Chapter 15: Endocrine System Flashcards
hormone
- “to excite”
- chemical messengers released into blood, to send signals throughout the body
- long distance chemical signals traveling thru blood or lymph
- endocrine system
Endocrinology
study of hormones and endocrine system
exocrine glands
produce non-hormonal substances and do this with ducts
ex. sweat, tears, saliva
Endocrine glands
- produce hormones
- ductless glands
- include: pineal gland, pituatary, thyroid, parathyroid, adrenal
Organs that perform both endocrine and other functions:
- hypothalamus
- thymus
- pancreas
- ovary(female)
- testis(male)
- placenta
organs W/ scattered endocrine cells
- -small intestine
- stomach
- kidneys
- heart
neuroendocrine organ
-hypothalamus because it functions in both nervous system but also produces and releases hormones
autocrine
exert effects on cells that secrete them
paracrine
act locally but on cells other than those that secrete them
2 major categories of hormones
- amino acid based
2. steroid based
Amino acid-based hormones
(made up of proteins, chains of amino acids)
1) water-soluble
2) attaches to EXTRAcellular receptors
3) can’t cross cell membrane
ex. antidiuretic hormone
steroid-based hormones
(made of lipids, with a cholesterol base):
1) lipid soluble
2) crosses cell membrane
3) attaches to INTRAcellular receptors
ex. estrogen and testosterone
eicosanoids
- ex. leukotrienes and prostaglandins-positive feedback
- biologically active lipids that have localized effects and thus fall in a separate category
target cells
tissue cells that are given hormone influences
5 ways hormones alter target cells:
1) induce secretion
2) stimulates protein synthesis within the cell( aldosterone in kidneys, more Na+K+ pumps)
3) induce mitosis ex. growth hormone
4) change membrane permeability/potential)
5) activate or inactivate enzymes ex. insulin
lipid soluble hormones(steroids & TH) work by
-direct gene activation since they can cross the cell membrane
Direct gene activation
In this method, hormones move into the target cells by DIFFUSION and attach to an intracellular receptor.
The hormone/receptor complex moves into the nuclear chromatin and attaches to a specific region of the cell’s DNA, causing a gene to be turned “on”.
This means that the gene is being transcribed (mRNA being made), then translated on a RIBOSOME in cytoplasm.
Specific proteins are then synthesized from this info to promote metabolic activities, or synthesis of other proteins
All the amino acid based hormones except thyroxin use
Second messenger systems
- the hormone is the 1st messenger in these systems and when is attaches to the receptors on the membrane of the target cell , it causes the formation of an intracellular second messenger
Best studied 2nd messenger system
1) cyclic AMP system
2) PIP-Calcium
3 plasma membrane components that act together in cyclic AMP are:
1- hormone receptor
2- G-protein
3- effector enzyme (adenylate cyclase)
Steps of Cyclic AMP
- a hormone(1st messenger) binds to its receptor on the plasma membrane
- This binding causes the receptor to change its shape and activates G-protein by causing GTP to attach to it
- When GTP attaches to G Protein and activates it, active G protein attaches to the enzyme Adenylate Cyclase
- It catalyzes the formation of the second messenger cyclic AMP from ATP
- Cyclic AMP activates protein kinase A. A kinase is an enzyme that catalyzes phosphorylation of proteins. The phosphorylation activates some proteins, & inhibits others.
6) The action of cAMP is short-lived becuase it is rapidly degraded by the intracellular enzyme phosphodiesterase.
PIP-Calcium Signaling mech.
- 2nd messenger system
- ADH, oxytocin, GnRH, and epinephrine act through it
hormones are triggers rather than informational molecules because…
a hormones receptor responds to a hormone binding by prompting the cell to turn on a pre-programmed function
3 factors that determine the extent of activation of target cells
1) blood levels
2) #of receptors on or in target cells
3) strength of binding between hormone and its receptor
upregulation
target cells form more receptors in response to rising blood levels of cells
ex. high estrogen levels cause cells to produce more progesterone receptors
downregulation
target cells become disensetised in high blood levels of hormones; they lose their receptors
ex. progesterone induces loss of estrogen receptors
Half-life
length of time that hormone’s blood level to decrease by half
hormones that have the shortest half life
water soluble ones
time req for a hormone to have effect
immediate, hours or days
time req of hormone action ranges from
10 seconds to several hours
permissiveness
one hormone can’t work completely without the other being present
ex. thyroid is necessary for reproductive development
synergism
each hormone will have the same effect alone but when together there is much larger effect
ex. glucagon and epinephrine together cause the release of glucose from the liver into the blood to by 150% of that of releases when each is working alone
antagonism
one hormone opposes the action of the other
ex. insulin which lowers blood glucose levels is antagonized by glucagon which raises glucose levels
3 types of stimuli can trigger release of hormones
- humoral stimuli
- neural stimuli
- hormonal stimuli
humoral stimuli
changes of blood level & certain levels ions or nutrients will trigger hormone release
ex. parathyroid hormone is secreted in response to low Ca2+ levels, others are insulin & aldosterone
neural stimuli
nerve fibers stimulate hormone release
ex. Sympathetic nervous system stimulates the adrenal medulla to release norepinephrine and epinephrine during stress
hormonal stimuli
- same hormones will cause the release of other hormones
ex. release of most pituitary hormones is regulated by releasing and inhibiting hormones produced by the hypothalamus. The anterior pituitary hormones can control release of other hormones. Once the hormones of the target gland are high, they then inhibit production of anterior pituitary hormones.
nervous system can override normal endocrine controls…
under severe stress , the hypothalamus and sympathetic nervous system centers are very active, and hormonal regulation of blood glucose levels is blocked, allowing extra glucose to circulate and provide fuel for more vigorous activity
Anterior pituitary hormones
- growth hormone GH
- thyroid-stimulating hormone TSH
- Adrenocorticotropic hormone ACTH
- Follicle-stimulating hormone FSH
- Luteinizing hormone-LH
- Prolactin PRL
Tropic hormones
-4 of the 6 ant. pituitary hormones- TSH, ACTH, FSH and LH- are TROPINS or tropic hormones.
These hormones regulate the secretory action of other endocrine glands. All ant, pituitary hormones except GH affect their target cells via a cyclic AMP second-messenger system.
Growth hormone GH
- nontropic
- anabolic hormone because it is a tissue building hormone
- GH stimulates most body cells to increase in size & divide
- Hypersecretion:children(gigantism), adults (acromegaly)
- Hyposecretion: children(pituitary dwarfism), adults -no prob
Thyroid Stimulating hormone TSH
- tropic
- release caused by TRH from anterior pituitary but there is no TIH
- rising blood levels of TH will inhibit TSH secretion
Adrenocorticotropic
- tropic
- AKA corticotropin
- stimulates the ADRENAL CORTEX to release corticosteroid hormones(glucosteroid) to help resist stressors.
- CRH from the hypothalamus triggers release and rising levels of gluco-corticoids inhibits release.
- ACTH has a daily rhythm with levels peaking in the morning.
- things like fever, low blood sugar and other stressors can change the normal ACTH rhythm by triggering CRH release
Gonadotropins- Follicle-stimulating hormone FSH, Luteinizing hormone LH
- tropic & nontropic
- act on gonads (testes & ovaries)
- role for FSH is to trigger gamete formation(sperm or egg)
- LH triggers secretion of reproductive hormones
- these are absent until puberty , when GnRH from the anterior pituatary begins to stimulate their release
Prolactin PRL
-nontropic
- stimulates milk production
-both PRH and PIH regulate its secretion
-PIH is also neurotransmitter dopamine(inhibits prolactin).
-levels rise briefly before the menstrual period; this causes breast tenderness & swelling
Hyposecretion- not a prob except for nursing women
Hypersecretion- -abnormality of adenohypophyseal tumors, in women causes inappropriate lactation, lack of menstrual cycle and in men, impotence.
Posterior pituitary hormones
- oxytocin
2. Antidiuretic hormones ADH or vassopressin
Oxytocin
- non-tropic
- peptide mostly from neurons in paraventricular nucleus of hypothalamus
- target organs: uterus, stimulates uterine contractions; initiates labor; breast; initiates milk ejection
- in nonpregnant, nonlactating females and males oxytocin is involved in sexual arousal and orgasms, also promotes nurturing & affectionate behavior
Antidiuretic hormone ADH or vasopressin
- non-tropic
- peptide, mostly from neurons in supraoptic nucleus of hypothalamus
- works against diuresis (urine production)
- ADH targets the kidney tubules via cAMP, and causes them to reabsorb more water, leading to lower urine production
- alcohol inhibits ADH secretion and leads to copious urination and next day hangover effects of dehydration
- AKA vasopressin because it can cause vaso constriction when blood pressure is too low
Hyposecretion of ADH
- Diabetes Insipidus(tasteless)- marked by large amounts of urine and intense thirst
- this can be caused by a blow to the head that damages the hypothalamus or posterior pituitary
hypersecretion of ADH
- syndrome of inappropriate ADH secretion (SIADH)
- can be caused by meningitis, injury or surgery to the brain or cancer cells that are secreting ADH
- symptoms include fluid retardation, headache, disorientation due to brain edema(brain swelling), weight gain, decrease solute concentration in the blood
thyroid gland hormones
- Thyroid hormone (TH) made up of : thyroxine (T4) and triiodothyroxine (T3) AND 2. CALCITONIN
-T4 is the main hormone, and T3 is actually a conversion from T4
-T4 has four bound iodine atoms and T3 has 3
IPFL2R52
- Thyroid hormone (TH) made up of : thyroxine (T4) and triiodothyroxine (T3) AND 2. CALCITONIN
Thyroid Hormone TH
- TROPIC
- TH is the body’s major metabolic hormone that affects virtually every cell in the body
- falling TH blood levels trigger release of TSH, and rising TH levels inhibit release of TSH
- also, GHIH, dopamine, rising levels of glucocorticoids, and high blood concentration of iodine inhibit TSH release
Hyposecretion of TH
- MYXEDEMA- hypothyroid syndrome; symptoms include: chills, constipation, thick dry skin, adema, you become lethargic and mentally slow
- MYXEDEMA resulting from the LACK of IODINE- Goiter (enlarged thyroid)
- in infants- CRETINISM- severe hypothyroidism, this leads to mental retardation, get sgort bodies with thick tongue and neck
- if diagnosed early enough, it is preventable by hormone relacement therapy.
Hypersecretion of TH
- autoimmune disorder-GRAVES DISEASE- abnormal antibodies produced against thyroid follicle cells, mimick TSH and that cuases release of TH
- symptoms include: EXOPTHALMOS (symptoms of hyperthyroidism)-protrusion of eyeballs
Calcitonin
- NON-TROPIC
- produced by parafollicular cells of the thyroid, lowers blood CA2+ levels, antagonizing effects of parathyroid hormone
- it acts on the skeleton, causing release of calcium from bone and inhibits bone resorption, and stimulates calcium uptake
parathyroid hormones
- these 4 glands are located posterior of the thyroid
- the hormone secreted by the parathyroids is the PARATHYROID HORMONE PTH
parathyroid hormone PTH
- NON-TROPIC
- elevates blood calcium levels in 3 ways:
1. increase CA2+ released by bone
2. enhance resorption CA2+ by kidney
3. Promote activation of Vitamin D by kidney -increase CA2+ absorption from food in intestine - vitamin D is ingested pr produced in its inactive form and must be transformed by the kidneys to vitamin D form.
hyperparathyroidism
- caused by a parathyroid gland tumor
- symptoms include: brittle bones (calcium is leeched out), depression of the CNS and formation of kidney stones due to excess calcium
hypoparathyroidism
- caused by parathyroid gland trauma or removal
- symptoms include TETANY-loss of sensation, muscle twitches and convulsions
hormones secreted by adrenal glands
Steroid hormones-3 classes for each layer of adrenal gland- CORTICOSTEROIDS
- outer-zona glomerulosa- MINERALCORTICOIDS
- middle-zona fasciculata- GLUCOCORTICOIDS
- inner- zona reticularis- GONADOCOTICOIDS
mineralcorticoids
- NON-TROPIC
- help water and mineral balance
- main is ALDOSTERONE- this hormone targets the distal parts of the kidney tubules, where it causes more K+ to be excreted in the urine, and more NA+ to be reabsorbed in the blood
- the result is that blood levels of NA + increase and blood levels of K+ decrease
- release is caused by low Na+ in the blood, low blood volume, low blood pressure, high blood K+
- effects ~20 min
- RENIN-enzyme that increases blood pressure
hypersecretion of aldosterone-mineralcorticoid
-ALDOSTERONISM, cuased by adrenal tumors
glucocorticoids- CORTISOL
- NON-TROPIC
- cortisol is secreted in sig. amounts
- ACTH( adrenocorticotropic hormone0 promotes cortisol release
- secretion follows diurnal pattern, levels highest in the early morning
- stress causes an increase in cortisol production, because cortisol promotes GLUCONEOGENESIS( formation of new glucose using fats & proteins)
effects of excessively high levels of cortisol
1) depress your cartilage and bone formation
2) inhibit inflammation by decreasing release of inflammatory chemicals
3) depress the immune system
4) promote chnages in cardiovascular, neural & gastrointestinal function
hypersecretion of cortisol
- CUSHING’S SYNDROME
- cause is high doses of glucocorticoid drugs
- other causes: an ACTH-releasing pituitary tumor or tumor of the lungs, kidneys , pancreas or adrenal glands
- symptoms of Cushings syndrome: moonface, a buffalo hump, bruise easily, poor wound healing
hyposecretion of cortisol
-ADDISON’S DISEASE- discoloration, weight loss, low blood glucose & sodium, rise in K+
gonadocorticoids
- NON-TROPIC
- these are androgens, male sex hormones
- their role contributes to the onset of puberty, sex drive in women
hypersecretion of androgens
-in females, production of a beard, male pattern body hair and enlarged clitoris
hormones secreted by adrenal medulla are..
1- epinephrine
2- norepinephrine
-these centers of the adrenal glands are part of the sympathetic nervous system
epinephrine
- NON-TROPIC
- released in larger amounts and is a better stimulator of metabolic activities, bronchiole dilation-and increased blood flow to the skeletal muscles
- also used ad HEART STIMULANT and to dilate bronchioles during acute asthma attacks or anaphalaxys
norepinephrine
- NON-TROPIC
- peripheral vaso-constriction and influences blood pressure
hyposecretion of both hormones of adrenal medulla
-no real effect, these hormones just intensify the activities of neurons
hypersecretion of adrenal medulla hormones
-caused by a tumor, causes uncontrolled sympathetic nervous system activity, hyperglycemia, increased metabolic rate, rapid heartbeat and palpitations, hypertension, intense nervousness and sweating-kicks body into overdrive
pineal gland hormone
- pineal gland secretes melatonin
melatonin
- TROPIC
- peaks during night
- powerful antioxidant and amine hormone derived from serotonin, causes drowsiness
pancreas hormone-producing cells
- 1)Alpha cells- produce GLUCAGON
- 2)beta cells-produces INSULINGLUCAGON
glucagon-alpha cells
-NON-TROPIC
-hyperglycemic hormone (raises blood sugar) that targets the liver
Promotes following actions in liver:
1. breakdown of glycogen to glucose (glycogenolysis)
2. synthesis of glucose from lactic acid and noncarbohydrate molecules (gluconeogenesis)
3. release of glucose to the blood by liver cells, causing glucose levels to rise
Insulin- beta cells
- NON-TROPIC
- hypoglycemic hormone (lowers blood suger)
- Does this in 3 main ways:
1. by enhancing membrane transfer of glucose into body cells especially fat and muscle cells( but not the liver, kidney and brain
2. by inhibiting the breakdown of glycogen to glucose
3. by inhibiting the conversion of amino acids or fats to glucose - elevated blood glucose levels or rising plasma levels of amino acids & fatty acids stimulate insulin release
hypersecretion of insulin
-hyperinsulinism; hypoglycemia, tremors, disorientation, convulsions
hyposecretion or hypoactivity of insulin
- Diabetes mellitus
- become nauseated -hyperglycemia
- this triggers “fight or flight” response that casues glycogenolysis( sugar breakdown), lipolysis(breakdown of fat) and gluconeogenesis making glucose levels even higher
signs of diabetes mellitus
1-polyurea-high urine leads to dehydration
2- polydipsia- excessive thirst
3- polyphagia- excessive hunger and food consumption ( because although glucose is produced it cannot be used)
does the posterior pituitary make hormones or just store and release them ?
- posterior does not actually make hormones , but stores and releases hormones made by the hypothalamus
what type of tissue is posterior pituitary made of?
- it is made of pituicytes and nerve fibers, not glandular tissue
does the anterior pituitary make hormones or just store and release them? what type of tissue is it made of?
- it both makes and releases hormones
- AKA known as Adenohypophysis and is made of glandular tissue
What 2 hormones are made in the hypothalamus and transferred to the posterior pituitary? How do they get there?
- Oxytocin and ADH(antidiuretic hormone)
- these hormones get to the posterior pituitary via neural connections called the “ hypothalamic-hypophyseal tract”
Is the connection between the posterior pituitary and the hypothalamus neural or vascular?
And, the anterior pituitary?
- it is a NEURAL connection called “ hypothalamic-hypophyseal tract”
- the anterior pituitary does NOT have a neural connection with the hypothalamus, but it does have a VASCULAR connection-“ the hypophyseal portal system)
What is the hypophyseal portal system?
- portal system is made up of primary & secondary capillary plexuses and intervening hypophyseal portal veins
- hormones travel from the hypothalamus to the anterior pituitary through this portal system
- these hormones are all either releasing or inhibitory that regulate other hormones.
what id the largest pure endocrine gland?
Thyroid
What is a colloid?
Thyroglobulin molecules + attached iodine , is stored in the follicles (holllow spherical structures0 that are in the internal thyroid structure
where are adrenal glands located?
Adrenal glands are located atop the kidneys (ad=near, renal=kidneys), these are known as the suprarenal glands(supra-above)
What is the collective name for all the hormones in the adrenal cortex?
Corticosteroids
what is major hormone secretion of Zona glomerulosa?
mineralcorticoids, aldosterone
what is the major hormone secretion of the zona fasciculata?
glucocorticoids, cotisol
what is the major hormone secretion of the Zona reticularis?
gonadocorticoids, androgens
What are the 2 main populations of hormone producing cells in the pancreas and does each hormone do?
- The alpha cells produce glucagon (hypergylcemic- raises blood sugar)
- The beta cells produce Insulin (hypoglycemic- lowers blood sugar)
What 3 ways does glucogan work?
Promotes following actions in liver:
- breakdown of glycogen to glucose (glycogenolysis)
- synthesis of glucose from lactic acid and noncarbohydrate molecules (gluconeogenesis)
- release of glucose to the blood by liver cells, causing glucose levels to rise
what 3 ways does insulin work?
- by enhancing membrane transfer of glucose into body cells especially fat and muscle cells( but not the liver, kidney and brain
- by inhibiting the breakdown of glycogen to glucose
- by inhibiting the conversion of amino acids or fats to glucose
- elevated blood glucose levels or rising plasma levels of amino acids & fatty acids stimulate insulin release
What enzymatic activities does insulin binding trigger?
1) catalyze the oxidation of glucose for ATP production
2) join glucose molecules together to form glycogen
3) covert glucose to fat
What stimulates insulin release?
- elevated blood glucose levels or rising plasma levels of amino acids & fatty acids stimulate insulin release
- other hyperglycemic hormones such as glucagon, epinephrine, etc, which act when blood glucose levels drop, indirectly stimulate insulin production by raising blood glucose
What causes Diabetes Mellitus?
- this disease results from either hyposecretion of insulin or hypoactivity of insulin
What is the difference between Type 1 and Type 2 DM? Which is more common? Which is treated by drugs and which by diet and exercise?
Type 1- (AKA IDDM-insulin dependent diabetes mellitus), people with this form must rely on insulin injections since their bodies cannot create insulin, immune system kills insulin producing beta cells.-less common (1 million), another treatment is pancreatic islet cell transplant( but needs immunodepression)
Type 2-NIDDM, is is often managed by diet and exercise alone, 12 million diagnosed MORE COMMON, people can make insulin, but their receptors are unable to respond to it
tropic vs. nontropic
Non-tropic hormones are hormones that directly stimulate target cells to induce effects. This differs from the tropic hormones, which act on another endocrine gland.
-ex. glucocorticoids, vasopressin, estrogen, testosterone, estrogen, oxytocin, epinephrine & norepinephrine
