Cell Signaling and Endocrine System Flashcards
What are the 5 types of chemical messengers?
Amino acid messengers
Amine messengers
Peptide/Protein messengers
steroid messengers
Eicosanoid messengers
what is the amino acid messengers function?
functions as a neurotransmitter of the central nervous system
where are amino acids synthesized?
synthesized in the neuron mostly
amino acid messengers are lipophobic and stores in __________ until released?
vesicles
what are amine messengers derived from?
Derived from all amino acids
what are amine messengers function?
can function as neurotransmitter, paracrine and hormones
amine messengers are catecholamines. what are three examples of catecholamines?
dopamine, norepinephrine and epinephrine
amine messengers are synthesized enzymatically in _________.
cytosol
serotonin is derived from?
tryptophan, precursor for melatonin
melatonin
hormone secreted by the pineal gland and is important for regulating circadian rhythm
what is histamine derived from? what is it involved in?
histidine and involved in inflammatory reactions
what are peptide/ protein messenger characteristics?
- fewer than 50 amino acids long
- proteins are long polypeptide chains
- lipophobic, stored in vesicles until released
in post translational modification prepropeptides are formed in the ?
lumen of rough endoplasmic reticulum
post translational modification is cleaved by?
proteolytic enzymes forming propeptide
in post translational modification where is propeptide sent to?
sent to the Golgi via smooth endoplasmic reticulum
what are the steps of post translational modification?
- prepropeptide is formed in the lumen of the rough ER
- then is cleaved by proteolytic enzymes froming propeptide
- then propeptide is sent to the golgi via smooth ER
- propeptide cleaves to peptide on golgi, secondary vesicles released
what are steroid messengers derived from?
cholesterol (lipophilic)
in steroid messengers, enzymes catalyze cholesterol in the?
smooth ER and mitochondria
T/F: steroid messengers must be synthesized on demand and released immediately
true
what are eicosanoid messengers derived from?
arachidonic acid (lipophilic)
in eicosanoid messgers, phospholipase A2 cleaves _______ _________ from membrane phospholipid.
arachidonic acid
what two pathways are eicosandoids produced by?
cyclooxygenase and lipoxygenase
autocines, paracrines, neurotransmitters are trnasported to _____ ____ via ______ _______ and quicly degrade.
target cells, simple diffusion
how are hormones transported?
via circulatory system in dissolved form or via carrier proteins
what is the process of signal transduction?
- chemical messengers bind to target cell receptors
- then the messenger/ receptor binding changes the activity of the cell
- receptor binds to only 1 messenger
affinity
the strength of binding between messenger and receptor
in singnal transduction, can messengers bind to more than one receptor?
yes
in signal transduction do target cells have multiple types of receptors?
yes
what do target cell response to a chemical messenger depend on?
- messenger concentration
- number of receptors
- affinity
- antagonistic messengers
up regulation
increased production of receptors
down regulation
decreased production of receptors
explain the process of intracellular receptors
- lipophilic hormones pass through membrane and bind to receptor in cytoplasm
- hormone receptor complex binds to hormone response element
- binging activates or deactivates gene
what are the three membrane bound receptors?
channel linked receptors
enzyme linked receptors
G protein linked receptors
what is the process of membrane bound receptors?
- lipophocic messenger cannot pass through plasma membrane
- so it binds to receptors situated within the plasma membrane
what are examples of channel linked receptors?
fast ligand gated ion channel
calcium channel
explain the function of channel linked receptors?
- functions as a second messenger by binding to calmodulin
- then calcium calmodulin complex activates protein kinase which alters cellular functioning
what is the function of enzyme linked receptors?
- functions as both as a receptor and an enzyme
- changes protein activity producing a response
how does the enzyme linked receptors for tyrosine kinase work?
messenger binds to receptor changing conformation which activates tyrosine kinase to catalyze the phosphorylation of intracellular protein
explain the process of G protein linked receptors work?
- bound receptor activates g proteins
- g protein functions as a link between receptor and other membrane proteins
- alpha subunit binds with GDP during inactive state
- messenger binds with receptor which causes g protein to release GDP and bind with GTP and become activated
- alpha subunit is released
- alpha subunit binds to ion channel changing conformation which opens/ closes the channel
explain cAMP second messenger system
- first messenger binds to receptor and actiates Gs protein
- alpha subunit binds and activates adelylate cyclase which catalyzes conversion of ATP to cAMP
-cAMP activates protein kinase A which transfers phosphate from ATP to protein causing signal transduction - termination of cAMP requires cAMP phosphodiesterase
- phosphoprotein phosphatase removes phosphate from protein
explain phosphatidylinositol second messenger system
- messenger binds to receptor activating Gs protein, releasing alpha subunit which binds to and activates phospholipase C
- phospholipase C catalyzes conversion of PIP2 to DAG and IP3
- DAG activates protein kinase C which catalyzes conversion phosphorylation of proteins
- IP3 triggers release of calcium from endoplasmic reticulum
- calcium combines with calmodulin activating protein kinase
explain the process of signal amplification
- one messenger binds to one receptor
- several G proteins are activated
- each G protein activates an adenylic cyclase
- each adenylic cyclase generates hundreds of cAMP molecules
- each cAMP activates protein kinase A
- each protein kinase A phosphorylates hundreds of proteins
what are the two important control systems to maintain homeostasis?
autonomic nervous system and endocrine system
autonomic nervous system
communicates via nerve impulses resulting in rapid short lived responses
endocrine system
communicates via hormones resulting in slower prolonged responses
what are three components of the endocrine system?
- endocrine cells and glands/organs
- hormones transported by circulatory system
- specific target cells that posses receptors that respond to specific hormone
what is the function of the endocrine system?
- reproduction
- metabolism
- osmoregulation
- growth and development
- digestion
- sleep/mood
what are two types of endocrine organs?
primary and secondary
primary endocrine organs function?
secrete hormones
secondary endocrine organ function?
secretion is secondary to some other function
what are examples of primary endocrine organs?
hypothalamus, pituitary gland, thyroid, pancreas, gonads
what are examples of secondary endocrine organs?
heart, liver, skin, stomach, small intestine, kidney
hypothalamus
forebrain region that coordinates both ANS and activity of pituitary gland
what does the hypothalamus control?
body temp, thirst, hunger, sleep, emotional activity
pituita (phlegm)
protrusion off hypothalamus, divided into anterior lobe and posterior pituitary lobe
what are two embryonic sources?
neurohypophyseal bud and rathkes pouch
neurohypophyseal bud
ventral outgrowth from forebrain derived from neuroectoderm, becomes posterior pituitary lobe
another name for posterior pituitary lobe?
neurohypophysis
Rathkes pouch
dorsal outgrowth of roof of mouth, derived from oral ectoderm, becomes anterior pituitary lobe
another name for anterior pituitary lobe?
adenohypophysis
what kind of tissue is the posterior pituitary lobe made of?
nervous tissue
Describe how the posterior pituitary lobe works
-contains axon terminal ends of hypothalamic neurons
- secretes 2 neurohormones into capilaary bed and then into general circulation
- neurosecretory cell bodies within supraoptic nucleus of hypothalamus synthesize oxytocin
- neurosecretory cell bodies within paraventricular nucleus of hypothalamus sythesize ADH
what does oxytocin do?
-stimulates contraction of smooth muscles of uterus during labor
- stimulates contraction of myoepithelial cells which release breast milk produced by milk secreting epithelial cells (milk letdown)
- social interactions (pair bonding, strong affinity to mate)
what does antidiuretic hormone (ADH) regulate?
water conservation
explain the process of ADH
-sensors in hypothalamus detect and increase in blood osmolarity or decrease in blood volume during times of dehydration
- then a release of ADH causes collecting ducts of nephron to be highly permeable to water which is then returned to the vasculature and increases blood volume and pressure
- solute concentrations become more dilute and ADH release is inhibited
how does alcohol inhibit ADH secretion?
causes dehydration and hangover associated with alcohol consumption
what are symptoms of diabetes insipidus?
hypo secretion of ADH, output of copious amounts of urine and intense thirst
when you drink alcohol, why do you pee alot?
Alcohol is a diuretic, which means it promotes increased urine production. When you drink alcohol, it inhibits the release of antidiuretic hormone, which is responsible for regulating the amount of water reabsorbed by the kidneys. Without enough antidiuretic hormone your kidneys reabsorb less water, leading to increased urine production and more frequent urination.
what kind of tissue is the anterior pituitary gland made of?
epithelial tissue
explain how the anterior pituitary lobe works
- tropin neurohormones are relased by neurosecretory neurons in the hypothalamus
- adenohypophyseal endocrine cells secrete hormone into general circulation
- tropin neurohormones may be releasing or inhibiting
explain the hypothalamic pituitary portal system works
- connects hypothalamus with anterior pituitary lobe
- hypothalamus secretes releasing or inhibiting tropin neurohormones into primary capillary bed
- tropin neurotransmitters travel to anterior lobe via portal vein and enter the second capillary bed
- tropin neurohormones leaves second capillary bed and stimulates release of hormones by adenohypophyseal endocrine cells
- if stimulated, adenohypophyseal endocrine cells release hormones into general circulation
secretion of tropin neurohormones is regulated by?
hypothalamic neural input
what is prolactin releasing hormone secreted by?
secreted from hypothalamus neurosecetory cells
what is the function of prolactin releasing hormone?
stimulates lactotrophs within anterior lobe to release prolactin
what is the prolactin inhibiting hormone secreted by?
secreted by hypothalamus neurosecretory cells
what is the function of theprolactin inhibiting hormone?
suppresses release of prolactin by lactotrophs
when do prolactin concentrations increase?
during pregnancy causing mammy gland enlargement
what is sustained PH release stimulated by?
infant suckling
what is the growth hormone releasing hormone secreted by?
hypothalamus neurosecetory cells
what is the function of the growth hormone releasing hormone?
stimulates somatotrophs within the anterior lobe to release growth hormone
what does growth hormone do in the liver?
stimulates the production of insulin like growth factors
what does insulin like growth factors in concert with growth hormone do?
stimulates growth, cell reproduction and regeneration (muscle and bone cell)
what is the growth hormone inhibiting hormone secreted by?
secreted by the hypothalamus nuerosecretory cells
what is the function of the growth hormone inhibiting hormone?
inhibits release of growth hormones by somatotrophs
T/F: growth hormone secretion has a circadian cycle that is highest during sleep and decreases with age
true
interstitial growth
increased length
appositional growth
increased thickness
epiphyseal plate
main site of longitudinal growth of the long bones
what effects do growth hormones have in children?
- increases calcium retention
- increases muscles mass through sarcomere hypertrophy
-promotes lipolysis - stimulates growth of all external organs (excluding brain)
- reduced uptake and retention of glucose by liver
- contributes to the maintenance and function o pancreatic islets
- stimulates the immune system
- increases deiodination of t4 to t3 (thyroid hormones)
what is the result of hyper secretion of growth hormone in children?
gigantism, abnormally but proportionally tall (epiphyseal plates are still active)
what is the result of hyper secretion of growth hormone in adults?
acromegaly, overgrowth of bones in the face, feet and hands (long bones cannot grow because plates are closed), appositional growth of bone only
what is the result of hyposecretion of growth hormone in children? in adults?
-pituitary dwarfism, abnormally but proportionally short (can be treated to some degree)
-in adults there is no problem regarding growth
Achondroplasia
connective tissue disorder
what is thyrotropin releasing hormone secreted by?
secreted by the hypothalamus neurosecertory cells
what is the function of thyrotropin releasing hormone?
stimulates thyrotrophs within the anterior lobe to released thyroid stimulating hormone
what does thyroid stimulating hormone do?
stimulates the thyroid gland to secrete thyroid hormones (T3 AND T4)
what do thyroid hormones do?
increases metabolism, promotes growth and development
what happens if thyroid hormone blood levels increase?
suppresses the release of thyroid regulating hormone by hypothalamus neurosecretory cells and thyroid stimulating hormones by thyrotrophs
what is corticotropin releasing hormine secreted by?
hypothalamus neurosecretory cells
what is the function of corticotropin releasing hormone?
stimulates corticotrophs within the anterior lobe to release adrenocorticotropic hormone
what does the adrenocorticotropic hormone do?
stimulates adrenal cortex to release glucocorticoid hormones (ex. cortisol)
when is cortisol released?
in response to stress
what happens when cortisol levels rise?
suppresses corticotropin releasing hormone and adrenocorticotropic hormone release
what is gonadotropin releasing hormone secreted by?
hypothalamus neurosecretory cells
what is the function of gonadotropin releasing hormone?
stimulates gonadotrophs within the naterior lobe to release follicle stimulating hormone and luteinizing hormone
what does follicle stimulating hormone do?
promotes egg and sperm development and stimulates the ovary to secrete sex hormone estrogen and the testes to secrete testoserone
what does luteinizing hormone do?
stimulates ovulation and secretion of sex hormone estrogen and progesterone in females and androgens in males
what happens when estrogen and androgen levels rise?
suppresses gonadotropin releasing hormone release
what is the difference between short and long negative feedback loops?
short negative feedback loops involve direct inhibition of hormone secretion by the product of the process it regulates and occur relatively quickly, while long negative feedback loops involve multiple steps and regulatory factors, occurring over a longer time frame.
pineal gland
endocrine tissue that secretes neurohomone melatonin
why is melatonin important?
manages your circadian rhythm, levels raise at night, and used as a sleep agent
where is the thymus gland located?
anterior superior mediastinum (in front of the heart and behind the sternum)
what does the thymus gland do?
secretes thymosin
what does thymosin do?
promotes the maturation of T lymphocytes
when is the thymus gland largest and most active?
during neonatal and pre adolescent periods
when does the thymus gland begin to atrophy?
early teens years (replaced by adipose tissue in adults)
where is the thyroid gland located?
lies below the thyroid cartilage of the larynx and is surrounded by a connective capsule
what extends from the capsule to divide the thyroid into irregular lobes?
trabeculae
what hormones are produced by the thyroid?
T3- triiodothyronine
T4- tetraiodothyronine (thyroxine)
what is the functional unit of the thyroid gland?
follicle
describe the structure of the follicle
- single layer of simple cuboidal follicular cells surrounding a lumen.
- lumen filled with colloid produced and secreted by follicular cells
what does colloid consist of?
mainly of thyroglobulin (thyroid gland, precursor and storage form of thyroid hormone)
T/F: thyroid gland is synthesized in RER and enters colloid in via exocytosis
True
what are located between follicles in the thyroid gland?
calcitonin producing cells (C cells)
what does calcitonin do?
lovers blood calcium levels
In the thyroid gland, iodine is actively transported from blood into follicular cell via?
Then sent passively into colloid via?
Na+/I- symporter, pendrin transporter
explain the synthesis of thyroid hormones
- tyrosine residues of thyroid gland are iodinated
- 1 iodine forms MIT, 2 iodide ions form DIT
- 2 iodinated tyrosines (MIT or DIT) on the same thyroid gland covalently bond
- 2 DITs combine and form T4, 1 MIT and 1 DIT form to make T3.
- they are attached to the thyroid gland and stored
explain the secretion of thyroid hormones
- Thyroid secreting hormone binds to follicular cell membrane-bound receptors which activates cAMP secondary messenger system
- phosphorylated proteins causes endocytosis of iodinated thyroid gland from colloid via phagocytosis
- once inside cell, vesicle fuses with lysosome
- various proteases cleave thyroid gland to produce free T3 and T4
- T3 and T4 pass through membranes and bind with carrier proteins in blood
deficiency of iodine lead to decreatsed production of T3 and T4, this enlarges the tissue and will cause?
goitre
what is caused by the hyper secretion of thyroid hormones?
hyperthyroidism (graves disease)
What are symptoms of graves disease?
-elevated metabolic rate, sweating, raid/ irregular heart rate, nervousness, weightloss, oily skin and bulged eyes
how is graves disease corrected?
thyroid gland removal or ingestion of radioactive iodine to destroy most active thyroid cells
what is the result of underproduction of thyroid hormones?
hypothyroidism
hyperthyroidism can cause congenital thyroid abnormalities and autoimmune disorders such as?
hashimotos thyroiditis
what are symptoms of hypothyroidism?
abnormal weight gain, tiredness hairloss, dry skin, bradycardia
cretinism
severly stunted physical and mental growth due to untreated congential deficinecy of thyroid hormones
how is hypothyroidism treated?
hormone replacement therapy
where is the parathyroid glands located?
located on the surface of the thyroid gland
what is the function of parathyroid glands?
secretes parathyroid hormone (helps regulate Ca2+ levles by increasing blood Ca2+ levels)
hypocalcemia
low blood Ca2+ levels
hypercalcemia
high blood Ca2+ levels
adrenal glands location?
located above the kidneys
what are the three layers of the adrenal cortex?
zona glomerulosa
fasciculata
reticularis
mineralocorticoids, function?
cells of the zona glomerulosa. regulate Na+ reabsorption and K secretion from kidneys
sex hormones from the adrenal cortex. function?
cells of the zona fasciculata and reticularis. stimulates sex drive in femials
glucocorticoids, function?
cells of the zona fasciculata and reticularis. regulates response to stress
adrenal medulla
