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07 Animal phys
endocrine system
Undergraduate 4

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Name the organs of the endocrine system with only endocrine function (4)
  1. pituatary
  2. parathyroid
  3. thyroid
  4. adrenal gland
Name the organs of endocrine system with mixed and uncertain function (12)
  1. Pineal (uncertain)
  2. hypothalamus (neuroendocrine organ)
  3. thymus
  4. heart
  5. stomach
  6. pancreas
  7. duodenum
  8. kidney
  9. skin
  10. ovaries
  11. placenta 
  12. testes
What are the 4 functions of secretions, and how do they act?
  1. Autocrine - secretion affects the secreting cell itself
  2. Paracrine - secretion affects neighboring cells
  3. Endocrine - secretion released into blood stream and affects distal target tissues
  4. Exocrine - secretion released onto the surface of the animal and other external structures
What is the defintion of a hormone 
  • Released by endocrine cells or neurons, these are chemical messengers that bring about changes by being released into the blood stream or hemolymph and are carreid to distal target organs
How to exocrine glands secrete?
Glands have ducts through which their nonhormonal products travel to the membrane surface and to the exterior (epithelial surface)
  1. How to endocrine glands secrete?
  2. What are the (ductless)endocrine glands?


  1. They release their substances into the surrounding fluid (ductless glands)
  • Pituatary
  • thyroid
  • parathyroid
  • adrenal
  • pineal
  • thymus
  • pancreas 
  • gonads
  • hypothalamus? 
How do hormones affect target cells? (4)
  1. Control the rate of enzymatic reactions
  2. Control transport of molecules across the cell membranes
  3. Control gene expression and protein synthesis
  4. Control stimulation of mitosis
What is the function of tropic hormones and what do they do?
  • Primary function is to regulate the production and release of other hormones
    • stimulates and maintain their endocrine target tissue
    • EX: TSH maintains the structural integrity of the thyroid gland, but also causes it to secrete its hormones
What is the def of nontropic hormone and what does it do?
  • Exerts its effects on nonendocrine target tissues
    • EX: thyroid hormone increases the metabolic activity of almost every cell in the body. 
What makes the endocrin system complex? (7)
  1. a single endocrine gland may produce multiple hormones
  2. a single hormone may be secreted by more than one endocrine gland
  3. a single hormone may have more than one type of target cell and may induce more than one effect
  4. a secretory rate may vary considerably over time
  5. a single target cell may be affected by more than one hormone 
  6. a single chemical messenger may be a hormone or a neurotransmitter
  7. some organs are purely endocrine whil others may have nonendocrine functions. 
What is the 4 classification of hormones?
  1. Peptide hormone - made of 3 or more AA (hydrophillic)
  2. Amine hormones - single AA (hydrophillic)
  3. Steroid hormones - derived from cholesterol (lipophyllic)
  4. Endocrine-disrupting chemicals (EDC's) - nonnative hormone like substances, by products of manufactured organic compounds. 

What is the pathway of peptide hormones (5 steps)

What is the mechanism of action (what are the two receptors used)

  • synthesized in RER as a preprohormone ->packaged into vesicles ->in Golgi processed into a prohormone, and then hormone+fragments ->released into ECF when cell is signaled to do so ->transported in blood, half life is minutes
  • Mechanism of action - bind to cell surface receptors (cAMP and tyrosine kinase). This open or closes membrane channels or can modulate metabolic enzymatic activity and/or transport proteins

When are steroid hormones synthesized?

Where are they bound? 

What is their halflife?

What is the mechanism of action?

How fast do they act

  1. Synth in SER, lipophillic, synthesized as NEEDED
  2. bound in the inactive form to protein carriers in blood
  3. half life is hours 
  4. mech - diffuses across cell membrane to cytoplasmic and nuclear receptors to interact with DNA. 
  5. SLOW cell response (hours)
  • What do amine hormones contain and what are they derived from? 
  • What can they mimic? 
  • What are the 3 thyroid hormones?
  • What do they do? 
  • what are the iodine containing hormones called? 


  1. Derived from typtophan/tyrosine, contain nitrogen
  2. may act like peptide (catecholamines) or steroids (thyroid hormones).
  3. thyroxin (T4), triiodothyromine (T3), Calcitonin.
  4. T4 and T3 both contain iodine, collectively called thyroid hormones. 
  1. What 2 sections make up the adrenal gland? 
  2. what 2 hormones are secreted?
  3. what else are they called.                
  1. Medullary and cortical sections, cortex secretes hormones
  2. epinephrine and norepinephrine
  3. also called catecholamines 
What is the mechanism of action of lipophillic hormones? (6)
  1. lipophillic hormone diffuses through plasma and nuclear membrane, binds with nuclear receptor
  2. hormone/receptor complex binds with hormone response element of DNA specific for it
  3. DNA binding  activated specific gene which produce complementary mRNA
  4. mRNA leaves nucleus 
  5. In cytoplasm, mRNA direct the synthesis of new proteins
  6. New proteins, either enzymatic or structural accomplish the target cells ultimate physiologic response to hormone. 
  1. What are endocrine disrupting chemicals (EDC)? 
  2. what are they manufactured from
  3. where are they released? 
  4. what to they do? 
  5. how are they converted? 
  6. what are some examples
  1. man made, nonnative hormone like substance
  2. by products of manufactured organic compounds 
  3. released into environment
  4. interfere with endocrine and neural behaviors of animals 
  5. can convert through environment or in liver of animal
  6. Dioxin, PCB, phenolics, phthalates and pesticides
  1. What is hormone specificity
  2. What does hormone target ineraction depend on (3)
  1. major hormones circulate to virtually all tissue, but for these to repond, must have a specific protein receptor on their plasma membrane 
  2. blood levels of hormone, the relative # of receptors, the affinity of the bond btwn the hormone and receptor
  1. How are endocrine glands stimulated (3)?
  2. define both means and give example
  1. stimualted by humoral, neural, and hormonal means 
  2. Humoral stimuli - changes levels of blood ions and nutrients. (dec in calcium ->inc in parathyroid hormone)
  3. Neural stimuli - nerve fiver stimulates hormonal release (pos nervous input to adrenal medulla ->release of catecholamine
  4. Hormonal stimuli (tropic hormones) - endocrine glands release their hormones in response to hormones produced by other endocrine organs (hypothalamic hormones ->anterior pituatary to release hormones-> other endocrine glands to produce even more hormones. 

Define and example:




  • one hormone must be present for the full effect of another hormone
    • thyroid hormone increases the effect of epinephrine
  • several hormones combine to produce effect greater than the sum of their individual effect
    • tesosterone needs FSH for normal sperm production
  • one hormone reduces teh effectiveness of a second hormone.
    • during preg, progesterone inhibits uterine response to estrogen

Actions of:

  • prothoracicotropic hormone
  • juvenile hormone
  • ecdysone hormone
  • eclosion hormone
  • bursicon hormone
  • produced by neurosecroty cells of brain
  • produced by non-neural cells near brain
  • steroid like hormone produced  by glands of thorax
  • a peptide hormone produced by cells near brain
  • produced by neurosecretory cells of the brain and nerve cord

What does the hypothalamus secrete and what do those secretions control? 

What is the pathway of the hypothalamus secretion? (3)

  • secretes hormones that control the secretion of ALL anterior pituatary hormones
  • section of hypothalamic hormone whichc controls secretion of anterior pituatary hormone which controls the secretion of a hormone from some other organ/gland. 
How many hormones does the anterior pituatary gland secrete. 
  • at least 8, 6 with well defined functions 
What is the pathway for hormone production in insects (look at the pic)
  1. brain
  2. corpus cadiacum (eclosion hormone is produced here)
  3. corpus allatum (PTTH and JH produced)
  4. goes to the prothoracic gland where alpha-ecdysone produced ->beta ecdysone
  5. nerve cord produces bursicon

hypothalamic-pituatary system

  • where is the pituatary located
  • what are the two lobes called 
  • located just below hypothalamus, in pocket of bone at base of brain 
  • consists of two adjacent lobes - anterior (adenohypophysis) and the posterior pituatary (neurohypophysis)
What are the two hormones of the posterior pituatary
  • oxytocin (breast and uterine contraction) and vasopressin (BP and kidney function)
  • made in hypothalamus, move down the neural axons and accumulate in the axon terminals in the posterior pituatary

What is the intermediate lobe? 

what does it secrete

what inhibits the secretion? 

What does the section control and regulate? (3)


  • rudimentary after birth in human fetus
  • secretes meanocyte-stimulating hormone (MSH)
  • inhibited by hypothalamic dopamine
  • MSH controls skin coloration via melanin
  • MSH may regulate food intake and suppress immune system
  • Where does the posterior pituitary receive input from? (2)
  • What does it store/release
  • How many hormones are produced by a neuron
  • recieves input from supraoptic and paraventricular nuclei 
  • vasopressin and oxytocin
  • produces single hormone
  • What does vasopressin do? (3)
  • what is it called in lower vertebrates
  • Antidiuretic hormone  (ADH)
    • enhances water retention
    • stimulates areriolar smooth muscle contractions
    • release due to increased plasma osmolarity
  • Called arginine vasotocin (AVT)
  • What does oxytocin do? (2)
  • What is it called in non mammals  
  • stimulates uterine contractions in mammals
  • promotes milk ejection from mammary glands
  • in nonmammals called Mesotocin (MT) - influences blood flow. 
Hypothalamic releasing hormones (7)
  1. corticotroping releasing hormone (CRH)
  2. thyrotropin releasing hormone (TRH)
  3. Growth hormone releasing hormone (GHRH)
  4. Somatostain (SS) also called growth hormone inhibiting hormone (CHIH)
  5. Gonadotroping releasing homrone (GnRH)
  6. Prolactin releasing hormone (PRH)
  7. Prolactin inhibiting hormone (PIH)
What are the six anterior pituatary hormones? (2 of them refer to other hormones)
  1. Gonadotropic hormone (follicle stimulating hormone FSH, and luteinizing hormone LH)
  2. growth hormone (GH)
  3. Thyroid stimulating hormone (TSH)
  4. Prolactin (PRL)
  5. AdrenoCorticoTropic Hormone (ACTH)
  6. Tropic hormone - TSH, ACTH, FSH, and LH

What are the functions of these anterior pituatary hormones :

  1. TSH
  2. ACTH
  3. Prolactin
  4. Growth hormone
  5. LH
  6. FSH
  1. Metabolic rate
  2. metabolic actions, stress response
  3. milk secretion
  4. growth/metabolic actions
  5. sex hormone sectrion (estrogen and progesterone in females, tesosterone in males)
  6. Gamete production (ova in females, sperm in males)
What is the vascular pathway between the hypothalamus and anterior pituatary? (6)
  1. hypophysiotropic hormones (releasing hormone and inhibiting hormones) produced by neurons in the hypothalamus enter the hypothalamic capillaries
  2. These hypothalamic capillaries rejoin to form the hypothalamic-hypophyseal portal system. This vascular link passes to the anterior pituatary
  3. here it branches into the anterior pituatary capillaries
  4. the hypophysiotropic hormones leave the blood across the anterior pituatary capillaries and control the release of anterior pituatary hormones
  5. on stimulation by the appropriate hypothalamic releasing hormone, a given anterior pituatary hormone is secreted into these capillaries. 
  6. the anterior pituatary capillaries rejoin to form a vein, through which the anterior pituatary hormone leave for ultimate distrubution throughout the body by the systemic circulation. 
What are the 4 metabolic and developmental hormones? 
  • Gucocorticoids and catecholamines
  • Thyroid hormones
  • growth hormones 
  • insulin and glucagon
What are the 5 hormones that regulate water and electrolye balance? 
  • vasopressin - prevents water loss
  • aldosterone - prevents sodium and water loss
  • atrial natriuretic peptide - increases sodium and water loss
  • parathyroid hormone - increases plasma Ca2+ levels 
  • calcitonin - decreases plasma Ca2+ levels. 
What are the 3 reproductive hormones? 
  • estrogen - female characteristics and secretions 
  • androgens - male characteristics and secretions
  • progesteron - supports estrogens
What can prostoglandins act as, and what tissues do they act on? 
  • may be paracrine or endocrine in nature
  • act on smooth muscles of many tissues. 
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