormone is common to all three glycoprotein hormones?
alpha subunit - the beta subunit differs which is what gives these hormones specificity
What is another name for the thyroid-stimulating hormone?
thyrotropin
FSH and LH are collectively referred to as
gonadotropins
What structure controls the production and secretion of anterior pituitary hormones?
hypothalamus
How does the hypothalamus control anterior pituitary secretions?
control is exerted hormonally rather than by nerve axons, using releasing hormones and inhibiting hormones
What are the two types of hormones secreted by neurons in the hypothalamus?
releasing hormones and inhibiting hormones
Describe and name the system that circulates releasing and inhibiting hormones from the hypothalamus.
the two hormones diffuse into blood capillaries at the base of the hypothalamus, then drain into small veins that run to the anterior pituitary; called the hypothalamohypophyseal portal system
What is a portal system?
circulatory structure in which two capillary beds are linked by veins
Which hormone stimulates the release of thyroid-stimulating hormone?
thyrotropin-releasing hormone (TRH)
Which hormone stimulates the release of adrenocorticotropic hormone?
corticotropin-releasing hormone (CRH)
Which hormone stimulates the release of FSH and LH?
gonadotropin-releasing hormone (GnRH)
Which hormones stimulates the release of the growth hormone?
growth hormone releasing hormone (GHRH)
Which hormones stimulate the release of prolactin?
TRH, oxytocin, vasoactive intestinal peptide
Which hormone inhibits the release of growth hormone?
somatostatin (a.k.a. growth hormone inhibiting hormone - GHIH)
Which hormone inhibits the secretion of prolactin?
prolactin-inhibiting factor (PIF) which is actually dopamine
Which hormone inhibits the secretion of melanocyte-stimulating hormone?
MSH-inhibiting hormone (MIH)
The hypothalamus and anterior pituitary are under what kind of feedback control?
negative feedback control
TSH causes the thyroid gland to release
thyroxine
What does thyroxine do?
affect metabolic rate
Give an example of a hormone that performs negative feedback inhibition on the anterior pituitary and hypothalamus
thyroxine
What specific element is needed for the thyroid gland to produce thyroxine?
iodine
What kind of areas lack iodine?
areas distant from seacoasts
If there is insufficient iodine and therefore insufficient thyroxine, what happens?
the hypothalamus/anterior pituitary release more TRH and TSH
What happens with elevated levels of TSH resulting from an iodine deficiency?
the cells enlarge to attempt to produce more thyroxine but the thyroid gland keeps getting bigger and bigger - a condition known as goiter
What is ovulation?
explosive release of a mature egg (oocyte) from an ovary
As the oocyte grows, what hormones are released?
as the oocyte grows, follicle cells surrounding it produce estrogen, which eventually tells the hypothalamus that the oocyte is ready for ovluation
What results after peak estrogen levels?
surge of LH from the anterior pituitary, which causes the release of the oocyte into the oviduct
When is the ovulation cycle’s positive feedback mechanism terminated?
the remaining tissue from the ovarian follicle forms the corpus luteum, which secretes estrogen and progesterone which inhibit FSH and LH
What is hypophysectomy?
surgical removal of the pituitary gland
Which anterior pituitary glands work through direct effects? (3)
growth hormone; prolactin; MSH
Which anterior pituitary glands work through indirect effects? (4)
ACTH, TSH, LH, FSH
Gigantism is caused by
the excessive secretion of GH in a growing child
Pituitary dwarfism is caused by
a deficiency in GH secretion during childhood
The growth hormone stimulates what factors to promote bone growth?
the growth hormone stimulates the production of insulin-like growth factors, which are produced by the liver and bone in response to GH stimulation
What do the insulin-like growth factors do?
stimulate cell division in the epiphyseal growth plates, and thus elongation of the bones
How does GH function in adults?
regulates protein, lipid, and carbohydrate metabolism
What is ghrelin?
peptide hormone released by the stomach between meals that is a potent stimulator of GH release, which implies an important linkage between nutrient intake and GH production
How does excessive GH secretion manifest in adults?
acromegaly, which can include a protruding jaw, elongated fingers, or thickening of skin
In amphibians, what does prolactin do?
promotes transformation of salamanders from terrestrial forms to aquatic breeding adults
The thyroid and parathyroid glands are derived from
primitive pharynx, which is the most anterior segment of the digestive tract
Which two glands are derived from the primitive pharynx?
thyroid and parathyroid glands
Where is the thyroid gland found? (2)
anterior to the heart; in humans, shaped like a bow tie and below the Adam’s apple
What are the only molecules in the body to contain iodine?
thyroid hormones (thyroxine contains 4 I atoms, triiodothyronine contains 3 I atoms)
Adults with hypothyroidism suffer from
low metabolism due to underproduction of thyroxine, which basically means a reduced ability to make use of carbs and fats
What are the symptoms of hyperthyroidism? (3)
fatigue, overweight, chills
What is the effect of hypothyroidism in children? (3)
impairs growth; impairs brain development; impairs reproductive maturity
What are the symptoms of hyperthyroidism? (4)
weight loss; nervousness; high metabolism; overheating
Thyroid hormones regulate enzymes controlling what types of metabolism?
regulate enzymes controlling carbohydrate and lipid metabolism in most cells
In developing humans, what is the relationship between thyroid hormones and the CNS?
thyroid hormones promote growth of neurons and stimulate maturation of the CNS
What is cretinism?
severe mental retardation resulting from hypothyroidism
Why are thyroid hormones important in amphibians?
they direct metamorphosis from an aquatic larva to a terrestrial carnivore
The thyroid/parathyroid glands work with ___ to regulate calcium homeostasis.
vitamin D
The thyroid/parathyroid glands work with vitamin D to regulate
calcium homeostasis
Calcitonin may have an important role in
bone remodeling in rapidly growing children
The parathyroid gland is composed of
four small glands attached to the thyroid.
A significant fall in blood Ca2+ levels can lead to
severe muscle spasms
PTH stimulates osteoclasts to
dissolve calcium phosphate crystals of the bone matrix and release Ca2+ into the blood
PTH stimulates the kidneys to
reabsorb Ca2+ from the urine, which leads to the activation of vitamin D
Vitamin D is produced in the
skin from a cholesterol derivative in response to UV light
Vitamin D is a derivative of
cholesterol
How does the Vitamin D molecule become activated?
gains one OH group from an enzyme in the liver, gains another OH group from an enzyme in the kidneys (stimulated by PTH)
What is the name for the active form of Vitamin D?
1,25-dihydroxyvitamin D.
What does the activated Vitamin D hormone do?
stimulates intestinal reabsorption of Ca2+ and helps raise Ca2+ blood levels to properly mineralize bone
What is rickets?
a condition of poor bone formation, caused by a deficiency in vitamin D
Where are the adrenal glands located?
just above each kidney
Each adrenal gland is composed of (2)
an inner portion called the adrenal medulla and an outer layer called the adrenal cortex
From where does the adrenal medulla receive neural input?
axons of the sympathetic division of the autonomic nervous system
The hormones secreted from the adrenal cortex are all ____ and are referred to collectively as ______.
they are all steroids and are collectively referred to as corticosteroids
What does cortisol do?
acts to maintain glucose homeostasis
In mammals, hormones that maintain glucose homeostasis are called
glucocorticoids
The secretion of glucocorticoids is regulated by
ACTH from the anterior pituitary
What do glucocorticoids do?
stimulate breakdown of muscle protein into amino acids, which are carried by blood to liver; stimulate liver to produce enzymes needed for gluconeogenesis
What is gluconeogenesis?
conversion of amino acids into glucose
When is glucose synthesis from protein especially important?
during long periods of fasting or exercise
Glucocorticoids are secreted in large amounts in response to
stress
What is prednisone?
cortisol derivative used as an anti-inflammatory agent
What is the other major corticosteroid, apart from glucocorticoids?
aldosterone
Aldosterone is classified as a
mineralocorticoid because it regulates mineral balance
What activates the secretion of aldosterone? (2)
activated by angiotensin II, a product of the renin-angiotensin system; high blood K+
What are aldosterone’s primary actions? (2)
reabsorbs Na+ from urine in kidneys; excretes K+ into urine in kidneys
What connects the pancreas to the duodenum?
pancreatic duct
What does the pancreas secrete?
bicarbonate ions and digestive enzymes into small intestine through the pancreatic duct
Insulin is secreted by
the beta cells of the islets of Langerhans
Glucagon is secreted by
the alpha cells of the islets of Langerhans
When a person eats carbs, what happens to blood glucose?
blood glucose rises
When blood glucose rises, what happens? (2)
secretion of insulin by beta cells is activated; secretion of glucagon by the alpha cells is inhibited
Insulin promotes the cellular uptake of
glucose into the liver, muscle, and fat cells
Insulin activates the storage of
glucose as glycogen in the liver and muscle or as fat in fat cells
What happens to insulin and glucagon between meals?
insulin secretion decreases and glucagon secretion increases, which promotes hydrolysis of stored glycogen or fat
T/F: insulin is the only hormone that promotes movement of glucose from blood into cells.
true, insulin is the only hormone that promotes movement of glucose from blood into cells.
Give another names for type I diabetes.
insulin-dependent diabetes mellitus
People with type I diabetes lack
insulin-secreting beta cells and thus produce no insulin
How do we treat type I diabetes?
insulin injections
Why must insulin be injected?
because it’s a peptide, if taken orally it would be digested
What is more common, type I or type II diabetes?
type II diabetes
Give another name for type II diabetes.
noninsulin-dependent diabetes mellitus.
What happens in type II diabetes?
patient has normal insulin levels, but cells have a reduced sensitivity to insulin
What percentage of diabetes cases are type II diabetes?
90%
Where is the pineal gland located?
roof of the third ventricle of the brain
The pineal gland evolved from
a medial light-sensitive eye
The pineal eye is still present in
primitive fish and some modern reptiles
Describe melatonin levels during various times o the day.
Melatonin levels in the blood increase in darkness and fall during daytime.
The secretion of melatonin is regulated by
the suprachiasmatic nucleus (SCN) of the hypothalamus
The suprachiasmatic nucleus functions as
the major biological clock in vertebrates
Where does T cell production occur in vertebrates?
thymus
The right atrium of the heart secretes
atrial natriuretic hormone
What does atrial natriuretic hormone do? (2)
stimulates kidneys to excrete salt and water in the urine; acts antagonistically to aldosterone
The kidneys independently secrete the hormone
erythropoietin
What is erythropoietin?
hormone that stimulates bone barrow to produce red blood cells
Prior to insect molting, neurosecretory cells on the surface of the insect brain secrete
prothoracicotropic hormone (PTTH), a small peptide
What does prothoracicotropic hormone do?
stimulates a gland in the thorax called the prothoracic gland to produce molting hormone
Give another name for the molting hormone.
ecdysone
What does ecdysone do?
high levels of edysone bring out the biochemical conditions for molting to occur
What does DES stand for?
diethylstilbestrol
What is DES?
synthetic estrogen given to pregnant women from 1940 to 1970 to prevent miscarriages
Why was DES infamous?
discovered that daughters exposed to DES had a higher chance of developing cervical cancer later in life
