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Endocrine System
Chapter 6
60
Veterinary Medicine
Undergraduate 1
09/21/2011

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Term
Exocrine
Definition

Secretes substances which act at the site

Ducts

Term
Endocrine
Definition

Seceretes substances which have actions at distant points, no ducts

Uses blood

 

Cellular communication systems somewhat like nervous system

 

Slower, mail vs. email

Term
Endocrine glands...
Definition

Secerete hormones, substances which are released into the bloodstream and have effects elsewhere in the body

Mediated by receptors on target cells, match hormone with receptor on cell

Term
Hormones
Definition
Molecules which are produced and secreted by one cells, but have effects on other cells, often distant
Term
How are hormones classified?
Definition

By structure

 

Peptides/Proteins: Insulin

Steroids: Estradiol

Amino Acid Derivatives: Thyroid

Fatty Acid Derivatives: Prostaglandis

Term
Secretion of endocrine hormones
Definition

Can be stored in secretory vessicles, released in a large bolus on signal, secretion as synthesixed

Many have short lifespan after release, inactivated rapidly, similar to neurotransmitters

Term
What do the control of endocrine hormones depend on?
Definition

The concentration

Concentration depends on the rate of synthesis, the rate of destruction, and the rate of delivery

 

Regulated by feedback loops

Term
Negative Feedback Loops
Definition

Similar to a thermostat

Effect produced by hormone acts to further production/release of that hormone

Results in a pulsed release of hormones

 

Variable concentrations in blood depending on sample

Term
Example of TSH feedback loop
Definition

Hypothalamus sends out thyroid releasing hormone

The pituitary releases thyroid stimulating hormone

Thyroid gland sends out thyroid hormones

 

Thyroid hormones reach hypothalamus

Too much, stop released thyroid releasing hormones

Term
Hypothalamus
Definition

Interface between nervous and endocrine systems

Temp, blood/fluid regulation

 

Close anatomical relatioship with pituitary via nerve fibers and release of hormones

Term
Pituitary
Definition
Master gland, regulates activity of many other endocrine glands
Term
Anterior Pituitary
Definition
Growth hormone, prolactin, ACTH, TSH, FSH, LH, ICSH
Term
Posterior
Definition
ADH, oxytocin
Term
Thyroid
Definition

Tyrosine->Tri-Iodothyronine->Thyroxine

 

Affects the uptake of oxygen by all the cells, esstential for normal growth

Term
Calcitonin
Definition
Lowers level of blood calcium by decreasing the rate of bone reabsorption
Term
Parathyroids
Definition

Near or embedded in thyroid gland

Works with calcitonin to regulate serum calcium

Primary, Secondary, or Nutritional

Term
Adrenal Glands
Definition

Sit on kidneys

 

Term
Adrenal Cortex
Definition

Outer

 

Glucocorticoids

Mineralcorticoids

Term
Adrenal Medulla
Definition

Inner

 

Adrenaline

Noradrenaline

Term
Pancreas
Definition

Endocrine/Exocrine

Insulin and glucagon

Term
Gonads
Definition
Progesterone, estrogen, testosterone
Term
Hypothalamus
Definition

Near optic chiasma

Various housekeeping functions

Sleep/wake, appetite, thermoregulation

Coordination of endocrine system->secretion of releasing/inhibiting hormones

Term
Hypothalmic-Pituitary Axis
Definition

Pituitary connects with hypothalamus

Vascular nerve input from hypothalamus to pituitary

Portal system to anterior pituitary

Neural input to posterior pituitary

 

STORED IN HYPOTHALAMUS, RELEASED IN PITUITARY

Term
Pituitary Gland
Definition

Anterior/posterior

Different embryologic origins

 

Anterior: Glandular tissue, hormones produced under direction of hypothalamus

 

Posterior: Neural

 

Term
Somatotropin - A.P.
Definition

Growth hormone

GHRH from hypothalamus, GH from A.P.

Anabolic (+) effects on protein metablosim

Catabolic (-) effects on adipose tissue

 

Insulin-like growth factor production by liver

Term
Prolactin- A.P.
Definition

Induces growth of alveoli of mammary gland

Stimulates lactogenesis

Effects on maternal behavior

 

BST: cow growth hormone->milk production

Term
TSH- A.P.
Definition

Thyroid stimulating hormone

Thyrotropic/Thrytopin

 

Stimulates growth and activity of thyroid gland

Term
ACTH- A.P.
Definition

Adrenocorticotropic Hormone

Release initiated by CRF

Stimulation of growth and activity of adrenal coretex

Feedback Loops to hypothalamus and pituitary for regulation

 

CNS can also release ACTH in emergency

Term
MSH- A.P.
Definition

Melanocyte-Stimulating Hormone

Stimulates color changes in amphibians and reptiles

Receptor for MSH seems to be involved in coat color in mammals

Term
FSH- A.P.
Definition

Follicle Stimulating Hormone

Stimulates development and growth of ovarian follicles

Estrogen secretion by follicles

Spermatogenesis by males

Term
LH/ITSH
Definition
Lutenizing hormone, stimulates ovulation/production of progesterone by corpus luteum of ovary, interstitial cells of testis-> testosterone
Term
Posterior Pituitary
Definition

Storage and release of two peptide hormones produced by hypothalamus, ADH and oxytocin

Transported in nerve fibers which originate in hypothalamus, stored in nerve endings

Released by nerve impulses

Term
ADH
Definition

Antidiuretic Hormone, vasopressin

Acts on kidneys to promote reabsorption of water

ADH insufficiency, central diabetes insipidus

Term
Oxytocin
Definition

Uterus-contractions

Mammary-myoepithelial cells

Sperm transport

Term
Thyroid
Definition

2 Lobes, lateral to larynx, isthmus

Composed of follicles-spherical cuboidal epithelium, contains thyroid hormone precursor made by cells, thyroglobulin

 

C cells inbetween follicles->calcitonin, parafollicular cells

Term
Thyroid Hormones
Definition

Synthesis/secretion regulated by hypothalamus and pituitary

T3 more active

Acts on virtually all cells of the body, increases basal metabolism, body heat, HR, contraction, output, necessary for normal growth, effects on fertility and hair coat

 

 

Term
How are thyroid hormones transported and metabolized?
Definition

Transported by being bound to proteins in blood

Metabolized by removal of iodine

Term
T3
Definition
Tri-Iodothyronine
Term
T4
Definition
Thyroxine
Term
Thyroid Abnormalities
Definition

Hypothyroidism: most common endocrine disorder in dogs, primary or seconday

 

Hyperthyroidism: most common endocrinopathy of cats, primary, middle age/senior cats

Term
Hypothyroidism-Canine
Definition

Most commonly a lymphocytic thyroiditis, autoimmune

Labs predisposed-greasy coat

Clinical signs, increase in weight, decrease in activity, greasy coat, slow, cardiac and neuromuscular

Term
Hyperthyroidism-Cats
Definition

Adenomatous Hyperplasia-thyroid gets bigger

Mature/Older cats

No breed dispositions, geographical-east coast

Clinical signs, decrease in weight, increase in appetite, crabby, greasy skin, rapid cardiac, muscle wasting

Term
Goiter
Definition

Enlargement of the thyroid gland in an attempt to increase secretion

 

Caused by iiodine deficiency, ingestion of goiterogenic plants

Term
Calcitonin
Definition

Made in various tissue in smallter amounts, but msotly from thyroid gland, C Cells, parafollicular cells

 

Peptide hormone

Helps regulate blood calcium levels

 

Inhibits release by suppressing osteoclast activity

Inhibits reabsorption in kidney tubules

Secretion regulated by levels in blood

Term
Parathyroid Hormones
Definition

Opposite effect of calcitonin

Main regulator of calcium and phosphorus lvls in serum

Protein hormone

Actions: mobilizes calcium from bone, increase calcium absorption in small intestines and kidney

Term
Adrenal Glands
Definition

Adjacent to cranial pole of kindey

Coretex and medulla

Term
Adrenal Cortex
Definition

Mineralcorticoids

Glucocorticoids

Sex Hormones-Androgen, estrogen

 

Hypothalamus->AP->AC

Term
Mineralcorticoids
Definition

Steroid hormones regulating electrolyte (sodium, potassium, chloride, phosphate) balence

 

Aldosterone-increases sodium retention

Term
Glucocorticoids
Definition

Cortisol, cortisone

Increase blood glucose levels

Catabolic effect->mobalize amino acids for gluconeogenesis, increase BP, antinflammatory, immunosuppressent, stress related functions

Term
Adrenal Medulla
Definition

Derived from nervous tissue

Produces and secretes: adrenaline and noradrenaline

Regulated by SNS

Fight/flight respons

 

FASTER AND MORE IMMEDIATE RESPONSE

Term
Hypoadrenocorticism-Canine
Definition

Insufficiency, autoimmune etiology

Lethargy, weakness, vomiting, weightloss

Synthetic hormone replacement

Iatrogrenic->cushings

Term
Hyperadrenocorticism-Dogs, cats, horses, ferrets
Definition

AP secretes excess ATCH

Primary adrenal tumors in ferrets

Can be iatrogenic

Term
Insulin
Definition

Protein hormone, made by beta cells of pancreatic inlet

Secreted in response to high glucose lvls

 

 

Term
Glycogen
Definition

The way animals store sugar, readily available

Plants->starch

Term
Insulin facilititates....
Definition

Transport of glucose into cells of body

Brain/liver do not require insulin for glucose update

insulin stimulates the liver to store glucose as glycogen

Term
Insulin and energy storage
Definition

Stimulates glycogen synthesis and storage in liver

Stimulates synthesis of fatty acids for storage in adipose tissue

Inhibits breakdown of fat in adipose tissue

Term
Glucose
Definition

Dextrose, simple sugar

Primary source of energy

 

80-120mg/dl

Ingestion of meal raises BG lvls, insulin release, BG lvls return to normal

Term
Diabetes mellitus
Definition

Type 1: beta cells of pancreas do not produce insulin

Type 2: cells of body become resistant to insulin

 

Animals with DM, elevated BG lvls, glucose unable to enter cells

Term
Ketoacidosis
Definition

Body thinks it is starving even though there is plenty of glucose

Breaks down fat for energy, production of ketones may exceed body's ability to remove them

 

Medical emergency

Term
Glucagon
Definition

Peptide hormone

Produced by alpha cells of pancreatic islets

Secreted in response to low lvls of BG

Acts on hepatocytes to break down glycogen to glucose

 

Stimulates gluconeogenesis, fatty acid breakdown in adipose tissue, cats very effecient

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