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122 Cards in this Set

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  • Back

What was the significance of Berthold's experiment?

He postulated existence of a substance that travels through the bloodstream to target organs.

This was in response to his experiment with castration and re-implantation of chickens.

What is a hormone?

a signaling molecule released by a cell and conveyed by the blood stream, by neural axons, or by local diffusion to cells in target tissues.

What's a hormone's chemical nature?

What does it do at the target tissue?

protein, peptide, catecholamine, steroid, or iodinated tyrosine derivative

regulates existing metabolic pathways (through 2ndary messangers) or regulates synthesis of enzymes and other proteins at the DNA level. In this way, it regulates the rates of specific reactions w/o itself contributing energy or initiating the process

Hormone releasing cells secrete hormones into the internal environment = ______ ________

Therefore, these cells are called _______ ___.

These cells can either be scattered through tissues, or they are parts of specialized _____ ___, collectively called ______ ______.

endocrine secretion

endocrine cells

endocrine glands, endocrine system

How are hormones transported in the body?

endocrine cells secrete hormones into extracellular fluid and these hormones move via diffusion (and thermal & random brownian motion), but this process is slow

so, some hormones travel via the bloodstream and are recognized by target tissues

What are the functions of the endocrine system?

to regulate:

1) metabolism

2) fluid status

3) growth

4) sexual development

5) reproduction

The endocrine & nervous system work together to maintain homeostasis.

Types of chemical communication:

1) Autocrine

2) Paracrine

3) Endocrine

4) Neurocrine

5) Neuroendocrine

acts on the cell which released it

acts on adjacent cells w/o entering the bloodstream

1st enters the bloodstream and then reaches target cells

secreted by neurons

interaction btw neurons and endocrine cells

What are the 5 categories of hormones?

1) peptide, protein, & glycoprotein hormones

2) catecholamine hormones

3) thyroid hormones

4) steroid hormones

5) Lipokines

Pepide and protein hormones:

What is the difference?

Examples of each...

How are they synthesized, stored, and secreted?

Peptide = fewer amino acid chains, < 50 chains = vasopresin, oxytocin. glucagon

Protein > 50 chains= insulin, growth hormone, prolactin

DNA => messenger RNA => preprohormone => prohormone => hormone

They are stored in secretory granules from golgi ap. and then secreted by exocytosis

Catecholamine hormones:

Examples? Synthesis? Storage?

Epinephrine, norepinephrine, dopamine

synthesized from amino acid tyrosine, stored in secretory granules, and released by exocytosis

Thyroid Hormones:

Thyroxine/T4; Triiodothyronine/T3

Synthesized from tyrosine and iodide

Stored extracellularly in follicles of thyroid gland as a component of a large protein molecule

lipophilic so must bind to carrier proteins to be transported in plasma, and (-) charged so require transporters for cell uptake

Steroid Hormones

cortisol, aldosterone, androgens, Vit D

synthesized from cholesterol


Increase secretion by mobilizing synthesis from cholesterol

Lipophilic , so transported in plasma bound to carrier proteins and they can enter cellular membranes

The dominant mechanism of regulating hormone secretion and release is ___ ___.

And these processes are common, ____, and critical for the _____________________.

negative feedback

= stable and critical for the maintenance of homeostasis

_______ ________ is rare and controls surges of hormone.

They are used when a ____ of hormone is required, such as luteinizing hormone surge before ovulation.

positive feedback


What happens to hormones after they are released into the blood stream?

What is the hormone half-life time?

1) hormones released into bloodstream

2) circulate either free or bound to other plasma constituents

3) eventually, they are taken up by cells

4) then they are degraded, or removed by urinary or biliary secretion

The time during which the hormone loses 50% of its biological activity

Describe the events that are triggered by hormones in target tissues?

1) Hormone binds to a specific receptor in the target cell

2) this initiates intracellular events leading to the final physiologic effect

3) the receptor activation triggers changes in enzyme activity or concentration

4) This leads to the regulation of multiple metabolic pathways and eventually changes detectable at the cell level or whole organism

Hormones are distributed blindly to all cells in the organism, yet only some respond to a signal.

What property of a cell determines whether it will be affected by a particular hormone?

The presence of receptors sensitive to that particular hormone

Where are receptors for lipophilic and lipophobic hormones found?

What is the result?

Water soluble/ lipophobic hormones bind to receptors in the target cell membrane. This either directly or via 2nd messengers regulates activity of existing enzymes=FAST

Water insoluble/lipophilic hormones bind to nuclear receptors. This regulates the gene transcription and synthesis of new enzymes or structural proteins = SLOW

What are 1st and 2nd messengers?

How are they activated?

And what are the consequences?

1st messenger = an extracellular substance that binds to a cell-surface receptor and initiates intracellular activity

2nd messenger = an intracellular substance (such as cyclic AMP) that mediates cell activity by relaying a signal from an extracellular molecule (as of a hormone or neurotransmitter) bound to the cell's surface

= activate protein kinases and these phosphorylate other proteins = physiologic effect

Protein and catecholamine most commonly activate _____ ______ secondary messenger systems.

What do the 2nd messengers do?

cAMP or IP3/DG

cAMP = activates protein kinase A (PKA), PKA = activates other enzymes by phosphorylating them and/or PKA can alter gene expression via CREB-CRE pathway in the nucleus

How can a relatively small amount of hormone produce a large response?

The intracellular signal amplification = one ligand can activate multiple G proteins, which each activate an enzyme that produces multiple molecules of 2nd messenger...

The hormone concentration and sensitivity of receptors determines the magnitude of the hormone effect

Describe the calcium/diacylglycerol messenger system

1) Hormone binds to a G-protein coupled receptor

2) Activation of phospholipase C

3) activation of diacylglycerol = activation of other enzymes = biological effects

4) Ca2+ mobilization due to the activation of Ca2+ channels on plasma membrane and ER = protein activation = biological effect

Describe the action of a steroid hormone...

1) Steroids can bind to receptors in the cell membrane, cytoplasm, or nuclear receptors

2) These receptors are transcription factors that regulate the synthesis of proteins

3) Products include: enzymes, structural proteins, receptor proteins, and transcriptional proteins

What is synergism of hormonal action?

in some instances, different types of hormones work together

This part of the pituitary...

* stains darker histologically due to containing lots of secretory cells

* controlled by hypothalamus

* also called Adenohypophysis

* originates from ectoderm of the oral cavity called Rathke's pouch

The anterior lobe of the pituitary

The posterior lobe of the pituitary

This part of the pituitary.....

*Also called Neural lobe or Neurohypophysis

* Originates from neural tissue

* Does NOT contain secretory cells

Describe the two categories of hormones the hypothalamus secretes...

Which hormones are released in the blood stream in the posterior pituitary?

Where do they come from?

And how did they get there?

oxytocin, antidiuretic hormone (ADH)

They are released by the hypothalamus into the posterior pituitary via long axons

Which hormones are secreted by the anterior pituitary?

Follicle-stimulating hormone (FSH), Luteinizing hormone (LH), Thyrotropin (TSH), Adrenocorticotropin (ACTH), Prolactin (PRL), Somatotropin (GH), Melanotropin (MSH)

How does the hypothalamus control secretion of hormones from anterior pituitary?

What is the role of the portal blood vessels?

The hypothalamus releases hormones from neurons and these hormones that either inhibit (inhibiting hormones) or stimulate (releasing hormones) the activity of the anterior pituitary endocrine cells travel via the hypophyseal portal veins to the anterior pituitary

Which pituitary hormones control activity of other endocrine glands?

Follicle-stimulating hormone (FSH), Luteinizing hormone (LH), Thyrotropin (TSH), Adrenocorticotropin (ACTH)

Which endocrine glands are controlled by the ANS?


Adrenal gland


Which part of the pituitary secretes the alphaMSH/melanocyte stimulating hormone?

What is the precursor?

What is the function of this hormone?

Which other pituitary hormone can also stimulate melanocytes?

Anterior Pituitary

Proopiomelanocortin (->ACTH -> MSH)

MSH stimulates production and dispersion of pigment melanin in skin melanocytes (=skin or hair coat darkening)

ACTH (Adrenocorticotropin)

The hypothalamic-pituitary system controls:

1) Water metabolism via ____

2) Lactation, milk secretion, & uterine contractions via ___ & ____

3) Skin pigmentation via ___

4) Body Growth via ____

5) Reproduction and gonads via ____ & ____

6) Activity of thyroid and adrenal glands via ____& ____


prolactin & oxytocin



FSH & luteinizing hormone (LH)

Thyroid stimulating hormone/TSH & ACTH (adrenocorticotropic hormones)

Name the 6 cell types in the anterior pituitary and what they secrete...

1) Gonadotroph = FSH & LH

2) Thyrotroph = TSH

3) Somatotroph = GH

4) Lactotroph = prolactin

5) melanotroph = melanotropin

6) Corticotroph = ACTH (adrenocorticotropin)

What is growth hormone?

Which gland secretes it?


Any other tissues that secrete it?

A protein produced by somatotrophs

secreted by anterior pituitary

regulated by hypothalamic GHRH & GHIH

smaller amounts secreted by mammary glands in cats, dogs, humans

What are the 2 main functions of GH?

1) Promotes Growth

2) Provides a ready source of energy during starvation

Describe the indirect actions of GH

= Anabolic action

= growth-promoting action, prevails in well-fed animals

1) GH stimulates liver to secrete IGF-1 (insulin-like growth factor 1)

2) IGF-1 stimulates lipogenesis, protein synthesis, cell multiplication & enlargement, deposition of extracellular matrix, and cartilage growth in long bone growth plates

Describe the direct actions of GH

= catabolic action

= fuel-mobilizing action, typically prevails in poorly fed animals

= stimulates gluconeogenesis in the liver -> glucose and lipolysis of fat cells -> FFA & glycerol

What are gigantism and acromegaly?

How do they develop?

Hypersomatotropismcan lead to Acromegaly: a disorder that is caused by chronic overproduction of growth hormone by the pituitary gland and is characterized by a gradual and permanent enlargement of the flat bones (as the lower jaw) and of the hands and feet, abdominal organs, nose, lips, and tongue and that develops after ossification is complete. As opposed to gigantism that develops before ossification is complete.

What is pituitary dwarfism?

= failure to secrete enough GH in young animals

= small stature, soft/"puppy" haircoat, hyperpigmentation, soft mandible, suppressed immune system, cardiac disorders, delayed epiphyseal closure, etc.

Another consequence of acromegaly or gigantism is diabetes mellitus. Why does this occur?

Growth hormone interferes with insulin intracellular signaling

How is synthetic GH used in the cattle market?

Is this safe?

What about meat?

It's used by the dairy industry to increase milk production, because bovine somatotropin prevents mammary gland cell death.

Yes, it's denatured by digestion and it's not active in humans. Also, the amount of IGF-1 in milk is negligible.

Federal law prohibits any hormone use in the poultry & pork industry.

Name two anterior pituitary gonadotropins.

What is their chemical nature?

How is secretion controlled?

Luteinizing hormone (LH) and follicle stimulating hormone (FSH) are released by gonadotrophs in the anterior pituitary

= Proteins

= controlled by GnRH (gonadotroph releasing hormone

What is the function of...

1) FSH

2) LH

1) Stimulates growth & maturation of immature ovarian follicles

And stimulates follicular granulosa cells to produce estrogen

2) Triggers ovulation and development of the corpus luteum (=produces progesterone)

And stimulates follicular theca cells to produce androgens

Name and describe the phases of estrous

Which cells of the ovary secrete estrogen and progesterone?

Which cells produce androgens?

Which pituitary hormones stimulate each of these cell types?

Granulosa cells, which are stimulated by LH

Theca cells, which are stimulated by FSH

Which phase of the estrous cycle is dominated by ovarian secretion of estrogen?

What about progesterone?

What are the effects on the endometrium?



Progesterone stimulates endometrial secretion in preparation for implantation and also supports pregnancy

Why is the change from negative to positive estrogen feedback important?

How does this affect the mature follicles?

Estrogen initially suppresses LH and FSH, but once it switches from this negative feedback to positive feedback high levels of estrogen stimulate LH surge

This triggers ovulation of the mature follicles

How would you describe gonadotropin release in males?

What are the target cells?

Which cells produce testosterone

Gonadotropins are released in a steady fashion to stimulate secretion of testosterone and estrogen and to support spermatogenesis

Leydig cells produce testosterone (important for sperm maturation) in response to LH

What are the functions of the


chorionic gonadotropin,

interferon tau,

produced by human blastocyst; rescues CL from regression by continuing the production of progesterone...pregnancy test

similar, but produced by bovine & ovine (sheep) trophoblasts

What are the functions of the placental


& relaxin ?

supports maternal metabolism and initiates milk synthesis, antagonizes maternal insulin

relaxes pelvic ligaments, increases oxytocin synthesis = preparation for parturition

How do prolactin and oxytocin regulate milk synthesis and ejection?

What triggers the release of these two hormones?

Prolactin is a polypeptide secreted by lactotrophs in the anterior pituitary and it stimulates lactogenesis in secretory alveolar cells

Oxytocin is a nanopeptide released in the posterior pituitary and it triggers milk ejection by stimulating contraction of myoepithelial cells

The suckling reflex triggers their release

What is galactorrhea?

secretion of milky fluid from breasts of males (or females), caused by hypothyroidism resulting in an increase in TRH and prolactin

What are other functions of


and prolactin?

facilitates contraction of uterine myometrial cells during labor; maternal behavior & bonding; contraction of sm. muscles during copulation; stimulate ADH receptors

stimulates maternal behavior and pair bonding; larval growth & osmoregulation in amphibians; photostimulation induced premigratory fattening in birds

What is ADH? and what is its main function?

What gland secretes it?

it's a nanopeptide secreted by the posterior pituitary that inhibits diuresis and controls blood volume, pressure, & osmolarity

How does ADH achieve its physiological effects?

increases water reabsorption by stimulating incorporation of aquaporins in the apical membrane of the collecting duct in the kidneys

also, it dilates renal and cerebral vessels, while constricting others

and in large amounts stimulates ACTH, which stimulates adrenal steroids = water preservation

What are the primary stimuli that trigger ADH secretion?

1) Osmoreceptors = detect changes in osmolarity in plasma = neurons themselves that synthesize & secrete ADH (detect this b/c these cells are sensitive to shrinking; cell shrinks = increase ADH & water reabsorption) 2) Baroreceptors in the heart later can detect changes in blood pressure and volume 3) Decrease in blood volume and pressure detected by the juxtaglomerular kidney cells stimulates secretion of renin, leading to formation of Angiotensin II, which is a strong stimulator of ADH & Aldosterone

What is diabetes insipidus?

How can it be treated?

A condition associated with insufficient ADH action; patients product large volumes of dilute urine; exhibit intense thirst

desmopressin = synthetic analog of ADH

Name the layers of the adrenal cortex and hormones secreted by cells in each layer...

What hormones are secreted by the adrenal medulla?

Which layers of the adrenal gland are under ACTH control?

zona fasciculata and zona reticularis

What is the precursor for the biosynthesis of hormones of the adrenal cortex?


What are the effects of cortisol on metabolism?

mobilization of fuel by opposing the action of insulin by making more glucose available in plasma and increasing appetite

What are other major effects of cortisol?

inhibits inflammatory and immune response;

triggers parturition and prepares fetus for birth; decreases Ca+ deposition; decreases ADH, TSH, & GH

What is Cushing's disease?

What are the most common treatments?

pituitary-dependent hyperadrenocorticism (PDH); excessive ACTH secretion

In horses, dopamine agonists and serotonin antagonists (suppress abnormal ACTH production)

In dogs, Mitotane, a DDT derivative used for controlled destruction of adrenal cortex


What is it's chemical nature?

Where is it secreted?

What triggers its secretion?

What are its functions?

It's a mineralocorticoid secreted by the zona glomerulosa of the adrenal cortex

It's released in response to 1) reduced volume of circulating fluid (detected & stimulated by renin/angiotensin) 2) High K+ in plasma

Functions: it facilitates reabsorption of Na+ and secretion of K+ & H+ by the kidney

Explain the operation of the renin-angiotensin system in the regulation of aldosterone.

Renal hypotension, decreased GFR, and Decreased Na+ concentration in distal tubular filtrate stimulates secretion of renin by juxtaglomerular cells.

Renin then catalyzes conversion of angiotensinogen (normally in the blood) to angiotensin I, and this is converted to Angiotensin II, which promotes the secretion of aldosterone by the adrenal cortex

What are other functions of angiotensins?


stimulates release of catecholamines from adrenal medulla

stimulates thirst

promote ADH secretion

What are ACE inhibitors?

ACE = Angiotensin converting enzyme is found in the lungs and other tissues, and it converts Angiotensin I to Angiotensin II (&III)

ACE inhibitors block this action, preventing the conversion of Angiotensin, and thus the adrenal cortex is not stimulated to secrete aldosterone. This results in a decrease in blood volume and pressure

What are the cellular effects of aldosterone?


1) Stimulates ATP production (required for Na+/K+ pump)

2) Stimulates the synthesis of Na+/K+ pumps (create concentration gradient allowing Na+ to enter cell via Na+ channels)

3) Stimulates Na+ channels to allow more Na+ influx

Why is a bilateral adrenalectomy fatal?

B/c w/o the adrenal glands there is no aldosterone, which leads to a loss of Na+ and therefore a loss of H2O and retention of K+ & H+

Then peripheral circulatory and renal failure due to the loss of water, which decreased the blood volume & pressure causing death

What is ANP?

Where is it secreted & how is this stimulated?

What is its function?

Atrial Natriuretic Peptide

Synthesized & secreted by atrial myocytes in response to atrial stretch (caused by hypervolemia, hypertension, hypernatremia)

Function: reduces both Na+ & fluid levels by natriuresis and diuresis, therefore it opposes actions of aldosterone, ADH, & angiotensin II

What is Addison's-like disease?



Adrenocortical insufficiency/ hypoadrenocorticism & it can be caused by autoimmune destruction of adrenal cortex, adrenal suppressive therapy (Mitotane), or prolonged glucocorticoid administration

anorexic, vomiting, diarrhea, PU/PD, hypotension, weak pulses & bradycardia, Hyponatremia, hyperkalemia, Acidemia, Increase in ACTH and decrease in cortisol & aldosterone

Prednisone (cortisol analog) & 9-alpha-fluorocortisol (synthetic mineralocorticoid)

Describe the adrenal medulla and its relationship to the sympathetic nervous system.

The adrenal medulla is a modified sympathetic ganglion

Its chromaffin cells secrete catecholamines epinephrine and norepinephrine in response to the activation of the sympathetic nervous system by stress

These hormones invoke the flight-or flight response

Which hormones are secreted by the adrenal medulla?

What triggers their release?

Which neurotransmitter stimulates the release of medullary hormones from chromaffin cells?

Epinephrine (most abundant) and norepinephrine are secreted by chromaffin cells

activation of the sympathetic nervous system by stress or emergency


____ and _____ stimulate the synthesis of norepinephrine and epinephrine.

ACTH (adrenocorticotropic hormone) and Cortisol

Describe the fight-or-flight response.

Emotional (anxiety; apprehension), Biochemical (hypoglycemia, hypoxemia, change in pH), or Physical (exercise, injury, hypotension, hypothermia) stress stimulates the sympathetic nervous system, which stimulates the secretion of catecholamines by the adrenal medulla.

The effects of these hormones on target tissues are the flight or fight response: Increased CO & renin release; vasodilation of skeletal m. arterioles; generalized vasoconstriction; relaxation of bronchiolar smooth m.; pupillary dilation; decrease insulin and increase glucagon

Which property of target cells explains the wide variety of physiological actions of epinephrine and norepinephrine?

The differential expression of alpha & beta receptors in target tissues

What are the main consequences of stimulation of

alpha 1,

alpha 2,

beta 1,

beta 2 adrenergic receptors?

Smooth muscle contraction (blood vessels, sphincters, pupil dilator, etc.); increased sweating

inhibition of NT & hormone release; decrease of insulin

Increase Cardiac Output

Smooth m. relaxation (respiratory), glycogenolysis, gluconeogenesis, lipolysis, increased hormone secretion

Describe the response of an organism to stress.

Stress causes the release of cytokines = stress signal sent to the brain

=>Hypothalamus activates the SNS

-> signal travels through spinal cord to adrenal medulla -> release of epinephrine = energy mobilization & cardiovascular redistribution

->Pituitary releases ACTH -> Cortisol secretion from adrenal cortex = energy mobilization & cardiovascular redist. & inhibit inflammation & immune response

=> Cortex stimulates the release of norepinephrine from neurons = arousal, behavioral activation, aggressiveness

What is pheochromocytoma?

in what species are you most likely to see it?


A catecholamine secreting tumor (most are in adrenal glands)

Older dogs

removal of tumor, drugs to control hypertension

Describe the structure of the thyroid gland.

Name 3 hormones secreted by this gland and their functions.

1) T3 (triiodothyronine) = most potent form produced from T4 in thyroid follicular cells or target tissues

2) T4 (thyroxine) = produced most by thyroid gland; synthesized, stored, and secreted by follicular cells

T3 & T4 = increase the basal metabolic rate = increase O2 use and thermogenesis

3) Calcitonin = polypeptide secreted by the parafollicular cells of thyroid gland; it acts to DECREASE Ca2+ in plasma

Describe the main steps in the synthesis and secretion of thyroid hormones.

1) Follicular cells synthesize thyroglobulin (TG) and trap I- (the thyroid gland stores 90% of bodies I-)

2) Tyrosine is iodinated and condensed = T4 or T3

3) T3 & T4 are freed from TG in follicular cells

4) T3 & T4 can exit and enter circulation = lipophilic, so must circulate bound to plasma proteins

5) Thyroid hormone transporters are required for transport across cell membranes

How is the secretion of thyroid hormones regulated?

Deviation from homeostasis (such as drop in core body temp.) are detected by the hypothalamus = secretes TRH (thyrotropin release hormone)

TRH=> stimulates secretion of TSH (thyrotropin) by the Anterior Pituitary

TSH => circulation => Stimulates Thyroid gland = release of T3 &T4 = stimulate basal metabolic rate in many cells => increase thermogenesis

Describe the main effects of thyroid hormones on calorigenesis, carb. & lipid metabolism, protein synthesis, bone, muscle, skin, and brain development.

calorigenic: Increase O2 consumption, BMR, panting, sweating, panting, & CO

Metabolism: increase glucose available & provide more fatty acids (lipolysis)

Protein synthesis = stimulated in pre-adolescence and inhibited w/ hyperthyroidism

Bone = maintain growth and g.plate closure

Muscle= maintain protein synthesis

Skin = maintain protein synthesis & turnover; maintain hair coat & gland activity

Brain development = stimulates





in which species is this most commonly seen?

T.Gland tumors; too high or low iodine in diet

Poor hair coat, diarrhea, vomiting, goiter, weak, weight loss, increased nail growth

Methimazole inhibits T4 formation, surgery, radioactive I

Common in Older cats


Common causes?



most common in ______

Hypothalamic lesion, pituitary lesion, thyroid lesion

Slow onset, loss of appetite, lethargy, obesity, constipation, bradycardia, bilateral alopecia, hypercholesterolemia

replacement therapy with synthetic thyroxine = levothyroxine

dogs (esp. golden ret., doberman pincher, great Dane, cocker spaniel, dachshund, Irish setter, boxer, poodle, Pomeranian)

Explain the difference between the primary, secondary, and tertiary hypothyroidism.

Primary hypothyroidism is when there's a lesion at the level of the thyroid resulting in no increase in T4, even after administering TSH

Secondary hypothyroidism: lesion at the level of the pituitary, resulting in no increase in TSH after administering TRH

Tertiary hypothyroidism: lesion at the level of the hypothalamus resulting in an increase in TSH after administering TRH

What is cretenism?

It is a condition of severely stunted physical and mental growth due to untreated congenital deficiency of thyroid hormones (congenital hypothyroidism)

Which gland secretes insulin and glucagon?

Describe the main structure and function of these hormones?

The Pancreas, specifically the pancreatic islets of Langerhans

they're peptides

function: rapid and powerful regulators of metabolism; they coordinate disposition of nutrient inputs from meals, flow of endogenous substrates during fasting

Name the 4 cell types and their percentage in the islets of Langerhans, as well as the hormone they secrete.

1) Alpha = 20% = Glucagon

2) Beta = 80% = Insulin

3) Delta = 1-5% = Somatostatin

4) PP cells = 1-2% = Pancreatic Polypeptide

True or False:

The islet tissue of the pancreas can regenerate


Name 4 hormones that oppose the anabolic function of insulin.




growth hormone

Which anatomical arrangement predisposes the liver to be the primary target of insulin and glucagon?

the liver receives lots of hormones (they're secreted into the portal blood) due to the hepatic portal vein bringing lots of nutrients from the gut to the liver

What are the effects of insulin in the insulin sensitive tissues (liver, muscles, adipose)?

insulin stimulates insulin sensitive tissues (possess insulin receptors) to store fuels...lipogenesis, glycogenesis, & protein synthesis in the liver

...glycogenesis/glucose uptake & protein synthesis in muscle

...fatty acid esterification & glucose uptake in adipose

Describe how insulin is secreted and its actions?

1) Elevated levels of glucose in plasma stimulates insulin secretion (as well as enteric hormones, glucagon, etc.)

2) Insulin binds to an insulin receptor, which is associated with tyrosine kinase

3) The binding of insulin stimulates the tyrosine kinase, which phosphorylates other enzymes that mediate the effects on glucose transport, as well as protein, fat, and carbohydrate metabolism

How does insulin facilitate glucose uptake in muscle and adipose tissues?

...what about in the liver?


Glucose enters cells via glucose transporters (GLUTs).

Insulin stimulates cells in adipose and muscle tissue to incorporate more GLUTs into their membranes = GLUT 4

In hepatocytes, insulin stimulates phosphorylation of intracellular glucose in order to maintain a high concentration gradient for glucose diffusion via GLUT 2

GLUT 3 mediates entry of glucose in neurons and it's insulin independent

What are the main triggers of glucagon secretion?

low levels of plasma glucose, high levels of amino acids,

What are the main effects of glucagon on flow of fuels?

How do these effects differ from the effects of insulin?

glucagon stimulates fuel breakdown in the liver, including glycogenolysis & gluconeogenesis, and lipolysis in adipose tissue

they are opposite to the actions of insulin = antagonistic

Define diabetes mellitus (DM).

In which species are you most likely to encounter this disease?

Diabetes mellitus is a condition in which the pancreas no longer produces enough insulin or cells stop responding to the insulin that is produced, so that glucose in the blood cannot be absorbed into the cells of the body.

Common in dogs

What are the most common causes of DM in domestic animals?

in humans?

Hypoinsulinemia caused by a lack of insulin due to auto-antibodies is most common cause in dogs. Other possible causes include: genetic predisposition, trauma, neoplasia, hormone induced beta cell exhaustion, target tissue insensitivity (most common in cats), dyshormonogenesis of insulin

In humans, destruction of pancreatic beta cells by auto-antibodies (type I) and insulin insensitivity (type II)

What are common signs of DM in dogs?

cataracts, hepatomegaly, polydipsia, anorexia, weight loss, depression, ketoacidosis, hyperglycemia, ketouria, glucouria, polyuria,cystitis

Resulting from malfunction of carb, protein, and lipid metabolism due to a lack of the effects of insulin, so there's unopposed fuel breakdown and a lack of fuel storage

Explain the effects of insulin withdrawal in DM animals.

Insulin withdrawal results in the malfunction of carbohydrate, protein, and lipid metabolism.

Insulin withdrawal results in the malfunction of carbohydrate, protein, and lipid metabolism.

How is DM I treated?

primarily insulin replacement therapy

How is DM II treated?

Weight loss (b/c hormones produced by adipose tissue are associated with insulin insensitivity)

Diet restrict carb intake and switch to high-protein and fiber diet

Hypoglycemic agents that increase insulin secretion, increase insulin sensitivity, and decrease glucose absorption

Insulin administration

What are the main functions of Ca 2+?

Muscle contraction, hormone & NT release, 2nd messenger, coagulation (it's an essential co factor), structural component of bone, etc.

Describe the processes that contribute to the levels of Ca2+ in plasma and extracellular fluid.

Ca Homeostasis is achieved by regulation of 1) Absorption in GI 
2) Storage in bone
3) Excretion by kidney

Ca Homeostasis is achieved by regulation of 1) Absorption in GI

2) Storage in bone

3) Excretion by kidney

Which 3 hormones contribute to the regulation of Ca2+ homeostasis?

And do they increase or decrease plasma Ca2+?

1) parathormone (PTH) = increases Ca 2+

2) VitD = increases Ca 2+

3) Calcitonin = decreases Ca 2+

Describe parathormone.

which cells secrete it?

what stimulates its secretion?

what are the main effects?

It's a protein secreted by chief cells of the parathyroid gland

Secretion is stimulated by a decrease in serum ionized Ca 2+ detected by calcium-sensing receptors in the membranes of chief cells

It stimulates bone resorption and Ca2+ renal reabsorption and indirectly the absorption of Ca2+ in the gut by stimulating VitD formation

How is vitD synthesized? how is this regulated? what are its functions?

It can be synthesized in the skin from cholesterol when exposed to UV light, then processed in the liver, but dogs & cats rely more on dietary VitD (also processed in the liver). This VitD has to be further processed by the kidney to its active form.

The conversion to an active form of VitD in the kidney is stimulated by PTH.

functions: increase Ca2+ and phosphate intestinal absorption and renal reabsorption, as well as increase bone resorption

Describe calcitonin. which gland secretes it? how is this regulated? what are its functions?

A peptide secreted by the thyroid gland in response to 1) high plasma Ca2+ 2) Gastrin (GI hormone)

Functions: DECREASE Ca2+ intestinal absorption, renal reabsorption, and resorption from bone

What are the main signs of hypercalcemia? causes? treatment?

Decreased Neuromuscular Excitability

Bones: dissolution of bone, pain, fractures

Groans: constipation, anorexia

Stones: nephrocalcinosis, PU/PD, metabolic acidosis

Moans: fatigue, muscle weakness & pain, joint pain

Overtones: depression, lethargy, confusion

Causes: primary hyperparathyroidism/tumor, vitD toxicosis

Treatment: diuretics

What are the main signs of hypocalcemia? causes? treatment?

Increased neuromuscular excitability

Muscle cramps & pain, seizures, muscle spasms, tetany, coagulopathies, eclampsia/convulsions, milk fever

Causes: primary hypoparathyroidism; renal failure

Treatment: iv or oral calcium, VitD

Why does calcium affect neuromuscular excitability?

Calcium blocks Na+ voltage-gated channels, so an increase in Ca2+/hypercalcemia leads to a Decrease in neuromuscular excitability

Decreased extracellular Ca2+ increases the RMP of cells making it easier for neurons to depolarize and propagate an AP = Increased neuromuscular excitability

Describe melatonin.

Gland location?


It's secreted by the pineal gland and synthesized from tryptophan

It's inhibited by light

It influences reproductive cycles of seasonal breeders

What initiates secretion of melatonin?

enzymatic activity and norepinephrine/SNS

What are the effects of melatonin on gonads...

in short day breeders?

long day breeders?

What species are included....

Melatonin acts on hypothalamus to reduce GnRH

In sheep, goats, fox, deer, and elk: as the photoperiod increases = less melatonin = fertility decreases

In horses, ring-tailed lemurs, hamster, groundhog: breeding season ends when daylight decreases = more melatonin

Race horse breeders like to prepare mares for breeding by putting them under artificial light in winter. Why?

Light inhibits melatonin and in horses melatonin reduces GnRH and thus LH & FSH & reproduction are reduced

What are some other functions of melatonin?

Sleep/wake cycle, enhances immune response, reduces thyroid function, stress response, reduces free radical formation

What is erythropoietin?

what secretes it?



It's a glycoprotein produced by the fetal liver and adult kidney

Secreted by peritubular capillary endothelial cells of the kidney

It's triggered by decrease in renal blood flow, decreased PO2 in blood to kidney, hypotension

Affects: stimulates erythropoiesis and Fe2+ uptake in small intestine

Lack of Erythropoietin can be caused by ____ results in _______, and can be treated using _____ ______ ____.

renal disease


Human recombinant EPO, Iron supplementation, transfusion