Endocrine System Flashcards
What is the difference between an exocrine and endocrine gland? What are they developed from?
Exocrine gland - secretes to the surface of the epithelium
- grows from the epithelial tract
- retains connection to the surface
Endocrine gland - secretes into the blood via capillaries
- the stalk from epithelium degenerates
- separated from epithelial surface
Describe the following: autocrine, signaling across gap junctions, paracrine, and endocrine. Give an example of each
Autocrine - cell targets itself or cells identical to itself
- embryonic development, pain, inflammation, apoptosis, interferon release
Gap junctions - allows ions to cross through ion channels
- smooth and cardiac muscle cells
Paracrine - targets cells that are different than the original sender via extracellular matrix, gets removed quickly
- NT’s
Endocrine - targets cells at longer distances and reaches them via bloodstream
- hormones
- signal is diluted
What are some of the main differences between NTs and hormones?
NTs
- can be gas molecule
- short distance to receptor
- rapid effects (milliseconds)
- nerve signal transmission and cell behavior
- strength of signal modulated by FREQUENCY of AP’s
Hormones
- can be lipid molecule
- can be short-long distance
- delayed effects - minutes to days
- changes cell behavior
- strength of signal is modulated by [hormone]
What are the factors that cell responses depend on?
- [hormone] in the blood - more hormone = more response
- relative number of receptors the target cell has for the hormone
- no receptors = no response - must be have receptors specific to hormone for effect - receptor-hormone affinity - the longer the hormone is bound, the longer the effect
What is up and down regulation in hormone receptors? What is an example of each?
up regulation - response to lack of hormone for the cell receptors to bind to, the cell will increase the amount of receptors in hopes for more opportunity to bind
- greater response to same magnitude of hormone release
- performed via exocytosis
ex. increase of T receptors in skeletal muscles after training
down regulation - response to chronic abundance of hormone, the target cell will decrease hormone receptors
- decreases sensitivity and response to an increase in hormone
- performed via endocytosis
ex. decrease in hormone receptors due to high insulin levels
What are the different hormone interactions? Give examples of the last two.
Synergistic - 2+ hormones that act on the same target cell and their effects are amplified
Antagonistic effect - maintaining homeostasis via opposite effects (negative feedback)
- Glucagon/insulin (blood glucose levels)
Permissive effect - the presence of one hormone is required to allow a second hormone to fully effect the target cell
- thyroid hormone increases the # of epinephrine receptors, has permissive effect on estrogen and progesterone
- cortisone has permissive effect on GH and epi/NE
What are the cell activities that are altered by hormones?
- changes plasma membrane permeability - affects membrane potential
- enzyme activation - synthesizes new proteins, induces secretory activity
- enzyme deactivation or activation - think protein kinases
- mitotic stimulation - for growth and reproduction
- increase in secretory activity
What are the amino acid derivatives hormones? Are they lipid or water soluble?
Small molecules structurally related to individual amino acids
Thyroid hormone - derivative of tyrosine
- lipid soluble
Melatonin and serotonin - derived from tryptophan
- water soluble
Catecholamines - water soluble, derivatives of tyrosine
- epi/NE secreted by adrenal medulla
- DA secreted by hypothalamus
Histidine - histamine
What are the peptide hormones?
made of chains of amino acids, synthesized on rER, uses 2nd messenger
glycoproteins from pituitary gland:
- thyroid stimulating hormone
- luteinizing hormone
- follicle stimulating hormone
Short polypeptide/small proteins
- hypothalamus: anti diuretic hormone
- pituitary: adrenocorticotropic hormone, growth hormone
- pancreas: insulin, glucagon
What are the steroid hormones? What broader group is this part of?
type of lipid soluble hormone
derived from cholesterol
synthesized in the sER
altered by attaching of side groups
can cross the plasma membrane to bind to cytoplasmic receptors
glands that secrete steroids originate from embryonic mesoderm
estrogens, progestins, testosterone, aldosterone, cortisol
What are the eicosanoid hormones and what broader group are they part of?
lipid hormone
derives from the fatty acid arachadonic acid
acts as local hormones or circulating hormones
produced by all cells besides RBC
prostaglandins, leukotriene, thromboxanes
Describe hydrophobic and hydrophilic hormone transportation in the blood. Which has a longer half life and why?
hydrophilic - has polar regions which interacts with polar water, does not require transport protein but cannot pass through membrane
- requires second messenger system
hydrophobic - no polar regions, requires transport protein to travel in blood, can cross membrane without receptor to cytoplasm/nucleus
have longer half life bc:
- transport protein protects from liver enzymes/kidney filtration
- protects circulating hormones
must become unbound to leave capillaries to reach target cell
What is the half life and what shortens a hormones half life?
half life - time it takes for 1/2 the hormone to be eliminated from the system
- metabolism - hormones get degraded by enzymes either in the blood or organs
- products get excreted or recycled - conjugation - chemically attaching water-soluble molecules like sulfate or glucuronic acid to increase likelihood of excretion of hormone by kidney or liver
- occurs mainly in the liver - excretion via:
- kidney: metabolized products of hormones secreted in the urine
- liver: contributes to breakdown of hormones, products get excreted in bile or filtered from blood and excreted by kidneys - active transport
What are some of the factors that lengthen a hormones half life?
- binding to plasma proteins - reduces the rate at which molecules diffuse through blood vessel walls by increasing size and decreasing solubility
- chemical structure
- carbohydrate component of glycoprotein hormones protects them from proteolytic enzymes in the blood
- lipid soluble hormones are not water soluble and are not degraded by proteolytic enzymes
What are G protein coupled receptors and what are their subunits?
guanosine nucleotide - GTP binding protein
- has subunits that hydrolyze GTP to GDP to release energy and trigger a cascade of enzymatic activities, typically resulting in the phosphorylation of molecules within the cell
alpha subunit - binds to GTP, excitatory (s) or inhibitory (i)
beta and gamma - couplet bound together and have inhibitory effects on cell
What are the hormones whose receptors are linked to G proteins and where do they originate from?
pituitary hormones (except growth and prolactin) - from the anterior pituitary gland
parathyroid hormone - parathyroid gland
glucagon - pancreas
epinephrine - medulla of adrenal gland
Describe enzyme coupled receptors and the effects they have when a hormone is bound.
does not have G protein, but activates intracellular enzymes by:
1. direct activation of cytoplasmic enzyme guanylate cyclase to form cyclic GMP
2. direct phosphorylation of intracellular enzymes
membrane-bound receptor contains an intracellular enzyme or is associated with another protein that acts as the intracellular enzyme
once activated, the intracellular enzyme can:
- increase/decrease the synthesis of intracellular mediatory molecules
- results in phosphorylation of intracellular proteins
What are some examples of hormones who use enzyme coupled receptors and where are they secreted from?
insulin - pancreas
growth hormone - anterior pituitary gland
prolactin - anterior pituitary gland
atrial natriuretic factor - atria of the heart
Describe the common steps of the activation of cellular activity utilizing G protein couples receptors.
- plasma membrane receptor is associated with G protein complex.
- alpha subunit is bound to GDP - hormone binds to receptor - GTP replaces GDP on alpha subunit.
- receptor changes shape and releases G protein
- alpha subunit with GTP separates from other subunits - active alpha subunit can either open Ca channel or activate membrane bound enzymes
- removal of P from GTP inactivates the alpha subunit
- reforms G protein with other subunits and binds to receptor
Describe the steps on how G coupled protein receptors activate the synthesis of cyclic AMP after the common steps
- activated alpha unit binds with adenylate cyclase - membrane protein enzyme
- adenylate cyclase converts ATP from the cytoplasm into cyclic AMP
- cAMP: second messenger that activates other enzymes - cyclic AMP activates reactions involving protein kinase (A) that phosphorylates other enzymes
- results in activation OR inhibition of further enzymatic reactions - phosphodiesterase deactivates cyclic AMP (and cGMP)
Describe how G protein coupled receptors activate calcium channels after the common steps
- activated alpha subunit separates and binds to the calcium ion channel in the plasma membrane
- causes Ca channel to open
- Ca by itself can act as a second messenger - Ca ions can bind to calmodulin
- Ca + calmodulin can act as second messengers to activate protein kinases - once hormone dissociates from receptor site, P from GTP on activated alpha unit is removed
- alpha unit no longer activated, dissociates from Ca channel and channel closes
Describe how G protein coupled receptors induce the synthesis of IP3 and DAG
- activated alpha subunit separates and activates phospholipase C - membrane bound enzyme
- phospholipase C acts on the plasma membrane lipid, phosphoinositol phosphate (PIP2) to divide it into two 2nd messengers:
- inositol triphosphate (IP3) - water soluble - goes into cytoplasm
- diaglycerol (DAG) - lipid soluble - stays in membrane - inositol triphosphate travels to ER or outer membrane of the cell and binds to Ca channels
- Ca can either act as second messenger by itself or bind to calmodulin to act as 2nd messenger together - Calcium interacts with diaglycerol (still in membrane) to activate protein kinase C
- protein kinase C can phosphorylate/dephosphoylate, or open Ca channels in membrane
Describe the direct activation of cyclic GMP
- hormone binds to membrane-bound receptor
- receptor is bound to membrane enzyme guanylate cyclase - inner surface
- once hormone is bound, guanylate cyclase is activated - guanylate cyclase converts guanine (guanosine) triphosphate (GTP) into cyclic GMP and releases 2 phosphate groups
- cyclic GMP acts as a second messenger and binds and activated intracellular enzymes to produce a cellular response
- phosphodiesterase breaks down cyclic GMP
Describe direct phosphorylation of enzymes by the hormone receptor. What does receptor act as?
- hormone binds to receptor
- intracellular region of receptor is activated to function as a phosphorylase enzyme
- phosphorylates specific proteins - once phosphorylated, these proteins produce change in cellular activity of the target cells
receptor also acts as a protein kinase bc it adds phosphates to cellular proteins
skips the second messenger, making it harder to control
Describe how hormones activate intracellular hormone receptors
- lipid bases hormones can diffuse through the plasma membrane of the target cell
- can enter the cytoplasm or the nucleus, depending on the target cell - hormones bind to corresponding cytoplasmic or nuclear receptor
- if the hormone binds to a cytoplasmic receptor, it creates a hormone-receptor complex that enters the nucleus via nuclear pores - the hormone/receptor complex binds to DNA in the nucleus
- transcription and RNA synthesis occur
- in cytosol, mRNA is translated and protein synthesis occurs
What are the names for the different parts of the pituitary gland? During development, what do they develop from?
neurohypophysis - posterior pituitary
- developed from infundibular process of the brain
- AKA pars nervosa
adenohypophysis - anterior pituitary
- developed from Rathke’s pouch - epithelial cells
- AKA pars distalis
pars intermedia - area of blood vessels and some anterior pituitary cells that forms a barrier between the two parts of the pituitary gland
List the hormones that the following hypothalamic nuclei produce. Which part of the pituitary releases these hormones?
Arcuate nucleus, paraventricular nucleus, supraoptic nucleus
Arcuate
- gonadotropin-releasing hormone - adenohypophysis
- growth hormone-releasing hormone - adenohypophysis
- dopamine - adenohypophysis
Paraventricular
- oxytocin - neurohypophysis
- corticotripic-releaseing hormone - adenohypophysis
- thyrotropin-releasing hormone - adenohypophysis
Supraoptic
- antidiuretic hormone - neurohypophysis
Describe the general venous portal system in regards to blood vessel types
artery - arteriole - capillary - venule - capillary - venule - vein
Describe how systemic hormones travel through the hypothalamic-hypophyseal portal system
adenohypophysis only
- Superior hypophyseal artery - blood enters through the superior hypophyseal artery and transports circulatory levels of circulatory hormones
- Capillary bed 1 - (median eminence) - systemic hormones diffuse via capillaries and interact with hypothalamic cells
- depending on [hormone], the hypothalamus can release hypothalamic releasing hormones via cap bed 1 - Portal veins - hormones travel via portal veins in the infundibulum to adenohypophysis
- Capillary bed 2 (adenohypophysis) - delivers hypothalamic relating factors, picks up anterior pituitary hormones
- fenestrated capillaries - hypophyseal veins - carries hormones from the adenohypophysis into circulation
- also carries hormones from the neurohypophysis into circulation
Name the following hormones, where they are synthesized, and what their receptors are in the pituitary gland: CRH, TRH, GHRH, GnRH, DA, ADH, oxytocin
CRH - corticotrophin-releasing hormone
- synthesized by paraventricular nuclei
- bind to corticotroph cells in adenohypophysis for ACTH synthesis
TRH - thyrotropin-releasing hormone
- synthesized by paraventricular nuclei
- binds to thyrotrophs for TSH synthesis
GRHR - growth hormone releasing hormone
- synthesized by arcuate nuclei
- binds to somatotrophs for growth hormone synthesis
GnRH - gonadatropin releasing hormone
- synthesized by arcuate nuclei
- binds to gonadotrophs for LH and FSH
DA - dopamine
- synthesized by the arcuate nuclei
- binds to lactotrophs to inhibit prolactin synthesis
ADH - antidiuretic hormone
- synthesized by the supraoptic nuclei
- transported via axons, stored in synaptic buttons of neurohypophysis
Oxytocin
- synthesized by the paraventricular nuclei
- transported via axons, stored in synaptic buttons of neurohypophysis
What effects do ADH and oxytocin have on the body? Where are they released from?
released from neurohypophysis
ADH - antidiuretic hormone: increases water reabsorption in kidneys to maintain blood volume/pressure
oxytocin - increases smooth muscle contraction of the uterus (positive feedback)
- stimulates milk release from the mammary glands
What effects do GH and TSH have on the body?
GH - growth hormone
- increases protein synthesis (AA uptake)
- increases fat break down
- reduces glucose usage
- stimulates cartilage and bone growth
TSH - thyroid stimulating hormone
- stimulated normal development and secretion of thyroxin from the thyroid gland
What effects do FSH and LH have on the body?
FSH - follicle-stimulating hormone
- male: stimulates sustentacular cells in the testes to release androgen-binding hormone
- female: stimulate ovarian release of estrogen and egg maturation
LH: luteinizing hormone
- male: stimulates testicular release of testosterone (interstitial cells)
- female: stimulates development of corpus luteum and release of progesterone
What effects do ACTH and prolactin have on the body?
ACTH - adrenocorticotropic hormone: stimulates release of testosterone, cortisol and aldosterone from the adrenal cortex
prolactin - stimulates milk production by mammary glands
In a healthy system, describe how the hypothalamic-hypophyseal-endocrine gland system works
- low [hormone] circulates through the blood reaches the hypothalamus via the superior hypophyseal artery - diffuses via capillary bed 1
- low [hormone] triggers hypothalamus to increase releasing hormone synthesis - increased level of releasing-hormone diffuses via cap bed 1 into the portal veins and goes to the adenohpophysis
- diffuses to adenohypophysis via cap bed 2 - adenohypophysis increases synthesis of hormone responding to releasing-hormone form hypo
- hormone gets released to inferior hypophyseal veins via cap bed 2 - stimulates specific endocrine gland to produce more circulatory hormone
In the hypothalamic-hypophyseal-endocrine gland pathway, what happens when there’s a tumor in the hypothalamus?
- increase in releasing hormone synthesis
- increase in hypophysis hormone synthesis
- increase in circulatory hormone synthesis: typically would tell hypothesis to stop producing releasing hormone, but does not stop it
In the hypothalamic-hypophyseal-endocrine gland pathway, what happens when there’s a pituitary adenoma?
pituitary adenoma - tumor of anterior pituitary gland
- increase in pituitary hormone
- increase in circulating hormone
- decrease in releasing hormone from hypothalamus: this does not decrease the pituitary hormone synthesis
In the hypothalamic-hypophyseal-endocrine gland pathway, what happens when there’s a tumor in the endocrine gland?
- increase in circulating hormone
- decrease in releasing hormone from hypothalamus
- decrease in pituitary hormone: this does not decrease the amount of circulating hormone
Say there is an adenoma that compresses the infundibulum and portal veins. What would be the consequences?
Compression stalk syndrome: there would be a decrease in hormones from both the adenohypophysis and the neurohypophysis due to blockage of the portal vein, resulting in decreased circulating hormone
ex. adenoma in corticotrophs
- causes increase in ACTH, which causes increase in cortisol
- decrease in all other pituitary hormones: LH, FSH, DA, ADH, GH, TSH, oxytocin
What is this structure? What does it release when it’s stimulated?
parathyroid gland - releases parathyroid hormone
What is this structure? What stimulates it, and what does it release when it’s stimulated?
thyroid gland
- stimulated by: thyroid-stimulating hormone
- releases: thyroxin
What is this structure? What stimulates it, and what does it release when it’s stimulated?
adenohypophysis
- stimulated by: releasing hormones from the hypothalamus - CRH, GHRH, GnRH, TRH, DA
- releases: corresponding hormone to stimulate endocrine gland - ACTH, GH, FSH/LH, TSH, prevents prolactin release, respectively
What is this structure? What does it release when it’s stimulated?
pancreas
- releases insulin and glucagon depending on blood sugar levels
What is this structure? What does it release when it’s stimulated?
neurohypophysis
- has axons directly from hypothalamic nuclei that allows it to release antidiuretic hormone and oxytocin
What is this structure? What stimulates it, and what does it release when it’s stimulated?
adrenal gland
- stimulated by adrenocorticotropic hormone
- releases testosterone, cortisol, aldosterone
What is this structure? What stimulates it, and what does it release when it’s stimulated?
thymus - unsure what stimulates it and what it releases
What is this structure?
thymus
What are these structures?
A - thyroid
B - parathyroid
What is this structure?
Pineal gland
Identify these structures
A - adenohypophysis
B - neurohypophysis
What are these structures?
A - adenohypophysis
B - neurohypophysis
C - infundibular stalk
D - hypothalamus
Identify the structures
Adrenal gland on the kidneys
Label these structures
A - hypothalamus
B - hypophysis
C - infundibulum
D - pineal gland
What is this structure?
thymus gland sitting on top of heart
- larger in children
Identify the structure
pancreas
- sits posterior to the stomach
Identify these structures. What ado they release?
hypothalamic nuclei
A - supraoptic nucleus: ADH
B - arcuate nucleus: GnRH, GRH, DA
C - paraventricular nucleus: Oxytocin, CRH, TSH
