MODULE 1 Flashcards
communications among cells, tissues and organs within an individual were considered to be generated and mediated by what systems?
either the NERVOUS SYSTEM or ENDOCRINE SYSTEM
nervous system communicated through what?
PHYSICALLY
This system communicated
physically, using electrochemical signals
between the brain and other organs, such as
muscle group, or signals from one organ to another, as in a reflex arc
NERVOUS SYSTEM
The nervous system communicated
physically, using electrochemical signals
between the brain and other organs, such as
muscle group, or signals from one organ to another, as in a _____________.
REFLEX ARC
This system
communicated via chemical blood-borne messengers, for instance between the pituitary gland and the adrenal cortex.
ENDOCRINE SYSTEM
endocrine system communicated via chemical blood-borne messengers, for instance between the _______ and the ________.
PITUITARY GLAND and ADRENAL CORTEX
The path taken by the nerve impulses in a reflex
REFLEX ARC
communication via the nervous system is ______.
very rapid
endocrine communication is ________
slower
TRUE OR FALSE
One cannot describe normal and abnormal function of the heart and blood vessels without including major aspects of the respiratory and nervous systems.
TRUE
TRUE OR FALSE
The nervous system is significantly dependent on hormones from the endocrine system for normal function.
TRUE
The nervous system is significantly dependent on hormones from this system for normal function.
endocrine system
it is considered a component of the endocrine system, is
highly integrated with the nervous system.
adrenal medulla
what is Endocrinology?
It is the study of communication within a living organism by means of hormones.
what is Hormones?
these are the chemical messengers of the endocrine system
- is the study of communication within a living organism by means of hormones.
Endocrinology
are the chemical messengers of the endocrine system
Hormones
was described as a chemical messenger secreted from a ductless gland, emptied directly into the circulation, and transported by the blood
hormone
example of a hormone secreted from a ductless gland, emptied directly into the circulation, and transported by the blood
hemocrine communication
this blood-borne communication is but one manifestation of the endocrine system
hemocrine communication
Components of the endocrine system that communicate by routes other than blood vessels
(PANS)
Paracrine
Autocrine
Neurocrine
Solinocrine
hormones are secreted
locally into the extracellular space only to self-regulate the very cells that released them
autocrine communication
involves secretion of
hormones from a cell directly into the surrounding extracellular space; the hormone then interacts with adjacent or nearby cells without being transported by blood
Paracrine communication
It delivers very high concentrations of the hormone to its target site.
Paracrine communication
involving secretion of
peptides or other neurotransmitter molecules by neurons
Neurocrine communication
is a specialized form of paracrine function in which the chemical messenger is transferred to a target cell via a synapse or neuromuscular junction
Neurocrine communication
Neurocrine communication involving secretion of
the following by neurons
peptides or other neurotransmitter molecules
Several hormones are secreted directly into the lumen of the gastrointestinal, respiratory and reproductive tracts. This type of communication is called
solinocrine
Several hormones are secreted directly into the following tracts.
lumen of the GI, Respiratory and Reproductive tracts
Example of solinocrine or hormones secreted directly into the lumen of the gastrointestinal, respiratory and reproductive tracts.
(GVCS3)
- Gastrin
- Vasoactive intestinal peptide
- Calcitonin
- Somatostatin
- Secretin
- Serotonin
TRUE OR FALSE
A single hormone can affect a single function, but this one-on-one action is very rare
TRUE
A single hormone can affect a single function.
Example of hormone on hemoglobin
synthesis by erythrocytes
erythropoietin
single hormones having multiple actions
example of hormone on enzyme synthesis, erythropoiesis, bone turnover, carbohydrate, and lipid metabolism
thyroxine
multiple hormones having single actions
regulation of lactation by the following hormones
(PPCOTS)
Prolactin
Placental lactogens Corticosteroids
Oxytocin
Thyroxine
Sex steroids
multiple hormones producing multiple
actions, give example of hormones
Reproductive steroids, Oxytocin, and Corticosteroids (ROC) on pregnancy, fetal development, and
parturition.
Hormone of pregnancy, fetal development, and
parturition
(ROC)
Reproductive steroids
Oxytocin
Corticosteroids
are vital for maintenance of the animal’s internal environment
Hormones and Nervous System
are essential for pre-and postnatal growth and development
Hormones and their actions
are also important in timing the cessation of growth
Hormones
TRUE or FALSE
Maintenance of an animal’s internal environment requires metabolic energy generated from nutrients
processed by enzymes regulated by hormones.
TRUE
The players of the endocrine system are hormones - including the following
(PALS)
Proteins
Amino acids derivatives.
Lipids
Smaller peptides
protein hormones include
prolactin and growth hormone
Glycoprotein hormones include
- Thyrotropin or Thyroid-Stimulating Hormone (TSH)
- Luteinizing hormone (LH), 3. Follicle-stimulating hormone (FSH)
Peptide hormones include
- Insulin
- Insulin-like growth factor-1 (IGF-1)
- Adrenocorticotropic hormone (ACTH)
examples of hormones that are derivatives of amino acids
Triiodothyronine (T3) and Catecholamines (such as epinephrine and
norepinephrine)
example of Catecholamines
epinephrine and
norepinephrine
The large category of lipidic
hormones includes the subcategories of
Steroids and Eicosanoids
subcategories of steroids consist of the following hormones
progesterone
estrogens
androgens
glucocorticoids
mineralocorticoids
subcategories of eicosanoids consist of the following hormones
prostaglandin
thromboxanes
leukotrienes
Whatever the chemical nature of hormones they all have several characteristics in common.
ENUMERATE
- They are present in the blood and other ECFs in low concentrations.
- the existence of mechanisms that direct hormones to their target cells and tissues.
The range of hormone concentration from in extracellular fluids:
10-11 to 10-9 M
The range of concentrations of nonhormonal amino acids, peptides, and lipids:
10-5 to 10-3 M
measurements of hormones in small samples of the following
serum, plasma, or urine
TRUE or FALSE
hormones are in low concentrations in extracellular fluids
TRUE
have high-affinity receptors to capture or bind hormones from the extracellular fluids
Cells
These receptors can reside on the external surface of the cell membrane
gonadotropin receptors
These receptors are located inside the cell, such as those in the cytoplasm or nucleus
estradiol receptors
synthesized by Leydig cells of the testis
testosterone
testosterone, synthesized by ________ of the testis
Leydig cells
the hormonally active form of testosterone in the male
Dihydrotestosterone
Dihydrotestosterone, the hormonally active form of ____________ in the male
testosterone
Dihydrotestosterone, the hormonally active form of testosterone in the male,
is produced by ___________ such as those of the prostate.
androgen-sensitive target cells
thyroxine (T4) is converted to T3 within cells of the pituitary gland to play a major role in the regulation of what?
TSH secretion
This hormone is converted to T3 within cells of the pituitary gland to play a major role in the regulation of TSH secretion.
thyroxine (T4)
Steps involved in synthesis and secretion of protein hormone.
- Hormone gene > transcription
- Messenger RNA > translation
- Hormone precursor (prohormone) > post-translational processing
- Mature hormone > secretion
- Secreted hormone
One anatomic feature that efficiently directs hormones to their target tissues
portal circulation
consists of blood flow from capillaries in one organ to a vein and then to capillaries in another organ
Portal circulation
hepatic portal circulation is structured so that insulin, secreted into capillaries of the endocrine pancreas, is carried by the hepatic portal vein to capillaries of the liver, where it exerts its major actions
hepatic portal circulation
Synthesis of peptide
and protein hormones begins with ___________ to yield messenger RNA (mRNA), which encodes a prohormone on the rough endoplasmic reticulum (RER)
transcription of DNA in the nucleus
the process by which amino acids are then polymerized into a polypeptide prohormone
translation
Newly synthesized prohormones are released into the ______________ where they are carried to the Golgi complex.
cisternae of the ER
The processed hormone is then released here
extracellular fluid
large protein also known as
prohormone
the initial synthetic product for peptide hormones
large protein (prohormone)
a 39-amino acid peptide
Adrenocorticotropin (ACTH)
Adrenocorticotropin (ACTH) is a 39-amino acid peptide
derived from a much larger precursor (235 amino acids) called
proopiomelanocortin (POMC)
much larger precursor
235 amino acids
Other peptides with hormonal activity derived from POMC include:
(i) melanocyte-stimulating hormone
(ii) beta-endorphin
(iii) beta-lipotropin
is synthesized as part of a larger precursor by the chief cells of the parathyroid gland
Parathyroid hormone (PTH)
Parathyroid hormone (PTH) is synthesized as part of a larger precursor by the ___________.
chief cells of the parathyroid gland
This precursor is a polypeptide of 113 amino acids, is synthesized on
ribosomes of the chief cells.
preproPTH
The precursor (preproPTH), is a polypeptide of what amino acids?
113 amino acids
The precursor (preproPTH), a polypeptide of 113 amino acids, is synthesized on
_____________.
ribosomes of the chief cells
PreproPTH is reduced in the endoplasmic reticulum to?
proPTH
PreproPTH is reduced in the endoplasmic reticulum to proPTH, with how many amino acids.
90 amino acids
An N-terminal hexapeptide then is cleaved within the Golgi region to form _________ with how many amino acids and molecular weight?
native PTH
84 amino acids
9,500 daltons
Other prohormones include:
(i) proinsulin
(ii) proglucagon
(iii) progastrin
(iv) procalcitonin
Pancreatic __________ is found within the sequence of a larger gastrointestinal form of glucagon
called enteroglucagon, glicentin, or glucagon-like immune reactivity
glucagon
Pancreatic glucagon is found within the sequence of a larger gastrointestinal form of glucagon
called
enteroglucagon, glicentin, or glucagon-like immune reactivity
a prohormone, is converted to the hormone triiodothyronine (T3) in the liver, kidney, brain, and pituitary gland
Thyroxine (T4)
Thyroxine (T4), a prohormone, is converted to the hormone ____________ in the liver, kidney, brain, and pituitary gland.
triiodothyronine (T3)
Thyroxine (T4), a prohormone, is converted to the hormone triiodothyronine (T3) in what organs?
liver, kidney, brain, and pituitary gland
are produced from androgen precursors, primarily androstenedione in females and
testosterone in males, by enzymes present in peripheral nonendocrine tissues
Estrogens
Estrogens are produced from androgen precursors, primarily _________ in females and _________ in males, by enzymes present in peripheral nonendocrine tissues.
androstenedione
testosterone
Characteristics of a true endocrine gland that separate it from other organs that also produce hormones
(i) Endocrine glands synthesize the hormone at faster rates
(ii) Efficiently process prohormones
(iii) Have mechanisms for releasing the hormone in a controlled manner
TRUE or FALSE
Usually, only small amounts of hormones are
stored by endocrine glands.
TRUE
It represents the storage form of the iodothyronines
thyroglobulin
their thyroglobulins are physically similar
humans, pigs, sheep, goats, and cattle
Thyroid follicles store abundant iodothyronines as _________
thyroglobulin
It store abundant iodothyronines as thyroglobulin, providing a mechanism to delay
hypothyroidism should synthetic mechanisms fail.
Thyroid follicles
Thyroid follicles store abundant ___________ as thyroglobulin
iodothyronines
where does hormone synthesized and stored
secretory vesicles
Ribosome
Prehormone
ER
Prohormone
HORMONE SYNTHESIS AND SECRETION
(i) Synthesis of peptide
and protein hormones begins with transcription of DNA in the nucleus to yield messenger RNA (mRNA),
which encodes a prohormone on the rough endoplasmic reticulum (RER).
(ii) Amino acids are then
polymerized into a polypeptide prohormone. Newly synthesized prohormones are released into the cisternae of the endoplasmic reticulum where they are carried to the Golgi complex.
(iii) There, the proteins are processed and packaged into secretory granules or vesicles by budding from the ER and Golgi membranes. The processed hormone is then released into the extracellular fluid.
(iv) Lastly, it bind membrane receptors, initiate protein modification & synthesis.
Golgi apparatus; Stored in secretory vesicles
Peptide hormone
hormones are secreted in what manner?
hemocrine manner
Water-soluble hormones
proteins and peptides
do not require additional carrier proteins for transport
Water-soluble hormones
insoluble hormones
iodothyronines and steroids
they require carrier proteins
insoluble hormones
It circulates in the blood in an unbound form or bound to specific corticosteroid-binding globulin (CBG, transcortin) or to plasma albumin.
Cortisol
a synthetic steroid used therapeutically
Progesterone & prednisolone
It also bind to corticosteroid-binding globulin (CBG)
Progesterone
Prednisolone
Aldosterone
Human CBG binds about how many percent of the plasma cortisol
70%
It binds about 70% of the plasma cortisol, but this proportion varies greatly among other animal species.
Human CBG binds about 70% of the plasma cortisol, but this proportion
varies greatly among other animal species.
How many percent of
iodothyronines are normally circulating in blood in the unbound form.
Less than 1%
plasma half-life of T4
7 days
TRUE or FALSE
dogs have only about 15% of the TBG as humans, and cats apparently have none
TRUE
the half-life of T4 in dogs is shortened significantly how many hours
10 to 16 hours
Abnormalities in transport may appear during ___________ but are not usually associated with endocrine dysfunction.
endocrine function tests (EFT)
means regulation of hormonal secretion from an endocrine gland by an effect of the circulating hormone that the gland itself produces
feedback control
generate more hormone
positive feedback
generate less hormone
negative feedback
A classic example of negative feedback
hypothalamus-pituitary-thyroid axis
normally functioning thyroid gland
euthyroid
thyrotropin-releasing hormone (TRH) from?
hypothalamus
thyrotropin-stimulating hormone from?
pituitary gland
When iodothyronine concentrations in the blood are inadequate (e.g., primary hypothyroidism) TRH secretion from the hypothalamus ________ to stimulate TSH secretion from the pituitary, and TSH
stimulates the thyroid gland to produce more T4 and T3.
increases
What feedback mechanism will occur if there is an increased blood concentrations of iodothyronines so that secretions of TRH and TSH are reduced.
negative feedback
TSH-secreting cell
adenohypophysial thyrotrope
Thyrotropin-Releasing Hormone (TRH)
Hypothalamus
Thyrotropin-Stimulating Hormone (TSH)
Anterior Pituitary Gland
hormones produced by thyroid gland
Tetraiodothyronine (T4)
Triiodothyronine (T3)
It produces the thyroid hormones (T3 & T4)
thyroid gland
It negatively controls PTH secretion
Ionized calcium
negatively controls glucagon and positively controls insulin secretion
glucose
The following are few hormones produced without feedback regulation
produced by the
placenta (equine chorionic
gonadotropin, progesterone, and estrogens)
hormones produced by these glands are free of feedback control
ectopic glands
glucocorticoids is secreted by?
adrenal cortex
In the horse, secretory pulses of ACTH in pituitary venous blood generally last ________ minutes or less and occur every _________ minutes.
10 minutes
15 to 25 minutes
In mares, the highest concentrations of cortisol in serum or plasma
occurs between ______ hours daily, and the lowest concentrations occurs from ________ hours.
0700 and 0900 hours
1900 to 2300 hours
All hormone receptors are what?
proteins
two functional domains of hormone receptors
(i) one that binds the
hormone (recognition domain)
(ii) the other that
regulates post-binding biochemical events
(coupling domain)
one that binds the
hormone
recognition domain
the other that regulates post-binding biochemical events
coupling domain
receptors located within the cell membrane
receptors for
neurotransmitters,
peptides, and proteins
receptors that reside within the cytoplasm or nucleus
receptors for steroids, vitamin D, and iodothyronines
lipophilic hormones
steroid hormones
steroid hormones
estrogens
progestogens
androgens
glucocorticoids
These DNA regions may be short polynucleotide sequences
called
promoter elements
are located “upstream” from the 5’ transcription initiation site of the gene
being regulated
hormone response elements
seem to modify the abundance of gene
products (i.e., proteins) by specifying the site on DNA where RNA polymerase attaches,
Promotor elements
affect the frequency of transcript initiation
hormone response elements
are lipophobic and do not
pass readily through the lipid-rich plasma membrane as do steroids and iodothyronines
Proteins
they have receptors in the plasma membrane and rely on intracellular messengers to transmit signals (signal transduction) to modify cellular functions
Proteins
one of the second messenger for hormones that bind to cell surface receptor
cyclic AMP (cAMP)
Cyclic AMP (3’,5’-adenylic acid) is derived from what?
ATP (adenosine triphosphate)
Cyclic AMP (3’,5’-adenylic acid) is derived from ATP (adenosine triphosphate) through the action of?
adenylate cyclase
Cyclic AMP (3’,5’-adenylic acid) is derived from ATP (adenosine triphosphate) through the action of
adenylate cyclase and is degraded by?
phosphodiesterase
Interaction of a hormone with its receptor causes activation or inactivation of?
adenylate cyclase
a process mediated by a
family of stimulatory and inhibitory regulatory proteins
adenylate cyclase
initial steps in signal transduction
(a) hormone binds to receptor on the outer surface of the plasma membrane
(b) receptor binding activates intramembranous
regulatory proteins
(c) stimulatory regulatory proteins increase adenylate cyclase activity
(d) adenylate cyclase catalyzes formation of cyclic AMP from ATP
an enzyme consisting of two regulatory units and two catalytic units
kinase
are enzymes that catalyze the conversion of inactive proenzyme to active enzymes
Kinases
The now-activated catalytic units promote the transfer of the γ-phosphate of ATP to a serine or threonine residue in certain proteins by a process called
protein phosphorylation
Protein phosphorylation
ultimately leads to diverse processes such as the ff
(i) gene activation and inactivation
(ii) steroidogenesis
(iii) secretion
(iv) ion transport
(v) carbohydrate and fat metabolism
(vi) enzyme induction
(vi)i cell growth and replication
Some hormone and target cells use these as intracellular messages.
ionized calcium or phosphatidylinositides
Changes in ionized calcium within the cell regulate a protein called
calmodulin
is also a component of the enzyme phosphorylase b kinase that converts inactive phosphorylase a to active phosphorylase b.
Calmodulin
can be considered a tertiary messenger because there are other signals between hormone binding to the receptor and intracellular fluxes of ionized calcium
calcium
These intracellular messengers activate what?
protein kinase C
is a type of in vitro competitive protein-binding assay in which radioactively
labeled and non-radiolabeled ligand, e.g., hormone, compete for a limited number of binding sites on a binding
protein
radioimmunoassay
use specific antisera as the binding proteins and radiolabeled hormones to measure corresponding non-radiolabeled hormones in biologic specimens such as serum, plasma, and urine
Radioimmunoassay
Radioimmunoassays have
several advantages over other quantitative procedures for hormones:
ENUMERATE
(a) small sample volumes are needed;
(b) one can assay many samples at a
time;
(c) little if any sample
preparation is required
can provide excellent specificity, accuracy,
sensitivity, and precision. In addition, most reagents are fairly stable, and there is rapid turnaround of results
Radioimmunoassays
disadvantages of Radioimmunoassays include
acquiring, handling, and disposal of
radioactive materials, expensive radiation detection equipment, limited availability of reagents for animal
hormones, and limited shelf life of reagents because of chemical and radioactive deterioration
four criteria for assay validity are:
(i) specificity
(ii) accuracy
(iii) precision
(iv) sensitivity
is defined as freedom from interference by substances other than the one intended to be
measured
Specificity
is the extent to which a set of measurements of a substance agrees with the exact amount of the substance that is present
Accuracy
is defined as the smallest amount of unlabeled hormone that can be distinguished from having
no hormone in the sample
Sensitivity
is the extent to which a given set of measurements of the same sample agrees with the mean
Precision
damaged by therapy
iatrogenic
TRUE or FALSE
If an endocrine gland fails to develop properly, is destroyed by disease, synthesizes a biochemically
defective hormone, or is damaged by therapy (iatrogenic), primary hypofunction results.
True
is often the result of an autoimmune process whereby the thyroid gland is
invaded by immune cells and the hormone-secreting cells are destroyed.
Primary hypothyroidism
can be due to insufficient secretion of TSH, but it should be distinguished
from “hypothyroxinemia”, which can be produced by concurrent disease, e.g., hyperadrenocorticism,
malnutrition, and certain drugs
Secondary hypothyroidism
which can be produced by concurrent disease, e.g., hyperadrenocorticism,
malnutrition, and certain drugs
hypothyroxinemia
Secondary hypothyroidism can be due to insufficient secretion of what hormone?
TSH
concurrent disease that produces hypothyroxinemia
hyperadrenocorticism
malnutrition
certain drugs
In dogs, this disease can occur as a result of a developmental defect whereby hormone-secreting
cells of the anterior pituitary gland fail to differentiate completely, leading to multiple deficiencies
panhypopituitarism
young puppies will express this condition because there is a lack of
growth hormone secretion
pituitary dwarfism
is aggravated by secondary hypothyroidism from lack of TSH secretion
Retarded growth
caused by reduced ACTH secretion
secondary hypoadrenocorticism
secondary hypoadrenocorticism caused by reduced ________ secretion
ACTH
owing to diminished FSH and LH secretion
hypogonadism
hypogonadism owing to
diminished ________ secretion
FSH and LH
TRUE or FALSE
Hyperfunction of endocrine glands causes the expression of several common endocrine disease in dogs and cats.
TRUE
is caused by excessive production of cortisol by the adrenal cortex
Hyperadrenocorticism
Hyperadrenocorticism is caused by excessive production of this hormone
cortisol
Hyperadrenocorticism is caused by excessive production of cortisol by this organ
adrenal cortex
an adenoma or carcinoma of the adrenal cortex is formed, producing cortisol that is not controlled by ACTH (Cushing’s syndrome)
Primary Hyperadrenocorticism (Cushing’s syndrome)
A condition caused by producing cortisol that is not controlled by ACTH
Primary Hyperadrenocorticism (Cushing’s syndrome)
results from excessive secretion of ACTH by the pituitary gland, causing morphologic and functional hyperplasia of
the adrenal cortex.
Secondary hyperadrenocorticism (Cushing’s disease)
is due to excessive autonomous secretion of parathyroid hormone
Primary hyperparathyroidism
Primary hyperparathyroidism is due to excessive autonomous secretion of this hormone
parathyroid hormone
Primary hyperparathyroidism or excessive secretion of parathyroid hormone leads to what problems?
- demineralization of bone
- hypercalcemia
- renal calculi
- calcification of soft tissues e.g., nephrocalcinosis
is one of the most common endocrinopathies in cats and is related to the
excessive secretion of iodothyronines by proliferative lesions of the follicular cells of the thyroid gland
Hyperthyroidism
Hyperthyroidism is one of the most common endocrinopathies in this animal
cats
Hyperthyroidism is the excessive secretion of this hormone
iodothyronines
in dogs and ferrets is caused by neoplasia of the pancreatic beta cells, leading to hypoglycemia
Hyperinsulinemia
Hyperinsulinemia in dogs and ferrets is caused by neoplasia of the pancreatic beta cells, leading to?
hypoglycemia
is an unfavorable response to therapy caused by the therapeutic effort itself
iatrogenic disease
A common iatrogenic endocrine disease is caused by inappropriate or excessive treatment of animals with?
glucocorticoids
The disease shows the same manifestation as Cushing’s syndrome, which is the spontaneous disease.
iatrogenic disease
GENERAL PRINCIPLES OF HORMONE ACTION
- Intracellular Action of Steroid Hormones
- Intracellular Action of
- Intracellular Actions of Protein and Polypeptide Hormones
