1 (16) The Endocrine System Flashcards
What is the difference between an endocrine gland and an exocrine gland?
exocrine: secretes products through ducts into body cavities or onto body surface
endocrine: secrete hormones into interstitial fluid and then enter the blood
What are the differences in circulating hormones, paracrine secretions, and autocrine secretions?
circulating hormones: pass into blood, act on distant cells
paracrine secretions: restricted to interstitial fluid, affects nearby cells
autocrine secretions: affect only the secreting cell
How are circulating hormones inactivated and/or removed from the body?
circulating hormones are inactivated by the liver and excreted by the kidneys
Compare and contrast the nervous system and the endocrine system. How do they affect each other?
nervous: affects muscles and gland secretion, takes milliseconds, effects are brief
endocrine: affects virtually all body tissues, may take hours, effects are longlasting
BOTH are coordinated by neuroendocrine system, some neurotransmitter act as hormones
Why do hormones, which area carried everywhere in the body by the blood, affect only certain organs?
hormones only affect specific target cells (on target organs) that have receptors which recognize that particular hormone
What hormones are steroids?
cortisol, aldosterone, estrogen, testosterone
Which hormone ONLY acts like a steroid?
thyroid stimulating hormone
What are steroid hormones made from?
lipids formed from cholesterol
How do steroids change what is going on inside a cell?
by entering cell, activating receptors in cell, activated receptor then turns genes on/off, and if gene is activated, a new protein is produced which alters the activity of the cell
How can steroids be administered?
orally
How do protein or peptide (water-soluble hormones) affect what goes on inside a cell?
by using a second messenger system
Describe the second messenger system in detail.
hormone (1st messenger) binds to receptor, receptor activates G protein, G protein activates adenylate cyclase, adenylate cyclase converts ATP to cAMP (2nd messenger), cAMP activates protein kinases, protein kinases trigger responses of target cell
What does the effect of hormone binding last only briefly?
cAMP is broken down by intracellular enzyme phosphodiesterase
How is the effect of hormone binding amplified within the cell?
the 2nd messengers initiate a cascade of reactions within the cell
What is meant by up-regulation and down-regulation of receptors?
up-regulation increases # of receptors
down-regulation decreases # of receptors
How are amino acid based hormones usually administered?
injection
Local hormones include prostaglandins and leukotrienes. What are they made from and what do they do?
arachidonic acid
prostaglandins: affect wide variety of tissues
leukotrienes: affect white blood cells
What are the three ways hormones may be regulated?
hypothalamus, internal environment, neural stimuli
Locate the pituitary gland. What bony structure protects it?
the sella turcica of the sphenoid bone
Describe the structure of the posterior pituitary gland. What is another name for it?
“neurohypophysis”
contains axons whose cell bodies are in the hypothalamus, neurosecretory cells secrete hormones made by the hypothalamus
What structure connects it to the hypothalamus?
infundibulum
Where are the pituitary gland’s hormones actually produced?
hypothalamus
What two hormones are stored and released from the posterior pituitary gland? What do these hormones do?
oxytocin: stimulates contraction of uterus and milk ejection from alveoli into ducts (controlled by positive-feedback)
antidiuretic hormone: increases water permeability in distal convoluted tubule and collecting ducts so water is reabsorbed into the body and less urine is formed (controlled by osmotic pressure of blood and blood volume)
How is the control of oxytocin unusual in the body?
because it is by a positive-feedback
What condition is caused by hypo-secretion of ADH?
diabetes insipidus
What common substances decrease ADH secretion?
alcoholic and caffeinated beverages
What increases ADH secretion?
high blood pressure, pain, stress
What is the structure of the anterior pituitary gland? What is its other name?
adenohypophysis or pars anterior
How is the anterior pituitary gland controlled by the hypothalamus?
via releasing/inhibiting-type hormones from the hypothalamus
What vascular structure aids in the hypothalamic control of the anterior pituitary gland?
superior hypophyseal artery
What seven hormones are produced by the anterior pituitary?
Human growth hormone, prolactin, thyroid stimulating hormone, adrenocorticotropic hormone, melanocyte stimulating hormone, follicle-stimulating hormone, luteinizing hormone
What is a tropic hormone?
regulates the secretory actions of other endocrine glands
What happens if a growth hormone is over or under-secreted while a child is growing?
over: results in gigantism, GH targets active epiphyseal plates
under: dwarfism, slowed bone growth
What happens if a growth hormone is over or under-secreted during adulthood?
over: acromegaly (overgrowth of bones areas due to GH, mainly bones of hands, feet, face)
under: usually no problems
What time of day is growth hormone secreted?
night
How does growth hormone affect metabolism?
enhances movement of amino acids into cells and stimulates proteins synthesis, stimulates breakdown of glucose so less leaves the blood and blood levels increase, stimulates bone grow directly
What other substances assists in growth?
- growth hormone-releasing hormone
* growth hormone-inhibitory hormone
What does the administration of growth hormone to normal adults or the elderly do?
increases muscle mass but not strength (can lead to fluid retention, joint and muscle pain, diabetes, may promote cancer)
What does prolactin do?
tells the body to make breast milk when a person is pregnant or breast-feeding
What does excess secretion of prolactin do in males?
high prolactin levels can cause galactorrhea, impotence (inability to have an erection during sex), reduced desire for sex, and infertility
What does excess secretion of prolactin do in females?
high levels of prolactin in the blood can stop the ovaries from making the hormone estrogen
What external factors can trigger the release of TSH?
exposure to extreme cold and emotional stress
What external factors can cause the release of ACTH? What is its daily rhythm?
injury, hypoglycemia, or exercise // peaks in the morning just before waking up
In lower organisms, what part of the pituitary produces MSH?
intermediate lobe of pituitary
In humans, MSH is linked with what other hormone?
ACTH
What inorganic substance is critical for the formation of the thyroid hormones T3 and T4?
iodine
How can we use iodine for treatment of hyper-secretion of T3 and T4?
radioactive iodine to kill off sections of the thyroid
Where can you get iodine?
iodized salt
Why is this the only hormone the body stores?
T3 and T4 control the basal metabolic rate, growth and development, thermoregulation, and reactivity of the nervous system
What happens when T3 and T4 are overproduced?
Grave’s disease: exophthalmos, goiter
What happens when T3 and T4 are underproduced?
Hashimoto’s disease (autoimmune), cretinism (stunted growth, mental retardation in childhood), myxedema (edema of facial tissues, sensitive to cold, dulled mental function)
What can cause the over/underproduction of T3 and T4?
excess/lack of iodine
Is calcitonin critical for calcium balance in the body?
no, as long as parathyroid glands are functional you should be good
What is critical for calcium balance in the body?
PTH
How do the two hormones that regulate calcium function together?
calcitonin decreases osteoclast activity, PTH increases osteoclast activity
What type of hormones are produced by the adrenal cortex?
mineralocorticoids
What are the three layers of the cortex and what hormones do they make?
Zona glomerulosa (outer): mostly aldosterone Zona fasciculata (middle): mostly cortisol Zona reticularis (inner): androgens (male sex hormones)
What diseases are caused by over/underproduction of cortisol?
over: Cushing’s syndrome
under: Addison’s disease
How do the androgens produced by the adrenal cortex affect males?
not significantly, overwhelmed by testosterone
How do the androgens produced by the adrenal cortex affect females?
contribute to female sex drive, may be converted into estrogen in other tissues which is especially important after menopause
Why is the adrenal medulla considered to be a sympathetic ganglion?
the hormones secreted are sympathomimetic
What hormones does the adrenal medulla produce and what do they do?
80% epinephrine and 20% norepinephrine
What do we call a tumor of the adrenal medulla?
pheochromocytoma
What is the difference between Type I (IDDM) and Type II (NIDDM)?
Type I: due to underproduction of insulin, injections needed to control blood glucose levels
Type II: due to lack of insulin receptors on cell membrane
What is a nickname for the pineal gland? Why is it called this?
“the third eye” // it hangs from the roof of the third ventricle in the diencephalon
What is the only valid claim for the use of melatonin?
jet-lag, but only resets the biological clock by an hour
What hormones does the thymus gland produce and what do they do?
thymosins, which promote production and maturation of T lymphocytes
Where is erythropoietin produced and what does it do?
kidneys, stimulates red blood cell production
Where is ANP produced and what does it do?
right atrium of the heart; causes sodium and water to be excreted into the urine and lost from the body, which decreases blood volume and therefore blood pressure
What produces leptins and what do they do?
adipose tissue; tell the body how much stored energy
How do the skin and digestive systems function as endocrine organs?
skin: produces cholecalciferol when exposed to UV light, modified by liver/kidneys, causes absorption of calcium from GI tract
GI systems: stomach and small intestines produce many hormones which affect digestion and the production of digestive enzymes (gastrin, cholecystokinin, secretin)
