Chapter 17 - Endocrine System Flashcards
the endocrine system influences metabolic activities via _______ transported in blood
hormones
the study of hormones and endocrine organs
endocrinology
which system responds slower but lasts longer: endocrine or nervous
endocrine
the endocrine system controls and integrates what 5 things
- reproduction
- growth and development
- maintenance of electrolyte, water and nutrient balance of blood
- regulation of cellular metabolism and energy balance
- mobilization of body defenses
- non-hormonal substances (sweat, saliva)
- have ducts to carry secretion to membrane surface
- release outside the blood
exocrine glands
- produce hormones
- lack ducts (ductless)
- release insdie the blood
endocrine glands
what are the endocrine glands
pituitary, thyroid, parathyroid, adrenal and pineal glands
what is the neuroendocrine organ
hypothalamus
what glands have exocrine and endocrine functions
pancreas, gonads, placenta
what tissues and other organs produce hormones
adipose cells, thymus cells in walls of small intestine stomach kidneys heart
2 main classes of hormones
amino acid based hormones
steroids
what do amino acid based hormones consist of
-amino acid derivatives, peptides and proteins
these are synthesized from cholesterol
gonadal and adrenocortical hormones
steroids
long distance chemical signals; travel in blood or lymph
hormones
chemicals that exert effects on same cells that secrete them
*not formal endocrine system
autocrines
locally acting chemicals that affect cells other than those that secrete them
*not formal endocrine system
paracrines
what are not considered hormones (2)
autocrines and paracrines
what are local chemical messengers
autocrine and paracrine
tissues with receptors for specific hormones
target cells
though hormones circulate systemically, only cells with ______ for that hormone are affected
receptors
mechanisms on hormone action on target cells may be able to: (5)
- alter plasma membrane permeability or membrane potential by opening or closing ion channels
- stimulate synthesis of enzymes or other proteins
- activate or deactivate enzymes
- induce secretory activity
- stimulate mitosis
hormones act at receptors in 1 of 2 ways, depending on chemical nature and receptor location
- water soluble hormones (all amino acid based hormones except thyroid hormone)***
- lipid soluble hormones (steroid & thyroid hormones)
***know for test
what hormones cannot enter the cell
water soluble hormones (all amino acid based hormones except thyroid hormone)
what hormones can enter the cell
lipid soluble hormones (steroid and thyroid hormones)
- act on plasma membrane receptors
- act via G protein second messengers
water soluble hormones
-act on intracellular receptors that directly activate genes
lipid soluble hormones
cAMP signaling mechanism steps - 5
- hormone (first messenger) binds to receptor
- receptor activates G protein
- G protein activates adenylate cyclase
- adenylate cyclase converts ATP to cAMP (second messenger)
- cAMP activates protein kinases that phosphorylate proteins
- activated kinases phosphorylate various proteins, activating some and inactivating others
- is rapidly degraded by enzyme
- intracellular enzymatic cascades have huge amplification effect
cAMP signaling mechanism
what does PIP2 stand for
phosphatidyl inositol biphosphate
-involves G protein and membrane bound effector phospholipase c
PIP2 - calcium signaling mechanism
what splits PIP2 into two second messengers
phospholipase c
what are the two second messengers formed from PIP2 when it splits
diacylglycerol (DAG) and inositol trisphosphate (IP3)
DAG activates protein ______; IP3 causes ____ release
kinase ; CA2+
what ions act as second messenger for PIP2
calcium
cGMP acts as second messengers for some hormones. what does cGMP stand for
cyclic guanosine monophosphate
intracellular receptors and direct gene activation for steroid hormones and thyroid hormone (5)
- diffuse into target cells and bind with intracellular receptors
- receptor-hormone complex enters nucleus; binds to specific region of dna
- prompts dna transcription to produce mRNA
- mRNA directs protein synthesis
- promote metabolic activities, or promote synthesis of structural proteins or protein for export from cell
target cells must have ______ _______ to which hormone binds
specific receptors
examples of specific receptors are:
ACTH receptors found only on certain cells of adrenal cortex
thyroxin receptor found on nearly all cells of body
Direct gene activation mechanism of lipid soluble hormones ( 5 steps)
- steroid hormone diffuses through the plasma membrane and binds an intracellular receptor
- receptor hormone complex enters nucleus
- receptor hormone complex binds specific DNA region
- binding initiates transcription of gene to mRNA
- mRNA directs protein synthesis
what 3 factors do target cells activation depend on
- blood levels of hormone
- relative number of receptors on or in target cell
- affinity of binding between receptor and hormone
target cells form more receptors in response to low hormone levels
up regulation
target cells lose receptors in response to high hormone levels
down regulation
these are controlled by negative feedback systems
vary only within narrow, desirable range
blood levels of hormones
endocrine gland stimulated to synthesize and release hormones in response to (3)
hormonal stimuli
neural stimuli
humoral stimuli
nerve fibers stimulate hormone release
neural stimuli
sympathetic nervous system fibers stimulate adrenal medulla to secrete ___
catecholamines
Stimulus: action potentials in preganglionic sympathetic fibers to adrenal medulla
- what is the response
- is this humoral, neural or hormonal stimuli
response: adrenal medulla cells secrete epinephrine and norepinephrine
neural stimuli
changing blood levels of ions and nutrients directly stimulate secretion of hormones
example: ca in blood
humoral stimuli
Stimulus: low concentration of CA in capillary blood
What is the response? Is this neural, humoral or hormonal stimuli?
Response: Parathyroid glands secrete parathyroid hormone (PTH), which increases blood Ca
Humoral stimuli
hormones stimulate other endocrine organs to release their hormones
hormonal stimuli
Stimulus: Hormones from hypothalamus
What is the response? Is this humoral, neural, or hormonal stimuli?
Response: Anterior pituitary gland secretes hormones that stimulate other endocrine glands to secrete hormones
Hormonal stimuli
hypothalamic hormones stimulate release of most ____ _____ hormones
anterior pituitary
____ _____ hormones stimulate targets to secrete still more hormones
anterior pituitary
what is the hypothalamic-pituitary target endocrine organ feedback loop
hormones from final target organs inhibit release of anterior pituitary hormones
nervous system modifies stimulation of _____ _____ and their negative feedback mechanisms
endocrine glands
what can override normal endocrine controls
nervous system
what hormones circulate in blood free and which ones are bound
- steroid and thyroid hormone are attached to plasma proteins
- all others circulate without carriers
the concentration of circulating hormone reflects what two things
- rate of release
2. speed of inactivation and removal from body
what 3 things remove hormones from blood
- degrading enzymes
- kidneys
- liver
time required for hormone’s blood level to decrease by half
half life
- these are limited
- ranges from 10 secs to several hours
- effects may disappear as blood levels drop
- some persist at low blood levels
duration of hormone activity
what is the onset of hormone activity
- some are immediate
- some hours to days
- some must be activated in target cells
what hormones act on same target at same time (3)
permissiveness, synergism, antagonism
one or more hormones oppose action of another hormone
antagonism
more than one hormone produces same effects on target cell —> amplification
synergism
one hormone cannot exert its effects without another hormone being present
permissiveness
pituitary gland has two major lobes
posterior - neural tissue
anterior - glandular tissue
these are transported to and stored in posterior lobe of pituitary
neurohormones
nuclei of hypothalamus synthesize neurohormones ____ and ____
this takes place in _____ lobe of pituitary
oxytocin & antidiuretic hormone (ADH)
posterior
downgrowth of hypothalamic neural tissue
neural connection to hypothalamus
posterior lobe of pituitary
originates as outpocketing of oral mucosa
vascular connection to hypothalamus
anterior lobe of pituitary
hypothalamus controls release of hormones from posterior lobe of pituitary
(4)
- hypothalamic neurons synthesize oxytocin or antidiuretic hormone (ADH)
- oxytocin and adh are transported down axons of hypothalamic - hypophyseal tract to posterior pituitary
- oxytocin and adh are stored in axon terminals in posterior pituitary
- when hypothalamic neurons fire, action potentials arriving at axon terminals cause oxytocin or adh to be released into blood
contains primary capillary plexus, hypophyseal portal veins, secondary capillary plexus
hypophyseal portal system of anterior lobe of pituitary gland
the hypophyseal portal system carries _____ and ____ hormones to anterior pituitary to regulate hormone secretion
releasing and inhibiting hormones
The hypothalamus controls release of hormones from the pituitary gland in two different ways - anterior lobe
- when appropriately stimulated, hypothalamic neurons secrete releasing or inhibiting hormones into the primary capillary plexus
- hypothalamic hormones travel through portal veins to the anterior pituitary where they stimulate or inhibit release of hormones made in anterior pituitary
- in response to releasing hormones the anterior pituitary secretes hormones into the secondary capillary plexus. in turn this empties into general circulation.
hypothalamic neurons synthesize
GHRH, GHIH, TRH, CRH, GnRH, PIH
hormones that come out of the anterior lobe of pituitary
GH, TSH, ACTH, FSH, LH, PRL
- inhibits or prevents urine formation
- regulates water balance
- target kidney tubules - reabsorb more water
- release also triggered by pain, low blood pressure and drugs
ADH
- strong simulant of uterine contraction
- released during childbirth
- hormonal trigger for milk ejection
oxytocin
hormones of the anterior pituitary hormone
*KNOW FOR TEST
- growth hormone (GH)
- thyroid-stimulating hormone (TSH)
- adrenocorticotropic hormone (ACTH)
- follicle-stimulating hormone
- luteinizing hormone (LH)
- prolactin (PRL)
- produced by somatotropic cells
- direct actions on metabolism
- increases blood levels of fatty acids; encourages use of fatty acids for fuel; protein synthesis - indirect actions on growth
- mediates growth via growth-promoting proteins - insulin like growth factors
- major targets - bone and skeletal muscle
growth hormone (GH)
GH release chiefly regulated by hypothalamic hormones
- growth hormone - release hormone (GHRH)
- stimulates release
- growth hormone-inhibiting hormone (GHIH)
- inhibits release
hunger hormone also stimulates release
ghrelin
hypersecretion in children results in
gigantism
hyposecretion in children results in
pituitary dwarfism
- produced by thyrotropic cells of anterior pituitary
- stimulates normal development and secretory activity of thyroid
- release trigged by thyrotropin releasing hormone from hypothalamus
thyroid stimulating hormone
- secreted by corticotropic cells of anterior pituitary
- stimulates adrenal cortex to release corticosteroids
adrenocorticotropic hormone (ACTH)
- follicle stimulating hormone (FSH) and luteinizing hormone (LH)
- secreted by cells of anterior pituitary
- FSH stimulates gamete (egg or sperm) production
- LH promotes production of gonadal hormones
gonadotropins (FSH and LH)
regulation of gonadotropin release
- triggered by gonadotropin-releasing hormone (GnRH) during and after puberty
- suppressed by gonadal hormones
- secreted by cells of anterior pituitary
- stimulates milk production
- role in males not well understood
- regulation of PRL release
- primarily controlled by prolactin inhibiting hormone
prolactin (PRL)
regulation of ACTH release
- triggered by hypothalamic corticotropin releasing hormone in daily rhythm
- internal and external factors such as fever, hypoglycemia, and stressors can alter release of CRH
another name for prolactin-inhibiting hormone
dopamine
regulation of thyroid hormone secretion
hypothalamus —-TRH— anterior pituitary —-TSH—– thyroid gland —- thyroid hormones —- target cells
thyroid gland has two lateral lobes connected by median mass. It is called
isthmus
-composed of follicles produce glycoprotein thyroglobulin
thyroid gland
fills lumen of follicles and is precursor of thyroid hormone
colloid
produce the hormone calcitonin
parafollicular cells
- affects virtually every cell in body
- actually two related compounds
* T4
* T3
thyroid hormone
has 2 tyrosine molecules + 4 bound iodine atoms
T4 (thyroxine)
has 2 tyrosines + 3 bound iodine atoms
T3 (triiodothyronine)
- major metabolic hormone
- increases metabolic rate and heat production
- regulation of tissue growth and development
- maintenance of blood pressure
thyroid hormone
this links together to form t3 and t4
iodinated tyrosines
this is endocytosed and vesicle is combined with a lysosome
colloid
T3 and T4 are cleaved and diffuse into ___
bloodstream
synthesis of thyroid hormone - 7 steps
- thyroglobulin is synthesized and discharged into follicle lumen
- iodine is trapped (actively transported in)
- iodide is oxidized to iodine
- iodine is attached to tyrosine is colloid, forming DIT and MIT
- iodinated tyrosines are linked together to form T3 and T4.
- thyroglobulin colloid is endocytosed and combined with a lysosome
- lysosomal enzymes cleave T4 and T3 from thyroglobulin and hormones diffuse into bloodstream
thyroid gland stores hormone where
extracellularly
this is synthesized and discharged into follicle lumen
thryoglobulin
this is actively taken into cell and released into lumen
iodides
iodide oxidized to
iodine
iodine attaches to _____, mediated by peroxidase enzymes
tyrosine
T3 and T4 are transported by
thyroxine-binding globulins
T4 and T3 both bind to ____ ____, but T3 is 10x more _____ than T4
target receptors ; active
these convert T4 to T3
peripheral tissues
what type of feedback regulates of TH
negative
rising TH levels provide negative feedback inhibition on release of
TSH (thyroid stimulating hormone)
this can overcome negative feedback during pregnancy or exposure to cold
hypothalamic thyrotropin releasing hormone
- this is produced by parafollicular cells
- has no known physiological role in humans
calcitonin
the antagonist to parathyroid hormone
calcitonin
at higher than normal doses:
- inhibits osteoclast activity and release of Ca from bone matrix - stimulates Ca uptake and incorporation into bone matrix
calcionin
functions:
- stimulates osteoclasts to digest bone matrix and release Ca to blood
- enhances reabsorption of Ca and secretion of phosphate by kidneys
parathyroid hormone
promotes activation of vitamin D: increases absorption of Ca by intestinal mucosa
parathyroid hormone
rising Ca in blood inhibits PTH release is what kind of feedback
negative feedback control
most important hormone in Ca homeostasis
PTH
4-8 tiny glands embedded in posterior aspect of thyroid
contain oxyphil cells
parathyroid glands
parathyroid cells secrete
parathyroid hormone (PTH)
- paired pyramid shaped organs atop kidneys
- structurally and functionally are 2 glands in one
adrenal glands
the part of the adrenal glands that is nervous tissue; part of the sympathetic nervous system
adrenal medulla
part of the adrenal glands that is 3 layers of glandular tissue
adrenal cortex
the adrenal cortex secretes
corticosteroids
the three layers of the adrenal cortex
zona glomerulosa
zona fasciculata
zona reticularis
zona glomerulosa produce _____
mineralocorticoids (aldosterone)
zona fasciculata produces ___
glucocorticoids (cortisol)
zona reticularis produces ____
gonadocorticoids (androgens)
aldosterone release is triggered by
- decreasing blood volume and blood pressure
- rising blood levels of K
the most potent mineralocorticoid
aldosterone
stimulates Na reabsorption and water retention by kidneys; elimination of K
aldosterone
these regulate electrolytes (primarily Na and K) in what
extracellular fluids
what is the importance of Na
affects ECF volume, blood volume, blood pressure, levels of other ions
what is the importance of K
sets resting membrane potential of cells
decreased blood pressure stimulates kidneys to release renin
renin angiotensin aldosterone mechanism
what triggers formation of angiotensin II
renin
what is a potent stimulator of aldosterone release
angiotensin II
what are the mechanisms of aldosterone secretion
renin angiotensin aldosterone mechanism
plasma concentration of K
ACTH
atrial natriuretic peptide
increased K directly influences zona glomerulosa cells to release aldosterone
plasma concentration of K
what causes small increases of aldosterone during stress
ACTH
blocks renin and aldosterone secretion to decrease blood pressure
atrial natriuretic peptide
- keeps blood glucose levels relatively constant
- maintains blood pressure by increasing action of vasoconstrictors
glucocorticoids
what are the 3 glucocorticoids
cortisol
cortisone
corticosterone
only glucocorticoid that is significant amounts in humans
cortisol (hydrocortisone)
- this is released in response to ACTH patterns of eating and activity and stress
- saves glucose for brain
- enhances vasoconstriction
cortisol
formation of glucose from fats and proteins
gluconeogensis
this is the prime metabolic effect is gluconeogenesis
cortisol
these are the most weak androgens converted to testosterone in tissue cells, some to estrogens
gonadocorticoids (sex hormones)
this may contribute to the onset of puberty; appearance of secondary sex characteristics; sex drive in women; estrogens in postmenopausal women
gonadocorticoids (sex hormones)
medullary chromaffin cells synthesize two hormones
epinephrine (80%)
norepinephrine (20%)
are the medullary chromaffin cells in the adrenal cortex or adrenal medulla
adrenal medulla
this stimulates metabolic activities, bronchial dilation and blow flow to skeletal muscles and heart
epinephrine
what influences peripheral vasoconstriction and blood pressure
norepinephrine
the effects are:
- vasoconstriction
- increased heart rate
- increased blood glucose levels
- blood diverted to brain, heart and skeletal muscle
medullary chromaffin cells
hyperglycemia, increased metabolic rate, rapid heartbeat and palpitations, hypertension, intense nervousness, sweating
hypersecretion
- not problematic
- adrenal catecholamines not essential to life
hyposecretion
short term stress uses what in the adrenal gland
adrenal medulla
prolonged stress uses what in the adrenal gland
adrenal cortex
effects of long term stress response
- kidneys retain sodium and water
- blood volume and blood pressure rise
- proteins and fats converted to glucose or broken down for energy
- blood glucose increases
- immune system surpressed
effects of short term stress response
- heart rate increases
- blood pressure increases
- bronchioles dilate
- liver converts glycogen to glucose and releases glucose to blood
- metabolic rate increases
- blow flow changes, reducing digestive system activity and urine output
small gland hanging from roof of 3rd ventricle
pineal gland
these secrete melatonin, derived from serotonin
pinealocytes
- the triangular gland partially behind stomach
- has both exocrine and endocrine cells
pancreas
- these produce enzyme rich juice for digestion
- exocrine
acinar cells
these contain endocrine cells in the pancreas
pancreatic islets
what is another name for pancreatic islets
islets of langerhans
these cells produce glucagon in the pancreas
alpha cells
these produce insulin in the pancreas
beta cells
- this causes increased blood glucose levels
- the major target is the liver
glucagon
breakdown of glycogen to glucose
glycogenolysis
synthesis of glucose from lactic acid and noncarbohydrates
gluconeogenesis
effects of glucagon
glycogenolysis
gluconeogenesis
release of glucose to blood
- lowers blood glucose levels
- enhances membrane transport of glucose into fat and muscle cells
- inhibits glycogenolysis and gluconeogenesis
- participates in neuronal development and learning and memory
effects of insulin
what is the normal blood glucose level
about 90 mg/100 ml
- this activates tyrosine kinase enzyme receptor
- triggers enzymes:
- catalyze oxidation of glucose of ATP production - first priority
- polymerize glucose to form glycogen
- convert glucose to fat
- cascade –> increased glucose uptake
insulin action on cells
what is the primary stimulus that influence insulin release
elevated blood glucose levels
factors that influence insulin release (5)
- elevated blood glucose levels
- rising blood levels of amino acids and fatty acids
- release of acetylcholine by parasympathetic nerve fibers
- hormones - glucagon, epinephrine, growth hormone, thyroxine, glycocorticoids
- somatostatin; sympathetic nervous system
glucose spilled into urine
glycosuria
this is due to hyposecretion or hypoactivity of insulin
diabetes mellitus
untreated ketoacidosis leads to….
hypernea - disrupted heart activity and O2 transport; depression of nervous system —> coma and death possible
fats used for cellular fuel is called…
lipidema
if lipidemia is severe - ketones from fatty acid metabolism into ….
ketonuria and ketoacidosis
3 cardinal signs of diabetes mellitus
polyuria, polydipsia, polyphagia
excessive hunger and food consumption
-cells cannot take up glucose and are starving
polyphagia
excessive thirst
polydipsia
huge urine output
polyuria
excessive insulin secretion
hyperinsulinism
what are causes of hypoglycemia
- low blood glucose levels
- anxiety, nervousness, disorientation, unconsciousness, even death
hormone producing structures in adipose tissue
leptin, resistin, adiponectin
appetite control; stimulates increased energy expenditure
leptin
insulin antagonist
resistin
enhances sensitivity to insulin
adiponectin
this secretes estrogens, progesterone, and hCg
placenta
gonads produce what type of hormones
steroid sex hormones
ovaries produce these two hormones
estrogen and progesterone
- maturation of reproductive organs
- appearance of secondary sexual characteristics
- with progesterone, causes breast development and cyclic changes in uterine mucosa
estrogen
testes produce which hormone
testosterone
- this initiates maturation of male reproductive organs
- causes appearance of male secondary sexual characteristics and sex drive
testosterone
what are the hormone producing structures of the gastrointestinal tract
enteroendocrine cells
what are the hormones of the enteroendocrine cells of the GI tract
gastrin
secretin
cholecystokinin
serotonin
this acts as a paracrine
serotonin
this stimulates pancreas, gall bladder and hepatopancreatic sphincter
cholecystokinin
this stimulates liver and pancreas
secretin
this stimulates release of HCl
gastrin
hormone produced by the heart
atrial natriuretic peptide (ANP)
decreases blood Na concentration therefore blood pressure and blood volume
atrial natriuretic peptide
hormones produced by the kidneys
erythropoietin and renin
this signals production of red blood cells
erythropoietin
this initiates the renin-angiotensin-aldosterone mechanism
renin
-large in infants and children; shrinks as age
thymus
the hormones produced by thymus
thymulin, thymopoietins and thymosins
- may be involved in normal development of T lymphocytes in immune response
- classified as hormones; act as paracrines
thymulin, thymopoietins and thymosins
hormone produced by osteoblasts (skeleton)
osteocalcin
- activated by insulin
- prods pancreas to secrete more insulin; restricts fat storage
- low levels in type 2 diabetes
osteocalcin
hormone produced by the skin
cholecalciferol
what is a precursor for vitamin D
cholecalciferol
what can affects hormone function
exposure to pesticides, industrial chemicals, arsenic dioxin, and soil and water pollutants
what are vulnerable to the effects of pollutants
sex hormones, thyroid hormone, glucocrticoids
what may explain the increase rates of cancer in some areas
interferences with glucocorticoids
what is letter A
pineal gland
what is letter B
hypothalamus
what is letter C
pituitary gland
what is letter D
thyroid gland
what is letter E
parathyroid glands
what is letter F
thymus
what is letter G
adrenal glands
what is letter H
pancreas
what is letter I
ovary
what is letter J
testis
