Endocrine System Flashcards
endocrine gland
ductless gland that secretes its product (hormone) directly into the blood
hormone
chemical substance synthesized and secreted by an endocrine gland into the blood and transported to a target organ where it causes effects
latencies
time from release of hormone until effects start to be seen
basics about how hormone works with target organ
hormone released from endocrine gland directly into blood stream. it travels in blood stream until it reaches TARGET ORGAN
basics about how hormone works with receptor
at target organ, hormone attaches to a specific RECEPTOR on target organ
basics about how hormone works with HRC
the resultant hormone-receptor complex (HRC) causes a change to be made in the target organ
characteristics of steroids
- structure similar to cholesterol
- derived from cholesterol or Vitamin D
- fat soluble (lipophilic or hydrophobic)
- –transported in blood via carriers proteins
- –diffuses through target cell membrane
- –attaches to intracellular receptor
- usually not stored, created as needed
- –longer latency periods
examples of steroids
cortisol
aldosterone
estrogen
testosterone
characteristics of non-steriods
- water soluble (hydrophilic or lipophobic)
- –travels dissolved in plasma
- –cant diffuse through cell membrane
- –attaches to receptors on outer surface of cell membrane of target cels (except T3/T4)
- large amounts stored in vesicles until needed
- –much shorter latency periods
4 amines
- Epinephrine & Norephinephrine
2. Triiodothryonine and Thyroxine
amines are derived from
tyrosine
Epinephrine and Norepinephrine
shortest latency and fastest acting
Triiodothryonine and Thyroxine (T3/T4)
- use carrier proteins in blood
- receptors located inside nucleus
- use direct gene activation
- longest latency (days) and slowest acting (months)
Peptides
- short amino acid chains (3-200)
- hypothalamus, pituitary, pancreas, heart, gut, and kidney hormones
Eicosanoids
- derived from Arachidonic Acid
- local hormones
- mostly NOT secreted by glands
- 3 TYPES: Thromboxanes, Leukotrienes, Prostaglandins
thromboxanes
-secreted by platelets; causes platlet aggregation
SOLUTION: blood thinner
Leukotrienes
- secreted by WBCs and spleen
- inflammation
Prostaglandins
- secreted by most cells upon membrane damage
- inflammation
- vasodilation
- sensitize spinal neurons to pain
- promote fever
Many common pain relievers inhibit enzymes needed for Eicosanoid formation
- anti-inflammatory
- analegic
- antipyretic: fever reduction
- antithrombotic: reduce clotting
Direct Gene Activation formation is used by
steroid hormones
- freely pass through target cell membrane because fat soluble
- attach to intracellular receptor
- HRC enters nucleus and gene activation
- transcription and translation
- resultant protesins
Direct Gene Activation results in
transcription of mRNA and translation of mRNA into proteins
Resultant proteins in Direct gene Activation cause
cellular effects
Second Messenger System Mechanism is used with
MOST non-steroid hormones
- cant cross cell membrane because water soluble
- attach to receptor on target cell surface
- HRC activates a G protein in the cell membrane
- G protein triggers reactions that lead to the formation of an intracellular 2nd messenger
- 2 messenger then causes a physiological response within a cell
cAMP
- most common and studied 2nd messenger
- G Protein activates adenylate cyclase catalyzing reaction of AP—-> cAMP
examples of second messengers
- cAMP
- cGMP
- calmodulin
- inositoitriphosphate (ITP)
- diacylglycerol (DAG)
- calcium ions
tropic
one hormone causes the release of another hormone
Negative Feedback System
- hormone secreted in response to a homeostatic imbalance
- hormone acts to restore homeostasis
- restoration of homeostasis inhibits further hormone secretion
Postive Feedback Loops
- homeostatic imbalance triggers hormonal release
- hormonal action triggers hormonal release
- used for amplification within a larger negative feedback system
examples of positive feedback loops
LH during ovulation
oxytocin during parturition
Down-regulation/desensitization
target cell decreases number of receptors available for a hormone
Up-regulation/ sensitization
target cell increases number of receptors available for a hormone
2 factors that determine hormonal activity
- Levels of Circulating Hormone
2. The number of available receptors on the target organ
Hypothalamus
control center of hypothalamus
What does Antidiuretic Hormone (ADH) do?
- posterior pituitary
- promotes H20 conservation/retention by directly causing reabsorption of H2O from kidney tubules into capillaries to maintain plasma volume
- faster water hormone
- elevated up to 48 hours. post-exercise
2 mechanisms of action from ADH
- Osmoreceptors in hypothalamus detect hemoconcentration. When hemoconcentrated, posterior releases ADH. ADH causes H2O reabsorption at kidneys into bloodstream (increase PV) restoring osmolality to normal
- Atria, carotid, and pulmonary arteries and aorta contain baroreceptos. When decreased blood pressure, baroreceptors are stimulated causing ADH secretion. ADH causes reabsorption of H2O into blood, increases plasma volume and therefore blood pressure
prolactin
- ALL stimulates lipolysis
- chronically high levels may lead to reproductive consequences in males and females
- fasting/high fat diets stimulate prolactin release
what are endorphins?
endogenous opioid mood-altering and analgesic neurotransmitters and neurohormones
“Runner’s High”
caused by endorphins
decrease anxiety, exhilaration, euphoria, increase pain tolerance, improved appetite control, decrease tension, anger, and confusion
2 training effects of endorphins
- training increase opioid produced, so decrease levels needed to induce a specific eggiest
- in trained person, opioids produced during exercise degrade more slowly, increase tolerance tolerance for prolonged exercise
Endorphins are a ________ addiction
“positive addiction
Anterior Pituitary
- releases its hormones in response to releasing/inhibiting factors from the hypothalamus
- prolactin, TSH, FSH, LH, ACTH, MSH, Endorphins, and GH (all tropic)
Thyroid Stimulating Hormone (TSH) (Thyropin)
-stimulates production and release of thyroid hormones and maintains normal growth and development of thyroid
Adrenocorticotropic Hormone (ACTH)
-stimulates production and secretion of hormones from adrenal cortex, especially cortisol
IGFs
Insulin-like growth hormones (somatomedin)
Major effects of Growth hormone
- increase fuel availability, sparing glucose for brain
- increase fat use
- decrease CHO use (the brain really like CHO)
- promotes favorable body composition by increasing Lean Body Mass and decreasing Fat Mass
Growth Hormone secretion falls about ___% of adolescent levels by old age, after adolescence
25
Why is Growth Hormone used as an Ergongenic Aid?
to enhance sports performance
Growth Hormone changes with age and used as an anti aging drug
accelerated with age, and increases energy with therapy
Which is greater within the growth hormone? Collagen growth or contractile growth?
Collagen growth is greater than contractile growth
low GH in children
Hypopituitary Dwarfism
low GH in adulrs
Simmond’s Disease
-premature aging due to tissue atrophy
how is Simmond’s Disease treated?
with right (injected)
T3/T4
-large stores
(functions same, only differ in rapidity and intensity of action)
-T4-90% release
-T3-90% activity
-use plasma proteins, transported into target cell, use direct gene activation
-long latency, slowest acting
-increase MR of most tissues, through increase enzyme activity
-Hyperthyroidism
-Hypothyroidism
Hyperthyroidism
symptoms include
- high BMR
- increase Tb
- heat intolerance
- increased appetite
- weight loss
- increase/high blood pressure
- enhanced fuel catabolism
- muscle atrophy
- decrease/low ovarian function
- exhausted
- but can’t sleep well, bug eyes
Hypothyroidism
- symptoms include low BMR
- decrease Tb
- decrease appetite
- weight gain
- decrease glucose metabolism
- high cholesterol
- arteriosclerosis
- ovarian function
- sleepiness
- husky voice
- poor hearing
- puffy/droopy eyes
incidence of disease (problems) and types in men vs. women
- 90% of thyroid disease occur in women
- -90% of thyroid diseases in men are cancerous
- -90% of thyroid diseases in women are benign
stimulus for calcitonin and PTH
-stimulated by high plasma Ca++
action of calcitonin and PTH
-acts to decrease plasma Ca++
PTH and bone remodeling
-stimulated by low plasma Ca++
-acts in increase plasma Ca++
-regulates plasma Pi
-targets bone and kidney
BONE: inhibits osteoclast activity. Osteoblast activity predominates, favoring deposition of Ca++ salts in bone
-opposition of calcitonin
-exercise increase PTH levels
–provides raw material for bone remodeling
-no training effect
Adrenal Cortex secretes over ___ cortiosteriods
30
mineralcorticoids
maintain electrolytes (mineral) balance (1 degree aldosterone)
glucocorticoids
maintain blood glucose (1 degree) cortisol
gonadocorticoids
same as hormones from gonads
catecholamines
- adrenal nedulla
- hormones and neurotransmitters
- epinephrine: mainly hormone
- norepinephrine: mainly neurotransmitter
80% of hormonal release is
Epinephrine
20% of hormonal release is
Norephrine
Effect od E/NE similar to SNS effects and their release is usually triggered by
SNS stimulation
Actions of Aldosterone
- promotes Na+ absorption from renal tubules. H2O follows Na+
- promotes K+ excretion and regulated pH because kidney exchange either K+ or H+ for Na+
Renin-Angiotensin System
- low plasma volume or blood pressure in renal artery or increase SNS stimulation to kidneys to release renin
- renin enters the blood where it converts angiotensinogen to angiotensin I
- in the endothelium of lung blood vessels, angiotensin converting enzyme (ACE) catalyzes the conversion of angiotensin I to angiotensin II
- angiotensin II causes strong vasoconstriction and aldosterone release
- vasoconstriction will increase blood pressure
- aldosterone will inquire Na+ and H2O which in turn increase plasma volume and blood pressure
Aldosterone is slower acting than ADH
-ADH is more active during exercise while aldosterone more active post-exercise, unless exercise duration > 1 hr.
Aldosterone elevation post-exercise
- Both ADH and aldosterone elevated 12-48 hours post exercise, decrease urine production and protect from dehydration
- responsible for increase plasma volume with training
- “Sports Anemia”-False + for anemia in athletes
Cortisol
- diurnal variations
- stress triggers secretion
- used as inflammatory
- tapering
- increased incidence of URTIs
Actions of Cortisol
-maintain plasma glucose by increasing availability of all fuels
increased incidence of URTIs in Cortisol
very high levels occur following long duration running
___- shaped relationship between exercise and incidence of URTIs
J-shaped
Open window Hypothesis
large increase in training or actual competition exposes highly trained athletes to abnormal stress that temporarily, but severely, decrease immune function
- 3-72 hours post exercise, with symptoms starting in 1-2 weeks
- EXAMPLE: marathoners at high risk after race
- –risk varies inversely with race times
Mainly hormone
Epinephrine
Mainly neurotransmitter
Norepinephrine
