endocrine physiology Flashcards
Endocrine system functions
metabolism
growth metabolism
energy metabolism
mineral metabolism
reproduction
endocrine system works by
feedback principle
message relay in the endocrine system
nervous system sends message to endocrine glands Endocrine glands produce and secrete hormones into blood
Hormones reaches the target organ
Target organ responds to the hormone and produces substance
Substance is picked up by receptors and brain stops sending message to endocrine glands
t/f endocrine system functions by amplification of signal which is the basis of sensitivity
true
one steroid molecule can activate a gene resulting in formation of
mRNA and enzymes
one protein molecule can influence the formation of
cAMP molecules
gland- are ductless glands that secrete products directly into the blood stream.
Endocrine gland
glands-release their products or secretion into the ducts leading to the lumen of other organs. (eg mammary gland, salivary gland, sweat gland)
exocrine glands
paracrine glands
in which the chemical messenger diffuses through the interstitial fluid to influence adjacent cells. (eg histamine, cytokines)
if the messenger acts on the cell of its origin, then it produces an autocrine effect. (eg insulin like growth factor produced by muscle to influence its effect on that cell – growth promoting effect)
autocrine effect
growth hormone has 2 effects
paracrine and autocrine
structure of endocrine glands
have different types of tissue in a organ
connective tissue
blood vessels
nerves
t/f often just one cell type inm and endocrine gland makes the hormone
true
t/f endocrine glands usually secrete more than one hormone
true
mechanisms in which endocrine and nervous system interact
direct interaction
neurohormones or neuropeptides
neurotransmitters
by direct interaction
endocrine cells of the adrenal medulla are directly controlled by preganglionic neurons of the adrenal medulla releasing hormones.
neurohormones and neuropetides
hormones derived from nerve cells
neurotransmitters
released from the synapse between nerve and effector cells
major endocrine glands in the body
Hypothalamus
Pituitary gland
Thyroid gland
Parathyroid gland
Thymus gland
Adrenal glands
Pancreas
Gonads (i.e., ovaries and testes)
Pineal gland
chemicals produced by endocrine organs and transported by vascular system to other tissues or target organ at a lower concentration
hormones
t/f hormones exist in biological active state for some time and are degraded or destroyed
true
protein hormones
GH
insulin
ACTH
peptide hormones
oxytocin
vassopressin
amino acid derivatives hormones
dopamine
melatonin
epinephrine
steroid or fatty acid derivative hormones
cortisol
progesterone
Vit D
gaseous hormones
nitric oxide
2 classes of hormones based on their solubility
water soluble
lipid soluble
catecholamines
water soluble hormones
and peptide/protein hormones
epinephrine and norepinephrine are an example of
catecholamines
steroid hormones are
lipid soluble hormones
name examples of lipid soluble hormones
include thyroid hormone
steroid hormones
fatty acid derived
Vitamin D3
steps of hormone synthesis
- protein hormones are synthesized as pre-hormones synthesized in ribosomes
- cleaved by rough endoplasmic reticulum to pro-hormones
*pro-hormones enters the golgi apparatus to form active hormones
active hormones are stored in
granules
hormones are released by
exocytosis
steroid hormones are synthesized and released in the
liver
steroid hormones synthesized in the liver are not
stored
2 classifications of secretion of peptides
regulated and constitutive
regulated secretion
cells stores the hormone in secretory granules and releases them in bursts when stimulated
most common pathway and allows cells to secrete a large amount of hormone over a short period of time
regulated secretion
constitutive secretion
cell does not store hormones but secretes it from secretory vesicles as it is synthesized
difference between regulated and constitutive secretion
regulated-stored in secretory granules
constitutive - not stores in cells, synthesized and secreted from secretory vesicles
thyroid hormones
made from amino acids
have intracellular receptors in the nucleus
continue to express their control functions for days or even weeks
difference between peptide hormones and amino acid hormones
thyroid hormone - intracellular receptor
peptide hormone - cell surface receptor
2 organs where steroid hormones are synthesized
tissues of gonads and adrenal gonads
steroid hormones produced in gonads
sex hormones
androgen - testosterone
estrogen - estradiol
progestins - progesterone
steroid hormones produced in adrenal gonads
Mineralocorticoids- (Aldosterone)
Glucocorticoids (Cortisol or corticosterone)
the precursor of steroid and lipid hormones is
cholesterol
rate limiting step of steroid hormones
conversion of pregnonolone to cholesterol
rate limiting step in synthesis of all steroid hormones
conversion of steroid hormone to prenenolone
cholesterol within the mitochondria is converted to
pregnenolone
enzyme that converts cholesterol to pregnenolone
CYP 11A1
The type of steroid hormone that is synthesized depends on
presence of specific enzymes within the cell.
For transport in blood,
steroids hormones bind to
plasma proteins like albumin
steroid hormone binding to albumin is high or low affinity / specific or non-specific?
low affinity and non-specific
how are steroids hormones usually eliminated?
inactivating metabolic and transformation and excretion in URINE AND BILE
t/f Steroid hormones bind to cell surface receptors
false, they do not bind to cell surface receptors
Hydrophilic
Short half lives
Cell surface receptors
peptide hormones
Hydrophobic
Longer half life
Intracellular receptors
steroid hormones
describe the secretion of epinephrine
secreted within seconds after stimulation, and develop action within seconds to minutes
5 mechanisms of control of hormone secretion
negative feedback
degree of activity of the target tissue
regulation of gene transcript and and translation involved in processing and in releasing it
positive feedback
cycling variations
example of hormones that are controlled by positive feedback mechanism
LH and oxytocin
cyclic variation in control of hormone secretion
seasonal changes
development and aging
diurnal cycle
sleep
mechanisms of hormone transport in blood
dissolved in the plasma (peptides and catecholamines)
bound to plasma proteins
(steroid and thyroid hormones)
define hormone receptor interactions
a protein that binds a ligand with high affinity and low capacity.
This binding must be SATURABLE.
How does a tissue become a target for a hormone?
by expressing a specific receptor for it
hormone-receptor interaction is defined by
equilibrium constant called the Kd, or dissociation constant.
dissociation constant measures if
the interaction is reversible and how easily the hormone is displaced from the receptor
QUANTIFYNG AFFININTY
3 types of hormones receptors
in or on the surface of the cell membrane (protein, and catecholamine hormones)
in the cell cytoplasm (steroid hormones)
in the cell nucleus (thyroid & steroid hormones)
receptors for water soluble proteins are found on
the surface of the target cell on the plasma membrane
coupled with second messenger systems
Receptors for the lipid soluble hormones are in
nucleus of the target cell
hormones diffuse by the lipid bilayer of plasma membrane
2 types of hormone receptors and activation
agonists
antagonists
agonists
molecules that bind the receptor and induce all the post-receptor events that lead to a biologic effect.
act like the “normal” hormone, although perhaps more or less potently
antagonists
molecules that bind to the receptor and blocks the binding of the agonist, but fail to trigger intracellular signaling events
t/f biological response can be achieved at concentrations of hormones lower than the required to occupy all receptor cells
true
examples of hormones that work with spare receptors (concentration is lower than the required to occupy all receptor cells)
insulin
LH
% of spare receptors
97
maximum biological response occurs when receptors are ocuppied on an avarage of
3%
more spare reeptors in the target cell =
more sensitivity to the hormone
lower concentration of hormone required to achieve half-maximal response
3 steps of the mechanism of intracellular receptors of steroid hormones (thyroid, retinoid and vit. D)
- receptors in the cytoplasm and nucleus
- binding to a specific regulatory promoter of the DNA sequence
- transcription of specific genes and formation of mRNA
how does intracellular signaling works?
formation a hormone-receptor complex
4 types of intracellular signaling
- ion channel-linked receptors
- G protein-linked hormone receptors
- enzyme-linked hormone receptors
- intracellular hormone receptors and activation of genes
In receptors for lipid-soluble hormones, what are the response elements?
Specific DNA sequences where the receptor-hormone complex binds
What is the consequence of the receptor-hormone complex binding to the response elements?
gene expression change and transcription of mRNA
The mRNA travels to the cytoplasm where it is translated into a protein
responses evoked by lipid soluble hormones are slow or fast?
SLOW
HORMONE activity is limited by
THE METABOLSIM of the hormone
2 mechanisms of hormone degradation
enzymatic rocesses
transforming into sulfates and glucuronides to be excreted in urine or bile via H2O
Mechanism of degradation of steroid hormones
in the liver
conjugation with sulfates and glucuronides
increases water solubility and is excreted in urine.
thyroid hormone degradation
Removal of iodine molecules
protein hormones are cleaved by
peptidases
hormonal measurements
bioassay-standarized curve constructed with the activity of the unkown
Chemical methods - chroma or spectrophotometry
Immmuno assay -ELISA OR radioactive
Endocrine diseases result from
hormone deficiency, hormone excess or hormone resistance
Hormone excess usually results in
DISEASE
hormone deficiency almost without exception, causes
DISEASE
CAUSES OF HORMONE DEFICIENCIES
genetic defects in hormone production
infection, infarction, tumor growth
autoimmune disrorders
Type 1 diabetes is a consequence of
hormone deficiency
