CH. 6 - Endocrinology

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Keywords

1. Acromegaly - disorder in adult with overproduction of growth hormone - overgrowth of bone

2. Adrenal Cortex - produces corticosteroids in response to stress

3. Adrenal Glands - atop of kidney.  Adrenal cortex and adrenal medulla are part of it

4. Adrenal Medulla - produces epinephrine and norepinephrine for flight or fight response

5. Adreno-corticotrophic hormone (ACTH) - produced by anterior or pituitary gland.  Stimulates glucocorticoids and cortical sex hormones. Regulated by corticotrophin releasing factor (CRF)

6. Aldosterone - regulate plasma levels of sodium and potassium and ultimately total excreted water volume.  Might cause hypertension.  Produced in adrenal cortex

7. Androgen - secreted by testes and adrenal cortex (minute amount).  For masculinity

8. Anterior Pituitary - synthesizes direct and tropic hormones.  Direct hormones: growth, prolactin, endorphines.  Tropic hormones: ACTH, TSH, LH, FSH, MSH

9. Antidiuretic hormone - Increases the permeability of the nephron collecting duct and thus promotes water reabsorption and increases blood volume.  Produced in hypothalamus, stored in posterior pituitary.

10. Auxin - plant hormone responsible for phototropism, geotropism, and inhibition of lateral buds

11. Bile - produced by gall bladder into small intestine and digests fat

12. Calcitonin - secreted by thyroid. Decreases plasma calcium level.

13. Cholecystokinin - released by small intestine in response to fat and causes release of bile

14. Chyme - partially digested food

15. Cortisol/Cortisone - produces in adrenal cortex.  Involved in glucose regulation

16. Cretinism - hypothyroidism in infants

17. Diabete mellitus - high blood glucose level, insulin out of whack

18. Endocrine glands - synthesize and secretes hormones directly into circulatory system

19. Endorphines - direct hormone inhibit the perception of pain secreted by anterior pituitary

20. Ethylene - stimulates fruit ripening.

21. Exocrine glands - secrete substance transported by ducts

22. Follicle-stimulating Hormone (FSH) - causes maturation of ovarian follicles and thus production of estrogen.  In males, stimulates maturation of seminiferous tubules and production of sperm.  Produced in anterior pituitary and is a tropic hormone.

23. Gastrin - produced by stomach and induces production of HCl

24. Geotropism - growth of plants away from gravity.

25. Gibberellins - stimulate rapid stem elongation. Inhibit formation of new roots.  Terminates dormancy of seeds and buds.  Stimulate production of phloem.

26. Glucagon - increases blood glucose level.  Produced by alpha cells of pancrea

27. Gluconeogenesis - formation of glucose from non-carb source like amino acids, glycerol

28. Goiter - bulge in neck resulting from hyperthyroidism

29. Hyperthyroidism - thyroid overstimulated, increased metabolism

30. Hypothalamus - located directly above the pituitary glands.  Controlled by brain, and produces hormones to interact with both pituitary glands.

31. Hypothyroidism - thyroid hormones are undersecreted, causes decrease metabolism

32. Insulin - lowers blood sugar level

33. Islets of Langerhans - small glandular structure in pancrea that makes glucagon and insulin

34. Kidney - when blood volume is low, produces Renin which would cause aldosterone production

35. Kinin - promote cell division.

36. Luteinizing Hormone (LH) - in females, stimulates ovulation and formation of corpus luteum.  In males, stimulates testes to make testosterone.  Produced in anterior pituitary.

37. Melanocyte-Stimulating Hormone (MSH) - produced by intermediate lobe that doesn't do anything.  Useful in frogs.

38. Melatonin - secreted by pineal gland, might has something to do with circadian rhythm

39. Oxytocin - produced by hypothalamus, stored in posterior pituitary.  It increases contractions during labor and also stimulates milk production.

40. Pancrea - both exocrine and endocrine organ.  Exocrine when producing digestive enzyme and transport through ducts to small intestine.  Endocrine when producing insulin or glucagon.

41. Parathyroid Gland - secretes PTH that offsets the effect of calcitonin

42. Parathyroid Hormone - increases the concentration of plasma calcium

43. Pineal Gland - tiny gland at base of brain that secretes melatonin

44. Pituitary Gland - 3 lobes, middle lobe is remedial.  Located at base of brain.

45. Phototropism - plant's tendency to grow toward sun.  Indoleacetic acid is the auxin responsible

46. Posterior Pituitary - also called neurohypohypsis.  Doesn't synthesizing own hormone.  Stores and secretes oxytocin and ADH.

47. Prolactin - direct hormone stimulates milk production secreted by anterior pituitary

48. Renin - secreted by the kidney, it converts a series of plasma protein that would stimulate the adrenal cortex to secrete aldosterone

49. Secretin - released by small intestine that triggers secretion of alkaline bicarbonate to neutralize acidic chyme

50. Somatotropin - direct growth hormone secreted by anterior pituitary

51. Thyroid - located on ventral surface of the trachea

52. Thyroid Hormones - consists of thyroxine and tri-iodothyronine

53. Thyroid-stimulating hormone (TSH) - tropic hormone produced by anterior pituitary.  Stimulates thyroids.

Chemical Regulation in Animals

1. General

1. Endocrine system

1. Means of internal communication, coordinating the activities of the organ systems

2. Endocrine glands synthesize and secretes hormones directly into circulatory system

3. ie - pituitary, hypothalamus, thyroid, parathyroids, adrenals, pancreas, testes, ovaries, pineal, kidney, gastroinstestinal glands, heart, and thymus

4. Some hormone regulate single type of cell or organ, some regulates wide range of actions

1. Specificity determined by the presence of receptors on target cells

2. Exocrine glands

1. Secrete substances that are transported by ducts

2. ie - gall bladder

2. Adrenal Glands

1. Situated on top of the kidney and consist of the adrenal cortex and adrenal medulla

2. Adrenal Cortex

1. Stimulated by ACTH (adrenocorticotrophic hormone) in response to stress and produces corticosteroids

2. Derived from cholesterol, there are three kinds of corticosteroids

1. Glucocorticoids

1. Involved in glucose regulation and protein metabolism

1. Raises blood glucose levels by protein breakdown and gluconeogenesis and decreasing protein synthesis

2. Raises the plasma glucose levels and reverse the effect of insulin

2. ie - cortisol and cortisone

2. Mineralocorticoids

1. Aldosterone is the major type of mineralocorticoids

1. Regulate plasma levels of sodium and potassium and total extracellular water volume

2. Causes active reabsorption of water in the nephron (kidney)

3. This causes raise in blood volume and blood pressure

4. In excess, it can cause excess retention of water and results in hypertension

3. Cortical sex hormones

1. Secretes androgens like androstenedione and dehydroepiandrosterone

2. Androgens produced mostly in testes in male

3. Over production in female may have masculinizing effects

3. Adrenal Medulla

1. Produces epinephrine (adrenaline) and norepinephrine (noradrenaline)

1. Belong in the catecholamine class - amino acid derived

1. Fight or flight response elicited

1. Increase conversion of glycogen to glucose in liver and muscle tissue

2. Rise in blood glucose level

3. Increase in basal metabolic rate

4. Increase the rate and strength of heartbeat

5. Dilate and constrict blood vessels to increase blood supply to skeletal muscle, heart, and brain and decreasing supply to kidneys, skin, and digestive tracts

2. Both are neurotransmitters

4. Control of Adrenal Hormones

1. Under the control of AdrenoCorticoTrophic Hormone

1. Stimulates production of glucocorticoids and se steroids

3. Pituitary Gland

1. General

1. Pituitary - also known as hypophysis

1. Small tri-lobed gland

2. Located at base of brain

3. Contains two main lobes, anterior and posterior

1. The third lobe is rudimentary and doesn't do anything

2. Anterior Pituitary

1. General

1. Synthesize direct hormones which directly stimulate target organs

2. Synthesize tropic hormones which stimulate other endocrine glands to release hormones

3. Controlled by hypothalamic secretions called releasing/inhibiting hormones/factors

2. Direct hormones

1. Growth Hormones

1. Also known as somatotropin

2. Promotes bone and muscle growth

3. Deficiency leads to dwarfism in children

4. Overproduction leads to gigantism in children

5. Overproduction in adult leads to acromegaly

1. Disproportionate overgrowth of bone in skull, jaw, feet, hands

2. Prolactin

1. Stimulates milk production and secretion in female mammary glands

3. Endorphines

1. Inhibit the perception of pain

3. Tropic Hormone

1. Adrenocorticotropic hormone (ACTH)

1. Stimulates adrenal cortex to synthesize and secrete glucocorticoids.  Regulated by corticotrophin releasing factor (CRF)

2. Thyroid-stimulating hormone (TSH)

1. Stimulates the thyroid gland to synthesize and release thyroid hormone including thyroxin

3. Luteinizing Hormone (LH)

1. Females - stimulates ovulation and formation of the corpus luteum

2. Males - stimulates interstitial cells of the testes to produce testosterone

4. Follicle-stimulating hormone (FSH)

1. Females - causes maturation of ovarian follicles which then secretes estrogen

2. Males - stimulates maturation of seminiferous tubules and sperm production

5. Melanocyte-Stimulating Hormone (MSH)

1. Secreted by intermediate lobe of the pituitary

1. Doesn't do anything in mammals

2. In frogs, it darken the skin via dispersion of molecules of pigment in melanophore cells

3. Posterior Pituitary (neurohypophysis)

1. General

1. Does not synthesize hormones, rather it stores and releases different kinds of hormone produced by the neurosecretory cells of the hypothalamus

2. Secretion is controlled by action potentials coming from hypothalamus

2. Oxytocin

1. Secreted during childbirth

2. Increases the strength and frequency of uterine muscle contractions

3. Induced also by suckling because it stimulates milk secretion

3. Antidiuretic hormone (ADH, vasopressin)

1. Increases the permeability of the nephron's collecting duct to water

1. Thus promotes water reabsoprtion and increasing blood volume

2. Secreted when plasma osmolarity increases or if blood volume decreases

4. Hypothalamus

1. General

1. Part of the forebrain and located directly above pituitary gland

2. Receives instructions from brain (and elsewhere) that would trigger the neurosecretory cells

1. This in term controls the posterior pituitary gland via negative feedback mechanisms and the actions of inhibiting and releasing hormones.

2. Interactions with Anterior Pituitary

1. Releases hormones that stimulate or inhibits secretions of anterior pituitary

1. GnRH - stimulates anterior pituitary to secret FSH and LH

1. This hormone travels through the hypothalamic-hypophyseal portal system

1. Blood from capillary bed flows through a portal vein into the anterior pituitary so any hormone from hypothalamus goes to anterior pituitary immediately

2. Controlled via negative feed back. When concentration of said glucose is too high, or aldosterone -- glucose or steroids will act as a inhibitor to hypothalamus.

3. Interactions with Posterior Pituitary

1. Hypothalamus synthesize both oxytocin and ADH and transport them via their axons for storage and secretion in the posterior pituitary.

5. Thyroid

1. General

1. Bi-lobed structure located on the ventral surface of the trachea

2. Produces and secretes

1. Thyroxin

2. Triiodothyronine

3. Calcitonin

2. Thyroid Hormones

1. General

1. Thyroxine and tri-iodo thyronine are derived from iodination of tyrosine

2. Necessary for growth and neurological development in children

3. Increases metabolism throughout the body

2. Hypothyroidism

1. Hormones undersecreted

2. Symptoms

1. Slowed heart rate and respiratory rate, Fatigue, Cold intolerance, Weight gain

3. In infants, is called cretinism

1. Can cause mental retardation and short stature

3. Hyperthyroidism

1. Hormone oversecreted

2. Symptoms

1. Increase metabolism, feeling of excessive warmth, profuse sweating, palpitations, weight loss, and protruding eyes

2. Thyroid often enlarges, forming bulge called goiter

3. Calcitonin

1. Decreases the plasma Ca²⁺ concentration by inhibiting the release of calcium ion from bone.

2. Regulated by plasma calcium ion level.

3. Antagonistic to parathyroid hormone

6. Pancreas

1. General

1. Both exocrine and endocrine organ

2. Exocrine function when cells secrete digestive enzymes into the small intestine via ducts

3. Endocrine function when small glandular structures produces glucagon and insulin for the blood.

2. Islets of Langerhans

1. Small glandular structure composed of alpha and beta cells

2. Alpha cells produce and secrete glucagon

1. Stimulates protin and fat degradation

2. Conversion of glycogen to glucose

3. Gluconeogenesis

4. Increases blood glucose levels

3. Beta cells produce and secrete insulin

1. Protein hormone that stimulates uptake of glucose by muscle and adipose cells, and the storage of glucose as glycogen in muscle and liver cells

2. Lowers glucose level

3. Stimulates the synthesis of fats from glucose and uptake of amino acids.

4. Underproduction of insulin results to diabetes mellitus

1. Hyperglycemia (high blood glucose levels)

7. Parathyroid Glands

1. 4 small pea-shaped structures in the posterior surface of the thyroid

2. Synthesize and secrete parathyroid hormone (PTH) that regulates plasma calcium level

3. Increases the calcium level of the plasma by stimulating calcium releases from bone and decreasing calcium excretion in kidney

4. Breakdown of bone releases both calcium and phosphate, and PTH stimulates excretion of phosphate by kidney.

8. Kidney

1. Produces Renin

1. When body's blood volume is low, kidney produces renin

1. Coverts plasma protein angiotensinogen to angiotensin I.

1. Then angiotensin I is coverted to angiotensin II

1. Angiotensin II stimulates adrenal cortex to secrete aldosterone

2. Aldosterone helps restore blood volume by increasing sodium reabsorption at the kidney leading to an increase in water.

9. Gastrointestinal Hormones

1. Gastrin

1. Ingested food stimulates stomach to secrete gastrin

2. Carried to the gastric glands and they'd secrete HCl

1. The pancreatic juice are also under this control

2. Secretin

1. Released by small intestine when acidic food enters

2. Stimulates the secretion of alkaline bicarbonate from pancreas to neutralize the partially digested food (chyme)

3. Cholecystokinin

1. Released by small intestine in response to presence of fat

1. Causes the contraction of gallbladder and release of bile

1. Bile helps digestion of fat

10. Pineal Gland

1. Located at the base of brain

2. Secretes melatonin

1. Possibly regulation of the circadian rhythms

2. Secretion regulated by light and dark cycles

3. Lightens the skin in primitive vertebrates

Mechanism of Hormone Action

1. General

1. Hormones are classified based on their chemical structures

1. Peptide hormones

2. Steroid Hormones

2. Two ways which hormones affect the activities of target cells

1. Extracellular receptors

2. Intracellular receptors

2. Peptides

1. These hormones ranges from short peptides such as ADH to big ones like insulin

2. Acts as messengers

3. Binds to specific receptors on surface of target cells and triggers series of enzymatic reactions

1. The result of each reaction acts as the next messenger for the next reaction

1. Inhibition usually occurs with the final product inhibiting the starting sequence

3. Steroid

1. These hormones are like estrogen and aldosterone

2. Composed of ring structures and produced by places we mentioned earlier

3. Because they are lipid soluble, they enter directly into the target and bind to receptor in the cytoplasm

1. This receptor-hormone complex then enters the nucleus and directly activates a gene expression and makes new proteins!

Regulation in Plants

1. General

1. Plant hormones are usually involved in growth only

2. Produced usually by growing parts of the plan like the meristematic tissues in the apical region.

3. Also produced in young, growing leaves and developing seeds

2. Auxins

1. Phototropism

1. Auxins are responsible for the tendency of the plants to bend toward the sun

1. When light strikes the plant on one side, the auxin supply on that side is reduced.

2. The illuminated side of the plant grows more slowly than the shaded side

3. This causes the stem to bend towards the light

4. Indoleacetic acid is an auxin associated

2. Geotropism

1. Negative

1. Causes shoots to grow upward away from gravity.

1. Thus if plant is turned to side, it's turn itself about to grow up

2. Gravity increases the concentration of auxin on the lower side of the horizontal plant and this stimulates lower side to grow faster and the plant to grow vertically.

2. Positive

1. Causes roots to grow towards gravity

2. Same as shoot, except effects are opposite

3. Inhibition of Laterla buds

1. In terminal bud of plant's growing tip, auxin moves downward and inhibit the development of lateral buds

2. Auxin also initiate formation of lateral roots while inhibiting root elongation

3. Gibberellins

1. Stimulates rapid stem elongation especially in plants that are stubby

2. Inhibits formation of new roots

3. Stimulates the production of new phloem cells by the cambium

4. Terminate the dormancy of seeds and buds

5. Induce biennial plants to flower during first year of growth

4. Kinins

1. Promotes cell division.

2. Kinetin is a type of cytokinin

3. Ratio of kinetin to auxin is important in determining the timing of differentiation of new cells

5. Ethylene

1. Stimulates fruits ripening

2. Induces senescence, or aging

6. Inhibitors

1. Blocks cell division and serve in growth regulation

1. Important to maintain dormancy in autumn and winter

2. Abscisic acid is one of the inhibitors and breaks down over time

7. Anti-auxins

1. Regulates the activity of auxins

ie - indoleacetic acid oxidase regulates the concentration of indoleacetic acid